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Cassini and Holmes
- DeirdreKelleghan
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16 years 6 months ago #54305
by DeirdreKelleghan
Cassini and Holmes was created by DeirdreKelleghan
I got this from JPL this evening.
The answer to Dave Lillis question which I passed on to those concerned re Cassini taking a look at Holmes.
Nov. 6, 2007
First of all, quite a few of the project members have been following Comet 17P/Holmes, and are very excited about this unique astronomical event.
However, there are three principal difficulties with pointing Cassini's cameras at Comet 17P/Holmes. First, it is quite close to the Sun as seen from Cassini. We cannot point our cameras very close to the Sun or sunlight will damage the instruments. Comet 17P/Holmes may be far enough from the Sun to target it - just barely - in about a week, but stray light from the Sun may make it impossible to take any useful measurements.
Second, Cassini is about six times as far away from Comet 17P/Holmes as the Earth is. Remember, Saturn is nearly 10 times as far from the Sun as the Earth, and the comet is still in the inner solar system. Ground-based telescopes and orbiting platforms like Hubble are much closer than Cassini is, and generally more able to conduct better science.
Third, since our spacecraft carries twelve instruments with twenty-seven associated investigations, we must design and build our sequences many months in advance to plan the detailed and optimized measurements our scientists (and the public) deserve. In order to add a new observation days or weeks in advance, we must work very hard to rebuild a piece of a sequence and test it thoroughly to make sure we don't make a mistake. Also, we have very little idle time on board the spacecraft, so observations of 17P/Holmes would have to replace interesting observations of some other very fascinating body in Saturn's system - and those are the measurements Cassini was built to take. We almost never do this - outside of responding to an anomaly - and only for the very highest priority activities.
Having said all that, however, there actually are Cassini scientists that are looking into the feasibility of taking some observations of Comet 17P/Holmes. It really is a very interesting astronomical event, and Cassini carries an Ultraviolet Imaging Spectrograph which could make observations that Earth-based instruments could not (since Earth's atmosphere blocks nearly all of the UV part of the spectrum). Also, imaging the comet and its tails from a different perspective could also be scientifically useful (as well as pretty cool!).
These potential observations are in a very primitive stage, and would have to be justified against the interference in our existing sequences, the added workload they would cause, and any risks associated with pointing close to the sun. But stay tuned, and perhaps we'll have something to add to the excitement in the coming months.
So now wait and see
how interesting 
Deirdre Kelleghan
President
Irish Astronomical Society 1937 - 2007
Public Relations Officer IFAS
www.deirdrekelleghan.com/
homepage.eircom.net/~irishas/index.htm
www.irishastronomy.org/
The answer to Dave Lillis question which I passed on to those concerned re Cassini taking a look at Holmes.
Nov. 6, 2007
First of all, quite a few of the project members have been following Comet 17P/Holmes, and are very excited about this unique astronomical event.
However, there are three principal difficulties with pointing Cassini's cameras at Comet 17P/Holmes. First, it is quite close to the Sun as seen from Cassini. We cannot point our cameras very close to the Sun or sunlight will damage the instruments. Comet 17P/Holmes may be far enough from the Sun to target it - just barely - in about a week, but stray light from the Sun may make it impossible to take any useful measurements.
Second, Cassini is about six times as far away from Comet 17P/Holmes as the Earth is. Remember, Saturn is nearly 10 times as far from the Sun as the Earth, and the comet is still in the inner solar system. Ground-based telescopes and orbiting platforms like Hubble are much closer than Cassini is, and generally more able to conduct better science.
Third, since our spacecraft carries twelve instruments with twenty-seven associated investigations, we must design and build our sequences many months in advance to plan the detailed and optimized measurements our scientists (and the public) deserve. In order to add a new observation days or weeks in advance, we must work very hard to rebuild a piece of a sequence and test it thoroughly to make sure we don't make a mistake. Also, we have very little idle time on board the spacecraft, so observations of 17P/Holmes would have to replace interesting observations of some other very fascinating body in Saturn's system - and those are the measurements Cassini was built to take. We almost never do this - outside of responding to an anomaly - and only for the very highest priority activities.
Having said all that, however, there actually are Cassini scientists that are looking into the feasibility of taking some observations of Comet 17P/Holmes. It really is a very interesting astronomical event, and Cassini carries an Ultraviolet Imaging Spectrograph which could make observations that Earth-based instruments could not (since Earth's atmosphere blocks nearly all of the UV part of the spectrum). Also, imaging the comet and its tails from a different perspective could also be scientifically useful (as well as pretty cool!).
These potential observations are in a very primitive stage, and would have to be justified against the interference in our existing sequences, the added workload they would cause, and any risks associated with pointing close to the sun. But stay tuned, and perhaps we'll have something to add to the excitement in the coming months.
So now wait and see
how interesting Deirdre Kelleghan
President
Irish Astronomical Society 1937 - 2007
Public Relations Officer IFAS
www.deirdrekelleghan.com/
homepage.eircom.net/~irishas/index.htm
www.irishastronomy.org/
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- Keenan
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16 years 6 months ago #54306
by Keenan
Interesting indeed - thanks to the JPL for explaining the difficulties, and to you for passing on the response.
It's nice to know that they didn't just ignore the question or fob it off with a canned reply.
If we "watch this space" and they do produce something, I'm sure it'll be spectacular and if they don't, at least we know why.
Either way, my thanks to Deirdre/Dave and JPL.
Replied by Keenan on topic Re: Cassini and Holmes
I got this from JPL this evening...
So now wait and see
Deirdre Kelleghan
Interesting indeed - thanks to the JPL for explaining the difficulties, and to you for passing on the response.
It's nice to know that they didn't just ignore the question or fob it off with a canned reply.
If we "watch this space" and they do produce something, I'm sure it'll be spectacular and if they don't, at least we know why.
Either way, my thanks to Deirdre/Dave and JPL.
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- DeirdreKelleghan
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