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Here's Looking At You, Kid, MGS Sees Mars Odyssey and Mars Express
djellison
post May 21 2005, 12:11 AM
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QUOTE
19th Dec:08:31 GMT:Eject command sent to Mars Express
 
20th Dec:All day:Retargeting of Mars Express on an orbital insertion course

24th Dec:Night:Final decision to steer Mars Express into a martian orbit

25th Dec:02:54 GMT:Beagle 2 lands on Mars

25th Dec:03:00 GMT:Mars Express orbital insertion


from beagle2.com

I wasnt sure about the Russian ones - I've been doing SO much reading for this talk I'm giving tomrrow that they all sort of fuzz into one smile.gif Before you know it i'll have MRO deploying Netlander and MO2k1 CPROTO'ing the MEX landing site....bluehghghghg

Doug
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edstrick
post May 21 2005, 02:52 AM
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The 1971 Soviet Mars missions included a cosmos <stranded in earth orbit or something>, Mars-2 and Mars-3. I believe the Cosmos was an orbiter only mission, trying to beat Mariner 71 orbiters there.

Mars 2 and Mars 3 deployed the landers before orbit insertion, like Mars express, then retrofired into orbit. Mars 2 lander entered too steep or something and may have burned up, while the orbiter got into a 19 day or so oribt, had attitude control failure, and was in a sun-pointing slow spin, unable to do "targeted" science.

Mars 3 lander survived landing briefly, but failed with no significant science return. The orbiter worked will for a few months, but had to use up it's "shoot-develop-and-readout" film supply and couldn't wait for the end of the great 1971 global dust storm to image the surface.

The 1973 Mars fleet consisted of Mars 4 and 5 orbiters and Mars 6 and 7 flyby's carrying landers (the orbits to mars were less favorable than in 71 and a full orbiter + lander was too heavy for the Proton booster)

Mars 4 failed orbit insertion and did a flyby.
Mars 5 made it into orbit, worked for a short period, and reportedly depressurized it's air-conditioned electronics compartment and died.
Mars 6 went silent at retrofire or impact <almost the same time, as with pathfinder and the airbag rovers)
Mars 7 was misdeployed and missed the planet.

The Soviets didn't have the heart to try in 75. Or so it seems. They switched to Venus with a direct modification of the Mars Orbiters and had a 100% success with the Venera 9 and 10 lander/orbiter pairs.
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tedstryk
post May 21 2005, 03:43 AM
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The Soviet Mars orbiters released their landers before atmospheric entry. Also, keep in mind that the Venera series was very long lived, and that the landing attempt was made many times before Venera 7 made it and then Venera 8 send back data, followed of course by Venera 9 and 10. Due to the different conditions (heat, but especially the thick Venusian atmosphere), their landing systems were very different than the Mars landers. Also, the cruise to Venus is shorter, making it easier on the typically short-lived Soviet spacecraft. It seemed that the Mars and Venera program coexisted until America took a clear lead on Mars and the Soviet Mars program kept failing, and the Venera program began to succeed.


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edstrick
post May 21 2005, 07:52 AM
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The Soviet planetary series consisted of poorly documented very early missions, the only ones we have real info and pics of are the Venera 1 flyby <no midcourse capability>

A second series started with Mars 1 and Zond 1 to Mars and Venus, also including Zond 3, a mars mission that missed the launch window and was sent past the moon on an engineering test mission and photo'd the back side that Luna 3 missed. None of the "block 2" mars missions made it, but the venera missions finally suceeded with progressively deeper atmosphere probes till Venera 8 was a full success. None of the veneus flyby missions worked, though. The history of the missions is complicated, with the series being transferred from one technical group to another. (Sort of as if Ranger had been taken from JPL and turned over to Goddard after the Ranger 6 failure)

The "block 3" vehicles were the 1970's through mid 80's Mars and Venera and Venus/Halley missions. Lots of failures at first, then they worked the bugs out of the basic design, together with generally rising reliability. They ended the series when the could no longer get parts which had become obsolete <in part>

The Phobos mission was a "block 4", more or less, and had new project teething problems... then the budget fell apart.
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Bob Shaw
post May 21 2005, 01:15 PM
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Doug (et al):

I was wrong about Mars Express entering orbit before releasing Beagle 2!

Unreserved congratulations to the MGS team...

Bob


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garybeau
post May 22 2005, 01:04 AM
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QUOTE (Bob Shaw @ May 19 2005, 04:18 PM)
I wonder whether MGS could image the derelicts orbiting Mars - even as streaks - despite their rather uncertain positions?  Apart from the mere interest value in finding Mariner 9, say, it'd also sort out the issue of whether or not one of the MER vehicles saw either a defunct spacecraft or a meteor in the sky last year (I forget which one of the Rovers it was, but have a feeling it was Opportunity). It'd be nice to (1) find the old birds (2) backtrack their orbits (3) rule them in (or out) and get a final answer...
*


I think the odds of MGS imaging one of the derelict spacecraft would be pretty remote at best. Not knowing the orbital elements of the spacecraft it would be like finding a needle in the haystack. I think the best chance would be to use the camera on one of the rovers pointed up at the sky in the plane of the last known orbit and keep taking a sequence of images until you catch a streak on a couple of sequential images. If you could repeat this on a couple of evenings / mornings you may have enough information to locate it with MGS. I have taken video of passing satellites here on earth just for the fun of it, and even knowing exactly what time they were going to rise, exactly in what part of the sky they will be and using a wide angle camera, it was still a tough catch.

http://i6.photobucket.com/albums/y207/garybeau/iss4.gif

This is a highly compressed and shortened version of the ISS going by. Can you imagine trying to locate this from a moving target with a narrow angle camera?
I think for MGS to catch an image of Mars Express is a pretty remarkable feat.

Gary
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Bob Shaw
post May 22 2005, 11:17 AM
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It certainly wouldn't be *easy*, but the MGS guys have already done such surprising stuff with their almost vintage spacecraft that I'd be unwilling to call anything 'too difficult' where they're involved!

Detection of old orbiters from the ground would be aided by one or two Martian environmental advantages - no clouds (generally) and lovely dark skies (the nearest streetlights never get much closer than about 30 million miles!).

I too have attempted to capture satellites from the ground - the latest was the ISS cruising past Jupiter on 9 May. Sadly, I was caught by surprise and my camera tripod still had a little wobble, so it's not the best of photos.
Attached thumbnail(s)
Attached Image
 


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garybeau
post May 22 2005, 04:13 PM
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Here's a bit of info on the difficulty MGS had in imaging the other orbiting spacecraft.

"All three spacecraft are moving at almost 7,000 miles per hour, and at 62 miles distance the field-of-view of the Mars Orbiter Camera is only 830 yards across. If timing had been off by only a few seconds, the images would have been blank. "

http://www.jpl.nasa.gov/news/news.cfm?release=2005-080

It's an awful big sky out there when you are peering through a "soda straw".
Does MGS carry a wide-angle camera as well?

I was surprised to hear that the Viking and Mariner orbiters may still be in orbit. They must have been in fairly low orbits for imaging?
I guess the fact that Mars has a thinner atmosphere and is a little further away from the influences of the Sun's solar wind, they don't degrade from their orbits as quickly as they do hear on earth. Not having a strong magnetic field to funnel the charged particles toward the planet may be a factor also.
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Guest_Analyst_*
post May 22 2005, 05:19 PM
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MGS has wide angle cameras as well. One medium (or better low) resolution imager used to prvide a context for the narrow angle MOC images and a global imager for "weather" reports. All these secondary cameras are integreted into MOC, located on top of the lense tube.

The orbits of Mariner 9 and Viking are not so low. These vehicles did not use aerobreaking and had a limited amount of fuel. It's fuel consuming to enter low polar mapping orbits like MGS or Odyssey. I guess their orbits are more like the one planned for MTO, maybe more inclined.

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djellison
post May 22 2005, 05:43 PM
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There are two WA cams on MOC - but they're almost identical - one is red, one is blue, they both have approx 140deg FOV, and about 3500 pixel CCD's. The context images are simply using the middle 400 or so pixels of the Red WA camera (thus the 250ish m/pixel resolution)

Doug
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Guest_Analyst_*
post May 22 2005, 06:57 PM
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I always thought the two cameras are different, because of the different resolution. But this makes much more sense. Thanks. Btw. 3.500 pixel CCD is not bad for a "small" camera in the mid nineties (Or were these part of Mars Observer? I don't think so, but I'm not sure.).

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djellison
post May 22 2005, 07:44 PM
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Much-info...

http://www.msss.com/mars/observer/camera/p...MOC/mgs_moc.gif

and

http://www.msss.com/mars/observer/camera/p.../moc_ijist.html
smile.gif

Doug
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Bob Shaw
post May 22 2005, 07:45 PM
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The way that planetary atmospheres behave can be counter-intuitive. As Mars has a weaker gravity than the Earth, in fact it's atmospheric envelope is relatively larger (though mostly thinner, and always much less massive). However, above a certain height it's actually *thicker* than the Earth's! The same holds true for more massive planets than our own - Jupiter's atmosphere drops off much more quickly than ours. So, the braking effect of the Martian atmosphere is probably quite important at what appear to be reasonably high altitudes (and I suspect that seasonal variations can make it's atmosphere lopsided, too!).


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garybeau
post May 22 2005, 10:31 PM
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Thanks for all the info, I guess with a 140 deg. FOV camera the odds of picking up one of the rogue satellites goes up dramatically. Without trying to sound too pessimistic, they would still have to get 3 or 4 good confirmed sightings with the WA before they could pin it down with the NA camera. Would the effort be worth the science return? -- Not sure..... I suppose it may tell you something about how the atmosphere has expanded and contracted over the intervening years.

Gary
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ilbasso
post May 23 2005, 10:37 AM
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The other difficulty is getting the viewing geometry just right. With a very wide-angle camera and distances involved, the old orbiters might not have much or any contrast against a bright Mars background. They'd be just a pixel or two wide, not enough to grab your attention. Ideally, you'd like to catch them against a dark background...which would be hard, since MGS is in a sun-synchronous orbit, isn't it?


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