[X] My Assistant

[Decepticon]

Should be a good one. Less than 2 weeks away.

[Decepticon]

Update: From tedstryk Thred.

09/23/2005 15 Distant Flyby (altitude = 91,000 km; 57,000 mi) of moon Calypso
09/23/2005 15 Distant Flyby (altitude = 70,000 km; 43,000 mi) of moon Mimas
09/23/2005 15 Distant Flyby (altitude = 98,000 km; 61,000 mi) of moon Prometheus
09/24/2005 15 Close Flyby (altitude = 1,500 km; 900 mi) of moon Tethys
09/26/2005 15 Close Flyby (altitude = 500 km; 300 mi) of moon Hyperion

[volcanopele]

Update: From tedstryk Thred.

hmm, didn't know about the Prometheus and Mimas encounters...

[tedstryk]

I really hope that they take advantage of Mimas flyby if it will cover regions not covered in the last flyby and is almost as close. The Tethys coverage looks spectacular!

[jmknapp]

Regarding the map above showing the expected m/pixel for the Tethys flyby, the best resolution seems to be 100 m/pixel. At closest approach--1500 km--wouldn't the narrow angle camera give quite a bit better resolution than that? That is, 0.35 degree FOV would span about 9.2 km at that distance. Divide by 1024 pixels across yields about 9 m/pixel. Do they not use the narrow angle camera?

[volcanopele]

Regarding the map above showing the expected m/pixel for the Tethys flyby, the best resolution seems to be 100 m/pixel. At closest approach--1500 km--wouldn't the narrow angle camera give quite a bit better resolution than that? That is, 0.35 degree FOV would span about 9.2 km at that distance. Divide by 1024 pixels across yields about 9 m/pixel. Do they not use the narrow angle camera?

Often times, the highest resolution images are difficult to target properly, so we just tell it to point to Tethys (or Enceladus, or any other satellite), and start snapping away. Or another instrument is prime and we have an even tougher time targeting precise features. So rather than promise that a specific location will be seen at high resolution by showing it on a coverage map like this, we just leave those images out. I think in the case of Tethys,UVIS is pointed at beta Tau at C/A so we just snap images at regular intervals in hopes of getting a few of the surface, not unlike that high resolution shot of Enceladus from July.

The other problem is smear. Yes, at closest approach, we should expect to get 9 m/pixel images of Tethys. But Cassini will be wizzing by so fast, that those images are likely to be smeared to some degree. Summing the images on board Cassini (cutting the resolution down to a max 18 m/pixel) like we did at Enceladus (remember that high res shot was 512x512), really helps to reduce the effects of smear.

In terms of Mimas, we will get similar class encounters of Mimas throughout the mission, IIRC.

[jmknapp]

Often times, the highest resolution images are difficult to target properly, so we just tell it to point to Tethys (or Enceladus, or any other satellite), and start snapping away.  ...In terms of Mimas, we will get similar class encounters of Mimas throughout the mission, IIRC.

Thanks for that detailed answer. I guess it's hard to point a 0.35 deg camera. Much easier to point software! Also, maybe the lighting at this pass isn't ideal? Here's a movie of what the Mimas flyby ideally might look like, assuming a perfectly-pointed narrow-angle camera:



http://cboh-t.cboh.org/~jmk/mimas.mpg

Note: 7.7 MB MPG file