Monday, November 17, 2014

ESA Rosetta mission: Philae lander OSIRIS NAC Camera captures landing data

This collection of images was acquired when Rosetta was about 15km above the surface of 67P

High-resolution pictures have now been released of the Philae probe in the act of landing on Comet 67P last Wednesday.

They were acquired by the OSIRIS Narrow Angle Camera (NAC) on the Rosetta satellite, which had dropped the little robot towards the surface of the "ice mountain".

The images are presented as a mosaic covering the half-hour or so around the "first touchdown," the probe then bounced to a stop about 1km away.

Philae lost battery power on Saturday and is no longer talking with Earth.

Scientists still have not located the craft's current resting spot.

But European Space Agency (ESA) controllers have not given up hope of hearing from the plucky robot again, if it can somehow get enough light on to its solar panels to recharge its systems.

Getting a precise fix on its location, to then photograph its present predicament would provide a better idea of whether this is likely to happen.

The new NAC images will certainly help in this respect because they show the direction the lander took as it bounced away.

At the weekend, ESA presented some fascinating views of the first touchdown taken by Rosetta's navigation cameras, but the OSIRIS NAC system has substantially better resolution.

It's a trap
The new mosaic is produced by the Max Planck Institute for Solar System Research, which operates Osiris.

It details Philae's descent, and the impact mark it leaves on 67P's surface. You then see the 100kg probe heading away on its initial bounce.

NB: All times are in GMT on Wednesday. The resolution is 28 cm/pixel.

This rebound reached hundreds of metres above the comet and lasted almost two hours.

When Philae came back down, it made another small leap, which took it into a high-walled trap.

Telemetry and pictures from the robot itself indicate this location is covered in deep shadow for most of 67P's day.

As a consequence, Philae receives insufficient solar power to re-boot and form a radio link to the orbiting Rosetta spacecraft.

ESA cannot be sure the robot will ever come back to life, but even if it does not the agency says it is "hugely happy" with what was achieved in the more than 50 hours following landing.

The probe managed to complete over 80% of its planned primary science campaign on the surface.

'Rock' hard
This data was pulled off the robot just before its sagging energy reserves dropped it into sleep mode.

Little of the results have so far been released by the various instrument teams. The one major exception is MUPUS.

This sensor package from DLR the German space agency's Institute for Planetary Research deployed a thermometer on the end of a hammer.

It retrieved a number of temperature profiles but broke as it tried to burrow its way into the comet's subsurface.

Scientists say this shows the icy material underlying 67P's dust covering to be far harder than anyone anticipated - having the tensile strength of some rocks.

It also helps explain why Philae bounced so high on that first touchdown.

The 4km-wide comet has little gravity, so when key landing systems designed to hold the robot down failed at the crucial moment, the probe would have been relying on thick, soft, compressive layers to absorb its impact.

However much dust it did encounter at that moment, it clearly was not enough to prevent Philae making its giant rebound.

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