Radar Sounding of Phobos by MARSIS
Abstract
We report preliminary results from the first observations of Phobos ever performed by an orbiting radar sounder. The MARSIS experiment on board ESA's Mars Express is a synthetic-aperture, orbital sounding radar that works by transmitting a low-frequency radar pulse that is capable of penetrating below the surface of a planetary body, and is reflected by any dielectric discontinuity present in the subsurface. MARSIS is optimized for deep penetration, having detected echoes down to a depth of 3.7 km over the South Polar Layered Deposits, and is capable of transmitting at four different bands between 1.3 MHz and 5.5 MHz, with a 1 MHz bandwidth. MARSIS has observed Phobos in the course of nine flybys so far. The latest flyby took place on July 28, 2008, when Mars Express reached a distance of only 96 km from Phobos. During these flybys MARSIS successfully collected several thousand echoes. Planning and commanding observations for these flybys was potentially risky for the instrument, and required the development of a special operation mode, including the storage of the unprocessed echoes in the internal mass memory. MARSIS successfully detected echoes from the surface of Phobos, and subsequent echoes that could be either coming from surface features away from nadir or be real subsurface features. The nature of secondary echoes will be analyzed, and implications for the internal structure of Phobos will be discussed. Results from these observations will have a profound impact on current space mission studies in which radar sounders are proposed to probe the interior of asteroids, such as in NASA's Deep Interior and in ESA's ISHTAR.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.P42A..06C
- Keywords:
-
- 6230 Martian satellites;
- 6964 Radio wave propagation;
- 6969 Remote sensing;
- 6974 Signal processing (0674)