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The Messenger
post Mar 14 2006, 07:34 PM
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QUOTE (Circum @ Mar 13 2006, 01:05 PM) *
The 2% lag in performance - Any clues as to why? TCM-2 was much more precise, or was there a performance correction during the burn as well?
During the NASA TV coverage, I believe I heard something about chamber pressures being slightly low, which was not a complete surprise since certain temperatures were also slightly low.

I didn't hear any explanation or further details about the low temperatures, but somehow I doubt it was 'new physics'. . . .

New physics would not seem to be necessary...but they cannot be eliminated, either cool.gif

Another aside, there have been new developments in hydrogen containment vessels compatible with the grueling temperature swings of solar space. Espect to see these leak-proof containers, and more dependance upon hydrogen fuels and propulsion systems in interplanetary space flight in the future.
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RNeuhaus
post Mar 15 2006, 03:23 AM
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QUOTE (Bob Shaw @ Mar 13 2006, 04:35 PM) *
Yes; I think Rodolfo has missed the four Soviet vehicles placed in orbit around Mars, though whether they still are is another issue.

Bob Shaw

Thanks to ljk4-1 and Bob. I have already checked about the Soviet's Mars program. Only four Russian cosmos probes are orbiting on Mars: Mars 2, 3, 5 and 6. 4 and 7 have missed and are on the solar orbit.

Rodolfo
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Guest_BruceMoomaw_*
post Mar 15 2006, 06:05 AM
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No, Mars 6 isn't orbiting Mars (and never did; it was a flyby that dropped off a lander). But Phobos 2 IS orbiting Mars (unless it's run into Phobos -- as suggested above -- which seems unlikely to me).
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edstrick
post Mar 15 2006, 10:27 AM
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Mars 2 was in a very very eccentric -- was it 19 days long? -- orbit. It would have been strongly pushed around by tidal effects and plausibly has hit the atmosphere by now.
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tedstryk
post Mar 15 2006, 10:34 AM
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QUOTE (edstrick @ Mar 15 2006, 10:27 AM) *
Mars 2 was in a very very eccentric -- was it 19 days long? -- orbit. It would have been strongly pushed around by tidal effects and plausibly has hit the atmosphere by now.

Actually, that was Mars 3. Mars 2 was in a short orbit, but had transmitter problems. And Mars 5 may still be in orbit.


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edstrick
post Mar 15 2006, 10:48 AM
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Yep.. you're right.
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Bubbinski
post Mar 15 2006, 09:55 PM
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QUOTE (SFJCody @ Mar 10 2006, 04:22 PM) *
Would be nice to have a Mars visualisation thingy that shows the locations of all four orbiters and two rovers.


I wonder if the latest Starry Night software fills this bill, it is advertised as tracking spaceprobes. That would be very nice to have.


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helvick
post Mar 15 2006, 10:07 PM
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QUOTE (Bubbinski @ Mar 15 2006, 09:55 PM) *
I wonder if the latest Starry Night software fills this bill, it is advertised as tracking spaceprobes. That would be very nice to have.

Celestia will do it but you'll have to search the forumsfor some add-ons to get all the current orbiters models and orbits.
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mcaplinger
post Mar 15 2006, 11:39 PM
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QUOTE (helvick @ Mar 15 2006, 02:07 PM) *
Celestia will do it but you'll have to search the forumsfor some add-ons to get all the current orbiters models and orbits.

The thread at http://www.unmannedspaceflight.com/index.php?showtopic=2367 goes into a tedious level of detail as to why Celestia orbital elements probably won't be correct for orbiters in low sun-sync orbits. The same is true for Starry Night. There's some hope that Celestia SampledOrbits can be defined that will be right over the time they cover, but there's still work left to do on that.


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Decepticon
post Mar 16 2006, 01:59 AM
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Does JPL take this stray probes into account when putting new probes into orbit?

Or is the risk factor to small to even worry?
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Guest_BruceMoomaw_*
post Mar 16 2006, 02:02 AM
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MUCH too small to worry about. Even in the environment of low Earth orbit -- which is now getting frighteningly crowded -- there have been only 2 or 3 significant collisions with small bits of junk (and a lot of those have been scattered by bursting rocket upper stages, or are drops of solidified metallic coolant from the leaky nuclear reactors on the old Soviet recon satellites -- two things we don't have to worry about in Mars orbit).
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mcaplinger
post Mar 16 2006, 02:52 AM
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QUOTE (Decepticon @ Mar 15 2006, 05:59 PM) *
Does JPL take this stray probes into account when putting new probes into orbit?

Part of the MRO MOI viewgraph package was a COLA (Collision Avoidance) analysis for Phobos, Deimos, and the currently operating orbiters. We don't really know where the dead ones are, so there is no sensible analysis that can be performed. As Bruce said, the probabilities are low, but for bodies with known ephemerides, the analysis is pretty easy, so it might as well be done.


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Gsnorgathon
post Mar 16 2006, 03:41 AM
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Any chance that MARSIS or SHARAD could be used to locate them?
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Bubbinski
post Mar 16 2006, 05:47 AM
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Isn't Marsis the Mars Express ground pointing radar? Interesting thought....even though the risk is low it would still be a great idea to try to track dead probes and scan the space around Mars. But I wonder how this could be done, do we even have radars on earth powerful enough (Arecibo?) to scan Martian orbital space?

More and more spacecraft will hopefully make it to Mars in the near future....it might be prudent now to start on a more extensive COLA/tracking/space debris reduction program before it becomes an issue. Same with the Moon.


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mcaplinger
post Mar 16 2006, 07:27 AM
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QUOTE (Gsnorgathon @ Mar 15 2006, 07:41 PM) *
Any chance that MARSIS or SHARAD could be used to locate them?

MARSIS uses wavelengths between 50 and 230 meters; SHARAD around 15 meters. I doubt either could detect an object as small as a spacecraft.


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