Rev 16 - Oct 2-21, 2005 - Telesto, Tethys, Dione D1, Dione-Telesto-Enceladus Options

[jmknapp]

How bright is Saturn-shine, compared to the normal sunshine?

How good of a picture can they get of the shadowed side under a full Saturn?

[tedstryk]

Ah, you're right. Just checked, Voyagers' digital tape recorders have a 500 megabit capacity...

I remember reading somewhere that it could hold thirty-something images.

[Guest_BruceMoomaw_*]

More like 100 images per recorder (or a little more; I'd have to recheck, but it's definitely over 100 each).

[Guest_BruceMoomaw_*]

Oh, excuse me; I thought you were referring to CASSINI'S recorders. Voyager's, I don't know about.

[tedstryk]

Does anyone know if the NT of Enceladus will be used? If it covers any "new" territory, it seems like a great opportunity. Also, repeat coverage for Enceladus is much more important than for a moon like Iapetus, since change detection is a priority.

[ugordan]

Does anyone know if the NT of Enceladus will be used?  If it covers any "new" territory, it seems like a great opportunity.  Also, repeat coverage for Enceladus is much more important than for a moon like Iapetus, since change detection is a priority.

Earlier in the thread I said:
"While Cassini will make a fairly close non-targeted approach to Enceladus, from the recently released Dione flyby description I figure there aren't any Enceladus observations programmed. Instead, the spacecraft will be engaged in a rather lengthy data downlink session at the time of C/A to Enceladus."

From 42 000 km, 74 deg phase, there is an opportunity for some pretty good ISS NA coverage, perhaps a 4x4 mosaic, but as I said, I don't believe any actual observations are planned...

[ugordan]

Oh, excuse me; I thought you were referring to CASSINI'S recorders.  Voyager's, I don't know about.

Well, if the figure for the 500 megabit (around 64 megabytes) Voyager recorder is true, IIRC the resolution of the Voyager ISS cameras is about 800x800 so that's about 640 kb per image. That would indeed turn out to be around 100 images max -- the advantage that Voyagers had over Cassini is that they could downlink new images in real time (at least during Jupiter and Saturn encounters) so the storage limit probably wasn't that big of an issue as is with Cassini.

[tedstryk]

Data Storage Subsystem
----------------------
The Digital Tape Recorder (DTR) was used to store data when
real-time communications with Earth were either not possible
or not scheduled. The DTR recorded data on eight tracks;
rates were 115.2 kilobits per second (record only), 21.6
kilobits per second (playback only), and 7.2 kilobits per
second (record and playback). Capacity of each track was 12
images or equivalent.

My original figure was based on the Uranus encounter. I forgot that this was shared with the other instruments.

[JRehling]

How bright is Saturn-shine, compared to the normal sunshine?

How good of a picture can they get of the shadowed side under a full Saturn?

It depends on which moon, and which phase Saturn is in from the moon's perspective. To answer this question without doing any math, I can tell you that they got very good saturnshine images of Iapetus, so have no fears about Dione, which receives orders of magnitude more saturnshine. The downside is that closer moons mean higher relative velocity, and thus shorter exposure times, but the added luminance will surely make up for that. We should get great images.

[Decepticon]

I really want the scan platform now.

Out of all the things to cut from the final design.

[ugordan]

I really want the scan platform now.

Out of all the things to cut from the final design.

Look at the bright side, instrument pointing turned out to be more accurate and steady (Dr. Carolyn Porco described the spacecraft as a "tripod in space" ) this way than it would have been with a scan platform. I don't miss the scan platform that much though it would have been nice to have a real-time downlink capability on Cassini instead of the 15 hr observation/9 hr downlink scheme...

Plus, it's one thing less to worry about getting stuck...

[Decepticon]

New pics In!



http://saturn1.jpl.nasa.gov/multimedia/ima...?browseLatest=1

[Decepticon]

I have NO WORDS!

[Decepticon]

Ahh here we go. http://saturn.jpl.nasa.gov/multimedia/imag...heQ=0&storedQ=0

[alan]

Telesto
http://saturn1.jpl.nasa.gov/multimedia/ima...5/N00041281.jpg