Author Topic: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011  (Read 252057 times)

Offline simonbp

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #600 on: 11/10/2011 03:41 PM »
The latest rumour on NK has it that the low-gain omnidirectional antenna is not visible from the ground stations as the first fuel tank (the one that was supposed to be disposed of after the first burn) covers it. Which in turn means that they cannot reset the spacecraft and send orders (the directional antennas have really small field of view so chances of a signal being in the way are non-existent). If that is the case, is there any chance that they could get lucky and get a shot at the directional receivers or perhaps put enough power so that the craft could detect the input on the low-gain antenna?

Reposting the diagram to be clear; do you mean the two cone-shaped low-gains on the cruise stage? If they are obscured, that really means that they didn't deploy...

Offline Nickolai

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #601 on: 11/10/2011 03:52 PM »
The latest rumour on NK has it that the low-gain omnidirectional antenna is not visible from the ground stations as the first fuel tank (the one that was supposed to be disposed of after the first burn) covers it. Which in turn means that they cannot reset the spacecraft and send orders (the directional antennas have really small field of view so chances of a signal being in the way are non-existent). If that is the case, is there any chance that they could get lucky and get a shot at the directional receivers or perhaps put enough power so that the craft could detect the input on the low-gain antenna?

Well, they were able to receive some telemetry from the spacecraft after separation from the LV so at least one antenna must be visible. Depending on their communications setup (which I would venture a guess, and this is based purely on speculation, is half-duplex since a mission like this has no real need for full-duplex) this antenna could be capable of both transmitting and receiving (half-duplex) or simply transmitting (full-duplex, and reception occurs on another frequency using another antenna). I'd bet it's the former, which means this rumor that the propellant tank is blocking the antenna is unlikely.

Offline InvalidAttitude

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #602 on: 11/10/2011 03:55 PM »

http://ria.ru/science/20111110/485724052.html

 [...]it was found out that the solar panels have deployed, the spacecraft is Sun-oriented, and the batteries are being recharged [...]

So I assuming the battery power is not an issue and there is more than 2 days left to rescue the mission. Correct me If I'm wrong...

Offline Nickolai

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #603 on: 11/10/2011 04:09 PM »

http://ria.ru/science/20111110/485724052.html

 [...]it was found out that the solar panels have deployed, the spacecraft is Sun-oriented, and the batteries are being recharged [...]

So I assuming the battery power is not an issue and there is more than 2 days left to rescue the mission. Correct me If I'm wrong...

Well, we don't know what orientation it's in at the moment. It could have oriented itself for the burn, failed to burn, and then kept that orientation. But if the batteries were reported fully charged to begin with then I guess they know they have at least 3 days from that point. Most information seems to point to a battery life of 3 days, but this contradicts the official statement from Roscosmos that controllers have 2 weeks to figure out the situation.

As was pointed out earlier, you want batteries to be fairly small to save weight. Since they're only used for nighttime passes (in the nominal case) they don't really need to last longer than a few hours really (orbital period of Phobos is 7h40m, half that time in night -> 3h50m), but of course designers will put in margin for cases like this. Since it doesn't need to last much longer than ~4h, 3 days seems like a more reasonable margin than 14 days. But we don't know the design specs. Perhaps they did design them for 14 days, perhaps for 3. We'll find out shortly I suppose, or not, if they fix it sooner.

Offline rcoppola

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #604 on: 11/10/2011 04:10 PM »
Where do we stand with how much time is specifically left before it's no longer possible to save the mission?

What is the orbital decay rate vs how much propellant margin there is to still get out of LEO?
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Offline Nickolai

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #605 on: 11/10/2011 04:12 PM »
Where do we stand with how much time is specifically left before it's no longer possible to save the mission?

What is the orbital decay rate vs how much propellant margin there is to still get out of LEO?

Good questions all, I'm sure mission controllers are trying to figure out the same thing.

Offline Nickolai

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #606 on: 11/10/2011 04:18 PM »
Looking back at the NK post that suggested one of the antennas is being blocked by the fuel tanks, the post is a little unclear. He suggests the aforementioned possibility, and then goes on to say

Quote
To all those talking nonsense about the communications system, everything installed on FG is the most reliable equipment there is, the most robust and trouble-free. The reason there is no telemetry is not because we aren't able to receive it, but because the SC is not outputting it.
(Post from Sab at: http://www.novosti-kosmonavtiki.ru/phpBB2/viewtopic.php?t=10631&postdays=0&postorder=asc&start=3949)

So perhaps it is possible that one of the antennas is blocked by a fuel tanks, but that this does not imply it will be impossible to communicate with the probe.

Offline rcoppola

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #607 on: 11/10/2011 04:19 PM »
Where do we stand with how much time is specifically left before it's no longer possible to save the mission?

What is the orbital decay rate vs how much propellant margin there is to still get out of LEO?

Good questions all, I'm sure mission controllers are trying to figure out the same thing.
I'm just wondering if it indeed was/is frozen in a burn posture, what kind of extra drag that's putting on it's orbit and increasing it's decay rate?
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Offline Nickolai

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #608 on: 11/10/2011 04:32 PM »
Where do we stand with how much time is specifically left before it's no longer possible to save the mission?

What is the orbital decay rate vs how much propellant margin there is to still get out of LEO?

Good questions all, I'm sure mission controllers are trying to figure out the same thing.
I'm just wondering if it indeed was/is frozen in a burn posture, what kind of extra drag that's putting on it's orbit and increasing it's decay rate?

Considering the cross section of this thing, I don't think drag will change appreciably for any orientation. It's very small as well, so it won't have too much drag on it. I think we've been hearing that orbital decay constraints give controllers a couple weeks before it re-enters naturally.

Offline Kaputnik

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #609 on: 11/10/2011 04:36 PM »
Would it be possible for a ground based telescope to get a good enough image to determine the SC orientation?
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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #610 on: 11/10/2011 04:38 PM »
Well, I know that this doesn't mean much but it looks moral is not high about the mission

http://abcnews.go.com/Technology/russia-scrambles-save-stranded-mars-moon-probe-phobos/story?id=14923797#.TrwC4vGqCRs

""I think we have lost the Phobos-Grunt," Vladimir Uvarov, a former top space expert at the Russian Defense Ministry, said in an interview Thursday in the government daily Rossiyskaya Gazeta."

Offline rcoppola

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #611 on: 11/10/2011 04:40 PM »
Where do we stand with how much time is specifically left before it's no longer possible to save the mission?

What is the orbital decay rate vs how much propellant margin there is to still get out of LEO?

Good questions all, I'm sure mission controllers are trying to figure out the same thing.
I'm just wondering if it indeed was/is frozen in a burn posture, what kind of extra drag that's putting on it's orbit and increasing it's decay rate?

Considering the cross section of this thing, I don't think drag will change appreciably for any orientation. It's very small as well, so it won't have too much drag on it. I think we've been hearing that orbital decay constraints give controllers a couple weeks before it re-enters naturally.
Crazy question time:
Is there anyway the ISS can help with the receiving or transmission of mission data to PG?
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Offline Vladi

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #612 on: 11/10/2011 04:40 PM »
Translation of the words of the Lavochkin guy on NK that I mentioned about an hour ago:

Quote
основная проблема состоит в том, что малонаправленные антенны МНА сейчас затенены сбрасываемым баком и управляющий сигнал для перезагрузки систем не проходит. Никто не предпологал, что придется работать в такой ситуации. Остронаправленная антенна ОНА сейчас в зачекованном положении. Для тех кто тут нес чушь про системы связи, все что установлено на АМС - самое надежное из того что есть, самое дубовое и безотказное. ТМИ нет, не потому что мы не можем ее получить, а потому что аппарат ее не выдает (по какой то причине), и сама по себе она не появится. Поздно вечером снова будут попытки передать управляющий сигнал. На этом все до завтрашнего рабочего дня. ПС старайтесь хотя бы не обижать тех людей, которые с вами инфой деляться. И не ведитесь на теории заговора. Нет в сми новой инфы, только из-за того что ее действительно НЕТ. И ни кто не хочет лишний раз светить свою фамилию сообщая неблагоприятные вести...

The main problem is that the low gain antenna is now shaded by the fuel droptank and the signal for rebooting the system does not reach the spacecraft. No one suspected that we would have to work in such a situation. The high gain antenna is not currently deployed (a bit unclear here). For those who doubt the comms system – all that is on the spacecraft is the most error-free and sturdy that there is. There is no telemetry not because we cannot receive it, but because the spacecraft is not sending it (for some unknown reason) and it will not appear by itself. Later tonight there will be a another attempt to send a signal. That was all for the working day yesterday. Please do not insult those people who try to give you information and do not start conspiracy theories. There is no additional info in the news only because in reality there is no new information and no one wants to appear and repeat the already known bad news.

Quote
от чистого сердца стараемся, для всех сопереживающих. А для тех кто говорит что в Лавке ничего делать не умеют, приходите к нам на работу инженерами или в цеха. Молодой специалист 14000 оклад плюс премия. Ждем. И все забыли про Электро и Спектр. Первая АМС в России за 15 лет, вы только вдумайтесь! Памятник поставить всем инженерам, которые в ттаких условиях работают!

For all concerned, we are trying with our entire hearth. For those who say that Lavochkin could not do anything, please come to work as engineers with us. A young engineer receives 14 000 roubles (note – about 500 dollars). We wait. And all forgot about Electro-L and Spektr. The first interplanetary probe in Russia for the last 15 years, just think about it! There should be a monument for those engineers that work in those conditions.

Offline Jim

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #613 on: 11/10/2011 04:46 PM »

Crazy question time:
Is there anyway the ISS can help with the receiving or transmission of mission data to PG?

Why would ISS be any different than any other spacecraft (HST, NPP, etc) in this instance?

Why not suggest TDRS, whose name has "data relay" in it?

Dont mean to sound snarky, just pointing out gaps in the thought process.
« Last Edit: 11/10/2011 04:49 PM by Jim »

Offline JRThro

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #614 on: 11/10/2011 04:52 PM »
Why not suggest TDRS, whose name has "data relay" in it?

Dont mean to sound snarky, just pointing out gaps in the thought process.

Okay, what about TDRS?  (joking)

Jim, pointing out gaps in people's thought process does sound, and is, snarky.  ;)

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