Author Topic: Fobos-Grunt Troubleshooting Latest (Part 2)  (Read 493230 times)

Offline hop

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #20 on: 11/14/2011 01:11 am »
Let me add my 2 kopecks to the mystery of the orbit rise and its hypothetical connection with attitude control firings.
Thanks for that detailed explanation.

One other thing that occurs to me is that Phobos-Grunts perigee is quite low (214km per http://www.n2yo.com/satellite/?s=37872 ), so it could be fighting noticeable torques for part of the orbit.
Quote
An easier question -- what's the delta RAAN between PhG and ISS, since we know the beta angle of the latter.
According to the above, PhG RAAN is 333.5837, vs 127.2529 for ISS.
 

Offline Lee Jay

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #21 on: 11/14/2011 01:22 am »
But we are given to understand that Phobos-Grunt may be holding attitude in solar inertial orientation, to maximize power.

Are we?  I wasn't under that impression.  Could it be that it is holding LVLH in anticipation of the burns that didn't occur?

Well, that's possible -- but if so, why, and with what sensors?

I have no idea as to how, but as to the why, wouldn't you want +x aligned with the velocity vector to make an orbit-raising burn?  Wasn't that what the first burn was to be?

Offline Comga

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #22 on: 11/14/2011 03:25 am »
Let me add my 2 kopecks to the mystery of the orbit rise and its hypothetical connection with attitude control firings.
Thanks for that detailed explanation.

One other thing that occurs to me is that Phobos-Grunts perigee is quite low (214km per http://www.n2yo.com/satellite/?s=37872 ), so it could be fighting noticeable torques for part of the orbit.
Quote
An easier question -- what's the delta RAAN between PhG and ISS, since we know the beta angle of the latter.
According to the above, PhG RAAN is 333.5837, vs 127.2529 for ISS.

Does that put them ~154 deg out, about as close to opposite as can be, and making any pass very quick?
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline hop

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #23 on: 11/14/2011 04:02 am »
Does that put them ~154 deg out, about as close to opposite as can be, and making any pass very quick?
I believe so, see plot here: http://www.n2yo.com/?s=37872|25544

Offline Jorge

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #24 on: 11/14/2011 04:56 am »
But we are given to understand that Phobos-Grunt may be holding attitude in solar inertial orientation, to maximize power.

Are we?  I wasn't under that impression.  Could it be that it is holding LVLH in anticipation of the burns that didn't occur?

Well, that's possible -- but if so, why, and with what sensors?

I have no idea as to how, but as to the why, wouldn't you want +x aligned with the velocity vector to make an orbit-raising burn?  Wasn't that what the first burn was to be?

I'd assume any +XVV pointing went the window once the spacecraft went into safe mode.
JRF

Offline Cbased

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #25 on: 11/14/2011 08:22 am »
Another official update:
http://www.federalspace.ru/main.php?id=2&nid=18258
I will translate the main bits. (This was all said by the head of Roskosmos Popovkin)

We have time till January (inclusive), the SC will stay on orbit. But the launch window closes in early December.

There is still a chance but we still can't receive any telemetry to understand what happened. The problem is that tracking stations are slow and "Phobos" is on an unplanned trajectory, hence the communication session lasts for only 7 minutes.

All systems of the spacecraft work nominally, it has got sun orientation, so we do have chances. At the moment specialists (engineers) conduct attempts to upload software.
 
To answer journalists' questions when it would be possible to say about the "spacecraft death", he said "it would be possible to talk about it in early December when the launch window is closed. We can start the predictions of the end of "Phobos" when orbit degradation reaches 180km.

He has also rejected rumours that the spacecraft had constructive defects. 
 
He has also highlighted the fact that there is no danger for Earth. There is no doubt that the spacecraft will explode upon the reenty (to the denser layers of atmosphere)

------
My own comment: "All systems of the spacecraft work nominally" - I wonder how do we know this if there is no telemetry?

Any news from ISS?
 
« Last Edit: 11/14/2011 08:24 am by Cbased »

Offline Cbased

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #26 on: 11/14/2011 11:08 am »
A slightly different version from RIA
http://ria.ru/science/20111114/488192899.html

The problem is the band/range - all our stations were designed for far/distant space. Phobos-Grunt is on an unplanned orbit of approximately 200km. The comms session with each of the measurement stations doesn't exceed 2 minutes (CBased: Note, this is different from 7min in the previous article)

There are several actions underway. Firsly, it is the acceleration (speed up) of the turning mechanisms. Secondly, it (the SC) was designed to start working at a distance of tens of thousands of kilometers from Earth, so the power of transmitters were tuned accordingly. We were afraid to "burn" SC with such strong signal. That's why there will be some preparation activities that we need to do.

Currently the window has been made wider and the power of transmitters has been reduced. The same was done by our partners at ESA at their 2 stations. That's why I am saying that we still have chances.

Offline JimO

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #27 on: 11/14/2011 11:21 am »
Does that put them ~154 deg out, about as close to opposite as can be, and making any pass very quick?

OK... Now somebody with competence in spherical trig can please take these two planes with this RAAN difference, and calculate their actual out-of-plane value -- the angle between their two planes, not just the angle between their two equator crossing longitudes. I've forgotten how to do it.


Offline simonbp

Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #28 on: 11/14/2011 01:53 pm »
He has also rejected rumours that the spacecraft had constructive defects.   

Well then, what the hell when wrong? Is he saying that it was designed to be hopelessly stuck in LEO?

Having a quality control problem is one thing. Denying that you have such a problem (when it's clear to the rest of the world that you do) strikes me as being like the alcoholic who denies he has a drinking problem as he pulls out the flask...

Offline JRThro

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #29 on: 11/14/2011 02:00 pm »
He has also rejected rumours that the spacecraft had constructive defects.   

Well then, what the hell when wrong? Is he saying that it was designed to be hopelessly stuck in LEO?

Having a quality control problem is one thing. Denying that you have such a problem (when it's clear to the rest of the world that you do) strikes me as being like the alcoholic who denies he has a drinking problem as he pulls out the flask...
Perhaps he was trying to differentiate between constructive (construction?) defects and software or programming problems.

Online ugordan

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #30 on: 11/14/2011 02:01 pm »
He has also rejected rumours that the spacecraft had constructive defects.   

Well then, what the hell when wrong?

Software problems?

Offline bolun

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #31 on: 11/14/2011 02:28 pm »
Russia still hopes to regain control of Mars probe

12:20 14/11/2011

Russia has time until the beginning of December to establish contact with its Phobos-Grunt unmanned spacecraft that is stranded at a low-Earth orbit after launch, the Russian space agency Roscosmos said on Monday.

More:

http://en.rian.ru/science/20111114/168681455.html
« Last Edit: 11/14/2011 02:29 pm by Chris Bergin »

Online Chris Bergin

Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #32 on: 11/14/2011 02:34 pm »
Guys, don't copy and paste articles unless:

1) They are press releases (such as Roscosmos content)
2) They are your own work on translation.

Always link regardless. The above post is an example of what is acceptable.

Anyone who copies and pastes articles into forums and just adds a link will be banned, as we've suffered from that and there's absolutely no excuse for it, because it's either malicious "I'll do what I want on the internet" or stupidity "what? copyright means you can't republish it externally?" - and we don't want either on here ;D

Offline Nickolai

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #33 on: 11/14/2011 04:26 pm »
Two questions:

1) What does this sentence mean?

Quote
In practice, solar inertial pointing clocks completely around the sky once every rev.

2) What possible explanation could there be for two different sources giving two different comm times (7 mins from the official source and 2 mins from RIA, as stated in above posts). Other than journalistic typo, is it possible that right now the session is 2 mins and with improvements to the tracking systems it could be increases to 7 mins?

Offline ChileVerde

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #34 on: 11/14/2011 05:03 pm »
Other than journalistic typo, is it possible that right now the session is 2 mins and with improvements to the tracking systems it could be increases to 7 mins?

Seven might be just possible if they can track horizon-to-horizon on a high-elevation pass. But such passes don't come along all that frequently. Attached are Heavens Above pass predictions for the next couple of days for Medvezh'i Ozera near Moscow and Sevastopol. Note that HA uses a 10 degree horizon mask.
"I canít tell you which asteroid, but there will be one in 2025," Bolden asserted.

Offline Moe Grills

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #35 on: 11/14/2011 05:11 pm »
   It's a shame. It's a shame.
:(

 There are a lot of Russian engineers, technicians, computer programmers right now who are hurtin' badly.
Not only is their pride hurt; they are humiliated.
FPE, I can empathize that being humiliated is awful!

WORSE!  Their job security is in peril. The Lavochkin and other Russian spacecraft firms that make these craft are NOT getting additional funding, in fact they are suffering funding cutbacks to interplanetary programs.

Don't think Putin is suddenly going to pour in Rubles to the BADLY UNDERFUNDED unmanned space program in Russia which is tottering on its legs; he has OTHER agendas to fund.

IMHO the sun is stetting on the Russian unmanned interplanetary program. It's time for nations like India, Japan, China and the US to pick up the slack. 

It was 15 years ago when Mars 96 went kaput; and 23 years since Russia
last sent a probe to Mars. Some of you weren't even born 23 years ago.

Offline Pheogh

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #36 on: 11/14/2011 05:24 pm »
Okay. So If I have this straight their going to try taking a video or pictures of the spacecraft from ISS to see if its tumbling or is otherwise damaged? Did they actually take pictures?

I don't think there was any indication that ISS personnel were going to inspect for damage. As far as I understand it, ground controllers were simply informing the crew that there will be a close pass, and it's up to the crew to decide what they want to do with that information.

Is that all? Does anyone know if the ISS crew took the opportunity?

Offline Jim

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #37 on: 11/14/2011 05:42 pm »
Two questions:

1) What does this sentence mean?

Quote
In practice, solar inertial pointing clocks completely around the sky once every rev.


 solar inertial pointing means it is always pointing at the sun.  From earth reference, it looks like the spacecraft is rotating one revolution per orbit.

Online Svetoslav

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #38 on: 11/14/2011 06:32 pm »
http://ria.ru/science/20111114/488740960.html

RIA Novosti reports that the crew of the ISS was not able to take pictures of Phobos-Grunt.

It's because the distance between P-G and ISS was too high- between 120-150 kms.

Offline Pheogh

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Re: LIVE: Fobos-Grunt Troubleshooting Latest (Part 2)
« Reply #39 on: 11/14/2011 06:41 pm »
http://ria.ru/science/20111114/488740960.html

RIA Novosti reports that the crew of the ISS was not able to take pictures of Phobos-Grunt.

It's because the distance between P-G and ISS was too high- between 120-150 kms.

Has there been any published imagery from ground based observers, detailed imagery?

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