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  • richardmitnick 6:56 am on December 18, 2019 Permalink | Reply
    Tags: "What’s up with Jupiter’s wandering magnetic field?", , , , , , Saturn   

    From PBS NOVA: “What’s up with Jupiter’s wandering magnetic field?” 

    From PBS NOVA


    In 2018 and 2019, data from NASA’s Juno mission revealed new discoveries about Jupiter’s bizarre magnetic field.



    In 2018, astronomers were on the hunt for Planet Nine, a mysterious and powerful celestial body thought to dwell billions of miles beyond Neptune. They found 12 new moons orbiting Jupiter instead.

    Then, in October of this year, astronomers made another astonishing moon discovery: 20 tiny “new” satellites around Saturn, allowing the ringed giant to unseat Jupiter as the planet in our solar system with the most moons. But as 2019 comes to a close, Jupiter, the largest and oldest planet in our solar system, is back in the spotlight for a new reason: its shape-shifting magnetic field.

    This still from an animation illustrates Jupiter’s magnetic field at a single moment in time. The Great Blue Spot, an-invisible-to-the-eye concentration of magnetic field near the equator, stands out as a particularly strong feature. Credit: NASA/JPL-Caltech/Harvard/Moore et al.

    In a recent study [Nature Astronomy], researchers compared observations of Jupiter’s magnetic field from NASA’s Juno spacecraft with those taken by Pioneer 10, Pioneer 11, Voyager 1, and Ulysses. They found that Jupiter’s field had changed in just a few short decades.

    NASA Pioneer 10

    NASA Pioneer 11

    NASA/Voyager 1

    How is this possible? And could it have happened if Jupiter’s core was more like our own planet’s?



    Sometimes the best way to find something is by not looking for it at all.

    Astronomers looking for Planet Nine—a celestial body predicted to orbit in the outer reaches of our solar system—stumbled upon 12 new moons orbiting Jupiter. By this latest count, our solar system’s largest planet now has 79 moons, more than any other.

    Astronomers made the discoveries using the Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile and the Subaru telescope on Mauna Kea, Hawaii.

    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level

    It took the team a while to make the required observations to confirm each moon’s existence. The smallest moon is just over a half-mile across, while the largest is about three miles in diameter. Some slipped in and out of view, complicating the task.

    Here’s Ben Guarino, reporting for the Washington Post:

    “Jupiter’s moons range in size from shrimpy satellites to whopping space hulks. Galileo discovered the first four of Jupiter’s moons, all huge, in 1610. The largest Galilean moon, Ganymede, is bigger than the planet Mercury. Those moons orbit close to Jupiter and travel in the same direction as the planet spins.

    The moons Sheppard spied are farther-flung and tiny, each no more than two miles in diameter. One moon detected by Sheppard and his colleagues is the smallest Jovian moon ever discovered. They named it Valetudo, after a daughter of Jupiter and the Roman goddess of hygiene and personal health.”

    The orbits of Jupiter’s moons

    Most of the newly discovered moons orbit opposite to Jupiter’s spin, what’s known as a retrograde orbit. But Valetudo, in addition to being the smallest discovered, orbits in prograde, or the same direction as the planet’s spin. That puts it on a possible collision course with a retrograde moon.

    Photo credits: NASA, Roberto Molar-Candanosa/Carnegie Institution for Science

    See the full article here .


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    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

  • richardmitnick 10:25 am on January 25, 2019 Permalink | Reply
    Tags: , , , , , Saturn,   

    From Science Magazine: “Missions expose surprising differences in the interiors of Saturn and Jupiter” 

    From Science Magazine

    Jan. 17, 2019
    Paul Voosen

    Material thousands of kilometers below the clouds of Jupiter and Saturn tugs subtly on orbiting spacecraft, revealing hidden structure and motions.
    NASA/JPL/Space Science Institute.

    A clever use of radio signals from planetary spacecraft is allowing researchers to pierce the swirling clouds that hide the interiors of Jupiter and Saturn, where crushing pressure transforms matter into states unknown on Earth. The effort, led by Luciano Iess of Sapienza University in Rome, turned signals from two NASA probes, Cassini at Saturn and Juno at Jupiter, into probes of gravitational variations that originate deep inside these gas giants.

    What the researchers have found is fueling a high-stakes game of compare and contrast. The results, published last year in Nature for Jupiter and this week in Science for Saturn, show that “the two planets are more complex than we thought,” says Ravit Helled, a planetary scientist at the University of Zurich in Switzerland. “Giant planets are not simple balls of hydrogen and helium.”

    In the 1980s, Iess helped pioneer a radio instrument for Cassini that delivered an exceptionally clear signal because it worked in the Ka band, which is relatively free of noise from interplanetary plasma. By monitoring fluctuations in the signal, the team planned to search for gravitational waves from the cosmos and test general relativity during the spacecraft’s journey to Saturn, which began in 1997. Iess’s group put a similar device on Juno, which launched in 2011, but this time the aim was to study Jupiter’s interior.

    Juno skims close to Jupiter’s surface every 53 days, and with each pass hidden influences inside the planet exert a minute pull on the spacecraft, resulting in tiny Doppler shifts in its radio signals. Initially, Iess and his team thought measuring those shifts wouldn’t be feasible at Saturn because of the gravitational influence of its rings. But that obstacle disappeared earlier this decade, after the Cassini team decided to end the mission by sending the craft on a series of orbits, dubbed the Grand Finale, that dipped below the rings and eliminated their effects. As a result, Iess and colleagues could use radio fluctuations to map the shape of gravity fields at both planets, allowing them to infer the density and movements of material deep inside.

    One goal was to probe the roots of the powerful winds that whip clouds on the gas giants into distinct horizontal bands. Scientists assumed the winds would either be shallow, like winds on Earth, or very deep, penetrating tens of thousands of kilometers into the planets, where extreme pressure is expected to rip the electrons from hydrogen, turning it into a metallike conductor. The results for Jupiter were a puzzle: The 500-kilometer-per-hour winds aren’t shallow, but they reach just 3000 kilometers into the planet, some 4% of its radius. Saturn then delivered a different mystery: Despite its smaller volume, its surface winds, which top out at 1800 kilometers per hour, go three times deeper, to at least 9000 kilometers. “Everybody was caught by surprise,” Iess says.

    Scientists think the explanation for both findings lies in the planets’ deep magnetic fields. At pressures of about 100,000 times that of Earth’s atmosphere—well short of those that create metallic hydrogen—hydrogen partially ionizes, turning it into a semiconductor. That allows the magnetic field to control the movement of the material, preventing it from crossing the field lines. “The magnetic field freezes the flow,” and the planet becomes rigid, says Yohai Kaspi, a planetary scientist at the Weizmann Institute of Science in Rehovot, Israel, who worked with Iess. Jupiter has three times Saturn’s mass, which causes a far more rapid increase in atmospheric pressure—about three times faster. “It’s basically the same result,” says Kaspi, but the rigidity sets in at a shallower depth.

    The Juno and Cassini data yield only faint clues about greater depths. Scientists once believed the gas giants formed much like Earth, building up a rocky core before vacuuming gas from the protoplanetary disc. Such a stately process would have likely led to distinct layers, including a discrete core enriched in heavier elements. But Juno’s measurements, interpreted through models, suggested Jupiter’s core has only a fuzzy boundary, its heavy elements tapering off for up to half its radius. This suggests that rather than forming a rocky core and then adding gas, Jupiter might have taken shape from vaporized rock and gas right from the start, says Nadine Nettelmann, a planetary scientist at the University of Rostock in Germany.

    The picture is still murkier for Saturn. Cassini data hint that its core could have a mass of some 15 to 18 times that of Earth, with a higher concentration of heavy elements than Jupiter’s, which could suggest a clearer boundary. But that interpretation is tentative, says David Stevenson, a planetary scientist at the California Institute of Technology in Pasadena and a co-investigator on Juno. What’s more, Cassini was tugged by something deep within Saturn that could not be explained by the winds, Iess says. “We call it the dark side of Saturn’s gravity.” Whatever is causing this tug, Stevenson adds, it’s not found on Jupiter. “It is a major result. I don’t think we understand it yet.”

    Because Cassini’s mission ended with the Grand Finale, which culminated with the probe’s destruction in Saturn’s atmosphere, “There’s not going to be a better measurement anytime soon,” says Chris Mankovich, a planetary scientist at the University of California, Santa Cruz. But although the rings complicated the gravity measurements, they also offer an opportunity. For some unknown reason—perhaps its winds, perhaps the pull of its many moons—Saturn vibrates. The gravitational influence of those oscillations minutely warps the shape of its rings into a pattern like the spiraling arms of a galaxy. The result is a visible record of the vibrations, like the trace on a seismograph, which scientists can decipher to plumb the planet. Mankovich says it’s clear that some of these vibrations reach the deep interior, and he has already used “ring seismology” to estimate how fast Saturn’s interior rotates.

    Cassini’s last gift may be to show how fortunate scientists are to have the rings as probes. Data from the spacecraft’s final orbits enabled Iess’s team to show the rings are low in mass, which means they must be young, as little as 10 million years old—otherwise, encroaching interplanetary soot would have darkened them. They continue to rain material onto Saturn, the Cassini team has found, which could one day lead to their demise. But for now they stand brilliant against the gas giant, with more stories to tell.

    See the full article here .


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  • richardmitnick 7:55 am on September 16, 2017 Permalink | Reply
    Tags: , , , , , , , , Saturn   

    From Goddard: “How Two Ground-based Telescopes Support NASA’s Cassini Mission” 

    NASA Goddard Banner
    NASA Goddard Space Flight Center

    Sept. 11, 2017
    Elizabeth Zubritsky
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    When NASA’s Cassini spacecraft plunges into the atmosphere of Saturn on Sept. 15, ending its 20 years of exploration, astronomers will observe the giant planet from Earth, giving context to Cassini’s final measurements.

    “The whole time Cassini is descending, we’ll be on the ground, taking data and learning about conditions on Saturn,” said Don Jennings, a senior scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and a co-investigator for a Cassini instrument called the Composite Infrared Spectrometer.

    The aftermath of a massive storm that erupted in Saturn’s northern hemisphere in December 2010 continues to be tracked by researchers, including observations planned using the new high-resolution iSHELL instrument at NASA’s Infrared Telescope Facility. Credits: NASA/JPL-Caltech/SSI

    This farewell is fitting for a mission that has been supported by similar observations throughout its lifetime. NASA’s Infrared Telescope Facility, or IRTF, and the W. M. Keck Observatory, in which NASA is a partner, have provided crucial contributions from the summit of Maunakea in Hawaii. Other U.S. and international telescopes also have investigated the Saturn system, complementing and enhancing the mission.

    NASA Infrared Telescope facility Mauna Kea, Hawaii, USA, 4,207 m (13,802 ft) above sea level

    Keck Observatory, Maunakea, Hawaii, USA.4,207 m (13,802 ft) above sea level

    “IRTF and other facilities have provided direct support to the Cassini–Huygens mission and made it possible to link that data to decades’ worth of earlier and ongoing ground-based studies,” said IRTF director John Rayner.

    NASA/ESA/ASI Cassini-Huygens Spacecraft

    “Through its daytime observing capabilities IRTF is able to provide almost year-round monitoring of planets in support of NASA missions.”

    Ground-based observations of Titan, the giant planet’s largest moon, helped with preparations for the Huygens probe mission early in Cassini’s exploration of the Saturn system. The probe was released after Cassini entered Saturn orbit and descended through Titan’s thick atmosphere to land on the surface.

    A coordinated ground campaign was organized to study Titan’s atmosphere and surface, to measure the wind speed and direction, to look at atmospheric chemistry and to provide global imaging.

    Eight facilities worldwide participated, observing before, during and after the Huygens probe mission, led by the European Space Agency. These included the Keck Observatory, which captured high-resolution images of the atmospheric weather patterns on Titan, and the IRTF, which helped determine the direction of Titan’s winds.

    “Ground-based observing played a crucial role, because at that time, it was the only way to determine the direction of Titan’s winds, which had the potential to affect Huygens’ descent to the surface,” said Goddard’s Theodor (Ted) Kostiuk, who led those observations at the IRTF and is now an emeritus scientist. “The Voyager flyby provided some information about Titan, but wind direction was one thing it could not tell us.”

    IRTF continues to be used for long-term studies of Saturn and Titan and their atmospheres, and to investigate Saturn’s moons, extending and complementing Cassini findings. The facility’s recently installed high-resolution infrared instrument, called iSHELL, will be deployed for ongoing studies of the aftermath of a massive storm that broke out in Saturn’s northern hemisphere in 2010. With its very high spectral resolution, iSHELL has been optimized for the study of planetary atmospheres.

    Cassini also has received plenty of aloha from the Keck Observatory, which has provided many sharp images and spectra of Saturn’s most famous feature – its rings. These studies are made possible by the high spatial resolution of Keck’s large aperture combined with a state-of-the-art adaptive optics system to correct for distortions caused by Earth’s atmosphere.

    “It’s been exciting to be involved in ground support of the Cassini orbiter over these many years,” said Observing Support Manager Randy Campbell of Keck Observatory. “This mission has given us an opportunity to work together toward a better understanding of some of the most beautiful and enigmatic objects in the night sky, Saturn and its moons.”

    During the summer of 2017, the Cassini team used Keck Observatory to take near-infrared spectroscopic data of the regions near Saturn’s equator, just as Cassini was diving between Saturn and its rings during its final orbits. The team also took Keck data of the polar magnetic fields to better understand the planet’s auroras, which are similar to Earth’s northern and southern lights. The Keck Observatory data will be used to verify Cassini’s data to provide a sort of “ground-truth” calibration of some of the on-board instruments of the orbiter.

    After Cassini, ground-based studies will continue, building on everything the spacecraft observed, and keeping the discoveries coming.

    For more information about NASA’s Infrared Telescope Facility, visit:


    For more information about the Keck Observatory, visit:


    See the full article here.

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    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

    NASA/Goddard Campus

  • richardmitnick 8:06 am on September 11, 2017 Permalink | Reply
    Tags: , , , , Saturn   

    From JPL-Caltech: “After Cassini: Pondering the Saturn Mission’s Legacy” 

    NASA JPL Banner


    September 7, 2017
    Preston Dyches
    Jet Propulsion Laboratory, Pasadena, Calif.

    NASA/ESA/ASI Cassini-Huygens Spacecraft


    NASA’s Cassini spacecraft has delivered a glorious view of Saturn, taken while the spacecraft was in Saturn’s shadow. The cameras were turned toward Saturn and the sun so that the planet and rings are backlit. (The sun is behind the planet, which is shielding the cameras from direct sunlight.) In addition to the visual splendor, this special, very-high-phase viewing geometry lets scientists study ring and atmosphere phenomena not easily seen at a lower phase.

    Since images like this can only be taken while the sun is behind the planet, this beautiful view is all the more precious for its rarity. The last time Cassini captured a view like this was in Sept. 2006, when it captured a mosaic processed to look like natural color, entitled “In Saturn’s Shadow” (see PIA08329.) In that mosaic, planet Earth put in a special appearance, making “In Saturn’s Shadow” one of the most popular Cassini images to date. Earth does not appear in this mosaic as it is hidden behind the planet.

    Also captured in this image are two of Saturn’s moons: Enceladus and Tethys. Both appear on the left side of the planet, below the rings. Enceladus is closer to the rings; Tethys is below and to the left.

    This view looks toward the non-illuminated side of the rings from about 19 degrees below the ring plane.

    Images taken using infrared, red and violet spectral filters were combined to create this enhanced-color view. The images were obtained with the Cassini spacecraft wide-angle camera on Oct. 17, 2012 at a distance of approximately 500,000 miles (800,000 kilometers) from Saturn. Image scale at Saturn is about 30 miles per pixel (50 kilometers per pixel).

    The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

    As the Cassini spacecraft nears the end of a long journey rich with scientific and technical accomplishments, it is already having a powerful influence on future exploration. In revealing that Saturn’s moon Enceladus has many of the ingredients needed for life, the mission has inspired a pivot to the exploration of “ocean worlds” that has been sweeping planetary science over the past decade.

    “Cassini has transformed our thinking in so many ways, but especially with regard to surprising places in the solar system where life could potentially gain a foothold,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at Headquarters in Washington. “Congratulations to the entire Cassini team!”

    Onward to Europa

    Jupiter’s moon Europa has been a prime target for future exploration since NASA’s Galileo mission, in the late 1990s, found strong evidence for a salty global ocean of liquid water beneath its icy crust. But the more recent revelation that a much smaller moon like Enceladus could also have not only liquid water, but also chemical energy that could potentially power biology, was staggering.

    Many lessons learned during Cassini’s mission are being applied to planning NASA’s Europa Clipper mission, planned for launch in the 2020s. Europa Clipper will fly by the icy ocean moon dozens of times to investigate its potential habitability, using an orbital tour design derived from the way Cassini has explored Saturn.

    NASA/Europa Clipper

    The Europa Clipper mission will orbit the giant planet — Jupiter in this case — using gravitational assists from its large moons to maneuver the spacecraft into repeated close encounters with Europa. This is similar to the way Cassini’s tour designers used the gravity of Saturn’s moon Titan to continually shape their spacecraft’s course.

    In addition, many engineers and scientists from Cassini are serving on Europa Clipper and helping to develop its science investigations. For example, several members of the Cassini Ion and Neutral Mass Spectrometer and Cosmic Dust Analyzer teams are developing extremely sensitive, next-generation versions of their instruments for flight on Europa Clipper. What Cassini has learned about flying through the plume of material spraying from Enceladus will help inform planning for Europa Clipper, should plume activity be confirmed on Europa.

    Returning to Saturn

    Cassini also performed 127 close flybys of Saturn’s haze-enshrouded moon Titan, showing it to be a remarkably complex factory for organic chemicals — a natural laboratory for prebiotic chemistry. The mission investigated the cycling of liquid methane between clouds in its skies and great seas on its surface. By pulling back the veil on Titan, Cassini has ushered in a new era of extraterrestrial oceanography ­– plumbing the depths of alien seas — and delivered a fascinating example of earthlike processes occurring with chemistry and at temperatures markedly different from our home planet.

    In the decades following Cassini, scientists hope to return to the Saturn system to follow up on the mission’s many discoveries. Mission concepts under consideration include spacecraft to drift on the methane seas of Titan and fly through the Enceladus plume to collect and analyze samples for signs of biology.

    Giant Planet Atmospheres

    Atmospheric probes to all four of the outer planets have long been a priority for the science community, and the most recent Planetary Science Decadal Survey continues to support interest in sending such a mission to Saturn. By directly sampling Saturn’s upper atmosphere during its last orbits and final plunge, Cassini is laying the groundwork for an eventual Saturn atmosphere probe.

    Farther out in the solar system, scientists have long had their eyes set on exploring Uranus and Neptune. So far, each of these worlds has been visited by only one brief spacecraft flyby (Voyager 2, in 1986 and 1989, respectively). Collectively, Uranus and Neptune are referred to as “ice giant” planets, because they contain large amounts of materials (like water, ammonia and methane) that form ices in the cold depths of the outer solar system. This makes them fundamentally different from the gas giant planets, Jupiter and Saturn, which are almost all hydrogen and helium, and the inner, rocky planets like Earth or Mars. It’s not clear exactly how and where the ice giants formed, why their magnetic fields are strangely oriented, and what drives geologic activity on some of their moons. These mysteries make them scientifically important, and this importance is enhanced by the discovery that many planets around other stars appear to be similar to our own ice giants.

    A variety of potential mission concepts are discussed in a recently completed study, delivered to NASA in preparation for the next Decadal Survey — including orbiters, flybys and probes that would dive into Uranus’ atmosphere to study its composition. Future missions to the ice giants might explore those worlds using an approach similar to Cassini’s mission.

    For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

    See the full article here .

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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  • richardmitnick 10:51 am on August 30, 2017 Permalink | Reply
    Tags: , , , , , CSIRO Canberra Deep Space Communication Complex Australia, Jonny Weeks, , Saturn   

    From CSIRO blog: “Space whisperers: the Aussies guiding Cassini’s suicide mission to Saturn” 

    CSIRO bloc

    CSIRO blog

    30 August 2017
    Jonny Weeks

    The grand finale of NASA’s epic 20-year mission to the ringed planet will be overseen from a deep space centre near Canberra. A photo essay by Jonny Weeks.

    On 15 September 2017 at about 10pm AEST, NASA’s Cassini spacecraft will plunge deep into the hostile atmosphere of Saturn on a historic but suicidal course. It’s the grand finale of a 20-year mission which has revolutionised our understanding of the solar system and sent home more than a quarter of a million stunning images of Saturn and its moons.

    Cassini’s instruments will be running to the last, capturing every possible byte of data from its closest encounter with the ringed planet before it ultimately evaporates.

    Some 1.2bn km away, in a valley just outside Canberra, Glen Nagle and his colleagues will be listening intently to what he calls the “whispers” from deep space. “I’m going to be here for 24 hours and I won’t be sleeping,” he says enthusiastically.

    Nagle (pictured above) works at the the Canberra Deep Space Communication Complex, aka Tidbinbilla tracking station, home to four antennas which help track and command the many spacecraft in our solar system.

    CSIRO Canberra Deep Space Communication Complex, Australia

    Run by CSIRO, Australia’s national science agency, but funded by NASA, Tidbinbilla is one of just three stations in NASA’s Deep Space Network (the others are in California and Madrid) and it is here that Cassini’s final radio signals will be received and relayed to a global audience.

    “We’re going to be responsible for capturing Cassini’s last breath of data,” Nagle says. “It’ll be a bittersweet moment.

    “NASA can’t do it without us because the other stations are completely facing in the wrong direction. Saturn will be in our skies, our field of view. It’s literally the way the planets have aligned.”

    Opened in 1965, Tidbinbilla is a serene station enveloped by national parks. It’s a place where the low hum of the moving antennas and the occasional paging announcements are the only sounds that punctuate the silence.

    The dishes look surprisingly small from a distance, dwarfed by nature itself, but up close their scale is imposing. The largest is 70m in diameter and 109m across its curvature – “you could throw a football field into it,” Nagle says – and weighs about 4,000 tonnes. They are almost millimetre-perfect parabolic surfaces.

    Each dish acts as both a gigantic ear and a gigantic loudspeaker, telling the spacecrafts how to behave, ensuring their health and collecting their data. The dishes operate night and day, whether or not the skies are clear to the naked eye.

    The 70-metre antenna at CSIRO Canberra Deep Space Communication Complex

    “At the present time we, Earth, have about 30 missions in the solar system, so about 40 individual spacecraft,” Nagle says. “We communicate with them using radio waves – the invisible part of the electromagnetic spectrum.

    “Spacecraft receive and transmit data as digital ones and zeros. It’s the same way that your phone receives a radio signal before your phone’s software turns it back into a picture, it’s just those ones and zeros. We don’t know whether the stream we’re receiving is a beautiful picture or some instrument data or some engineering data or whatever it is.”

    The DSN doesn’t handle satellites in Earth’s orbit – the kind that are used for mobile communications, observation, weather prediction, GPS and so on. “They’re literally too close for us,” Nagle explains. “We just talk to the missions that have headed out across the solar system.”

    The furthest of them, Voyager 1, is so far from Earth that it seems a minor miracle its signal can be heard at all.

    NASA/Voyager 1

    For Nagle, a self-confessed space buff since childhood who is now the outreach and administration lead at Tidbinbilla, it’s a thrilling thought.

    “Right now Voyager 1 is roughly 20.7bn km away and moving further away by about 1.4million km every day,” he says. “That’s about four and a quarter times further away than Pluto. So it’s way out there. It takes over 30 hours to get a signal there and back.

    “To give you some idea of what that signal is like now: Voyager transmits at around 19 watts, about half the power it’s taking to run the lightbulb in your fridge. So imagine already trying to see half your fridge light from four and quarter times as far away as Pluto – you’re not going to see it.

    “And it gets even smaller because as that signal travels across that 20bn km of space it spreads out, it becomes thinner and more diffuse.

    “In fact,” he adds excitedly, “the signal we get is equivalent to only about one twenty billionth – billionth with a b! – of the amount of power that’s generated by a typical watch battery. But you’re still getting the information, the ones and zeros, and even though it’s very weak all of the information is still there.”

    Up on the dish

    Michael Murray (right) fixing the gears on DSS35.

    Up high on dish number DSS35, there’s a minor problem which needs to be fixed. The ball gears are not meeting correctly and the dish’s ability to slowly pivot – as it must do to track the craft while the Earth rotates – is being compromised.

    “Currently we’re inserting a bit of solder to measure the backlash in the gear,” says antenna technician Michael Murray. “We measure the crush on the solder and that’ll give us an idea of what the backlash is.”

    As with everything in space exploration, precision counts. And yet, oddly, just a few metres away there’s a kink in the safety rail where a section has been cut away and awkwardly repositioned.

    John Howell, the survey electronics technician, laughs. “When they built this antenna they realised the rail was in the way and they had to cut this out [for the dish to be able to fully rotate]. We do months and months of testing when things are first built, we move everything very slowly, and when they got to this bit they realised, ‘Oh no, it’s not going to work.’ We blame the engineers.”

    John Howell, survey electronics technician, pointing out the mistake in a handrail. It had to be repositioned when the engineers realised the dish could not rotate fully.

    Howell has been employed at Tidbinbilla by CSIRO for the past 15 years – the same duration as Nagle – but, unlike his colleague, his knowledge of the science is more cursory.

    “People ask me what are they tracking today and I say, ‘I’ve got no idea.’ As long as my things point to where they’ve got to point … I mean, when we’ve got a major ‘level one support’ happening like the Mars rovers landing or Cassini then it’s quite interesting, but apart from that some of the scientific stuff is way above my head.”

    He adds: “But I am interested in the Voyager probes. It takes forever to get a signal to them and back at the speed of sound” – “light,” Nagle interrupts apologetically – “Oh sorry, the speed of light!” Howell continues.

    “They left when I was still in primary school. I find it hard to believe we can talk to something that far away. It blows my mind.”

    A view to the north of the station from DSS35.

    Coiled springs

    In the recently built control centre – a place Matthew Purdie, senior link controller, describes as “the heart of the station” – activity is decidedly slow. You might imagine a hive of scientists huddled around monitors awaiting fresh data but in fact there’s only one CSIRO scientist based at Tidbinbilla and his research role is detached from the day-to-day communications performed on behalf of NASA and the other space superpowers. NASA’s scientists are located at the Jet Propulsion Laboratory in the US.

    Purdie and his team of controllers are patiently monitoring banks of screens, waiting for the rare occasion when a command fails or for the more alarming news that a craft has become inoperable or gone missing. Occasionally they have to call the JPL to tell them their craft are sick.

    Matthew Purdie, senior link controller, in the control centre.

    “We refer to ourselves as coiled springs,” Purdie says. “We’re sort of employed to handle things when they go wrong. Most of the time we’re looking for green on our screens. If everything’s green we’re good; if it goes orange or red we’re in trouble.”

    Behind him, a box of on one of his screens turns orange. “Oh, that’s nothing to worry about,” he says assuredly. “That’s a ‘carrier out of lock’. It’s spacecraft 74. We lost the signal but it was an expected loss of signal because the craft occultated – it went behind Mars.

    “Right now I’m on antenna DSS34, so I’m tracking three spacecraft: MRO [Mars Reconnaissance Orbiter], Maven and Mars Odyssey. I’d have to get out the book to tell you exactly what each spacecraft is doing. We know the technical side of our spacecraft, what bit rates they use, command frequencies and all that stuff, but quite often we forget why they’re there.”

    Purdie knows plenty about Cassini, however, and has been on duty for some of its recent dives – the series of 22 daring orbits between Saturn and its rings which have given the craft a unique perspective on the planet and the surrounding bands of dust, rock and ice.

    Disappointingly, Purdie already knows his shift patterns will cause him to miss the finale next month. He’s tempted to come to work anyway.

    “I like being part of history and science,” he says. “I like the fact that I’ve been here for landings and launchings and things like that. Years ago they used to go around to each of the stations and ask for a ‘Go? No go?’, so you’d have to say, ‘DSS45 is a go!’ That was so cool, I loved doing that. They don’t do that any more.”

    A close-up view of the largest dish on site showing the parabolic surface. The tall cone-like structure in the middle is the transmitter-receiver system. The cone is the height of a five-storey building.

    One giant leap

    Australia’s involvement in space exploration is six decades old and even though Nagle thinks “Australia doesn’t see itself as a space-faring nation” it has played a critical role in some of the most inspiring moments in the history of humankind.

    “The dish out the front is the one from Honeysuckle Creek that received and relayed to the whole world the first pictures of Neil Armstrong walking on the moon in 1969,” Nagle explains. He must have regaled people with the full story a thousand times or more, yet he makes it sound anything but tiresome.

    “NASA’s original intention was to use their dish in California to transmit the pictures to the world and show America winning the space race,” he says. “When Neil came out of the spacecraft the first thing he needed to do was switch on a camera which was mounted upside down so that he could later pick it up with his big, gloved hand. NASA were going to flip the picture but the video technician called in sick that day and his backup forgot.

    “Eventually they flipped it but it was highly contrasted because the signal was going to ground somewhere. Mission control couldn’t show that to the world and Neil wasn’t going to wait.”

    At the critical moment, Honeysuckle Creek had a perfect image. “When NASA saw that,” Nagle continues, “they flipped the switch to Australia and 600 million people around the world watched Neil come down the ladder, put his left foot on the surface of the moon and say, ‘One small step for man, one giant leap for mankind.’

    “I was an eight-year-old kid sitting in front of the television, glued to the screen, watching humans walk on the moon in glorious black and white. I had no idea that 40 years later I’d be working at the place where I can look out of my window at the dish that brought me those pictures.”

    Greg Boyd, senior network administrator, at his desk at Canberra Deep Space Communication Complex.

    That enduring sense of wonder is shared by Greg Boyd, the senior network administrator at Tidbinbilla.

    “I love the science,” he says. “When I first started I was into everything. We used to have these things called twixes, well before we had emails. They were advisories about what was happening and I’d be reading all this groovy stuff that’s going on.

    “As time goes on you become blase. Not jaded; blase. But I’m doing my dream job and I’ve been doing it for the last 25 years. Where else can a boy from Australia work for NASA and really be critically involved in their missions? This is it.”

    The night’s sky over Tidbinbilla showing the Milky Way.

    As night falls over Tidbinbilla, low-lying clouds initially block the views overhead. A group of kangaroos gathers by the perimeter fence, intrigued by the faint, eerie noises emanating from the site.

    By 3am the clouds have finally dissipated and the vast, star-spangled sky is simply breathtaking. Somewhere out there, Cassini is looping the loop between Saturn and its rings.

    In its lifetime Cassini and its accompanying probe, Huygens, have revealed many of the secrets of the Saturnian system: how the particles that make up Saturn’s rings range in size from smaller than a grain of sand to as large as mountains; how Titan, one of the moons, has prebiotic chemistry as well as rain, rivers, lakes and seas; how icy plumes of water are spraying upwards from “tiger stripe” fractures on Enceladus, an otherwise frozen moon.

    It has also witnessed giant hurricanes at both of Saturn’s poles and captured the first complete view of the north polar hexagon – not bad for a one megapixel camera. The finale should reveal yet more about the interior of the planet as the craft measures its gravity and magnetic field.

    The decision to hurl Cassini into Saturn’s deadly, gaseous atmosphere next month has been made through necessity and responsibility. The craft has run out of fuel and contains a nuclear battery; NASA’s scientists fear it might contaminate one of the surrounding moons should it crash into them.

    “We have to dispose of the spacecraft safely,” says deputy project scientist Scott Edgington, who’s based in California, “because Titan and Enceladus have been shown to be places where there are conditions for habitability, conditions that we think are appropriate for life.

    “So our navigators came up with this series of grand finale orbits, flying through the gap between the planet and the rings, and eventually ending in Saturn’s atmosphere. When the scientists saw that plan they were like, ‘Wow, this is unexplored territory, we’re going to learn so many new things.’ So starting April this year we entered into the grand finale orbits. It’s hard to believe we’re almost done.”

    Of the final descent, he says: “Think of it as we’re sniffing the atmosphere. It will set the ground truth for past measurements and even future measurements. That’s something I’m really looking forward to.”

    A ‘stacked’ star-trail photograph. Created from 162 individual exposures and made over 81 minutes, it shows the progression of the stars around the south celestial pole.

    Life and death

    At Tidbinbilla the following morning, the anticipation in the visitors centre is just as palpable. “It’s this generation’s Voyager,” says Jonathan Kent, a self-proclaimed “hack astronomer”. “I think it’s capturing people’s minds and hearts and reinvigorating our interest in space.”

    Ten-year-old Scout Miller is proof. She’s at the centre with her family, and talk of the discoveries made by Cassini and Juno – NASA’s mission to Jupiter which delivered a tranche of close-up images of the planet’s red spot – has made her wonder what else might be out there.

    “There must be alien life,” she says. “We can’t be the only people. It can’t just be a coincidence that we just appeared and no one else has, and that this is the only planet with the right things for life.”

    Many of CSIRO’s staff at Tidbinbilla share her optimism and, even though Nagle forewarns that life may never be found due to the sheer scale and age of the universe, he says: “It would be a fantastic thing to find because it would answer the most fundamental questions we have: Is it just us? Are we alone? Is the universe full of life? Are we the first life? Are we the last?”

    Future missions to Saturn and its moons may yet reveal some answers, but for Cassini the deadly denouement is imminent.

    “Cassini’s going to end its life as a shooting star in the atmosphere of a giant ringed world,” says Nagle. “There’s no more poetic way for a spacecraft to finish what has been a magnificent mission.”

    The rear of DSS43 as the sun rises at the start of a new day of tracking.

    See the full article here .

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  • richardmitnick 9:19 am on July 27, 2017 Permalink | Reply
    Tags: , Has Cassini found a universal driver for prebiotic chemistry at Titan?, Saturn   

    From ESA: “Has Cassini found a universal driver for prebiotic chemistry at Titan?” 

    ESA Space For Europe Banner

    European Space Agency

    26 July 2017

    Ravi Desai
    Mullard Space Science Laboratory, University College London
    Email: r.t.desai@ucl.ac.uk

    Andrew Coates
    Mullard Space Science Laboratory, University College London
    Email: a.coates@ucl.ac.uk

    Nicolas Altobelli
    ESA Cassini–Huygens Project Scientist

    Tel: +34 91 813 1201

    Email: nicolas.altobelli@esa.int

    Markus Bauer

    ESA Science Communication Officer

    Tel: +31 71 565 6799

    Mob: +31 61 594 3 954

    Email: markus.bauer@esa.int

    Chemistry in Titan’s atmosphere.

    The international Cassini-Huygens mission has made a surprising detection of a molecule that is instrumental in the production of complex organics within the hazy atmosphere of Saturn’s moon Titan.

    NASA/ESA/ASI Cassini-Huygens Spacecraft

    Titan boasts a thick nitrogen and methane atmosphere with some of the most complex chemistry seen in the Solar System. It is even thought to mimic the atmosphere of early Earth, before the build-up of oxygen. As such, Titan can be seen as a planet-scale laboratory that can be studied to understand the chemical reactions that may have led to life on Earth, and that could be occurring on planets around other stars.

    In Titan’s upper atmosphere, nitrogen and methane are exposed to energy from sunlight and energetic particles in Saturn’s magnetosphere. These energy sources drive reactions involving nitrogen, hydrogen and carbon, which lead to more complicated prebiotic compounds.

    These large molecules drift down towards the lower atmosphere, forming a thick haze of organic aerosols, and are thought to eventually reach the surface. But the process by which simple molecules in the upper atmosphere are transformed into the complex organic haze at lower altitudes is complicated and difficult to determine.

    One surprising outcome of the Cassini mission was the discovery of a particular type of negatively charged molecule at Titan. Negatively charged species – or ‘anions’ – were not something scientists expected to find, because they are highly reactive and should not last long in Titan’s atmosphere before combining with other materials. Their detection is completely reshaping current understanding of the hazy moon’s atmosphere.

    In a new study published in The Astrophysical Journal Letters, scientists identified some of the negatively charged species as what are known as ‘carbon chain anions’. These linear molecules are understood to be building blocks towards more complex molecules, and may have acted as the basis for the earliest forms of life on Earth.

    The detections were made using Cassini’s plasma spectrometer, called CAPS, as Cassini flew through Titan’s upper atmosphere, 950–1300 km above the surface. Interestingly, the data showed that the carbon chains became depleted closer to the moon, while precursors to larger aerosol molecules underwent rapid growth, suggesting a close relationship between the two, with the chains ‘seeding’ the larger molecules.

    “We have made the first unambiguous identification of carbon chain anions in a planet-like atmosphere, which we believe are a vital stepping-stone in the production line of growing bigger, and more complex organic molecules, such as the moon’s large haze particles,” says Ravi Desai of University College London and lead author of the study.

    “This is a known process in the interstellar medium, but now we’ve seen it in a completely different environment, meaning it could represent a universal process for producing complex organic molecules.

    “The question is, could it also be happening within other nitrogen-methane atmospheres like at Pluto or Triton, or at exoplanets with similar properties?”

    “The prospect of a universal pathway towards the ingredients for life has implications for what we should look for in the search for life in the Universe,” says co-author Andrew Coates, also from UCL, and co-investigator of CAPS.

    “Titan presents a local example of exciting and exotic chemistry, from which we have much to learn.”

    Cassini’s 13-year odyssey in the Saturnian system will soon draw to a close, but future missions, such as the international James Webb Space Telescope and ESA’s Plato exoplanet mission are being equipped to look for this process not only in our own Solar System but elsewhere.

    NASA/ESA/CSA Webb Telescope annotated


    Advanced ground-based facilities such as ALMA could also enable follow-up observations of this process at work in Titan’s atmosphere, from Earth.

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    “These inspiring results from Cassini show the importance of tracing the journey from small to large chemical species in order to understand how complex organic molecules are produced in an early Earth-like atmosphere,” adds Nicolas Altobelli, ESA’s Cassini–Huygens project scientist.

    “While we haven’t detected life itself, finding complex organics not just at Titan, but also in comets and throughout the interstellar medium, we are certainly coming close to finding its precursors.”

    See the full article here .

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  • richardmitnick 1:10 pm on July 18, 2017 Permalink | Reply
    Tags: >ESA Estrack network, , , , , NASA DSN Network, , Saturn   

    From ESA: “Ground stations go dancing with Cassini’ 

    ESA Space For Europe Banner

    European Space Agency

    A complex coordinated ‘dance’ between ESA and NASA tracking stations is following Cassini during its Grand Finale.

    15 July 2017


    NASA/ESA/ASI Cassini-Huygens Spacecraft

    In Cassini’s Grand Finale orbits – the final chapter of its nearly 20-year mission – the spacecraft travels in an elliptical path that sends it diving at tens of thousands of kilometers per hour through the 2400-km space between the rings and the planet where no spacecraft has ventured before.

    Ring Crossing: In this still from the short film Cassini’s Grand Finale, the spacecraft is shown diving between Saturn and the planet’s innermost ring. Credit: NASA/JPL-Caltech.

    May, June and July have been busy months for Cassini, as a series of complex ground-station tracking passes involving ESA’s Deep Space Antennas (DSA) and NASA’s Deep Space Network (DSN) captured a series of Grand Finale radio science passes.

    In Cassini’s Grand Finale orbits – the final chapter of its nearly 20-year mission – the spacecraft travels in an elliptical path that sends it diving at tens of thousands of kilometers per hour through the 2400-km space between the rings and the planet where no spacecraft has ventured before.

    May, June and July have been busy months for Cassini, as a series of complex ground-station tracking passes involving ESA’s Deep Space Antennas (DSA) and NASA’s Deep Space Network (DSN) captured a series of Grand Finale radio science passes.

    The Cassini mission has performed radio science observations many times during its time at Saturn. Previously, the mission relied solely on the antennas of NASA’s Deep Space Network for these observations.

    Now, the addition of new ESA tracking capabilities is helping provide the continuous signal reception needed during Cassini radio science activities. But it means the two agencies’ networks must work closely together.

    Hearing the distant shout

    ESA deep space ground stations began working with Cassini last year, conducting a series of test ‘passes’ – a ‘pass’ occurs when a spacecraft arcs into line-of-sight visibility above a station and continues until it disappears below the station’s horizon as Earth rotates – using their large, 35-meter-diameter, 630-tonne antennas pointed with exquisite accuracy at Cassini in the sky, listening for the craft’s call from Saturn.

    Estrack New Norcia

    In an initial test on 10 August 2016, ESA’s tracking station at New Norcia, Western Australia, received signals transmitted by Cassini across 1.4 billion km of space – the most distant ‘catch’ ever for an ESA station.

    Now, during the 22 ‘inside-the-rings’ orbits of the Grand Finale, ESA stations are putting into practice the experience learned last year and are receiving Cassini’s signals, focussing on radio science gravity and ring occultation measurements, and delivering the data received to scientists in the U.S. and Europe for scientific analysis.

    Tugged by gravity & passing through particles

    The gravity experiments aim at measuring Saturn’s gravitational field with an unprecedented level of detail in order to gain insights into the planet’s interior structure, and at constraining the scenario of formation of Saturn’s rings by determining the rings’ mass.

    Variations in Cassini’s orbit – even minute ones – from its expected trajectory can be detected by analysing the Doppler shift in the craft’s transmitted signal[1], enabling the tugs due to gravity to be studied and measured.

    The radio science occultations aim at analysing the fine-scale structure of the rings and the physical properties of its particles.

    Radio science occultations occur when the signals that Cassini transmits to the ground stations pass through the rings – affecting the signals in certain ways that can be studied and analysed.

    Dipping and diving

    The 22 Grand Finale orbits are bringing Cassini between Saturn and its rings; the spacecraft’s closest approach to Saturn, reached during each passage through the ring plane, ranges between approximately 1655 km and 3910 km with respect to Saturn’s ‘1 bar level.’ (This the place in the atmosphere where air pressure is the same as at sea-level on Earth. It’s also approximately the height of Saturn’s tallest clouds.)

    For six of these closest approach passages (the last one to occur on 19 July), the spacecraft had its High Gain Antenna pointed toward Earth to perform radio occultation measurements of the rings and the radio science gravity experiments.

    These radio tracking passes run for very long periods – lasting up to 37 hours, meaning that no single ESA or NASA station has visibility of Saturn for the entire pass.

    Uninterrupted receipt of signals

    For Cassini radio science, receipt of the craft’s signal must be uninterrupted in order to obtain measurements of Saturn’s gravitational effects on the spacecraft without gaps.

    To achieve the extra-long passes that Cassini needs, and since we can’t simply slow down Earth’s rotation, a series of very technically challenging, real-time handovers of Cassini’s received signal was planned between multiple ESA and NASA ground stations.

    This effort involves antennas located in Argentina (ESA), California (NASA), Spain and Australia (ESA and NASA).

    “We are now getting into a new mode of radio science, giving much more accurate measurements of gravitational effects compared to previous observations where the effects of ring density on radio signal propagation were the main topic of study,” Daniel Firre, ESA Service Manager for NASA cross support.


    Visibility: why the ESA-NASA station activity is so complex

    As mentioned above, a pass starts when a spacecraft rises into line-of-sight view above one local horizon, seen from the station’s location, and continues until it drops out of sight below another horizon, the movement being due to the station rotating with the planet (good example with pictures here from when an ESA station tracked NASA’s Juno Earth flyby in 2013).

    Tracking Juno: Here it comes and there it goes

    A pair of photos of ESA’s Malargue station that perfectly illustrate how the Agency’s tracking efforts progressed last night.

    At left, the huge 35m dish antenna is pointing more or less straight up as Juno approached Earth high above Argentina. Of course, Earth rotates, so the antenna had to be continuously tracked down and rotated.

    At right, finally, as Juno dipped out of line-of-sight below the horizon, the station lost contact with the spacecraft with the antenna pointed low toward the East.

    The craft continued en route to make closest approach above S. Africa a few minutes after the right-hand image was taken.

    ESA Malargüe station pointing almost vertically up as NASA’s Juno spacecraft approaches from deep space over Argentina on 9 October 2013. Credit: ESA

    ESA Malargüe station as Juno zooms out of view Credit: ESA

    Since the Earth is rotating, a routine tracking pass link from any single ground station to a planetary mission typically can last only a few hours – but Cassini radio science needs much longer.

    In comparison, for Earth missions (which typically orbit Earth 14 times per day), passes last just a few minutes!


    Complex ‘station dance’

    The handover plan between antennas to receive the spacecraft’s signal has been organised to provide the necessary continuous coverage, and has necessitated very close technical and organisational cooperation between the two networks across multiple continents.

    Incredibly, there can be up to seven stations involved in a single pass.

    The graphic below illustrates how each ground station tracks Cassini’s signal during these passes. Each station is represented by a different colour. Cassini’s signal is tracked as Saturn (and hence Cassini) rises and sets in the sky above each station.

    Typical multi-station, ESA-NASA tracking pass for Cassini Credit: NASA/JPL-Caltech
    C – NASA Canberra DSN
    NN – ESA New Norcia DSA
    M – NASA Madrid DSN
    ML – ESA Malargüe DSA
    G – NASA Goldstone DSN

    Note that the optimum angle for the ground station antennas is between 25 and 30 degrees above the horizon; below this “cut-off angle,” there are too many things that could disturb the communication link with the spacecraft.

    As a result, ESA’s stations in the southern hemisphere are in the best position to receive the Cassini’s signal due to Saturn’s location in the sky right now. This can be clearly seen in the diagram, where M(adrid) and G(oldstone) have visibilities of around 30 degrees, while Malargüe and New Norcia are at nearly 80 degrees.

    Cassini is a sophisticated spacecraft; it can receive signals in X-band and transmit in S-band, X-band and Ka-band (details on these frequencies here).

    For the radio science passes, Cassini is transmitting and the stations on Earth are receiving; every time one receiving station rotates out of view, the succeeding station picks up, and there is a five-second overlap to avoid losing contact (note that the coloured coverage arcs in the graphic above overlap).

    Not all the stations can receive all three of Cassini’s frequencies; nonetheless, the station-to-station handovers are so well coordinated that it is always possible to receive at least two of them.

    Feeling the pull of a gas giant

    Saturn’s gravity field and the mass of the rings are detected by means of what are called “range rate” measurements – basically, measuring the rate at which the distance from the ground station to the spacecraft varies. These measurements are enabled by Cassini’s on-board X-band radio system, along with the five DSN and two ESA stations working in tight coordination.

    Gravity field measurements are obtained by comparing the detected speed of the spacecraft (technically, its radial velocity, with accuracies of about 0.05 mm/s) to a model of the spacecraft’s orbit that takes in consideration the effects of the Doppler shift.

    Cassini radio science observations will provide crucial clues on how and when Saturn and its rings formed, as well as their relation to its moons: a large ring mass would allow the rings to be as old as the Saturnian system, formed 4.5 billion years ago, while a smaller ring mass suggests that the rings must be much younger, possibly formed by the breakup of a large comet or small moon.

    Ring occultations

    As described above, occultation observations happen when the rings partially block Cassini’s radio signals enroute to Earth.

    During the Grand Finale, these observations are taking advantage of the spacecraft’s ultra-close perspective on the rings, which allows the radio signal to systematically sweep across the ring system from quite close.

    The campaign tracked occultations during the six radio science gravity orbits (the so-called “RSS orbits” when Cassini’s radio science subsystem was active) and two “Ring Segment” orbits (orbits 276 and 282 – see the Grand Finale orbit guide for details).

    The Grand Finale orbits take Cassini between the planet and its rings. Credit: NASA JPL-Caltech

    The radio occultations are short in duration (less than 26 minutes), starting almost immediately after Cassini dives through the ring plane, and they cover the entire main ring system. The technique can measure up to three frequencies, profiling the ring structure and constraining the structures’ physical properties.

    Credit: NASA/JPL-Caltech.

    The collective ring coverage of the RSS Grand Finale occultations is unprecedented in the Cassini mission. Never before has such a close occultation observation technique been attempted.

    “By marshalling the two agencies’ stations together, the overall science return from Cassini is being significantly enhanced, as their sensitive radio ‘ears’ can listen for signals from the craft as it is tugged by gravity or as the signals pass through the rings, providing additional, important information to help us understand this incredible system,” says Nicolas Altobelli, ESA’s Cassini-Huygens project scientist.

    These powerful scientific insights are being made possible through intense coordination and cooperation between the ground stations of ESA and its NASA partners – truly a technical and expertise tour de force within a Grand Finale.

    Recent news

    Most distant catch for an ESA station

    Catching Cassini’s call

    Countdown to Cassini’s Grand Finale

    More information

    NASA DSN Network

    ESA Estrack network

    See the full article here .

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  • richardmitnick 8:10 am on April 26, 2017 Permalink | Reply
    Tags: , , , , , Saturn   

    From ESA: “Countdown to Cassini’s Grand Finale” 

    ESA Space For Europe Banner

    European Space Agency

    25 April 2017
    Nicolas Altobelli
    ESA Cassini–Huygens Project Scientist

    Tel: +34 91 813 1201

    Email: nicolas.altobelli@esa.int

    Markus Bauer

    ESA Science Communication Officer

    Tel: +31 71 565 6799

    Mob: +31 61 594 3 954

    Email: markus.bauer@esa.int

    NASA/ESA/ASI Cassini Spacecraft

    ESA/Huygens Probe from Cassini landed on Titan

    Cassini grand finale. No image credit

    After nearly 13 years in orbit around Saturn, the international Cassini–Huygens mission is about to begin its final chapter: the spacecraft will perform a series of daring dives between the planet and its rings, leading to a dramatic final plunge into Saturn’s atmosphere on 15 September.

    On 22 April, Cassini successfully executed its 127th and final close flyby of Saturn’s largest moon, Titan.

    The manoeuvre put the spacecraft onto its ’grand finale’ trajectory: a series of 22 orbits, each lasting about a week, drawing closer to Saturn and passing between the planet’s innermost rings and its outer atmosphere. The first crossing of the ring plane will occur on 26 April.

    With the repeated dives in this yet unvisited region, the mission will conclude its journey of exploration by collecting unprecedented data to address fundamental questions about the origin of Saturn and its ring system.

    Launched in 1997, the Cassini-Huygens spacecraft embarked on a seven-year voyage across the Solar System, eventually reaching Saturn in July 2004. Several months later, the Cassini orbiter released ESA’s Huygens probe, which landed on Titan on 14 January 2005 – the first landing in the outer Solar System.

    The mission has greatly contributed to our understanding of the Saturnian environment, including the giant planet’s system of rings and moons.

    Combining the data collected in situ by Huygens and the observations performed by Cassini during flybys of Titan, the mission revealed the atmospheric processes of this moon and their seasonal evolution, as well as the surface morphology and interior structure, which may include a liquid water ocean.

    Enshrouded by a thick nitrogen-dominated atmosphere and partly covered by lakes and rivers, Titan has a weather and hydrological cycle that bears some interesting similarities to Earth. However, there are important differences: the key component there is not water, like on our planet, but methane, and the temperature is very low, around –180°C at the surface.

    Over its 13-year mission, Cassini will have covered about half of Saturn’s orbit, in which the planet takes 29 years to circle the Sun. This means that the spacecraft has monitored two seasons on Titan, an object that can teach us much on the past and the future of Earth.

    Enceladus plumes
    Released 03/04/2014
    Copyright NASA/JPL/Space Science Institute
    Dramatic plumes, both large and small, spray water ice out from many locations along the ‘tiger stripes’ near the south pole of Saturn’s moon Enceladus. The tiger stripes are fissures that spray icy particles, water vapour and organic compounds. More than 30 individual jets of different sizes can be seen in this image, which is a mosaic created from two high-resolution images captured when Cassini flew past Enceladus and through the jets on 21 November 2009. This view was obtained at a distance of about 14 000 km from Enceladus.

    Another of Cassini’s breakthroughs was the detection of a towering plume of water vapour and organic material spraying into space from warm fractures near the south pole of Saturn’s icy moon, Enceladus. These salt-rich jets indicate that an underground sea of liquid water is lurking only a few kilometres below the moon’s icy surface, as confirmed by gravity and rotation measurements.

    A recent analysis of data collected during flybys of Enceladus with the Cassini Ion Neutral Mass Spectrometer also revealed hydrogen gas in the plume, suggesting that rock might be reacting with warm water on the seafloor of the moon’s subsurface ocean. This hydrothermal activity could provide a chemical energy source for life, enabling non-photosynthetic biological processes similar to the ones found near the hydrothermal vents on the Earth’s ocean floor and pointing to the potential habitability of Enceladus’ underground ocean.

    Following over a decade of ground-breaking discoveries, Cassini is now approaching its end. With little fuel left to correct the spacecraft trajectory, it has been decided to end the mission by plunging it into Saturn’s atmosphere on 15 September 2017. In the process, Cassini will burn up, satisfying planetary protection requirements to avoid possible contamination of any moons of Saturn that could have conditions suitable for life.

    Grand finale orbits
    Released 25/04/2017
    Copyright NASA/JPL-Caltech/Erick Sturm
    Illustration of the trajectory of the Cassini mission between November 2016 and September 2017.
    Following a series of ring-grazing orbits that started in November 2016 (grey), the mission executed its 127th and final close flyby of Saturn’s largest moon, Titan, on 22 April 2017. The orbit of Titan is shown in yellow. This manoeuvre put the spacecraft onto its ‘grand finale’ trajectory: a series of 22 orbits, each lasting about a week, drawing closer to Saturn and passing between the planet’s innermost rings and its outer atmosphere (blue). Eventually, Cassini will plunge and burn up into Saturn’s atmosphere on 15 September 2017 (orange), satisfying planetary protection requirements to avoid possible contamination of any moons of Saturn that could have conditions suitable for life.

    The grand finale is not only a spectacular way to complete this extraordinary mission, but will also return a bounty of unique scientific data that was not possible to collect during the previous phases of the mission. Cassini has never ventured into the area between Saturn and its rings before, so the new set of orbits is almost like a whole new mission.

    These close orbits will be inclined 63 degrees with respect to Saturn’s equator and will provide the highest resolution observations ever achieved of the inner rings and the planet’s clouds. The orbits will also give the chance to examine in situ the material in the rings and plasma environment of Saturn.

    With its radio science investigation, Cassini will measure Saturn’s gravitational field as close as 3000 km from Saturn’s upper cloud layers, greatly improving the current models of the planet’s internal structure and winds in its atmosphere. Scientists expect the new data will also allow them to disentangle the gravity of the planet from the tiny pull exerted on the spacecraft by the rings, estimating the total mass of the rings to unprecedented accuracy. ESA ground stations in Argentina and Australia will help receive Cassini’s radio science data, providing a series of 22 tracking passes during the grand finale.

    ESA Norcia tracking station
    Published on Aug 2, 2012
    Clip recorded in April 2012 showing ESA’s 35m deep-space tracking station at New Norcia, Australia, swinging into action to conduct a communication pass. DSA-1 is designed for deep-space satellite missions and provides daily support to Mars Express, Rosetta and Venus Express for routine operations. The mechanical movable structure weighs 580 tonnes. Engineers can point it with a speed of 0.4 degrees per second in both axes (horizontal and vertical). Its Servo Control System provides the highest possible pointing accuracy under the site’s environmental, wind and temperature conditions. More details via http://bit.ly/96u55A

    The New Norcia station, DSA 1 (Deep Space Antenna 1), hosts a 35-metre deep-space antenna with transmission and reception in both S- and X-band and is located 140 kilometres north of Perth, Western Australia, close to the town of New Norcia. DSA-1 is designed for communicating with deep-space missions and provides support to spacecraft such as Mars Express, Rosetta and Gaia for routine operations.

    Malargue, Mendoza, Argentina – Europe opens state of the art satellite tracking station.ESA’s Malargüe Station

    The grand finale orbits will also probe the planet’s magnetic field at similarly close distances. Previous observations have shown that the magnetic field is weaker than expected, with the magnetic axis surprisingly well aligned with the planet’s rotation. New data to be collected by the Cassini magnetometer will provide insights to understand why this is so and where the sources of magnetic field are located, or whether something in Saturn’s atmosphere has been obscuring the true magnetic field from Cassini until now.

    Cassini between Saturn and the rings. No image credit.

    While crossing the ring plane, Cassini’s Cosmic Dust Analyzer will directly sample the composition of dust particles from different parts of the ring system, whereas the Ion Neutral Mass Spectrometer will sniff the upper atmosphere layers of Saturn to analyse molecules escaping from the atmosphere as well as water-based molecules that originate from the rings.

    “At last, we have now reached the final and most audacious phase of this pioneering mission, pushing the spacecraft once again into unexplored territory,” says Nicolas Altobelli, ESA Cassini project scientist.

    “We are looking forward to the flow of exciting new data that Cassini will send back in the coming months.”

    Cassini–Huygens is a cooperative project of NASA, ESA and ASI, the Italian space agency.

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 3:17 pm on April 19, 2017 Permalink | Reply
    Tags: , , , , , Nine Ways Cassini-Huygens Matters, Saturn   

    From JPL-Caltech: “Nine Ways Cassini-Huygens Matters” 

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    No writer credit

    NASA’s Cassini spacecraft and ESA’s Huygens probe expanded our understanding of the kinds of worlds where life might exist.

    NASA/ESA/ASI Cassini Spacecraft

    With discoveries at Saturn’s moons Enceladus and Titan, Cassini and Huygens made exploring “ocean worlds” a major focus of planetary science. Insights from the mission also help us look for potentially habitable planets — and moons — beyond our solar system.

    Life as we know it is thought to be possible in stable environments that offer liquid water, essential chemical elements, and a source of energy (from sunlight or chemical reactions). Before Cassini launched in 1997, it wasn’t clear that any place in the icy outer solar system (that is, beyond Mars) might have this mix of ingredients. By the next year, NASA’s Galileo mission revealed that Jupiter’s moon Europa likely has a global ocean that could be habitable. Since its 2004 arrival at Saturn, Cassini has shown that Europa isn’t an oddball: Potentially habitable ocean worlds exist even in the Saturn system — 10 times farther from the sun than Earth.

    When the Cassini mission started, scientists presumed Enceladus was too small to generate and hold onto the heat required to maintain subsurface reservoirs of liquid water. Cassini’s discovery of intense geologic activity near the moon’s unexpectedly warm south pole — complete with towering jets of icy spray — sent shockwaves through the space science community. After over a decade of investigation, the mission eventually determined that Enceladus hosts a global liquid water ocean, with salts and simple organic molecules, and likely even hydrothermal vents on its seafloor. Thanks to Cassini, Enceladus is now one of the most promising places in our solar system to search for present-day life beyond Earth.

    Saturn’s largest moon, Titan, offered tantalizing hints that it, too, could help us understand whether life could have evolved elsewhere. Cassini and ESA’s Huygens probe (which landed on Titan’s surface) found clear evidence for a global ocean of water beneath Titan’s thick, icy crust and an atmosphere teeming with prebiotic chemicals. Based on modeling studies, some researchers think Titan, too, may have hydrothermal chemistry in its ocean that could provide energy for life. On its frigid surface, which hosts vast seas of liquid hydrocarbons, scientists wonder, could Titan be home to exotic forms of life “as we don’t know it”?

    At Saturn’s largest moon, Titan, Cassini and Huygens showed us one of the most Earth-like worlds we’ve ever encountered, with weather, climate and geology that provide new ways to understand our home planet.

    Titan is 10 times farther from the sun than Earth and much colder, but Cassini showed it to be the only other place in our solar system with stable liquid on its surface and a kind of “hydrological” cycle involving methane rather than water.

    Flowing liquid hydrocarbons at Titan make for eerily Earthlike landscapes — they carve branching channels and steep canyons into rock-hard ice; they settle into lakes and seas with gently sloping shorelines and sheltered bays; they tumble water-ice “rocks” into rounded pebble shapes like those in earthly rivers.

    Titan’s landscape also shares other similarities with Earth. Large, arid swaths of dunes gird the moon’s equatorial regions. Composed of organic materials that settle out of Titan’s thick, hazy atmosphere, these dunelands are sculpted by winds in ways similar to dunes in places like Namibia and the Sahara. Scientists have also spotted volcano-like mounds that, if indeed volcanic in nature, would erupt slushy lavas made of water rather than molten rock.

    From its perch in space, Cassini has been watching Titan’s climate cycle play out over the years, with seasonal changes bringing bright, feathery methane rain clouds that dump precipitation on the landscape. Huygens saw clear evidence of a landscape that experiences intermittent but heavy floods, not unlike places in the American desert southwest.

    Titan’s smoggy atmosphere resembles an extreme version of the skies above Los Angeles on a day with poor air quality. And, more importantly, Titan’s atmosphere is thought to be similar to early Earth’s before life developed here. Titan provides perhaps the best stage in the solar system to watch the organic chemistry that led to the origin of life on Earth billions of years ago. Titan can also be considered a possible analog for the future Earth. Its methane cycle gives us a hint of what Earth’s water cycle might look like in the far future as the increasingly brighter-burning sun changes the stability of water in our oceans and atmosphere. The seas at Titan’s poles might be remnants of larger bodies of liquid that once covered much more of the moon’s surface.​

    Cassini is, in a sense, a time machine. It has given us a portal to see the physical processes that likely shaped the development of our solar system, as well as planetary systems around other stars.

    Cassini has provided a brief glimpse into deep time in the Saturn system. The rings, for example, are a natural laboratory for processes that form planets — a mini solar system, if you will. They show us how objects clump together and break apart. And in the ripples we can read the history of impacts into the rings. We also see “propeller” features that obey the same physical processes that form planets.

    Moons in the Saturn system are also time capsules preserving histories of bombardment and other forces at play over time. At Titan, in particular, we have access to the kinds of complex carbon chemistry that might have taken place on Earth in its “prebiotic” days. During the Cassini mission’s finale, data about the planet’s interior and the mass of the rings will provide a powerful insights about their formation and evolution.

    The length of Cassini’s mission has enabled us to observe weather and seasonal changes, improving our understanding of similar processes at Earth, and potentially those at planets around other stars.

    While other missions flew past Saturn or trained telescopes periodically from afar, Cassini has had a front-row seat for approximately 13 years — nearly half a Saturn year (northern winter to the start of northern summer) — to epic changes unfolding before its very eyes.

    This long-lived robotic observing platform, bristling with science instruments, provided an unparalleled glimpse into what happens as weather and climate conditions on the planet and Titan respond to the seasons — sometimes rather abruptly. Among the most amazing changes Cassini captured: the eruption of a once-every-30-years storm (one of the most powerful ever seen in the solar system), methane rainstorms at Titan and the appearance and disappearance of features such as the “magic island.”

    Over a longer span of years, the color of Saturn’s northern hemisphere shifted as the ring shadows retreated southward — changing from the surprisingly bluish tones seen upon arrival to the hazy, golden hues most observers are familiar with. On Titan, Cassini witnessed a vortex filled with complex organic chemicals forming over its south pole, and saw sunlight glinting off of the lakes in its northern hemisphere as the sun rose over them.

    The spacecraft’s patient eyes also were rewarded with new views of Saturn’s north pole as winter ended there and the sun rose once more. Cassini’s infrared sensors measured temperatures across the rings as the sun set on one side and rose on the other, revealing new details about the structure of ring particles. It used the onset of wintry darkness at the south pole of Enceladus to obtain an unambiguous reading of the amount of heat coming out of the moon’s interior. And it saw the mysterious ring features called spokes (wedge-shaped features in the rings that rotate along with the rings like the spokes in a wheel) appear and disappear — apparently a seasonal phenomenon.

    Cassini revealed Saturn’s moons to be unique worlds with their own stories to tell.

    Planet-size Titan and diminutive Enceladus stood out in Cassini’s in-depth survey of Saturn’s moons. But the mission showed that every moon in the Saturn system is a unique character with its own mysteries, and many of Saturn’s satellites are related in surprising ways.

    For example, Cassini data enabled scientists to confirm earlier suspicions that Phoebe is likely an object from the outer solar system beyond Neptune, captured by Saturn’s gravity long ago. Phoebe also turns out to be key to the two-toned appearance of the moon Iapetus: As Phoebe sheds its dark dust, it coats the leading side of Iapetus and causes ice to heat up and migrate to the moon’s opposite side.

    Cassini also gave scientists a better understanding of why Hyperion looks like a giant sponge or wasp’s nest tumbling through space. Researchers determined that the moon’s density is so low that impacts tend to compress its surface rather than blasting it out, and the material that is launched into space tends to escape for good, thanks to Hyperion’s low gravity.

    Cassini found that Enceladus is not only active, but that its geologic activity is creating Saturn’s E ring and spray-painting the surfaces of several of the other moons with its highly reflective ice particles.

    The mission also followed up on a mystery from the early 1980s when NASA’s Voyager spacecraft flew by the Saturn system and saw bright wispy terrains on Dione. Cassini found that the features were in fact a vast network of canyons. Cassini also detected hints of a faint atmosphere that might have been outgassed from the moon’s interior.

    And Cassini watched closely over many years how Prometheus interacts with Saturn’s F ring to create features like “streamers,” “plumes” and “drapes.”

    Cassini showed us the complexity of Saturn’s rings and the dramatic processes operating within them.

    Although Cassini scientists are still working on determining the exact origin of Saturn’s main system of rings — and hope to collect data that will answer this question as its mission draws to a close — they have learned along the way that there are in fact, many ways to form rings around a planet.

    There is a diffuse ring that is created out of the bits of water ice jetted out by the moon Enceladus (the E ring). There are rings that were created because of the material thrown off when meteorites hit moons (such as the G ring and the two rings discovered by Cassini in images from 2006 — the Janus-Epimetheus ring and the Pallene ring). There are rings controlled by interactions with moons, like the F ring, which is regularly perturbed by Prometheus, and the narrow ringlets that share the Encke Gap with Pan.

    In addition to the rings’ origins, Cassini’s close-up examination has also revealed propeller-shaped features that mark the locations of hidden moonlets. The processes involved in the formation of such objects are thought to be similar to how planets form in disks around young stars.

    Cassini also helped explain Saturn’s “spokes,” first spotted during the Voyager flybys of the early 1980s. Cassini scientists figured out that they are made of tiny ice particles that are lifted above the surface of the rings by an electrostatic charge, the way a statically-charged balloon held over a person’s head will lift hairs. Their charge appears to be related to the angle of sunlight striking the rings — a seasonal effect.

    The changing angle of the sun also showed scientists an array of vertical structures in the rings, including fluffy peaks of material as high as the Rocky Mountains at the outer edges of the A and B rings. The vertical structures and the shadows they cast also revealed wavy patterns in the parts of the rings that resemble a miniature Milky Way, giving scientists insight into the way galaxies form.

    Some of Cassini’s best discoveries were serendipitous. What Cassini found at Saturn prompted scientists to rethink their understanding of the solar system.

    You can only get to know a planet so well with remote and sporadic observations. To truly understand the dynamics of a place as complicated and interesting as Saturn, you have to go there and stay to explore.

    Towering jets of ice and water vapor pouring out of a moon as tiny as Enceladus were a huge surprise (explaining why Voyager flybys in the early 1980s saw that the moon had a young surface), as was the later finding that the moon has an ocean under its icy crust. Scientists also had not expected to find Saturn’s magnetosphere — the region around the planet strongly influenced by Saturn’s magnetic field — to be filled with an electrically excited gas, or plasma, of oxygen. It turned out this was another surprise from Enceladus, as the water vapor from its plume is broken apart by sunlight and the liberated oxygen spreads out through Saturn’s magnetic bubble. Cassini detected this oxygen on approach to Saturn, but its origin was perplexing at first.

    No one knew for sure what kind of environment ESA’s Huygens probe would find when it came to rest on Titan’s surface, so Huygens was built either to land on hard ground or float, if need be. Cassini later showed scientists that most of the moon’s lakes and seas were near the north pole, and most of the moon’s landscape was more like the Arizona desert. Cassini also observed a surprisingly rich variety of complex, organic chemicals forming in Titan’s atmosphere.

    Another unexpected finding — which endures as a mystery — is the irregularity of Saturn’s day (how long the planet takes to make one rotation on its axis). At Jupiter, a beacon-like burst of radio waves known as “kilometric radiation” beams out with clock-like regularity once a day. But Saturn’s kilometric radiation isn’t consistent. It’s somewhere between 10.6 and 10.8 hours. That might not seem like a big discrepancy, but for such a fundamental property as the planet’s rotation period, it’s frustratingly imprecise for scientists. They hope to settle the score by the time the mission ends by flying Cassini close enough to the planet to tease out the true answer from the magnetic field.

    Cassini represents a staggering achievement of human and technical complexity, finding innovative ways to use the spacecraft and its instruments, and paving the way for future missions to explore our solar system.

    The Cassini-Huygens mission is an international collaboration involving three space agencies, with 19 countries contributing hardware to the flight system. The Cassini spacecraft carries 12 instruments, Huygens carried six more, and scientists from 26 nations are participating in the investigations. Among the many pioneering technologies of the mission are new solid-state data recorders with no moving parts that have since replaced tape recorders, solid-state power switches (space-based versions of circuit breakers), and advanced solid-state electronics. The spacecraft has over 9 miles (14 kilometers) of cabling and 22,000 connections.

    Cassini was able explore the entire Saturn system in a way inconceivable with conventional propulsion. Building on the techniques used by the Galileo mission to Jupiter, Cassini mission planners designed flybys of the moon Titan to utilize the moon’s gravity to navigate around the Saturn system and maximize the science return of the mission. Titan became, in a way, Cassini’s virtual “gas station” since the spacecraft couldn’t possibly have brought enough fuel for a tour this long and complex. Each of Cassini’s 127 targeted Titan flybys changed the spacecraft’s velocity (on average) by as much as the entire Saturn orbit insertion burn. The exquisite optimization techniques developed during Cassini will enable planning for future exploration that can use similar approachs. Chief among these opportunities is NASA’s planned mission to explore Jupiter’s moon Europa using multiple flybys, known as the Europa Clipper.

    Cassini has required an extremely complex schedule for determining which instrument’s observations can be made at any given moment. Cassini’s intricate observation sequences, often timed to fractions of a second, are frequently planned many months or years before they are executed by the spacecraft. The collaboration between multiple teams with often differing objectives has become an exemplary model for future missions.

    Over the course of almost 20 years in space, Cassini also showed that you can teach an old dog new tricks, as the mission team found new ways to use its instruments and engineering systems that their designers had not foreseen. These include using the radar instrument to plumb the depths of Titan’s seas; tasting the plume of Enceladus with instruments meant to sample Titan’s atmosphere; scanning the rings with a radar originally designed to bounce signals off of Titan’s surface; and having the Deep Space Network’s highly accurate frequency reference fill in for the radio science instrument’s lost ultra-stable onboard frequency reference. In a unique collaboration, the attitude control and navigation teams joined with the instrument teams to develop a consolidated model of Titan’s atmosphere. Cassini will finish its mission repurposing the instruments that sniffed Titan’s atmosphere and Enceladus’ plume once more, this time to sample the Saturn atmosphere itself.

    The mission has also had some rather surprising earthly benefits. A Cassini resource exchange, created prior to launch to help team members trade and effectively share power, mass, data rates and budget, has become a model for how to manage other types of international collaboration, including carbon trading.

    When Cassini plunges into Saturn’s atmosphere, it will have spent nearly every last drop of fuel it’s carrying, a fitting end to a spacecraft that pushed itself to the limit…and in many ways, beyond.

    Cassini revealed the beauty of Saturn, its rings and moons, inspiring our sense of wonder and enriching our sense of place in the cosmos.

    Earthlings have cast their gaze upward at Saturn since ancient times, but it was Cassini’s decade-plus odyssey in orbit there that revealed the true splendor of what is arguably the most photogenic planet in our solar system.

    The mission returned stunning views of complex, swirling features in Saturn’s atmosphere, draped by the graceful ring shadows that slowly shift with the seasons.

    The spacecraft also revealed the bewildering variety of Saturn’s moons and helped us see each one as a unique world in its own right. One has a noticeable ridge around its equator and a two-toned color pattern (Iapetus); one looks like the “Death Star” from Star Wars (Mimas); one looks like a sponge (Hyperion); another looks like a flying saucer (Atlas); another looks like a potato (Prometheus); another looks like a ravioli (Pan).

    Cassini has shown us icy ringscapes that are at once magnificent in their sheer physical extent and exquisitely delicate in their expression of the subtle harmonies of gravity. These ringscapes mesmerize with the myriad designs embossed in them — the changing pattern of thick and thin, ruffles that stand as high as the Rocky Mountains, icy waves generated by small moons interacting with the rings, and “streamers” and “mini-jets” created in the ribbon-thin F ring by interactions with Prometheus.

    The views that have been perhaps the most awe-inspiring are panoramic scenes that encompass the entire Saturn system, including those with the planet and rings backlit, and the tiny glow of our far-off, blue home planet visible far across the gulf of outer space.

    Cassini carries 12 science instruments to collect a wide range of information about the Saturnian environment. These sophisticated devices take images across the infrared, visible and ultraviolet light spectra, detect dust particles, and characterize Saturn’s plasma environment and magnetosphere.

    The Cassini-Huygens spacecraft during vibration and thermal testing in 1996.

    Cassini-Huygens is one of the most ambitious missions ever launched into space. Loaded with an array of powerful instruments and cameras, the spacecraft is capable of taking accurate measurements and detailed images in a variety of atmospheric conditions and light spectra.

    The spacecraft was launched with two elements: the Cassini orbiter and the Huygens probe. Cassini-Huygens reached Saturn and its moons in July 2004, beaming home valuable data that has transformed our understand of the Saturnian system. Huygens entered the murky atmosphere of Titan, Saturn’s biggest moon, and descended via parachute onto its surface – the most distant spacecraft landing to date.

    Cassini-Huygens is a three-axis stabilized spacecraft equipped for 27 diverse science investigations. The Cassini orbiter has 12 instruments and the Huygens probe had six. Equipped to thoroughly investigate all the important elements that the Saturn system may uncover, many of the instruments have multiple functions. The spacecraft communicates through one high-gain and two-low gain antennas. It is only in the event of a power failure or other such emergency situation, however, that the spacecraft communicates through one of its low-gain antennas.

    Three Radioisotope Thermoelectric Generators – commonly referred to as RTGs – provide power for the spacecraft, including the instruments, computers, and radio transmitters on board, attitude thrusters, and reaction wheels.

    In some ways, the Cassini spacecraft has senses better than our own. For example, Cassini can “see” in wavelengths of light and energy that the human eye cannot. The instruments on the spacecraft can “feel” things about magnetic fields and tiny dust particles that no human hand could detect.

    The science instruments can be classified in a way that can be compared to the way human senses operate. Your eyes and ears are “remote sensing” devices because you can receive information from remote objects without being in direct contact with them. Your senses of touch and taste are “direct sensing” devices. Your nose can be construed as either a remote or direct sensing device. You can certainly smell the apple pie across the room without having your nose in direct contact with it, but the molecules carrying the scent do have to make direct contact with your sinuses. Cassini’s instruments can be classified as remote and microwave remote sensing instruments, and fields and particles instruments – these are all designed to record significant data and take a variety of close-up measurements.

    The remote sensing instruments on the Cassini Spacecraft can calculate measurements from a great distance. This set includes both optical and microwave sensing instruments including cameras, spectrometers, radar and radio.

    The fields and particles instruments take “in situ” (on site) direct sensing measurements of the environment around the spacecraft. These instruments measure magnetic fields, mass, electrical charges and densities of atomic particles. They also measure the quantity and composition of dust particles, the strengths of plasma (electrically charged gas), and radio waves.

    See the full article here .

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    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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  • richardmitnick 2:23 pm on April 19, 2017 Permalink | Reply
    Tags: , Saturn,   

    From JPL-Caltech: “Cassini Heads Toward Final Close Encounter with Titan” 

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    April 19, 2017
    Preston Dyches
    Jet Propulsion Laboratory, Pasadena, Calif.

    Cassini will make its final close flyby of Saturn’s moon Titan on April 21 (PDT), using its radar to reveal the moon’s surface lakes and seas one last time. Credit: NASA/JPL-Caltech

    NASA’s Cassini spacecraft will make its final close flyby of Saturn’s haze-enshrouded moon Titan this weekend. The flyby marks the mission’s final opportunity for up-close observations of the lakes and seas of liquid hydrocarbons that spread across the moon’s northern polar region, and the last chance to use its powerful radar to pierce the haze and make detailed images of the surface.

    Closest approach to Titan is planned for 11:08 p.m. PDT on April 21 (2:08 a.m. EDT April 22). During the encounter, Cassini will pass as close as 608 miles (979 kilometers) above Titan’s surface at a speed of about 13,000 mph (21,000 kph).

    The flyby is also the gateway to Cassini’s Grand Finale — a final set of 22 orbits that pass between the planet and its rings, ending with a plunge into Saturn on Sept. 15 that will end the mission. During the close pass on April 21, Titan’s gravity will bend Cassini’s orbit around Saturn, shrinking it slightly, so that instead of passing just outside the rings, the spacecraft will begin its finale dives which pass just inside the rings.

    The flyby is Cassini’s 127th targeted encounter with Titan. A targeted flyby is one for which the spacecraft uses its rocket engine or thrusters to accurately aim toward the encounter.

    Cassini’s radar instrument will look for changes in Titan’s methane lakes and seas, and attempt for the first (and last) time to study the depth and composition of Titan’s smaller lakes. The radar instrument will also search a final time for Titan’s “magic island,” a mysterious feature in one of the moon’s seas that changed in appearance over the course of several flybys. Scientists hope to gain additional insights to help them determine whether the feature is waves, bubbles, floating debris, or something else entirely.

    More information about Cassini’s final Titan flyby is available at:


    The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter.

    More information about Cassini:



    See the full article here .

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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