HomeFirst look at the MARSIS radar data for Phobos
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.
Andrea Cicchetti
For the MARSIS Team
08-06-2010 • 16:36:27
Just wanted to express interest in any data on the Phobos flyby. This is some of the most interesting objects in our solar system.
07-05-2010 • 21:10:09
There appear to be grooves on the surface of Phobos. What natural force would cause these grooves to appear?
28-04-2010 • 17:42:27
I am wondering if this question has been resolved for anyone in the Express team's satisfaction? What is the prevailing opinion in the team?
Has anyone considered whether electric discharges between Phobos and Mars via the plasma torus would have established a pattern of reflectivities and non-reflectivities on the surface of Phobos that would help to explain the echo patterns?
Thanks.
--Joseph
08-04-2010 • 23:08:57
Hello Andrea, I worked during my thesis on the MARSIS radar at the InfoCom Department in Rome with Professor Picardi and in particular I was involved in adaptation to broadband matching network circuits between the transmitter and antenna. I have proposed solutions with active circuits much appreciated by Prof. Picardi. But once I graduated I followed the path of mobile telecommunications. The passion for remote sensing is still in me. Regards Roberto Lonoce
24-03-2010 • 23:37:47
So, how are you anticipating getting internal structure out of the signal. Is is straight time-of-flight, or would the profile of the reflected peak differ from the transmitted peak, giving (possibly) surface reflection, internal reflections, and even a back-side reflection?
25-03-2010 • 10:36:44
The main peak that you see is generated by Phobos’s surface reflection of the transmitted pulses. Actually we are improving the performance of the on ground processing of the data in order to better classify the secondary reflections that could have been generated by surface clutter.
24-03-2010 • 18:09:30
I find it intruiging that the ESA phobos blog team have chosen to use the wording "structure" as apposed to natural formations , structure would suggest either biological or artificial creation.
are ESA seriously suggesting the possibility that the phobos moon has artifical structures inside ?
24-03-2010 • 16:46:24
Where are the radar images?
25-03-2010 • 10:58:55
In order to generate radar images useful to the community it is necessary to reconstruct the radar observation geometry for each single collected echo. This is a very difficult task, it takes a lot of time and efforts. However we hope to be able to distribute a light version of the first images as soon as possible.
Thank you for your interest
24-03-2010 • 14:52:29
Its interesting that the ESA phobos blog team have chosen to use the word structure , since strucure really only applies to biological or artifical arrangement of materials to create an object! The current theories on the creation of Phobs are either , coalescence of space debris during the formation of mars , or collision ejecta from mars , then surely the moon would have internal geological formations not structures!
Why have ESA chosen to use the word structure here , are you hinting at something artificial ??
25-03-2010 • 12:10:39
We didn’t mean to any Phobos formation theory. With a radar like MARSIS, it is possible to detect eventually internal geological structures( layers, …). We wish that further studies on the obtained results will contribute on the Phobos science investigation.
Thanks Andrea
24-03-2010 • 01:37:29
Andrea Cicchetti of the MARSIS radar team.
"375 micro seconds of radar reflections in a graph (decibels vs. microseconds) from an 240 km approach on March 7th, 2010 of Phobos with a radar signal frequency at 4 mega hertz.
Was this a scan moving across Phobos or centered on Phobos during the approach?
Where are the data for the rest of the echos?
What does the one brief, large amplitude on the graph mean?
One (sub-surface) layer or one crater ridge encountered?
The MARSIS team's preliminary analysis seems very crude, having now switched the radar scanning from Mars to Phobos.
When will the other Phobos data be released? When will the Mars radar data be released? Please post a link on the internet.
Larry H., layman in America."
25-03-2010 • 16:50:54
The large amplitude on the graph is the surface signature of Phobos. Regarding the SC pointing attitude, the +Z axes of MEX was pointed toward the centre of Phobos with a certain drift that I am unable to quantify.
The MARSIS data, both on Phobos and Mars will be available ASAP through the ESA official archive. Just to point it out that the main MARSIS’s target remains Mars where the radar is routinely collecting science data. The Phobos flyby season occurs about every six months when the Phobos trajectory encounters the MEX’s orbit with a reasonable distance (below 400 Km for the radar). All the on-ground software have been designed for the Mars data processing. However thanks to the efforts of the MARSIS team it has been possible to, partially, re-configure the SW’s algorithms for the Phobos processing, that is till on going.
Thanks
Andrea
23-03-2010 • 21:35:31
where are the pictures of Phobos ? Why is it thaking so long?
23-03-2010 • 21:21:11
Is there an image generated by this instrument?
23-03-2010 • 20:51:38
Where are the radar images and the rest of the Phobos images for that reason?
Why is everything taking so long?
23-03-2010 • 09:53:51
375 micro seconds of radar reflections in a graph (decibels vs. microseconds) from an 240 km approach on March 7th, 2010 of Phobos with a radar signal frequency at 4 mega hertz.
Was this a scan moving across Phobos or centered on Phobos during the approach?
Where are the data for the rest of the echos?
What does the one brief, large amplitude on the graph mean?
One (sub-surface) layer or one crater ridge encountered?
The MARSIS team's preliminary analysis seems very crude, having now switched the radar scanning from Mars to Phobos.
When will the other Phobos data be released? When will the Mars radar data be released? Please post a link on the internet.
Larry H., layman in America.