Author Topic: ISRO Mars Orbiter Mission - Nov 2013 launch to September 2014 arrival - UPDATES  (Read 437515 times)

Offline Star One

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Excellent news glad they recovered from the minor setback they had.

From the schedule of burns I saw earlier on this thread there appears to be something like a two week gap between the penultimate manoeuvre & the final firing to leave Earth orbit. Is this to allow equipment to be further checked out before it departs or is there more to it than this?

Offline seshagirib

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Excellent news glad they recovered from the minor setback they had.

From the schedule of burns I saw earlier on this thread there appears to be something like a two week gap between the penultimate manoeuvre & the final firing to leave Earth orbit. Is this to allow equipment to be further checked out before it departs or is there more to it than this?

From the orbits of mars and earth, at the moment mars is ahead of earth, but the earth which moves faster in the inner orbit is catching up with mars. If the s/c were to leave earth orbit now it would have to travel a longer distance by itself. However if it leaves the earth orbit at end of the month, the earth would have carried it closer to mars and hence a lower travel distance.

My guess is that leaving earth's orbit around the end of the month results in an energy optimized trajectory.

Offline Star One

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Excellent news glad they recovered from the minor setback they had.

From the schedule of burns I saw earlier on this thread there appears to be something like a two week gap between the penultimate manoeuvre & the final firing to leave Earth orbit. Is this to allow equipment to be further checked out before it departs or is there more to it than this?

From the orbits of mars and earth, at the moment mars is ahead of earth, but the earth which moves faster in the inner orbit is catching up with mars. If the s/c were to leave earth orbit now it would have to travel a longer distance by itself. However if it leaves the earth orbit at end of the month, the earth would have carried it closer to mars and hence a lower travel distance.

My guess is that leaving earth's orbit around the end of the month results in an energy optimized trajectory.

Thanks. I wondered if it was something like this that was the reason for the delay.

Offline plutogno

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Excellent news! The next opportunity for a burn near perigee (one orbit later than this) appears to be around 46h45m later. That's almost two days, so ~02:45 IST on Nov 14, if my spreadsheet calculations are correct. It would be great to get a confirmation of that timing from ISRO, though!

Note also that the two intermediate orbits, the one at 78100 and the one at 118400 km have a total period of 1615+2798 = 4413 minutes.
Two revolutions in a 350 x 100000 km orbit would have taken about 4460 minutes, so at the next perigee MOM will be more or less in the same point in space where it would have been if it had been inserted in the correct orbit from the start. I am definitely expecting the next maneuver for that time (shortly after 22UTC on Nov 13)!

edit: this of course assumes that the original targeted orbit was 350 x 100000 km
« Last Edit: 11/12/2013 04:52 PM by plutogno »

Online LouScheffer

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Excellent news glad they recovered from the minor setback they had.

From the schedule of burns I saw earlier on this thread there appears to be something like a two week gap between the penultimate manoeuvre & the final firing to leave Earth orbit. Is this to allow equipment to be further checked out before it departs or is there more to it than this?

From the orbits of mars and earth, at the moment mars is ahead of earth, but the earth which moves faster in the inner orbit is catching up with mars. If the s/c were to leave earth orbit now it would have to travel a longer distance by itself. However if it leaves the earth orbit at end of the month, the earth would have carried it closer to mars and hence a lower travel distance.

My guess is that leaving earth's orbit around the end of the month results in an energy optimized trajectory.
This is correct.  MAVEN is headed directly to Mars (no stay in earth orbit) and the window is from Nov 18th to Dec 7th (but other sources have a 36 day window, see http://www.space-flight.org/docs/2013_winter/FinalProgram.pdf ).  Assuming the optimum is in the middle of the window, the best time to leave Earth for Mars near the end of November.

Offline vyoma

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Satellite trackers are now reflecting changes in apogee and perigee. Attaching data taken after Nov 12th supplementary maneuver
(source: http://www.n2yo.com/satellite/?s=39370)

By the way, any updates on payload tests? Especially camera :)
« Last Edit: 11/14/2013 06:22 AM by input~2 »

Offline seshagirib

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^perigee is lower than the previous reported ~345km??

Offline input~2

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MOM orbit at epoch of most recent TLE (Nov 12, 0003UTC):

269 x 117868 km x 19.29
Argument of perigee: 287.14



Offline Star One

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^perigee is lower than the previous reported ~345km??

Is there anything to be concerned about with such a lower than expected perigee?

Offline ss1_3

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Offline Ben the Space Brit

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^perigee is lower than the previous reported ~345km??

Is there anything to be concerned about with such a lower than expected perigee?

Well, lower perigee means more drag from the upper atmosphere (c.f. Skylab). So, in the long run, the orbit is going to be less stable and will decay faster. In the time-scale that MOM is scheduled to remain in its parking orbit, probably not.
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Offline Star One

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^perigee is lower than the previous reported ~345km??

Is there anything to be concerned about with such a lower than expected perigee?

Well, lower perigee means more drag from the upper atmosphere (c.f. Skylab). So, in the long run, the orbit is going to be less stable and will decay faster. In the time-scale that MOM is scheduled to remain in its parking orbit, probably not.

Is there likely to be any attempt to raise the perigee with the next burn?

Offline JWag

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I would've thought they deliberately lowered the perigee to take advantage of the Oberth effect when doing the final escape burn. 

Disclaimer: I'm not a rocket scientist and may have no idea what I'm talking about.
« Last Edit: 11/14/2013 07:19 PM by MondoMor »

Online hop

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I would be cautious about assuming the "change" in perigee is a real change in the orbit.

If you look at the previous posts by vyoma, the perigee values have bounced around between 270-350 km before (e.g. http://forum.nasaspaceflight.com/index.php?topic=29440.msg1117771#msg1117771), but burns around perigee and drag shouldn't change the perigee altitude much. I don't have a good feeling what normal perturbations would be in that kind of orbit, but 80 km seems like a lot.

Different sources may also not be directly comparable http://forum.nasaspaceflight.com/index.php?topic=29440.msg1118227#msg1118227

Offline Danderman

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I would've thought they deliberately lowered the perigee to take advantage of the Oberth effect when doing the final escape burn. 


Unless you mean that "deliberately lowered the perigee" = letting natural drag reduce the perigee, any propulsive maneuver to lower the perigee would waste precious propellant.

Online hop

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Unless you mean that "deliberately lowered the perigee" = letting natural drag reduce the perigee, any propulsive maneuver to lower the perigee would waste precious propellant.
The effect of drag on perigee would be negligible in any case, drag is mostly at perigee, which will only lower the apogee.

Offline sdsds

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Is there any chance there had been a very small retrograde maneuver (e.g. using RCS thrust) at the prior apogee resulting in the lower perigee, and this change wasn't reported until after the subsequent apogee-raising burn?
-- sdsds --

Offline seshagirib

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I would've thought they deliberately lowered the perigee to take advantage of the Oberth effect when doing the final escape burn. 

Unless you mean that "deliberately lowered the perigee" = letting natural drag reduce the perigee, any propulsive maneuver to lower the perigee would waste precious propellant.

The trajectory design for TMI might have required them to lower the perigee (?)

The previous abnormal (4th) manoeuvre might have raised the perigee as a side effect, because the ACT's fired after the LAM failed to fire, thus the delay resulted in applying the thrust at sub-optimal positon in the orbit.....just guessing.

Added later:  Would be nice if "someone" can post the expected orbital parameters after each of the orbit rising manoeuvres.

« Last Edit: 11/15/2013 03:46 AM by seshagirib »

Offline vyoma

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Next orbit raising maneuver: 2 AM IST (approx), Nov 16.
http://www.thehindu.com/sci-tech/science/some-lunar-spell-on-way-to-mars/article5353014.ece
Quote
November 16, around 2 a.m., is when the craft is due to get its orbit raised for the fifth time and also the last time near the Earth. (ISRO discounts the November 12 correction as a supplement of the fourth operation.)

Quote
In the next few days through November 30, some payloads or instruments on the orbiter are to be switched on as part of trials.

Offline plutogno

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according to http://www.zarya.info/Calendar.php the perigee will be further reduced in tonight's burn

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