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#460
by
iamlucky13
on 24 Nov, 2011 00:38
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I guess they could jettison unused mass (like the Chinese satellite) to gain more delta V but that has its own political raminifcations.
Unfortunately, this is almost certainly not an option.
Not to mention China wouldn't be too thrilled about having their spacecraft discarded as excess baggage.
Quite true, although if it had been an option and it came down to China losing their mission, or China losing their mission
and forcing Russia to lose theirs, they'd likely accept the painful reality.
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#461
by
Cbased
on 24 Nov, 2011 00:53
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In fact, I can see quite an opposite scenario now. If there is only enough propellant to reach Mars orbit but not Phobos then a Chinese mission might become a success afterall!
P.S. tried to call the station in Perth to say thank you, but no one answered - might be still too early there (they're a few hours behind Melbourne)
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#462
by
robertross
on 24 Nov, 2011 01:51
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#463
by
Chris Bergin
on 24 Nov, 2011 01:57
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As a minor note, your diagram of the spacecraft is labeled slightly differently than Anatoly Zak's.
While his content is copyrighted, so that's a moot point, ours is actually from Roscosmos! I think we'll stick with the Russian Space Agency
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#464
by
jekbradbury
on 24 Nov, 2011 02:08
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Wikipedia has a more relevant plot from the 2005 window used by Mars Reconnaissance Orbiter
http://en.wikipedia.org/wiki/Porkchop_plot
Blue contours are characteristic energy. Red lines are transfer times.
The minima on the lower left is the type 1 trajectory. If you view it full size so you can see the numbers, you will notice it is faster, but takes a hair more energy.
This paper:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080012680_2008012531.pdf has a version of the same porkchop plot for the 2011 launch window (Figure 3 on page 3). It looks like the original launch date was aimed right for the minimum-energy Type II trajectory, while the minimum-energy Type I trajectory was one with a launch date of November 18. Both trajectories are still possible, with Type II incurring a much larger energy penalty than Type I.
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#465
by
iamlucky13
on 24 Nov, 2011 03:24
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As a minor note, your diagram of the spacecraft is labeled slightly differently than Anatoly Zak's.
While his content is copyrighted, so that's a moot point, ours is actually from Roscosmos! I think we'll stick with the Russian Space Agency
Sounds good to me! I should learn to let your always excellent info speak for itself more.
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#466
by
Danderman
on 24 Nov, 2011 03:56
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To sum up recent developments, it appears that one ground station in Australia is reporting reception of partial telemetry from the spacecraft. Is that correct?
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#467
by
ChrisC
on 24 Nov, 2011 04:53
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#468
by
Svetoslav
on 24 Nov, 2011 05:15
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#469
by
woods170
on 24 Nov, 2011 05:55
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http://www.roscosmos.ru/main.php?id=2&nid=18324
Roscosmos informs us that telemetry information has been received during TWO sessions and it has been given to the specialists at NPO Lavochkin.
Good. It means they can establish repeated contact with FG over multiple passes. That makes for a good communications platform.
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#470
by
Svetoslav
on 24 Nov, 2011 06:44
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#471
by
Svetoslav
on 24 Nov, 2011 06:46
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#472
by
Liss
on 24 Nov, 2011 06:59
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Svetoslav, thank you for your efforts for communicating between NK and NSF. But please be careful in mentioning sources. In the latter case, the source is not NK but BBC-Russian quoting John Holt from the Perth station. Unfortunately they did not say which pass was not successful and which (second of two this night) was.
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#473
by
Svetoslav
on 24 Nov, 2011 07:11
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Yes, you are right.
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#474
by
Moskit
on 24 Nov, 2011 08:12
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http://www.gazeta.ru/social/2011/11/24/3846434.shtml(rough translation, just excerpts)
Telemetry has been received from Fobos-Grunt. So far it is telemetry from radio module only. Next task - receive telemetry from onboard computer of F-B.
Rene Pishel said at 1am Moscow time: "I can confirm we linked with the station and reiceved data. We hope it contains telemetry, but it still needs to be decrypted".
However not everything went as planned. There were 5 attempts to communicate with station, each only 6-7 minutes long.
"I do not have yet complete information about communication results of the first and other windows. I can only say that the second window at 1:57 was not used due to fact that it was much shorter than other windows". As far as he knows there was a link at 8:16 window.
Lavotchkin anounced that there were two windows when telemetry was received.
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#475
by
Ben the Space Brit
on 24 Nov, 2011 08:25
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So, to summarise, the Perth ground station has good a communications link with the probe. Telemetry has been received but, at this time, the design team at Lavoichin are still crunching the bytes - no conclusions have been reached as yet, at least none that have reached the public domain.
Issues at the moment are:
1) Time critical - will they be able to find the problem before the window closes?
2) Have they got the battery chargers working again to permit operations in Earth's shadow? If not, any recovery is going to be slow and fraught with problems;
3) What is the problem? If it's software, it's potentially fixable if the power problem has been resolved. Even if the propulsion module is a dud, then there may be a work-around if there are redundant systems. If that doesn't work (and remember - time critical), then the mission is a scrub and they should use the reminaing RCS fuel for a controlled re-entry over a safe disposal zone like the mid-Pacific.
Overall, the guys are Lavoichin are in the metaphorical hot seats right now. Everything depends on what they can learn from the probe's telemetry. I'm sure that their managers are demanding Powerpoint status reports every half-hour on the half-hour.
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#476
by
Moskit
on 24 Nov, 2011 08:46
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I would not say the link is good yet. So far two commands sent directly to radio module seem to have been received and acted upon: "turn on carrier frequency" (on 23rd) and "send emergency telemetry" (this night). Communication with the main computer is still not established yet, I think.
http://www.rbcdaily.ru/2011/11/24/focus/562949982128750"Communication in the second window was successfull, but signal was weak and short, only 6 minutes" said Rene Peshel. "There is no confirmation that it contained valid telemetry"
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#477
by
scpc
on 24 Nov, 2011 09:13
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#478
by
JimO
on 24 Nov, 2011 09:33
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Interpreting weak TM streams can be messed up by the absence of clear punctuation in the bitstream [where does each data 'word' begin?], but often that problem can be overcome by locating unchanging sequences which usually mean constant data fields, and using them as timing marks to interpret other portions of the bitstream. It takes a little work, often with long hardcopy printouts, but it has been done -- most spectacularly with the last gasps of data from the dooned, tumbling 'Columbia' orbiter in 2003.
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#479
by
JimO
on 24 Nov, 2011 09:43
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Interfax [0938 GMT] is quoting some "former commander of the missile attack early warning army", Lieut. Gen. Nikolai Rodionov, as claiming Ph-G "could have been disabled by external influence caused by emissions from a powerful U.S. radar in Alaska".
(REQUIRES URL LINK. Material is Copyrighted).
