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View Full Version : Cassini and the minor moons of Saturn



M_Welander
2004-Nov-05, 06:01 PM
I and probably many with me have already marked the dates when Cassini will encounter the larger satellites of Saturn. But I have been unable to find any official information from NASA concerning encounters with the minor moons.

Using NAIF's SPICE I've written a small program that calculates the times of the closest approach between Cassini and the minor moons of Saturn. It also calculates approximately how large the moon will look in the narrow angle camera at that time. At the moment, the program incorrectly assumes that all bodies are spherical, and it does not calculate the phase angle.

This means the numbers calculated are only approximations, and should be taken with a grain of salt. I have, however, used the program to calculate past far encounters with some of the larger moons, and the results I get seem to match images from the narrow angle camera within a few pixels.

A few examples of encounters that seem interesting to me:


2004-12-15 100 px Epimetheus
2004-12-15 50 px Pandora
2004-12-16 110 px Prometheus
2005-01-16 90 px Janus
2005-02-16 150 px Pandora
2005-03-09 70 px Helene
2005-03-30 50 px Telesto
2005-04-14 100 px Pan
2005-04-15 50 px Calypso
2005-04-15 460 px Epimetheus
2005-06-08 60 px Atlas
2005-06-10 270 px Hyperion
2005-07-14 190 px Janus
2005-08-02 200 px Prometheus
2005-09-05 150 px Atlas
2005-09-05 450 px Pandora
2005-09-23 60 px Calypso
2005-10-11 370 px Telesto
2007-06-12 370 px Prometheus
2007-07-20 190 px Helene
2007-12-03 3200 px Epimetheus
2008-02-20 290 px Janus


The reason I'm posting here is twofold:

First, although I'm fairly sure the program works for the larger moons, I'm not exactly 100% certain it will work for future encounters with the minor moons. If it doesn't, it's a rather pointless piece of code. That is why I'd like to ask if anyone here has access to official information on one or more of these encounters, that I could use to verify that the program really does work?

Second, assuming my calculations are in fact reasonably correct, I have noticed that several of the "close" encounters with the minor moons happen very close in time to important encounters with the larger moons. This leads me to believe the Cassini team will focus on the larger moon, and taking no images of the smaller. I'd like to know if anyone here can confirm this, and if possible expand on NASA's strategy for Cassini and the minor moons?

Evan
2004-Nov-05, 06:12 PM
I don't expect they will bother taking pictures of anything unless the image is large enough in pixles to resolve at least the largest possible features to a useful level of detail. They like to keep the manouvering to a minimum.

M_Welander
2004-Nov-05, 06:32 PM
Yeah, that's why I only included encounters that are significantly larger than what we've seen in previous images.

Evan
2004-Nov-05, 07:13 PM
I also read that the imaging team temp data storage budget on the craft is pretty seriously constrained. They will be saving it for the most important shots.

It's hard to keep in mind the Cassini technology is a decade old.

M_Welander
2004-Nov-05, 07:22 PM
Yes, but does anyone actually know the strategy for one or more of these encounters? Does anyone know if they even exist or are simply miscalculated by me?