[X] My Assistant

[Decepticon]

Another flyby coming soon. Interesting observations include radar swath of Huygens landing site.

Just before CA. http://space.jpl.nasa.gov/cgi-bin/wspace?t...porbs=1&brite=1

From above... http://space.jpl.nasa.gov/cgi-bin/wspace?t...porbs=1&brite=1

I really missed VP encounter updates So I tried my best at showing the Hemisphere to be imaged during the flyby.

[RPascal]

One of the most exciting questions for me is, if the radar swath data will result in a definite decision how the Huygens mosaic and Cassini ISS/VIMS correlate.
Some month ago I tried to find this correlation, with the result that I felt I had to introduce a relatively large calibration mismatch to find a good visual agreement of Huygens and ISS. But now it has come to my knowledge that Huygens radar, as well as radar tracking of Huygens from earth, seems to be in good agreement with the timer height calibration, so it looks as I have to give up this idea.
http://www.beugungsbild.de/huygens/ISS_huy...correlate3.html

Does anybody know what radar resolution is expected at the Huygens landing site?
Will ISS also obtain some high resolution images?

--René

[ugordan]

Does anybody know what radar resolution is expected at the Huygens landing site?
Will ISS also obtain some high resolution images?

My uneducated guess would be that radar data won't have a very high resolution. If jmknapp's image is correct (I can't play the movie right now so I'm not sure about changing geometry during the encounter), Cassini's sub-spacecraft point is close to the Huygens' landing site at 4800 km so that's bound to move away from the site near C/A. That would make the radar illumination angle very oblique so data quality could be degraded. That said, the resolution might still beat ISS resolution and it sure wouldn't hurt to have even a low res pass over the landing site.
As far as ISS coverage is concerned, I notice that the solar phase angle is not optimal for imaging -- the landing site is fairly close to the terminator so the contrast would be degraded. They probably won't do very high resolution mosaics on this pass. At least over the Huygens site.

Just my 2c...

[JRehling]

My uneducated guess would be that radar data won't have a very high resolution. If jmknapp's image is correct (I can't play the movie right now so I'm not sure about changing geometry during the encounter), Cassini's sub-spacecraft point is close to the Huygens' landing site at 4800 km so that's bound to move away from the site near C/A. That would make the radar illumination angle very oblique so data quality could be degraded.
Just my 2c...

At C/A, not only will the angle be oblique, but the Huygens site will not be at *ITS* C/A. Remember that Titan's radius is a significant fraction of the distance here, and C/A is the time when Cassini is closest to Titan -- but only at one point! The time when Cassini is closest to the Huygens site will be earlier, so viewing the Huygens site at "proper" C/A would not only give you worse coverage of the Huygens site, but also miss out on coverage of the subspacecraft point at proper C/A.

Radar pixel size drops off inverse with distance while radar illumination drops off to the inverse fourth power of distance. I suspect we'll take whatever imagining of the Cassini site we can get, and if it identifies anything at all it could still help with registering Cassini/Huygens imagery.

[ljk4-1]

At C/A, not only will the angle be oblique, but the Huygens site will not be at *ITS* C/A. Remember that Titan's radius is a significant fraction of the distance here, and C/A is the time when Cassini is closest to Titan -- but only at one point! The time when Cassini is closest to the Huygens site will be earlier, so viewing the Huygens site at "proper" C/A would not only give you worse coverage of the Huygens site, but also miss out on coverage of the subspacecraft point at proper C/A.

Radar pixel size drops off inverse with distance while radar illumination drops off to the inverse fourth power of distance. I suspect we'll take whatever imagining of the Cassini site we can get, and if it identifies anything at all it could still help with registering Cassini/Huygens imagery.

Is there any evidence of surface movement on Titan? I wonder if Huygens will "drift" during Cassini's lifetime?