I have just received the following information from Andrea Cicchetti of the MARSIS radar team. Congratulations to all of those involved; I look forward to the full analysis. -- Stuart
MARSIS, the radar aboard the Mars Express orbiter, has successfully observed Phobos again. MARSIS is a multi-frequency, synthetic aperture, orbital sounding radar that operates in the range 1.3-5.5 MHz with a 1 MHz bandwidth.
The closest flyby in which MARSIS operated during this fruitful Phobos season took place on March 7th 2010, during the 7915th orbit of Mars Express, when the orbiter reached a minimum distance from the surface of Phobos of about 112 km. For instrument safety reasons, the radar software blocks operations when the target is closer than 240 km. Therefore the team had to devise a new set-up of the main navigation parameters, allowing them to reduce the minimum operational distance down to 175 km, while maintaining a high level of safety for the instrument’s hardware.
During this flyby, MARSIS successfully collected 6478 echoes from Phobos in just 72 seconds. The carrier frequency was centred at 4.0 MHz with a 1 MHz bandwidth. Taking advantage of the instrument’s internal mass-memory facility, it was possible to store and then downlink the raw unprocessed echoes.
Credit: ESA and MARSIS team.
After the ground-processing of science data, it was found that the radar worked successfully during the flyby. The figure above shows echoes reflected by Phobos as the highest peak in the signal, clearly above the noise level. Scientific analysis of the results is still ongoing. The main quest is the determination of the origin of detected echoes: are they reflections from various surface features of Phobos, or have they been produced by the internal structure of the moon?
The MARSIS radar was originally designed solely for the observation of Mars. However, thanks to the Italian operations team, working in collaboration with the international instrument science team, it was possible to re-configure it to allow the observation of Mars’ moon Phobos, a unique target, thereby expanding the scientific capabilities of the mission.
In the first phase of the data analysis, the main goal was to validate a new operative configuration of the onboard software and hardware. The scientific analysis of existing and future data will provide us with new and unique insights on the nature of Phobos’ interior.
For the MARSIS Team