Philae / Rosetta lander

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comet, ESA, lander, NASA, Philae, Rosetta

Philae

The 100-kilogram Rosetta lander is provided by a European consortium under the leadership of the German Aerospace Research Institute (DLR). Other members of the consortium are ESA and institutes from Austria, Finland, France, Hungary, Ireland, Italy and the UK.

The box-shaped lander is carried on the side of the orbiter until it arrives at Comet 67P/Churyumov-Gerasimenko.

Once the orbiter is aligned correctly, the lander is commanded to self-eject from the main spacecraft and unfold its three legs, ready for a gentle touchdown at the end of the ballistic descent.

On landing, the legs damp out most of the kinetic energy to reduce the chance of bouncing, and they can rotate, lift or tilt to return the lander to an upright position.

Immediately after touchdown, a harpoon is fired to anchor the lander to the ground and prevent it escaping from the comet’s extremely weak gravity. The minimum mission target is one week, but surface operations may continue for many months.

Philae’s instruments

The lander structure consists of a baseplate, an instrument platform, and a polygonal sandwich construction, all made of carbon fibre. Some of the instruments and subsystems are beneath a hood that is covered with solar cells.

An antenna transmits data from the surface to Earth via the orbiter. The lander carries nine experiments, with a total mass of about 21 kilograms. It also carries a drilling system to take samples of subsurface material.

http://www.esa.int/Our_Activities/Space_Science/Rosetta/The_Rosetta_lander

Landing Site / Philae lander

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comet, ESA, lander, NASA, Philae, Rosetta

ESA confirms the primary landing site for Rosetta
15 October 2014

ESA has given the green light for its Rosetta mission to deliver its lander, Philae, to the primary site on 67P/Churyumov–Gerasimenko on 12 November, in the first-ever attempt at a soft touchdown on a comet.

Philae’s landing site, currently known as Site J and located on the smaller of the comet’s two ‘lobes’, was confirmed on 14 October following a comprehensive readiness review.

Since the arrival, the mission has been conducting an unprecedented survey and scientific analysis of the comet, a remnant of the early phases  of the Solar System’s 4.6 billion-year history.

At the same time, Rosetta has been moving closer to the comet: starting at 100 km on 6 August, it is now just 10 km from the centre of the 4 km-wide body. This allowed a more detailed look at the primary and backup landing sites in order to complete a hazard assessment, including a detailed boulder census.

The decision that the mission is ‘Go’ for Site J also confirms the timeline of events leading up to the landing.

Rosetta will release Philae at 08:35 GMT/09:35 CET on 12 November at a distance of approximately 22.5 km from the centre of the comet. Landing will be about seven hours later at around 15:30 GMT/16:30 CET.

With a one-way signal travel time between Rosetta and Earth on 12 November of 28 minutes 20 seconds, that means that confirmation of separation will arrive on Earth ground stations at 09:03 GMT/10:03 CET and of touchdown at around 16:00 GMT/17:00 CET.

A short manoeuvre must then take place around two hours before separation. This will set Rosetta on course to release Philae on the right trajectory to land on the comet. The final critical Go/No-Go for separation occurs shortly after this manoeuvre.

After the release of Philae, Rosetta will manoeuvre up and away from the comet, before reorienting itself in order to establish communications with Philae. All being well, Rosetta and its lander will begin communications about two hours after separation.

During the seven-hour descent, Philae will take images and conduct science experiments, sampling the dust, gas and plasma environment close to the comet.

It will take a ‘farewell’ image of the Rosetta orbiter shortly after separation, along with a number of images as it approaches the comet surface. It is expected that the first images from this sequence will be received on Earth several hours after separation.

Once safely on the surface, Philae will take a panorama of its surroundings. Again, this is expected back on Earth several hours later.

The first sequence of surface science experiments will begin about an hour after touchdown and will last for 64 hours, constrained by the lander’s primary battery lifetime.

Longer-term study of the comet by Philae will depend on for how long and how well the batteries are able to recharge, which in turn is related to the amount of dust that settles on its solar panels.

In any case, it is expected that by March 2015, as the comet moves closer in its orbit towards the Sun, temperatures inside the lander will have reached levels too high to continue operations, and Philae’s science mission will come to an end.

The Rosetta orbiter’s mission will continue for much longer. It will accompany the comet as it grows in activity until their closest approach to the Sun in August 2015 and then as they head back towards the outer Solar System.

This unprecedented mission will study how a comet evolves and give important insights into the formation of our Solar System, and the origins of water and perhaps even life on Earth.

http://www.esa.int/Our_Activities/Space_Science/Rosetta/ESA_confirms_the_primary_landing_site_for_Rosetta

Cometwatch / Rosetta

Tags

comet, ESA, NASA, Rosetta

ESA – European Space Agency
Rosetta Blog

Cometwatch – 28 October

This four-image NAVCAM montage comprises images taken on 28 October – shortly before moving to the pre-lander delivery orbit – from a distance of 9.7 km from the centre of comet 67P/C-G, or roughly 7.7 km from the surface.

The corresponding image scale is about 65 cm/pixel, so each 1024 x 1024 pixel frame is about 665 m across. The montage has been slightly tweaked and the central vignetting reduced. The four original frames are provided at the end of the post.

The montage nicely ‘joins the dots’ with the region presented in the 8 October montage.

Given the peculiar low-density, low-gravity nature of a comet, it is perhaps dangerous to make direct analogies with Earth-like features and processes. But until we have the science team’s analysis of what they think is actually happening on this comet, analogies might nevertheless still provide a useful way of trying to decipher what we are seeing.

In a number of places in this region, there is an impression that the prevalent dusty material covering the surface is not particularly stable and that it occasionally gives way, perhaps in a similar way that snow on a mountain side may become dislodged, giving rise to an avalanche or, alternatively, a rockfall or landslide.

For example, look in the lower third of the top left image. There you’ll see what looks like a crack close to the edge of the cliff, suggesting that this portion might eventually collapse, similar to the way a snow cornice on a mountain ridge peels away. This feature is also visible in the 8 October image.

Another example can be seen in the lower right corner of the bottom right image, where material appears to have slid over the edge of a cliff.

On Earth, avalanches are typically triggered by an increased load, leading to the mechanical failure of a slab of material under gravity, or due to melting snow as a result of increased solar radiation. On a comet, presumably the latter process is more likely to occur, with sublimation-based erosion acting to weaken the surface material, resulting in a collapse.

http://blogs.esa.int/rosetta/2014/10/31/cometwatch-28-october/

Also see:
http://www.esa.int/spaceinimages/Images/2014/10/Comet_on_28_October_NavCam

Rosetta and the comet

Tags

comet, ESA, Rosetta

Comet 67P on Aug. 3, 2014. ESA’s Rosetta probe snapped this image of its target, Comet 67P on Aug. 3, 2014 from a distance of 177 miles (285 kilometers). Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

I’ve been following the progress of the ESA Rosetta spacecraft recently as it neared Comet 67P/Churyumov-Gerasimenko.

After a ten-year journey, today it arrived!

Here’s a link to the ESA live broadcast this morning. http://www.space.com/17933-nasa-television-webcasts-live-space-tv.html

More about Rosetta and the comet from Space.com online today:

Europe’s Rosetta Spacecraft Makes Historic Arrival at Comet
By Miriam Kramer, Staff Writer | August 06, 2014 06:00am ET

After a decade in space and 4 billion miles, Europe’s Rosetta spacecraft has made history: For the first time ever, a robotic probe from Earth is flying with a comet and will soon enter orbit.

The European Space Agency’s Rosetta spacecraft arrived at its target, Comet 67P/Churyumov-Gerasimenko, today (Aug. 6) to end a 10-year journey across the solar system. The spacecraft performed an engine burn that brought it about 62 miles (100 kilometers) from the comet’s surface.

Comet 67P/C-G and Rosetta are now flying about 251 million miles (450 million kilometers) from Earth. Engineers on the ground had to program the probe to go through a series of complicated burns and maneuvers to make the spacecraft’s rendezvous with the comet a possibility.

“This is the end of 10 years of interplanetary flight,” Rosetta Flight Director Andrea Accomazzo said during ESA’s live comet rendezvous webcast Wednesday.

Applause broke out in Rosetta’s mission control center in Darmstadt, Germany, where a crowd of ESA dignitaries and officials had gathered to watch the historic event.

“We’re at the comet! Yes!” exclaimed Sylvain Lodiot, Rosetta’s spacecraft operations manager, once the probe’s successful arrival at Comet 67P/C-G was confirmed.
….

Rosetta is expected to stay in orbit around Comet 67P/C-G until the end of 2015. “We’re going to going to ride along with this comet. We’re going to have a ringside seat,” Matt Taylor, ESA Rosetta project scientist, said Wednesday as the spacecraft arrived at Comet 67P/C-G. “It’s going to be an awesome ride. Stay tuned.”

Link to entire article: http://www.space.com/26740-rosetta-spacecraft-comet-arrival.html