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Comet observation from Mars, comets close encounters to Mars in 2013 and 2014
MaG
post Feb 25 2013, 10:07 PM
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Is there is any possibility to observe comets in near future from surface of Mars and/or from Mars orbiters. Which types of instruments are possible to use?

For example (http://ssd.jpl.nasa.gov/horizons.cgi - position Mars 0deg Longitude, 5deg south Latitude, time UTC):
1) Comet C/2012 S1 (ISON)
2013-Oct-01 17:19UTC RA 23 07 44.73 DE +69 27 46.0 MAG 2.93 r 1.637007919902 delta 0.07246306543080

So there is relativly very close encounter in October 2013, about 11 million km from Mars..

2) Comet C/2013 A1 (Sidding Spring)
2014-Oct-19 20:59UTC RA 10 49 50.64 DE -60 38 09.5 MAG -8.29 r 1.401218071277 delta 0.00070643344409

There is still maybe not so precise orbit BUT, there is ONLY about 105 000 km (65 000 miles) encounter from Mars.
Especially the second comet, if this orbit will be OK, is very interesting target to observe.


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CAP-Team
post Feb 27 2013, 08:44 PM
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The sight from mars on C/2013 A1 should be spectacular! I tried to simulate it with Celestia, its appearance in the sky should be huge!
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mcaplinger
post Feb 27 2013, 09:01 PM
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QUOTE (MaG @ Feb 25 2013, 03:07 PM) *
I can ask only, if there is any possibility to observe comets in near future from surface of Mars...

I think it's a safe bet that any extremely bright comet will get imaged. Dimmer objects will likely not be visible and at some brightness the attempt probably won't be made.


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Hungry4info
post Feb 27 2013, 09:31 PM
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Update.

"Today, at the ISON-NM observatory, new astrometric measurements were received for this comet. Based on the existing measurements, more accurate orbital elements were calculated. The results of the second calculation for the close approach show that the comet might pass just 41,000 km (0.000276 a.u.) from the planetís centre, that is less than 37,000 km from its surface!"


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mcaplinger
post Feb 27 2013, 09:38 PM
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QUOTE (Hungry4info @ Feb 27 2013, 02:31 PM) *

From that site:
QUOTE
Having a very tenuous atmosphere, the surface of the red planet will be subject to intensive bombardments by microparticles which, among other things, might cause malfunction of the space probes currently there.

I'm thinking this is unlikely to be a threat to the rovers and probably not to orbiters either.


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SFJCody
post Feb 28 2013, 12:59 AM
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QUOTE (Hungry4info @ Feb 28 2013, 07:31 AM) *
"Today, at the ISON-NM observatory, new astrometric measurements were received for this comet. Based on the existing measurements, more accurate orbital elements were calculated. The results of the second calculation for the close approach show that the comet might pass just 41,000 km (0.000276 a.u.) from the planetís centre, that is less than 37,000 km from its surface!"


Less than the apoapsis for India's Mars Orbiter Mission (80,000km).
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machi
post Feb 28 2013, 02:05 AM
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I'm still missing more excitement about this. smile.gif
If flyby distance will be really around ~50 000 kilometers, than this event is comparable to the encounter of Halley comet with so called Halley armada.
We can have up to five orbiters with superior instruments which can probe Hale Bopp class cometary nucleus with cameras and spectrometers in multiple wavelengths.
Some orbiters (MEx, MAVEN, Mangalyaan) have instruments for direct examination of atoms, ions and another particles.
We have flyby worth of one billion dollars for free! tongue.gif


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nprev
post Feb 28 2013, 02:56 AM
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Thing is, none of the orbiters have been designed for a comet encounter. I'm a little worried about sandblasting, but also wondering how much ACS fuel expenditure would be needed to do a good job of observation; every burn shortens their operational lifetimes, and this thing will be really moving at closest approach.

I dunno; as the oldest orbiter, might be a good job for MODY. MRO could do something amazing, no question, but doubt that the mission's management would go for more than a set or two of obs, if that.

All that said: Yeah, I'm actually pretty pumped!!! smile.gif


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machi
post Feb 28 2013, 03:22 AM
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QUOTE
Thing is, none of the orbiters have been designed for a comet encounter.


Yes, it will not be easy. But I think that all teams, which have spacecrafts around Mars, are very experienced and they will handle it.
BTW, It's even more fantastic. It can be our first close observation of long period comet visiting us directly from Oort cloud!


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Explorer1
post Feb 28 2013, 05:18 AM
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How long is MAVEN's commissioning phase anyway? Hopefully a month is long enough to get ready and calibrated.

This whole thing reminds me of Shoemaker-Levy and Galileo all over again, but multiplied many times; including ISON it's less than one Mars year between two close comet encounters; looks like these sorts of coincidences aren't limited to Earth...
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nprev
post Feb 28 2013, 05:25 AM
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Meh. The wonder of statistics (which are tedious to compute, but always quite fascinating to grasp).


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mcaplinger
post Feb 28 2013, 05:33 AM
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QUOTE (nprev @ Feb 27 2013, 07:56 PM) *
also wondering how much ACS fuel expenditure would be needed to do a good job of observation; every burn shortens their operational lifetimes, and this thing will be really moving at closest approach.

Both cameras with any resolution on MRO are linescan anyway, so the target moving is a feature, not a bug. It may only be necessary to repoint the s/c, which can be done on the reaction wheels with very little fuel usage. Even if scanning is needed, the wheels can likely do it. A more substantive problem is that the resolution isn't that great -- 125x worse than what we get on Mars (750 meters/pixel for CTX, around 40 m/pxl for HiRISE.)

That said, this is still more than 1.5 years away and the ephemeris and even the size of the comet are uncertain, so detailed planning is premature.


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fredk
post Feb 28 2013, 04:31 PM
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We've made (and survived) many comet encounters with several spacecraft, at distances of several hundred km down to a couple hundred km (Deep Impact, Stardust, etc). Those were smaller comets, but Giotto survived the Halley encounter at about 600 km. Of course those missions were designed for comet encounters, not for Mars orbit.

My guess, based on flux conservation, is that the density of particles in the coma drops like roughly the inverse square of the distance from the coma nucleus. So even if C/2013 A1 turns out to be Halley class, at a distance of 40 000 km, the density of particles would be thousands of times lower than what Giotto experienced. The latest ephemeris gives 7th magnitude at its brightest from earth, so that sounds like it isn't Halley class, which means the particle density would be even lower. On the other hand, the encounter velocity will be considerably higher for C/2013 A1 than for previous comet encounters, so any dust hits would have a greater impact.

Of course this is still early days, and brightness estimates will be improved. Most crucially, as mcaplinger said, orbital elements will be improved. The big question now is what is the uncertainty in the close-approach Mars distance? The blog quoted above stated that the comet "might pass just 41,000 km... from the planetís centre". Is that a lower limit? What's the upper limit? That would give us a better sense of what the Mars close-approach distance will be.

Anyway, based on these numbers, I'd expect no real concern for the orbiters, and even less for the rovers.

And I too can't wait for this encounter!
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tasp
post Feb 28 2013, 05:34 PM
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Looking forward to those Kodak moment pictures this site is famous for!! Even Hubble might snap some compelling images during the passage?

Maybe too much to hope for but possibly there is some fragmentation close to the sun to make an even better show at Mars.
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Explorer1
post Feb 28 2013, 06:27 PM
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And for those wondering about an impact, remember: Mars is an even smaller target than Earth, in a very large solar system!
I expect this to go rather like it did with Apophis; the probability of a collision will go up as predictions get more refined, and than it will drop when the error ellipse no longer includes the planet. See here: http://en.wikipedia.org/wiki/File:Apophis_ellipse.svg

In other words, the news might get worse (for Mars's health) before it gets better. Merely passing through the coma/tail seems far more likely.
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