Mars Comet Encounter Observations, C/2013 A1 Siding Spring, 19 Oct 2014 Options

[walfy]

News release from NASA mentions this possible future observation for the rovers:

"...Rover cameras may be used to observe the comet [Siding Spring] before the flyby, and to monitor the atmosphere for meteors while the comet's dust trail is closest to the planet..."

What are the chances that Deimos or Phobos could get in the shot along with the comet? That would be extraordinarily cool!

[James Sorenson]

Here is at leased one Opportunity. This one is at 4:06:27 UTC Local Mars Time. on Oct 19. I'm sure there are probably many more opportunity's as well. I'm sure Starry Night isn't that accurate when rendering the approximate tail, coma size and brightness of the comet, but roughly



By the way, I'd advise these two posts and further discussions on the comet be moved to the astronomical observations thread.

[nprev]

Great work, James, and thanks for pointing this out. Hopefully any MER project people who pop in here will take note!

Per your suggestion, this thread will be for observations of this event regardless of the source.

[JohnVV]

Deimos and Siding Spring on Oct 18 at 00:28 UTC
from Gale


Phobos Oct 18 13:30UTC


on the 19'th Phobos rises into the tail

[nprev]

Nice, John!

I've been looking for magnitude estimates during closest approach with no luck. Understand that this is often a matter of guesswork for comets anyhow, but I calculated around mag -3 from Mars for the coma. Hopefully the tail will be at least that bright per a given unit of area; should be quite a show!

[JohnVV]

the comet tail above is 100% guessing

that and there is no real good way , right now, to use a real value in celestia
( the tails NEED some recoding in c++ and opengl )

and look at the last comet ( ison)
it was supposed to be GREAT!!!!, and HUGE!!!! ,and mind blowing !!!

then fizzled out on thanksgiving day

[nprev]

Well, yeah; think that an astronomer once said something like they're 'as unpredictable as cats'. I used what looked to be a middle-of-the-road activity index, and given the extremely close periapsis hoping that -3 is a conservative estimate. Still, we'll have to wait & find out.

[James Sorenson]

Also great work John . I agree. It's all guess work with regard to the brightness and how big the comets tail will be. looks like at the time of closest approach, the comet will be below the horizon for Curiosity and Opportunity could be set up to image it. It will be daylight then as well for Oppy. The hours and nights before and after closest approach all look like great imaging opportunity's. At the time of that photo opportunity that I noted, SN gives an estimated -1.07 apparent mag. For Oppy it will be early morning after sunrise at closest approach, SN gives an estimated apparent mag of -8.00. I'd take this figure with a grain of salt and agree with you of a -3.00 or maybe less. I sure hope we are both wrong.

[Mongo]

Well, yeah; think that an astronomer once said something like they're 'as unpredictable as cats'. I used what looked to be a middle-of-the-road activity index, and given the extremely close periapsis hoping that -3 is a conservative estimate. Still, we'll have to wait & find out.

That was David Levy: “Comets are like cats: they have tails, and they do precisely what they want.”

Great, memorable quote, and quite true.

[Deimos]

No topic like this is complete without a word of caution

During the morning before closest approach CA (for MER) and the evening after (MSL), the coma is comparable in size to the camera FOV. So the magnitude -5 comet is spread over a million pixels. That's a 15 magnitude downer, if the brightness were uniformly distributed--though it is not. JPL's horizons tool is currently saying around -5 for CA, and the comet has been running sightly brighter than that prediction (as seen from Earth). But the bigger and more impressive it looks in Starry Night, the harder it will be to see anything. Navcam is ~20x less sensitive than MCAM RGB (or Pancam L1 or MAHLI), so wide-field images are not simple. The comet is an AM object inbound, and a PM object outbound. I think people on this forum are familiar with the energy problems associated with the AM side, especially for Opportunity, which would need to skip deep sleep.

That said, various photo ops have been identified, but of course all plans are subject to the tactical operations context at the time--and the dust storm conditions (L_s=218, yikes). But figure the nucleus itself is within a factor of a couple of the size of Deimos, and the comet is maybe 20x further away. So there should be something to see, whether the comet is especially active or not.

Also, of course, cameras in orbit are free of many of the rover's constraints.

[bkellysky]

The Minor Planet Center
http://scully.cfa.harvard.edu/cgi-bin/retu...&o=CK13A010
and
Visual Comets in the Future
http://www.aerith.net/comet/future-n.html

predict about magnitude +8 1/2, as seen from Earth, about the time of closest approach to Mars. Not that our view has much to do with the ability to see the comet from Mars.
I only say this because it would be cool to have Mars and the comet together in the telescope eyepiece and be able to say 'they are actually near each other in space, not just in the sky!' at our monthly star party in October. That's often not the case as you can see with the pairing of planets, and our Moon and stars in August.
Good luck to observers on Earth and on and near Mars!!! It's going be very exciting to see what we can see.

[mcaplinger]

Also, of course, cameras in orbit are free of many of the rover's constraints.

But come with some significant ones of their own -- they're mostly linescan, with very limited exposure times, and optically not very fast.

I expect that every available instrument will make an attempt, but if no visually spectacular product comes of it, I won't be too surprised.

[JohnVV]

and on the inbound leg the optics WILL be pointed AWAY from the incoming DUST ( moving at 25,000 KPH )

now on the outbound leg , that is very different

[machi]

they're mostly linescan, with very limited exposure times, and optically not very fast.

The most interesting of the linescan cameras is undoubtedly HiRISE as it's only camera which has chance to actually photograph nucleus of the comet.
HiRISE has relatively large freedom of exposure times (line times are from 76 microseconds up to at least 67 msec, equivalent exposure time 0.0006 to at least 4 seconds).
Bigger limitation is probably accuracy of spacecraft's pointing (effects of spacecraft pointing jitter and yaw error).

[Phil Stooke]

They have shown they can deal with that for the Phoenix and MSL parachute descent images, so this should be well within their capabilities. Should be fascinating.

Phil