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#580
by
spacelev
on 25 Nov, 2011 16:45
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#581
by
spacelev
on 25 Nov, 2011 16:53
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At the orbiter-forum figured interesting window on the route start Earth - gravmanevr Venus - gravmanevr the Earth - Mars with access to the orbit of Phobos.
(
http://www.orbiter-forum.com/showthread.php?p=317551&postcount=372)
Check out March 12, 2012
The span of Venus June 26, 2012
The span of Earth April 27, 2013
Ascent to orbit Mars September 10, 2015
Should be enough fuel available
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#582
by
Jim
on 25 Nov, 2011 16:55
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But the spacecraft is not thermally configured for a Venus flyby
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#583
by
Trouquel
on 25 Nov, 2011 17:19
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Some confirmations from an insider posted to Novosti Kosmonavtiki forum:
(verbatim translation from Russian)
"Confirmed that an emergency frame was received on November 23rd by a ground station in Perth (Australia) from onboard radiosystem of the cruise stage. This frame was not decoded successfully in Lavochkin (prime contractor of the mission). Confirmed that a similar frame was received by a ground station in Baikonur on November 24th. Since that moment any other attempts to communicate either from Baikonur or from Perth failed. The spacecraft keeps silence.
Analysis of the emergency frame didn't yield too much. The frame contained the status of some parts of the onboard radiosystem of the cruise stage, working voltages on buses of the radiosystem, temperatures of some parts of the radiosystem. It was also noted that the data bus is functional. The frame also contained the history of switching between the primary and backup transmitter. All this data didn't allow to analyse the contingency very much.
More, while simulating on a test bench various conditions for star tracker malfunctioning and receiving from it some invalid data, they couldn't reproduce mission disruption similar to what has occurred in orbit. Taking into account that circuits controlling the main engine unit are redundant.
Beside Russian tracking, Americans also formally confirmed stable Sun-tracking attitude of the spacecraft.
One of the possible cases being considered for the secondary emergency, communications restore and loss may be connected to the power supply configuration. After charging current from the solar panels drops and the batteries are discharged, chemical power supply (having capacity for almost half a day) is engaged and the batteries become disconnected. In this case the current will appear when the solar panels are sunlit and disappear in Earth shadow.
Taking into account the off-nominal behaviour of the spacecraft, the batteries don't get connected when the current from the solar panels reappears.
Attempts to communicate go on. Commands are being sent to downlink a telemetry frame from the onboard radiosystem (as done successfully before), to downlink telemetry from the flight computer, to switch on the batteries.
No one thinks about the flight to Mars. They hope as a minimum to raise the orbit and work with the spacecraft. As a maximum..."
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#584
by
Trouquel
on 25 Nov, 2011 17:26
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Seems the data received so far (barely emergency frames) provides no clues for the reason why it didn't raise the apogee after the launch...
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#585
by
Svetoslav
on 25 Nov, 2011 19:01
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http://www.russianspaceweb.com/phobos_grunt_launch.html#11_25 According to reliable sources, ground controllers were continuing sending commands to Phobos-Grunt to downlink telemetry frames, as had been achieved earlier and, in addition, to downlink telemetry from the BKU flight control computer and commands to activate onboard rechargeable battery.
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#586
by
Svetoslav
on 25 Nov, 2011 19:33
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I am sorry, I didn't read the latest posts here (and I guess many people already left the thread) ... I know that you were informed that ESA won't try until Monday...
http://ria.ru/science/20111125/497969656.html... but RIA Novosti has announced that ESA has decided to make some communication attempts during the night between Friday and Saturday.
So... stay tuned.
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#587
by
iamlucky13
on 25 Nov, 2011 19:49
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And a big welcome - and thanks - to Gatewave and Kukushk for the above!
Welcome to the site's forum!
Thanks been following this thread on the forum quietly and thought to join up as this place is a great source of information and users who really know their stuff.
Question if I may, to establish open communication channel with the space craft in the X band with very narrow beam the space craft needs to be quite steady in its orbit without any movement in its X or Y axis correct?
Even a slight spin will basically break the communication line as the directional antenna will not be point down to earth at all time during these passes.
So just the fact that anyone was able to establish communication and downlink any data is an indication that the space craft is quite stable or even if spinning this spin rate is very slow, and perhaps because of this slow spin rate the repeated communication was not possible in the latest series of passes over the Perths station (antenna was not pointing down during the pass).
Could someone please confirm if this thought is logical?
Thanks
The antenna in question is a low gain antenna. It has a very broad beam spread. In theory, you will still get a signal with a tumbling spacecraft, but it may be intermittent, because coverage isn't necessarily in every direction.
However, the fact that spotters who have watched for overhead passes have reported the apparent brightness of Fobos-Grunt doesn't change independently suggests it is not tumbling.
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#588
by
clongton
on 25 Nov, 2011 19:51
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I am sorry, I didn't read the latest posts here (and I guess many people already left the thread) ... I know that you were informed that ESA won't try until Monday...
http://ria.ru/science/20111125/497969656.html
... but RIA Novosti has announced that ESA has decided to make some communication attempts during the night between Friday and Saturday.
So... stay tuned.
Thank you. The translation is much appreciated.
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#589
by
JimO
on 25 Nov, 2011 19:59
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In the avalanche of reports referring to more than a dozen tracking passes over several days, keeping them straight really requires somebody produce a common reference timeline so we can avoid confusion over delayed, repeated, garbled accounts of different or identical pass results.
Such a timeline should include the Phobos-Grunt orbit number per the NORAD TLEs, the Universal Time of the comm passes at which stations, including passes that were not worked, or for which no response was noticed.
With such a reference timeline available, and continuously updated, our contributions, questions, and cross-references can unambiguously latch onto specific events, and we may impose some order on the chaotic but rich and valuable bits that are swirling across our screens. Patterns may emerge.
Would this task be readily doable by some enthusiast in the audience?
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#590
by
hop
on 25 Nov, 2011 20:14
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Such a timeline should include the Phobos-Grunt orbit number per the NORAD TLEs, the Universal Time of the comm passes at which stations, including passes that were not worked, or for which no response was noticed.
Robert Christy is doing something along these lines:
http://www.zarya.info/Diaries/Misc/PhobosGrunt1.php#log
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#591
by
savuporo
on 25 Nov, 2011 23:00
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I'm betting that if/when Roscosmos evaluates rescue/servicing options, they will not find one that costs less than building and launching another Phobos-Grunt, and will therefore quite sensibly reject rescue/servicing.
Its a fairly safe bet.
However, if they could just do another Soyuz with Fregat upper stage ( which is basically FG propulsion module ) and another drop tank, with minimum hardware for docking/berthing/mating, and just use this as a extra delta-v module, that would probably not run them more than $30-40M, for "saving" a $170M total mission - and also saving Chinese first ever deep space probe.
Again, totally far out there, but not entirely impossible - assuming a ton of things, i.e. that electronics and attitude control of the probe can be made to work, that it can be moved to a stable ( MEO ? ) parking orbit etc etc.
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#592
by
hop
on 25 Nov, 2011 23:29
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However, if they could just do another Soyuz with Fregat upper stage ( which is basically FG propulsion module ) and another drop tank, with minimum hardware for docking/berthing/mating, and just use this as a extra delta-v module, that would probably not run them more than $30-40M, for "saving" a $170M total mission - and also saving Chinese first ever deep space probe.
This is insane. Can we stop with the fantasy stuff ?
PG has no docking system, it's not designed to be serviceable. As far as we know, the Russians have no existing capability to robotically rendezvous and capture an uncooperative target, let alone hook up a new propulsion system. That would require development of an entirely new, specialized spacecraft.
but not entirely impossible
In the "doesn't violate the laws of physics as we know them" sense it's possible. In sense of something that people in the real world would do, it's not just impossible, it's complete nonsense. There's zero chance it would be attempted.
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#593
by
clongton
on 25 Nov, 2011 23:45
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Have they determined what PG's orbital parameters are with sufficient accuracy to determine its rate of decay and likely re-entry date?
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#594
by
Jorge
on 26 Nov, 2011 00:00
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I'm betting that if/when Roscosmos evaluates rescue/servicing options, they will not find one that costs less than building and launching another Phobos-Grunt, and will therefore quite sensibly reject rescue/servicing.
Its a fairly safe bet.
It's an absolutely safe bet.
However, if they could just do another Soyuz with Fregat upper stage ( which is basically FG propulsion module ) and another drop tank, with minimum hardware for docking/berthing/mating, and just use this as a extra delta-v module, that would probably not run them more than $30-40M, for "saving" a $170M total mission - and also saving Chinese first ever deep space probe.
Again, totally far out there, but not entirely impossible - assuming a ton of things, i.e. that electronics and attitude control of the probe can be made to work, that it can be moved to a stable ( MEO ? ) parking orbit etc etc.
As hop wrote, the Russian automated rendezvous system (Kurs) is a cooperative system and requires transponders on the target vehicle in order to work. P-G also lacks any kind of docking hardware. Therefore it is possible to state, categorically, that it is impossible for the Russians to rescue P-G with the systems they have on hand.
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#595
by
hop
on 26 Nov, 2011 00:10
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Have they determined what PG's orbital parameters are with sufficient accuracy to determine its rate of decay and likely re-entry date?
No. These things are highly uncertain in the best of times, and PGs orbital behavior has been particularly odd. It does appear to be acting a bit more normally now. See
http://www.satflare.com/track.php?q=phobos#LNEWAnatoly Zak quotes Russian space forces predicting January or February:
http://www.russianspaceweb.com/phobos_grunt_launch.html#11_24Where's the Space Shuttle when we need her. Oh - sorry. 
NASA wouldn't take a shuttle anywhere near PG. This is just about as big a fantasy as savuporo's post.
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#596
by
Jorge
on 26 Nov, 2011 00:11
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As hop wrote, the Russian automated rendezvous system (Kurs) is a cooperative system and requires transponders on the target vehicle in order to work. P-G also lacks any kind of docking hardware. Therefore it is possible to state, categorically, that it is impossible for the Russians to rescue P-G with the systems they have on hand.
Where's the Space Shuttle when we need her. Oh - sorry.
Seriously, we wouldn't have done it even if the shuttle was still flying. NASA would have been required to charge full-cost and there's no way the Russians would pay it. Plus the safety issues - the lack of sufficient hardware inhibits on the propulsion system would kill the idea right away, among many other issues such as EVA safety.
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#597
by
Lee Jay
on 26 Nov, 2011 00:39
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The only type of "rescue" or satellite servicing that seems like it might have a business case is something like ASTRO. ASTRO was a pretty successful demonstration. Doing remote refueling doesn't require a docking system, doesn't require humans or EVAs, and doesn't require the robot to do anything super-complex like working on Hubble. I doubt that would be practical here even if they do get control over P-G, but it might be for other spacecraft, especially those in GEO where moving between objects requires very little delta-V and the spacecraft themselves don't use enormous quantities of fuel. I could also see it being practical in the event that JWST is working beautifully and is running out of practical mission operational time only because of lack of fuel.
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#598
by
Chris Bergin
on 26 Nov, 2011 00:44
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We've been over this rescue stuff before. Let's not go over it again folks.
Thanks.
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#599
by
ChileVerde
on 26 Nov, 2011 02:10
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Have they determined what PG's orbital parameters are with sufficient accuracy to determine its rate of decay and likely re-entry date?
IF the more normal decay behavior that began a few days ago continues, reentry around 5-15 January is predicted. But, given PG's orbital antics to date, don't put money on that.
