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

1
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.

2
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.

4
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

3
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.

4
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.

5
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 .

Please help promote STEM in your local schools.

STEM Icon

Stem Education Coalition

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.

ESA50 Logo large

Advertisements