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  • richardmitnick 7:32 pm on September 19, 2017 Permalink | Reply
    Tags: , , , Cassini End of mission,   

    From NASA: Two Cassini videos, one is 1-1/2 hours, the other is 5 hours. 


    Streamed live on Sep 15, 2017
    Friday, Sept. 15, 7-8:30 a.m. EDT: Cassini mission’s “Grand Finale.” Live commentary. See inside mission control as we awaited the FINAL signal and science data from our Cassini spacecraft. After two decades in space, NASA’s Cassini mission to Saturn is at the end of its remarkable journey of exploration.
    Cassini Mission Latest Status
    Cassini End of Mission Timeline
    NASA’s Jet Propulsion Laboratory invites you to watch live about everything from Mars rovers to monitoring asteroids to cool cosmic discoveries. From the lab to the lecture hall, get information directly from scientists and engineers working on NASA’s latest missions. http://www.jpl.nasa.gov

    5 hours
    Streamed live on Sep 15, 2017

    This stream follows NASA TV as it follows the end of Cassini. The completion of it’s Grand Finale will see the spacecraft dive into the atmosphere of Saturn bringing its mission to a close.

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    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

  • richardmitnick 5:48 am on September 16, 2017 Permalink | Reply
    Tags: Cassini End of mission, ,   

    From JPL-Caltech: “NASA’s Cassini Spacecraft Ends Its Historic Exploration of Saturn” 

    NASA JPL Banner


    September 15, 2017

    Dwayne Brown
    NASA Headquarters, Washington

    Laurie Cantillo
    NASA Headquarters, Washington

    Preston Dyches
    Jet Propulsion Laboratory, Pasadena, Calif.

    Saturn’s active, ocean-bearing moon Enceladus sinks behind the giant planet in a farewell portrait from NASA’s Cassini spacecraft. This view of Enceladus was taken by NASA’s Cassini spacecraft on Sept. 13, 2017. It is among the last images Cassini sent back.

    A thrilling epoch in the exploration of our solar system came to a close today, as NASA’s Cassini spacecraft made a fateful plunge into the atmosphere of Saturn, ending its 13-year tour of the ringed planet.

    NASA/ESA/ASI Cassini-Huygens Spacecraft

    “This is the final chapter of an amazing mission, but it’s also a new beginning,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at NASA Headquarters in Washington. “Cassini’s discovery of ocean worlds at Titan and Enceladus changed everything, shaking our views to the core about surprising places to search for potential life beyond Earth.”

    Spacecraft operations team manager for the Cassini mission at Saturn, Julie Webster is seen after the end of the Cassini mission.

    Telemetry received during the plunge indicates that, as expected, Cassini entered Saturn’s atmosphere with its thrusters firing to maintain stability, as it sent back a unique final set of science observations. Loss of contact with the Cassini spacecraft occurred at 4:55 a.m. PDT (7:55 a.m. EDT), with the signal received by NASA’s Deep Space Network antenna complex in Canberra, Australia.

    NASA Canberra, AU Deep Space Network

    This montage of images shows the location on Saturn where the NASA spacecraft entered Saturn’s atmosphere.

    “It’s a bittersweet, but fond, farewell to a mission that leaves behind an incredible wealth of discoveries that have changed our view of Saturn and our solar system, and will continue to shape future missions and research,” said Michael Watkins, director of NASA’s Jet Propulsion Laboratory in Pasadena, California, which manages the Cassini mission for the agency. JPL also designed, developed and assembled the spacecraft.

    Cassini’s plunge brings to a close a series of 22 weekly “Grand Finale” dives between Saturn and its rings, a feat never before attempted by any spacecraft.

    “The Cassini operations team did an absolutely stellar job guiding the spacecraft to its noble end,” said Earl Maize, Cassini project manager at JPL. “From designing the trajectory seven years ago, to navigating through the 22 nail-biting plunges between Saturn and its rings, this is a crack shot group of scientists and engineers that scripted a fitting end to a great mission. What a way to go. Truly a blaze of glory.”

    As planned, data from eight of Cassini’s science instruments was beamed back to Earth. Mission scientists will examine the spacecraft’s final observations in the coming weeks for new insights about Saturn, including hints about the planet’s formation and evolution, and processes occurring in its atmosphere.

    “Things never will be quite the same for those of us on the Cassini team now that the spacecraft is no longer flying,” said Linda Spilker, Cassini project scientist at JPL. “But, we take comfort knowing that every time we look up at Saturn in the night sky, part of Cassini will be there, too.”

    Cassini launched in 1997 from Cape Canaveral Air Force Station in Florida and arrived at Saturn in 2004. NASA extended its mission twice – first for two years, and then for seven more. The second mission extension provided dozens of flybys of the planet’s icy moons, using the spacecraft’s remaining rocket propellant along the way. Cassini finished its tour of the Saturn system with its Grand Finale, capped by Friday’s intentional plunge into the planet to ensure Saturn’s moons – particularly Enceladus, with its subsurface ocean and signs of hydrothermal activity – remain pristine for future exploration.

    While the Cassini spacecraft is gone, its enormous collection of data about Saturn – the giant planet, its magnetosphere, rings and moons – will continue to yield new discoveries for decades to come.

    “Cassini may be gone, but its scientific bounty will keep us occupied for many years,” Spilker said. “We’ve only scratched the surface of what we can learn from the mountain of data it has sent back over its lifetime.”

    NASA Recap: Saturn End of Mission. 1 hour.

    An online toolkit with information and resources for Cassini’s Grand Finale is available at:


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

    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 5:29 am on September 16, 2017 Permalink | Reply
    Tags: Cassini at Saturn, Cassini End of mission,   

    From ESA: “Cassini concludes pioneering mission at Saturn” 

    ESA Space For Europe Banner

    European Space Agency

    15 September 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


    The international Cassini mission has concluded its remarkable exploration of the Saturnian system in spectacular style, by plunging into the gas planet’s atmosphere.

    Confirmation of the end of mission arrived at NASA’s Jet Propulsion Laboratory at 11:55 GMT/13:55 CEST with the loss of the spacecraft’s signal having occurred 83 minutes earlier at Saturn, some 1.4 billion km from Earth.

    Last Enceladus plume observation

    With the rocket propellant for manoeuvering the spacecraft fully expended as planned touring Saturn and its moons for the last 13 years, the mission concluded with the intentional plunge into the gas planet. This ensures that Saturn’s icy moons, in particular ocean-bearing Enceladus, do not risk being contaminated by microbes that might have remained on board the spacecraft from Earth, and are left pristine for future exploration.

    Cassini spent the last five months diving between Saturn’s rings and atmosphere in a series of 22 grand finale orbits culminating in a final farewell to Titan on Monday, which set it on course for Saturn.

    The grand finale orbits were supported by ESA ground stations, which received signals from Cassini to gather crucial radio science and gravitational science data.

    ESA DSA-1 New Norcia, Western Australia. Credit: ESA

    NASA Deep Space Network
    Canberra, AU

    Madrid, Spain

    Goldstone, Mojave Desert, USA


    Cassini’s final image – natural colour view

    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

    Atmospheric entry began about a minute before loss of signal, and the spacecraft sent scientific data in near real-time until its antenna could no longer point towards Earth. Its last images were sent yesterday, before the final plunge, and during its final moments it made the deepest ever measurements of the plasma density, magnetic field, temperatures and atmospheric composition in Saturn’s atmosphere.

    “Cassini has been revolutionising our views of the Saturn system since the moment it arrived, and for 13 incredible years right until the very end today,” says Alvaro Giménez, ESA’s Director of Science.

    “This mission has changed the way we view ocean-worlds in the Solar System, offering tantalising hints of places which could offer potentially habitable environments, with Titan giving us a planet-sized laboratory to study processes that may even be relevant to the origin of life on Earth.”

    Launched on 15 October 1997 and arriving in Saturn’s orbit on 30 June 2004 (PDT), Cassini carried ESA’s Huygens probe that landed on Titan on 14 January 2005. During its two and half hour descent it revealed the surface that had been previously been hidden by the moon’s thick hazy atmosphere, showing a world with eerily Earth-like landscapes.

    Cassini would continue to make exciting discoveries at Titan from orbit, with its radar finding lakes and seas filled with methane and other hydrocarbons, making it the only other known place in our Solar System with a stable liquid on its surface. In the moon’s atmosphere Cassini detected numerous complex organic molecules, some of which are considered building blocks of life on Earth.

    First colour view of Titan’s surface

    Saturn’s moon zoo

    Saturn’s moons continued to surprise, with one of the major discoveries of the entire mission the detection of icy plumes erupting from fissures in the southern hemisphere of Enceladus. Later discoveries would indicate hydrothermal activity at the bottom of a sea floor, hinting at this world as one of the most promising places to search for life beyond Earth.

    The mission also showcased the unique characteristics of Saturn’s many other moons, from Iapetus and its equatorial ridge to Hyperion, which looks like a giant sponge, and from ravioli-shaped Pan, to Mimas, which resembles the Death Star from Star Wars.

    Many of Cassini’s discoveries can be attributed to the longevity of the mission, which included two mission extensions, allowing the spacecraft to cover half of Saturn’s seasonal cycle.

    First, a two-year extension was granted to observe changes as Saturn reached equinox, when the Sun shone edge-on to the rings. Subsequently, an additional seven years was given to follow up on earlier discoveries at Enceladus and Titan, and watch as summer sunlight fell on to the northern hemisphere of Saturn and its moons while winter darkness moved in on the south.

    This long-term monitoring allowed scientists to watch seasonal changes, including how weather patterns in Saturn’s dynamic atmosphere evolved, and revealing the long-lived north polar vortex inside a hexagon-shaped jet stream. Cassini also watched how Titan’s hydrocarbon cycle evolved with the seasons, its clouds raining methane onto the surface.

    Saturn’s ring features

    The extended mission time was also crucial to track the evolution of small-scale dynamical features in the rings, like the ‘propellers’, disturbances in the rings created by moonlets. Over time the ‘spokes’ in Saturn’s rings – features that rotate along with the rings like the spokes in a wheel – appeared and disappeared with the seasons. And at equinox, the exquisite detail of the vertical structures in the rings, driven by gravitational perturbations of nearby moons, was revealed.

    “Cassini and Huygens represent an astonishing scientific, technological, and human achievement,” says Nicolas Altobelli, ESA’s Cassini project scientist.

    “The mission has inspired us with awe-inspiring images, including those humbling views looking across more than a billion kilometres of space back to the tiny blue dot of our home planet.

    Cassini’s Pale Blue Dot
    Released 23/07/2013 9:16 am
    Copyright NASA/JPL-Caltech/Space Science Institute
    In this rare image taken on 19 July, the wide-angle camera on the international Cassini spacecraft has captured Saturn’s rings and our planet Earth and Moon in the same frame.
    The dark side of Saturn, its bright limb, the main rings, the F ring, and the G and E rings are clearly seen; the limb of Saturn and the F ring are overexposed. The ‘breaks’ in the brightness of Saturn’s limb are due to the shadows of the rings on the globe of Saturn, preventing sunlight from shining through the atmosphere in those regions. The E and G rings have been brightened for better visibility.

    Earth, 1.44 billion km away in this image, appears as a blue dot at centre right; the Moon can be seen as a fainter protrusion off its right side. The other bright dots nearby are stars.
    This is only the third time ever that Earth has been imaged from the outer Solar System. The first image was taken by NASA’s Voyager-1 in 1990 and famously titled “Pale Blue Dot”. In 2006, Cassini imaged Earth in the stunning and unique mosaic of Saturn called “In Saturn’s Shadow – The Pale Blue Dot”.
    The new images marked the first time that inhabitants of Earth knew in advance that their planet was being imaged. That opportunity allowed people around the world to join together in social events to celebrate the occasion.
    This view looks towards the unilluminated side of the rings from about 20º below the ring plane.
    Images taken using red, green and blue filters were combined to create this natural colour view. The images were obtained with Cassini’s wide-angle camera on 19 July at a distance of 1.212 million km from Saturn, and 1445.858 million km from Earth. The illuminated areas of both Earth and the Moon are unresolved here. Consequently, the size of each ‘dot’ is the same size that a point of light of comparable brightness would have in the wide-angle camera.

    While it is certainly sad when a mission ends, it is also a time to celebrate this pioneering journey, which leaves a rich scientific and engineering legacy to pave the way for future missions.”

    Mission planners already have the next generation of ocean-world explorers lined up, although this time it’s Jupiter that will get the limelight. ESA is preparing to launch the Jupiter Icy Moons Orbiter, Juice, in 2022, with a key focus on the habitability potential of the large ocean-bearing satellites Europa, Ganymede and Callisto, while NASA is planning the Europa Clipper mission for dedicated flybys of that icy moon.

    ESA/Juice spacecraft

    NASA/Europa Clipper

    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 12:23 pm on September 14, 2017 Permalink | Reply
    Tags: , , , Cassini End of mission, , ,   

    From U Arizona: “After Farewell Kiss, Cassini Takes the Plunge” 

    U Arizona bloc

    University of Arizona

    Sept. 13, 2017
    Daniel Stolte

    In the upper reaches of Saturn’s atmosphere, the Cassini spacecraft will use its thrusters to point its antenna toward Earth until it breaks up. (Credit: NASA/JPL-Caltech)

    For UA scientists who contributed to NASA’s Cassini-Huygens mission, the Grand Finale of humanity’s tour of the Saturn system marks the end of an era.

    When NASA’s Cassini spacecraft careens to its final destination, the upper atmosphere of Saturn, it will take with it a sizable chunk of University of Arizona space research history. After a journey of 4.9 billion miles, and one month shy of 20 years in space, the probe is programmed to end its voyage exploring the Saturnian system through a deliberate plunge into the second-largest planet of the solar system.

    The spacecraft’s fateful dive on Friday will be the final beat in the mission’s Grand Finale — 22 weekly dives, begun in late April, through the gap between Saturn and its rings. According to NASA, no spacecraft has ever ventured so close to the planet before.

    “Cassini-Huygens is a classic example of a ‘flagship’ mission, accomplishing tremendous science in many disciplines over many years,” said Alfred McEwen, a UA professor of planetary sciences, on Monday as he prepared to leave for Pasadena, California. There, at NASA’s Jet Propulsion Laboratory, he would attend the final moments of the mission, along with other UA planetary scientists who have participated in the project.

    NASA’s Cassini spacecraft delivered this glorious view of Saturn on Dec. 18, 2012, 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. (Credit: NASA/JPL-Caltech/Space Science Institute)

    NASA chose to end the mission by safely disposing of the spacecraft, burning it up in Saturn’s atmosphere rather than allowing it to run out of fuel and committing its fate to an aimless tumble and potential crash onto one of Saturn’s moons. Mission scientists were especially concerned about contaminating Titan or Enceladus, the two Saturnian moons where life as we know it might be possible — a possibility discovered by Cassini’s multiple flybys.

    When it launched, Cassini-Huygens was the biggest, most complex interplanetary spacecraft ever flown. In 2004, it arrived in the Saturn system, carrying with it a robotic passenger in form of the Huygens probe, contributed to the mission by the European Space Agency, or ESA. On Jan. 14, 2005, Huygens would make history as the first — and, so far, only — humanmade object to touch down on a world in the outer solar system. Through the eyes of Huygens, an instrument built by UA scientists and engineers, people on Earth could watch as the probe hurtled through the opaque and hazy atmosphere enshrouding Titan.

    The probe was equipped with an instrument called DISR, short for Descent Imager/Spectral Radiometer. Led by Martin Tomasko, a now-retired research professor at the Lunar and Planetary Laboratory, UA scientists joined their ESA colleagues in Germany to follow Huygens with six science experiments as it descended through Titan’s thick atmosphere until it touched down on a virtually unseen surface. In addition to images taken with DISR, the lander recorded data that enabled LPL staff scientist Erich Karkoschka to gather surprising clues about Titan’s surface many years after the event.

    Cassini-Huygens is a “flagship mission” and has the track record to show it. (Credit: NASA/JPL-Caltech)

    Monitoring the Moon Titan

    During many flybys, Cassini monitored the dynamic Titan using its camera suite and an instrument called VIMS, a Visual and Infrared Mapping Spectrometer. Built at Jet Propulsion Laboratory under the leadership of Robert Brown, operations for VIMS moved to the UA when Brown assumed a position as professor at LPL. According to Brown, VIMS has been taking spectra over areas of Saturn, its rings and moons so scientists can discover what these objects are made of.

    Those observations revealed details about the cycle of methane, which on Titan takes the role of water on Earth — forming clouds, raining down and forming lakes, as well as freezing into ice. In all those observations, Cassini’s cameras played an important role, said McEwen, who is a team member of the craft’s imaging science subsystem. Those cameras, over the years of photographing Saturn, its rings and moons, created some of the most visually beautiful images of the solar system.

    Cassini’s imaging team leader Carolyn Porco was appointed to the mission while on the faculty at LPL, where she had been working on NASA’s Voyager mission, and was a co-originator of the idea to use Voyager-1 to take portraits of the planets, including the famous Pale Blue Dot image of Earth.

    Earthrise. Credit: NASA/JPL. https://www.wessexscene.co.uk/science/2017/01/29/the-pale-blue-dot/

    Surface observations on Titan are planned at LPL, and then sent to the Cassini Imaging Central Laboratory for Operations, or CICLOPS, at the University of Colorado, Boulder, which Porco heads as director.

    “From there, the necessary commands are sent to JPL and then to the spacecraft,” McEwen explains.

    Another one of Saturn’s moons, ice-clad Enceladus, rose to stardom during several flybys over the course of the mission. Enceladus plows along the orbit of the E Ring, Saturn’s second-from-outermost ring, which reaches extremely far out into space, brushing up against the orbit of Titan.

    “There was speculation that the moon had something to do with the E Ring,” McEwen says.

    During multiple close flybys, Cassini used its full science payload to detect and analyze water-rich plumes erupting from the moon’s south pole far into space, a spectacular discovery that McEwen considers one of the highlights of the entire mission.

    “We saw that these plumes are quite large and extensive,” he recalls. “Because we were able to measure their composition with Cassini’s instruments, we could show that (tiny particles from those eruptions) are the source of the E Ring.”

    The Last Closest Approach

    Evidence for subsurface oceans of water were discovered by Cassini inside both Enceladus and Titan, making them prime targets for future NASA missions.

    Cassini made its last closest approach to Titan on Sept. 11 at 12:04 p.m. PDT, at an altitude of 73,974 miles (119,049 kilometers) above the moon’s surface, causing the spacecraft to slingshot into its final approach to Saturn — but not before it would send final images from Titan to Earth, eagerly awaited by scientists, including McEwen.

    “Previously, we saw thunderstorms in Titan’s southern hemisphere when it was summer there,” he says, “and because it’s now the northern summer solstice, we are hoping to see cloud activity and perhaps thunderstorms in the northern hemisphere.”

    Cassini will be doing science even after being gripped by Saturn’s gravity, pulling it into destruction, by measuring the composition, temperature and other properties of Saturn’s atmosphere.

    “The spacecraft will be transmitting data until the very end, and we’ll be there when it stops,” McEwen says. “It won’t go very deep, because it is not a probe designed to go deep, but still deeper than anything else.”

    When Cassini arrived at Saturn, where one “year” lasts 29.5 Earth years, the gas giant went through northern winter, and Cassini was there to witness the planet’s change of seasons.

    The end of the mission, McEwen says, is “not unexpected,” adding that the plan to end with a solstice mission, followed by a plunge into Saturn, was put in place about seven years ago.

    Still, “this mission has been going for so long, it’s a little hard to believe that it’s over,” he says.

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    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium? An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

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

    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 3:37 pm on April 12, 2017 Permalink | Reply
    Tags: , , , Cassini End of mission,   

    From JPL: “NASA’s Deep Space Network relays first command sequence for NASA’s Cassini Mission to Saturn’s Grand Finale.” 

    NASA JPL Banner


    April 11, 2017
    Kristen Walbolt
    Sasha Samochina

    Mission Control Cassini. NASA

    NASA/ESA/ASI Cassini Spacecraft

    NASA Deep Space Network

    Throughout Cassini’s nearly 20-year mission, the flight team on Earth has transmitted between four and 10 weeks of commands to the spacecraft at a time. This transmission on April 11, 2017, was special. The team sent one of the final command sequences, which will control Cassini while it flies toward and eventually through the gap between Saturn’s innermost ring and the planet itself. These orbits are known as Cassini’s Grand Finale, the series of 22 dives through the gap, dipping into Saturn’s atmosphere and occasionally through the D ring.

    The computer commands were transmitted about 8:30 a.m. PDT (11:30 a.m. EDT) via NASA’s Deep Space Network. It takes nearly an hour and a half of light-travel time from Earth for the commands to reach the spacecraft at Saturn. Cassini will now autonomously execute that Grand Finale sequence for the next six weeks. Another command sequence will continue the Grand Finale orbits, which last for five months.

    Like all of Cassini’s work, this command sequence started with the science. Scientists working with different spacecraft instruments and disciplines met with the flight team to integrate their respective planned observations with one another and with the engineering team. That led to Sequence 99, or S99, the Grand Finale. These final orbits will tell us more about Saturn’s structure and its magnetic and gravitational fields. Cassini’s instruments will also sample icy ring particles, improving our understanding of the composition and origins of Saturn’s rings. Meanwhile its cameras will take amazing images of Saturn’s rings and clouds from closer than we’ve ever been before.

    On Sept. 15, 2017, Cassini’s final orbit will send it into the planet. The spacecraft’s final images will have been sent to Earth several hours before its final plunge, but even as Cassini makes its fateful dive into the planet’s atmosphere, it will be sending home new data in real time. Key measurements will come from its mass spectrometer, which will sample Saturn’s atmosphere, telling us about its composition until contact is lost.

    How it Feels
    Cassini Flight Team member Jo Pitesky describes what it is like to command the spacecraft.

    Jo Pitesky. No image credit.

    “I’ve been on Cassini on and off for 13 years. The first time I sent a command to the spacecraft was four or five years ago, which was also the first time that I was responsible for creating and approving the files that get sent up. Having my ‘fingerprints’ on the actual files made me feel very nervous. Even though everything gets checked by a team, it felt like I was personally responsible for what what happens happen on board.”

    “Some of that same feeling comes through for me when I send up a command file for a new sequence. If we need to send the file in the middle of the night (unfortunately, we don’t always get Deep Space Network time scheduled at convenient hours) we can set up a time-delayed process so that we don’t have to get up at 3 a.m., but if the schedule allows, we perform the ‘uplink’ live, on special monitor phones. It feels both formal and incredibly cool. Formal, because we have a script and a process to make sure that we are sending the right command at the right time. We carefully check the name of the file, the time that the file was created, and other identifiers. Cool, because it sounds like something out a movie. ‘Cassini ACE, this is S75 SIP lead on FSO CORD over,’ and ‘You have a GO for radiation of file zulu 0750 foxtrot.’

    Even though I’ve now done this many times, there’s a little kid inside me that is thinking, “This is so cool!'”

    Saturn 99 At a Glance

    Grand Finale begins: April 26, 2017

    Top speed of spacecraft: (relative to Earth): 76,806 mph

    Commands executed by Cassini at Saturn: ~2.5 million

    One-way transmission time from Earth to Saturn: 80 minutes

    Grand Finale orbits: 22 dives between Saturn and its innermost ring

    End of mission: Sept. 15, 2017

    Science planners Sherwin Goo, left, and Rudy Boehmer begin the process to send the commands that will launch Cassini’s Grand Finale. It will take the commands 80 minutes to travel from Earth to the spacecraft at Saturn once they are relayed via NASA’s Deep Space Network. Once Cassini receives the data, it will store the commands, and begin executing them on April 14, in time to begin the Grand Finale on April 26, 2017.

    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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