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TOPIC: Rosetta mission


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RE: Rosetta Deep impact

ESA`s comet chaser Rosetta will take part in one of the world`s largest astronomical observation campaigns - the Deep Impact event - while on its cruise to Comet 69P/Churyumov-Gerasimenko.
Rosetta will be watching from 29 June to 14 July 2005.

Deep Impact is a NASA mission to send a 370 kg copper `impactor` probe to Comet 9P/Tempel 1 on 4 July 2005.
Tempel 1 is a short-period comet, whose orbit runs between those of Mars and Jupiter. There is scientific interest in comets because their composition carries important information about the origin of the Solar System, as they have remained basically unchanged since then.


Rosetta, with its set of very sensitive instruments for cometary investigations, will use its capabilities to observe Tempel 1 before, during and after the impact. At a distance of about 80 million kilometres from the comet, which will be lying about 90 degrees from the Sun, Rosetta will be in the most privileged position to observe the event from space.

The observing geometry will be favourable for observations with Rosetta`s microwave spectrometer, MIRO, and the VIRTIS visual and IR mapping spectrometer. MIRO will concentrate on the chemical composition and temperature of the gas.
VIRTIS will analyse thermal emission by the comet to determine the composition of the dust ejected, and thus reveal the comet`s mineralogy.
In addition, Rosetta will be the spacecraft carrying the best available ultraviolet instrument, ALICE, to monitor the event.
ALICE will analyse the gas coming from the impact and tell about its chemical composition.

The ALICE ultraviolet imaging spectrometer analyses gases in the coma and tail and measures the comet`s production rates of water and carbon monoxide/dioxide. Also provides information on the surface composition of the nucleus.
The orbiter's scientific payload includes 11 experiments, in addition to the Lander. Scientific consortia from institutes across Europe and the United States have provided these state-of-the-art instruments. All of them are located on the side of the spacecraft that will permanently face the comet during the main scientific phase of the mission.

The Rosetta OSIRIS imaging system will also provide images of the comet`s nucleus from a far-away distance. Scientists also hope to make a 3D reconstruction of the dust cloud around the comet by combining the OSIRIS images with those taken from ground observatories.

Rosetta`s observations will provide a unique data set complementary to the observations from the Deep Impact spacecraft and the ground-based telescopes. Before impact, Rosetta will observe Tempel 1 during three full rotations of the comet around its axis.
This allows characterising the variations of the comet`s state over rotation and time, and preparing for the observations during and after impact.
Rosetta will look at the comet continuously.
In the initial phase (starting on 29 June 01:34 CEST), when the comet is expected to change only slowly due to its rotation, Rosetta will take the time to study or `dwell` on several areas on the coma of Tempel 1.

About fifteen minutes before impact (due at 07:44 CEST), Rosetta will start observing the comet with shorter dwell time, as fast changes are expected due to the impact. At 09:19, about one hour and a half after impact, Rosetta will go back to the monitoring mode as before the impact for 10 more days.

Rosetta will contribute to the major objectives of the Deep Impact mission.
The spacecraft`s instruments will measure the composition of the crater and its ejected material - a cloud of dust and gas cloud expected to expand and reach its maximum brightness about 10 hours after impact.
Rosetta will also monitor the changes in the natural outgassing of the comet following the impact.
With these observations, Rosetta may also help to confirm if the impact has permanently triggered new activity on the comet.

-- Edited by Blobrana at 16:40, 2005-06-20



Posts: 131433
Rosetta mission

ESA's comet chaser mission Rosetta took these infrared and visible images of Earth and the Moon, during the Earth fly-by of 4/5 March 2005 while on its way to Comet 67P/Churyumov-Gerasimenko.



Europe's comet-chasing probe Rosetta has launched successfully into space on a daring journey to chase and land on a comet. at 0717 GMT on the 2nd March. The launch of Europe's Rosetta space mission, which aims to chase and then land on a comet, has been delayed due to bad weather and technical problems. The probe is due to depart from Kourou in French Guiana on the first stage of its 7bn-kilometre, 10-year journey to reach the comet Churyumov-Gerasimenko.

In 2014, Rosetta will reach the comet and deliver a lander to its surface.
The £600m spacecraft on an Ariane 5 G+ rocket was due to launch at 0736 GMT on Thursday 26th February (and on the 27th) and there were two launch opportunities, at 07:17 and 07:37 GMT on March 2nd.

The Rosetta mission had a launch instant rather than a launch window. This means it can only launch at 07:36 GMT. With a launch window, mission controllers can try later on the same day if conditions improve. Once up in space, Rosetta will be placed in orbit around Earth before departing for the outer Solar System. The Ariane rocket consists of boosters, a core section, or stage, an upper stage and the probe itself. The probe and upper stage are known collectively as the stack. Two minutes after lift off, the rocket jettisoned its boosters leaving the rest of the rocket to ascend to a height of 4,000km.

After about 10 minutes, the rocket begins to fall back towards Earth. As this happens, the core stage separates from the stack.



The core re-enters the atmosphere while the stack remains in orbit, using the Earth's gravity to build up velocity for Rosetta's "escape". After a further two hours, the upper stage separates from Rosetta, leaving the probe to begin its journey.
During the course of its 10-year journey, the probe will round the Sun four times before reaching 67P/Churyumov-Gerasimenko. The probe will perform three close fly-bys of the Earth and one of Mars in "slingshot" manoeuvres that will use the planets' gravity to help the probe build up speed. Rosetta will need this extra velocity if it is to intercept the comet as it streaks past Jupiter towards the Sun.
Over half of the 3,000 kg spacecraft's mass is fuel, to enable it to complete its epic trip around the Solar System.
By May/June of 2014, Rosetta will enter orbit around the comet and begin edging towards its nucleus. The orbiter's cameras will then map the nucleus in detail to help scientists choose a suitable landing site. After this has been chosen, Rosetta will despatch its lander Philae to the comet's surface. Approaching the nucleus at walking speed, Philae will fire two harpoons to anchor itself down. During Rosetta's rendezvous with the comet, commands from Earth will take about 50 minutes to reach the spacecraft. So the probe has been designed with a degree of autonomy, allowing it to think for itself. Rosetta will have to cope with temperatures that fall to -150 Celsius beyond the planet Jupiter. The mission is due to end in December 2015.

Click to listen! LIVE Real-Player stream of the Rosetta mission.
Click to listen! RE-RUN Real-Player stream of the Rosetta Launch.
Click to see! Launch Clip of Ariane 5 G+ rocket .

Click to see! latest photo of 67P/Churyumov-Gerasimenko.

Rosetta is named after the stone that explained Egyptian hieroglyphics, thus laying bare the culture of the Pharaohs to modern eyes.
Its lander, Philae, is so called after an obelisk that itself provided a key to understanding Rosetta.

On Mar 11, 2004 The European Space Agency selected a pair of asteroids of high scientific interest, well within the fuel budget, that Rosetta will fly past on its way to meet up with Comet 67P/Churyumov-Gerasimenko.

The first target is Steins, which is only a few kilometres across will be visited by Rosetta on 5 September 2008 at a distance of just over 1700 kilometres. This encounter will take place at a relatively low speed of about 9 kilometres per second during Rosetta's first excursion into the asteroid belt between the orbits of Mars and Jupiter.
The second asteroid is Lutetia; a 100 km asteroid which Rosetta will pass within about 3000 kilometres on 10 July 2010 at a speed of 15 kilometres per second. This will be during Rosetta's second passage through the asteroid belt. Rosetta will obtain spectacular images as it flies by these primordial rocks. Its onboard instruments will provide information on the mass and density of the asteroids, thus telling us more about their composition, and will also measure their subsurface temperature and look for gas and dust around them.
The selection of these two excellent targets was made possible by the high accuracy with which the Ariane 5 delivered the spacecraft into its orbit. This of course leaves sufficient fuel for the core part of the mission, orbiting Comet 67P/Churyumov-Gerasimenko for 17 months when Rosetta reaches its target in 2014.


Rosetta Status Report 3 May 2004:

For the first time the spacecraft was rotated such that the payload could point towards the Earth. This gave MIRO and VIRTIS the opportunity to take calibration measurements using the Earth as a target. Close monitoring of the thermal environment continues, and the experience with the Earth pointing attitude has resulted in a further restriction on the range of allowed attitudes. The Sun is now allowed in a range from ń4 to +50 degrees from the +X axis in the X/Z plan, at least until after perihelion is reached on 25 May.

Philae's Challenge:     Landing on Powder or Ice?

Rosetta's lander Philae will do something never before attempted: land on a comet. But how will it do this, when the kind of surface it will land on is unknown? With the surface composition and condition largely a mystery, engineers found themselves with an extraordinary challenge; they had to design something that would land equally well on either solid ice or powder snow, or any state in between. In the tiny gravitational field of a comet, landing on hard icy surface might cause Philae to bounce off again. Alternatively, hitting a soft snowy one could result in it sinking. To cope with either possibility, Philae will touch as softly as possible. In fact, engineers have likened it more to docking in space.
Landing on a comet is nothing like landing on a large planet, you do not have to fight against the pull of the planet's gravity, and there is no atmosphere. The final touching velocity will be about one metre per second. That is near a walking pace. However, as anyone who has walked into a wall by mistake will tell you, it is still fast enough to do some damage. So, two other strategies have been implemented. Firstly, to guard against bouncing off, Philae will fire harpoons upon contact to secure itself to the comet. Secondly, to prevent Philae from disappearing into a snowy surface, the landing gear is equipped with large pads to spread its weight across a broad area - which is how snowshoes work on Earth, allowing us to walk on powdery falls of snow. When necessity forced Rosetta's target comet to be changed in Spring 2003 from Comet Wirtanen to Comet 67P/Churyumov-Gerasimenko, the landing team re-analysed Philae's ability to cope. Because Comet Churyumov-Gerasimenko is larger than Wirtanen, three times the radius, it will have a larger gravitational field with which to pull down Philae.
In testing it was discovered that the landing gear is capable of withstanding a landing of 1.5 metres per second - this was better than originally assumed. In addition, Rosetta will gently push out the lander from a low altitude, to lessen its fall. In the re-analysis, one small worry was that Philae might just topple, if it landed on a slope at high speed. So the lander team developed a special device called a ėtilt limiter', and attached it to the lander before lift-off, to prevent this happening. In fact, the unknown nature of the landing environment only serves to highlight why the Rosetta mission is vital in the first place. Astronomers and planetary scientists need to learn more about these dirty snowballs that orbit the Sun.

-- Edited by Blobrana on Friday 16th of October 2009 10:42:12 PM

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