Leonard David's INSIDE OUTER SPACE

The Philae lander would only be a few pixels across in images acquired by the Rosetta orbiter’s Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS). Most candidates fail after more detailed study. From these images, only the data acquired by OSIRIS in this image reveals a promising candidate.
Credit: ESA/Rosetta/NAVCAM; ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

For months, there has been a dedicated search for a three-legged lander dropped off by ESA’s Rosetta spacecraft – now circling the comet 67P/Churyumov-Gerasimenko.

There are now some candidate images that could reveal Philae’s whereabouts.

Complex search

On November 12, 2014, the European Space Agency’s Philae lander “hopped” roughly one kilometer away from its planned landing site.

Philae’s harpoons designed to anchor the probe to the comet failed to fire and the ice screws in its feet were unable to secure the lander to the surface.

That search is complex because even when fully illuminated by the Sun, Philae will be just a few pixels across in images acquired by the Rosetta orbiter’s Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS).

This series of 19 images, acquired by the Rosetta orbiter’s Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) on 12 November 2014, shows the Philae lander during its descent towards Comet 67P/Churyumov-Gerasimenko.
Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Possibility of contact

“The possibility of contact [with Philae} is improving as the comet moves closer to the Sun, and the chances of Philae receiving sufficient heat and energy are increasing,” explains Project Leader Stephan Ulamec from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR).

Philae’s exact location could be determined when the lander wakes up from hibernation and provides further scientific data.

To do so, the lander needs to generate at least five watts of power and have an operating temperature above minus 45 degrees Celsius. Given those power and temperature requirements, the lander would switch itself into operating mode.

Slightly more energy – a total of 19 watts – is needed to communicate with the DLR team here on Earth.

Active comet

For the communications unit on board the Rosetta orbiter to be able to transmit the status of Philae, the orbiter’s flight path must allow it to “see” the lander.

Currently, the Rosetta orbiter is flying about 200 kilometers above the comet.

Since 67P/Churyumov-Gerasimenko is now always active and is ejecting gas and dust into space, the flight plan for Rosetta has become even more challenging.

“In recent weeks, the team at the DLR Lander Control Center has been preparing for the operation of Philae and its instruments…now we hope that it will get in touch with us,” says DLR’s Ulamec.

Credit: DLR

Rosetta is an ESA mission with contributions from its Member States and NASA.

Rosetta’s Philae lander is funded by a consortium headed by DLR, the Max Planck Institute for Solar System Research (MPS), CNES and the Italian Space Agency (ASI).