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Posted by: cIclops Apr 9 2005, 08:20 PM

Real problems or more negative journalism?

http://www.newscientist.com/article.ns?id=dn7246

Posted by: TheChemist Apr 10 2005, 12:10 PM

Well, the article was calm and contained mainly quotes from the respective instrument scientists, so I don't think it falls under negative journalism.
Let's hope the rest of the instruments hold up, we ain't done exploring yet

Posted by: cIclops Apr 10 2005, 02:39 PM

Here is a slightly different official view as given by the Cassini status report for April 6:

http://www.nasa.gov/mission_pages/cassini/media/cassini-040605.html

Considering that Cassini hasn't finished the first year of its four year primary mission in Saturn orbit and with a quarter of its instruments not performing properly, it seems odd that Mitchell says: "Cassini has been working remarkably well considering the duration and complexity of the mission."

Posted by: BruceMoomaw Apr 10 2005, 02:51 PM

No, the reports are real -- and, as Mitchell said, given the extraordinary complexity of this mission, the sheer number of scientific instruments on it, and the fact that the thing has been flying for almost 8 years, this sprinkling of malfunctions is quite reasonable. (The very first science instrument malfunction on Cassini occurred just a few months after launch, when its Ka-band translator failed -- somewhat reducing the accuracy of its precision radio tracking for gravity-field measurements during flybys of the various moons, although the failure had little effect on its radio occultations for studies of atmospheres and ring structure).

Note that the problem with CIRS seems to be mostly a consequence of their unsuccessful attempts to utilize the failed motor in the MIMI experiment. Note also that -- as always with spacecraft -- when a part breaks, it's usually a moving part.

Posted by: Jeff7 Apr 10 2005, 02:54 PM

Well they have called Cassini the largest, most complicated probe ever sent to another planet. And they even sacrificed some of the extra features, like booms for the instruments - instead, they're fixed to the probe's main body.

7 years just to get there....quite a trip. And add a particularly active solar flare season to that.
I was a bit surprised though that they used the main antenna as a shield while going through the rings. It just didn't seem like a good thing to do - kind of useless to have a lot of data stored in a craft orbiting Saturn, unable to make the trip to Earth.
I just wonder if the antenna did a good enough job? The lens on the narrow angle camera has acquired a good bit of dust too.

Posted by: remcook Apr 11 2005, 08:36 AM

The CIRS problem exists at least since SOI and has gotten worse with time. But hopefully it can be fixed. They're now in the progress of analysing the cause more in depth.

Posted by: MahFL Apr 11 2005, 03:40 PM

"I was a bit surprised though that they used the main antenna as a shield while going through the rings."

I believe the main antenna was designed to act as a shield as well as an antenna.

Posted by: alan Apr 11 2005, 06:27 PM

Could that be why the instruments are fixed to the body of the spacecraft instead of being on a boom, so they are easier to protect when Cassini passes throught the E-ring?

Posted by: Gsnorgathon Apr 11 2005, 08:47 PM

Cassini's lack of a steerable instrument platform is strictly budgetary. I wish I didn't know that Cassini was originally intended to have one; every time I think of the fact that radar and the other instruments can't be pointed at the same target I get this feeling that ranges from steamed to just bummed.

With an instrument platform, there wouldn't be any of this nonsense about having to wait for overlapping radar and image swaths. You'd just get them both in one go.

Posted by: cIclops Apr 11 2005, 09:42 PM

Yep. The same could be said of the long trajectory with its two Venus and one Earth gravity assists which extended the mission duration considerably and contributed to the current problems with three instruments.