Applied
Geophysics
  Planet Formation   Space Physics &
Space Sensorics
   
         figure: ESA

Rosetta at the comet

Since August, 6 2014 Rosetta is in orbit around the comet 67P/Churyumov-Gerasimenko. On the November, 12 the Rosetta mission reached one of its highlights when the lander Philae was separated from the orbiter to land on the comet's surface. Both the magnetometer on board the orbiter (RPC-Mag) as well as the magnetometer on board the lander (ROMAP) recorded the different events on this day.

Separation of the Philae


PRC-MAG confirms separation
ROMAP confirms separation

The separation of the lander left a clear signature in the magnetic field data at 08:35 UTC recorded by the orbiter magnetometer. The lander creates his own magnetic field which is superimposed on the background magnetic field. As this influence disappears after separation it can be seen as a clear jump in the data. In the same way the lander magnetometer is also influenced by the orbiter's presence and a similar jump can be seen in the magnetic field data obtained by the lander instrument.

Boom deployment


ROMAP deployment

The instrument ROMAP (Rosetta Lander Magnetometer and Plasma Monitor) is located at the end of a boom. During the journey to the comet the boom was retracted to the lander body. After separation this boom deployed and the magnetometer changed its position relative to Philae's body. This was recorded and confirmed by the magnetometer at 08:56 UTC.

Landing on the surface of the comet


Landungen
EMD der Landungen

After seven hours of decent Philae arrived at the desired landing site at 15:34 UTC. There the lander rebounced and floated above the comet's surface for another two hours. The comet's gravity pulled Philae back to the ground and the lander touched the surface for the second time at 17:25. Once again it bounced back into space and stayed on the ground after the third landing at 17:31. With each ground contact the landing gear of Philae was moving while adapting to the ground. These movements have been detected by ROMAP and every single touchdown left specific signatures in the data (left figure).

With the help of appropriate analyses methods the measured events can be seen more clearly in the data. In the right figure the second and third touchdown are shown after a method called EMD (Empirical Mode Decomposition) was applied to the data. The EMD is a numerical procedure to find and separate the intrinsic modes of a time series.

 
updated: 01/08/2015 IMPRESSUM webmaster responsible: Prof. Dr. K.-H. Glaßmeier