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Mars Orbiter Mission Update: Supplemental burn planned for today

Posted by Emily Lakdawalla

2013/11/11 10:09 CST

Topics: Mars Orbiter Mission (MOM), mission status

EDITED Nov 11 3:46pm PST: ISRO now reports the supplemental orbit raise maneuver was successful. Next burn planned for November 16 IST (likely November 15 PST).


Yesterday, the Mars Orbiter Mission was commanded to perform a rocket burn that would have raised the apogee of its orbit around Earth from 71,623 kilometers to about 100,000 kilometers. The spacecraft began its burn, but underperformed, raising the apogee only to 78,276 kilometers. ISRO has planned a supplemental burn for November 12 at 05:00 IST (today at 15:30 PT / 23:30 UT) in order to make up the deficit.

Mars Orbiter Mission supplemental maneuver November 11, 2013

ISRO

Mars Orbiter Mission supplemental maneuver November 11, 2013

ISRO issued a statement today explaining the anomaly. Here is the full text, with my comments interspersed:

Supplementary Orbit Raising Manoeuvre Planned for Mars Orbiter Spacecraft

In the fourth orbit-raising operation conducted this morning (Nov 11, 2013), the apogee (farthest point to Earth) of Mars Orbiter Spacecraft was raised from 71,623 km to 78,276 km by imparting an incremental velocity of 35 metres/second (as against 130 metres/second originally planned to raise apogee to about 100,000 [1 lakh]* km). The spacecraft is in normal health. A supplementary orbit-raising operation is planned tomorrow (November 12, 2013) at 0500 hrs IST to raise the apogee to nearly 1 lakh km.

"The spacecraft is in normal health" -- it is not in safe mode, a status confirmed today by NDTV reporter Pallava Bagla. The statement went on to talk about the successful testing and operation of major primary and backup spacecraft systems:

During the orbit-raising operations conducted since November 7, 2013, ISRO has been testing and exercising the autonomy functions progressively, that are essential for Trans-Mars Injection (TMI) and Mars Orbit Insertion (MOI).

During the first three orbit-raising operations, the prime and redundant chains of gyros, accelerometers, 22 Newton attitude control thrusters, attitude and orbit control electronics as well as the associated logics for their fault detection isolation, and reconfiguration have been exercised successfully. The prime and redundant star sensors have been functioning satisfactorily. The primary coil of the solenoid flow control valve was used successfully for the first three orbit-raising operations.

Mars Orbiter Mission has a much higher degree of redundancy and autonomy than past Indian spacecraft. When a spacecraft in Earth orbit runs into a snag, it can usually safely quit work and hang around orbiting Earth until engineers can figure out the problem. And it can be more cost-effective to plan and launch multiple missions than it is to build a lot of redundancy into a single mission -- it's like self-insuring rather than paying for the very costly insurance of redundant systems and the excess mass and complexity they bring.

But one-of-a-kind deep-space craft need to be able to respond appropriately to all kinds of problems and still know how to "phone home" for help; and it's so much trouble to get a spacecraft to Mars that your spacecraft is its own spare. The logic and autonomy required for a robot to not shut down in the face of a problem, identify the problem correctly, diagnose malfunctioning systems, shut them down safely, and switch over to appropriate backups, are complex and challenging to engineer. The Mars Orbiter Mission represents the most difficult challenge in spacecraft autonomy that India has faced yet. And this weekend, the artificial intelligence of their spacecraft was put to its first real test:

During the fourth orbit-raising operations held today (November 11, 2013), the redundancies built-in for the propulsion system were exercised, namely, (a) energising the primary and redundant coils of the solenoid flow control valve of 440 Newton Liquid Engine and (b) logic for thrust augmentation by the attitude control thrusters, when needed. However, when both primary and redundant coils were energised together, as one of the planned modes, the flow to the Liquid Engine stopped. The thrust level augmentation logic, as expected, came in and the operation continued using the attitude control thrusters. This sequence resulted in reduction of the incremental velocity.

I'll admit that I am having trouble parsing this paragraph. For instance, it's not clear to me whether both primary and backup valves to their main engine were supposed to be operated together, or if that was a mistake, or if it was a surprise that it didn't work to operate them together. "As one of the planned modes" makes it sound like it was intentional (or, at least, that it should have worked), but evidently it didn't work to operate them together. And why did the flow of fuel to the engine stop? Because the spacecraft detected a problem and stopped it, or because (for some reason) flow didn't proceed with both valves commanded to operate at the same time?

At least, when flow stopped, it sounds like the spacecraft successfully detected that and attempted "thrust augmentation" by using the attitude control thrusters to support the planned orbit maneuver. That is good logic to have in place when you are planning a must-not-fail event like a planetary orbit insertion maneuver. However, the final sentence is concerning, because it sounds like the augmentation with the attitude control thrusters did not accomplish what it should have. Rather than increasing the spacecraft's velocity, "This sequence resulted in reduction of the incremental velocity." That sounds bad for two reasons: it sounds like the autonomous function didn't accomplish what it should have, and it also means that precious fuel was wasted. If the orbit adjustment maneuver had simply been an underburn (the main rocket didn't fire for long enough), then there would have been no cost to fuel reserved. But if the attitude adjustment rockets actually reduced the spacecraft's velocity, that would have cost fuel.

Or maybe the final sentence doesn't mean that at all. Maybe they meant to say "This sequence resulted in reduction of the [planned] incremental velocity," explaining why they only got 35 m/s of increased velocity instead of the planned 130. I'm not sure. So I don't know whether we have two anomalies or just one. Regardless, ISRO is unconcerned enough to proceed with a supplemental burn immediately.

The statement ends:

While this parallel mode of operating the two coils is not possible for subsequent operations, they could be operated independently in sequence.

Again, I am left wondering if it was a surprise to mission operators that it did not work to operate both the primary and backup valves to the main rocket engines at the same time. Looking to media reports for quotes from officials makes it seem as though it was a surprise, but one that they say isn't a problem because they won't need to do it in the future. (If that's true, then why test it?) Here are a few statements:

  • In an NDTV story, Pallava Bagla reports: "ISRO Chairman K Radhakrishnan told NDTV today, 'The space craft is healthy and it encountered a problem when a specific redundancy test was being conducted and it failed to reach the desired velocity it was to achieve.' A failure analysis committee will examine why this problem happened, he said, but added that crucially, not much fuel was wasted in the failed attempt.
  • From the BBC, a story based on conversation with reporter Pallava Bagla: "In that redundancy test, two coils in the liquid engine were supposed to be energised simultaneously....Mr Bagla told BBC News that the attempt on Monday morning used up about 2kg of the craft's 852kg fuel load. But he added that the spacecraft's insertion into Earth orbit after launch on 5 November had been so precise, 6kg of liquid fuel had been saved. Even with Monday's glitch, the mission still had a fuel surplus of 4kg."
  • An unnamed official spoke with Wall Street Journal blogger Joanna Sugden: "The fault was discovered when two coils in the satellite, which are responsible for speeding the satellite up and slowing it down, were turned on at the same time. This led to a blockage of fuel and oxidants to the main liquid-rocket engine. 'The satellite’s engine doesn’t work when both coils are simultaneously on,' a spokesman for the ISRO told The Wall Street Journal. 'This is not at all a setback, we got our redundancies [backup plans] checked by this process,' said the spokesman, who declined to be named. He said it was not necessary for both coils to be on at the same time during the rest of the flight plan."

According to the BBC story, assuming today's supplemental burn goes well, the final apogee raise maneuver -- which will take them to about 192,000 kilometers -- is to take place on November 16; the spacecraft will be sent to Mars on December 1.

*"Lakh" is a term used in India, even when communicating in English, to mean 100,000 (which is written "1,00,000"), while "crore" means 10,000,000 (written "1,00,00,000"). They don't typically use "million" or "billion" in India.

 

Or read more blog entries about: Mars Orbiter Mission (MOM), mission status

Comments:

Rahul K: 11/11/2013 11:23 CST

Excellent coverage Emily, much appreciated.

Antariksh: 11/11/2013 11:27 CST

Hi Emily, Nice write-up. It seems to me that ISRO was testing one of the redundancy modes where they had planned to operate both primary and redundant valves simultaneously, which ideally should be used during critical burns like MOI. Since, it did not work out, the augmentation logic stepped in and provided what ever thrust was available from 8 22N thruster. Now, ISRO will have to use if/else on the valves during MOI.

Emily Lakdawalla: 11/11/2013 11:58 CST

If that's the case, though, it seems to me a major problem (and a surprise) that it didn't work. Surely they tested operating the motor with both valves open on Earth? If they expected it to work in space and now it does not, does that make Mars orbit insertion riskier? If they expected it to work in space and it didn't, wouldn't you expect further testing of the system to understand why before they depart for Mars (or indeed before they operate the main engine again)? I'm still quite confused.

Randeep: 11/11/2013 03:55 CST

Well & simply explained, person like me cannot understand orbital science language, however we need to know how close probe get to Mars yet. All these newspaper like BBC & NDTV's correspondent fail to explain what is going on. Great correspondent always can explain that is understandable to all. Unless you cares how smart NDTV & BBC are if nobody understand there reports.

Sumit Raj: 11/11/2013 04:16 CST

Nice explanation Emily.. I know ISRO will sort it out and they would work on their Backup plan. Just we need to wait for next supplemental burn at 5am (IST). Sometime it happens when you tested the stuffs on earth work properly but does not work during mission in Space. Engineers and Scientists will manage it for sure, they must have got some idea.

Leonidas Papadopoulos: 11/11/2013 05:59 CST

Breaking news from MOM's Facebook page: "The supplementary orbit raising manoeuver of ISRO's Mars Orbiter Mission spacecraft, to raise the apogee height to about 1 lakh km completed successfully. Velocity added is 124.9 m/s." Great news!!

Anonymous: 11/11/2013 06:22 CST

Hurray!!! the manouevre is successful. From their update page: http://isro.gov.in/mars/updates.aspx

Prasanna: 11/11/2013 08:28 CST

It seems that some logic controller did not allow the LAM to fire with both valves open and only allowed sequential firing.The launch saved 6 Kgs of fuel because of the precise injection not requiring additional maneuvers..2Kgs were wasted in the 4th burn (only 25% increase in apogee) so we still have 4 Kgs of extra fuel.

Anonymous: 11/11/2013 08:52 CST

If that's the case, though, it seems to me a major problem (and a surprise) that it didn't work. --- I suppose it would have been a cause of failure of the mission if they had not tested it on the first place. Now they know the problem and can easily switch to other slightly complex redundancy modes for MOI. Surely they tested operating the motor with both valves open on Earth? If they expected it to work in space and now it does not, does that make Mars orbit insertion riskier? ---- Since its one of the planned redundancy modes, they must have tested it on earth. Now they need to find out why it didn't work in space. This finding will help in foolproofing future missions with direct TMI. Now as far as MOI is concerned, I don't see any problem. Ideally , both prime and redundant valve should be used, but they can also use other redundancy modes like using the redundant valve only if prime valve doesn't work during MOI. If they expected it to work in space and it didn't, wouldn't you expect further testing of the system to understand why before they depart for Mars (or indeed before they operate the main engine again)? I'm still quite confused. ----- they have already mentioned in their press release that they wont be using this mode in subsequent operations, so I don't think they gonna wait for any inquiry report.

pavan: 11/11/2013 09:01 CST

Emily, Good news is that this minor glitch is solved in the supplementary burn carried out today(Tuesday 5AM IST) and the apogee is successfully raised from 78276 km to 118642 km!! Way to go ISRO!! Now put MOM in cruise mode to MARS..we are all proud of you and with you!!

Premnath Kudva: 11/11/2013 09:34 CST

Excellant report there Emily, solved several doubts that were there in my mind, but have sowed some more. Next few days will make it clear.

madhu: 11/11/2013 10:52 CST

Nice explanation Emily.. thanks a lot

Deoy: 11/12/2013 04:42 CST

Thanks Emily, for your nice and simple explanations. Based on the latest manoeuvre, (raising the apogee to 1.18 Lakh km) do ye have any info on how much fuel burnt or how much fuel saving achieved by ISRO

Shaiju: 11/12/2013 04:42 CST

Thanks Emily! This was the best description I have seen on this subject. Though there are still some confusion over the ISRO explanation, I would prefer to be positive. I would have liked to see the mission carried out by GSLV Mk III which could have bypassed these manueavers with much better fuel back up, whatsoever the ingenuity of ISRO 's slingshot approach should be applauded.

appa: 11/12/2013 04:59 CST

Awesome blog. Wish there is more clear update from ISRO. The http://www.n2yo.com/?s=39370 doesn't show apogee of 1.18 lakh km, Altitude starts to fall from 71,800 KM. Not sure whether it is tracking or satellite problem

Vinodh: 11/12/2013 12:06 CST

Thanks Emily, if you see the ISRO website, it say primary and redundant coils and not valves, they were energising both the coils (primary & redundant) to start the valve operation, for some reasons it did'nt work. They also say it was one of the planned modes, means they should have tested all modes on ground, need to wait and see from ISRO what exactly went wrong.

Anonymous: 11/13/2013 12:38 CST

Is the orbit raising done when Mangalayan is at perigee or apogee?

Kishore: 11/13/2013 03:52 CST

Here is something that puzzles me. The so called "supplementary" burn ideally must have taken place at the perigee to get the maximum benefit from the Oberth effect. The 5am IST time they chose meant that the supplementary burn took place at some random point in the orbit. This is not the most fuel efficient maneuver. Anybody has an explanation?

Nik D: 11/15/2013 04:53 CST

The fifth orbit raising manoeuvre of Mars Orbiter Spacecraft, starting at 01:27 hrs(IST) on Nov 16, 2013, with a burn Time of 243.5 seconds has been successfully completed.The observed change in Apogee is from 118642km to 192874km.

Kevin: 11/15/2013 06:37 CST

Kishore: I'm no expert, but I don't think Oberth applies here. Oberth works when dropping down into a well from your starting point, but when you're trying to escape from the planet you launched from, I don't think it matters where you burn, as long as the burns are prograde. But I would love to have somebody explain the reasoning behind this flight plan. I don't think it matters whether the orbits are orbital or circular. But I have no idea why they are spending several weeks doing larger and larger elliptical orbits. Why not just a single hyperbolic burn? I think the fuel required is the same.

prasanna: 11/15/2013 07:44 CST

Kevin, the Oberth effect indeed applies here.Every perigee burn is raising the apogee and increasing the subsequent perigee velocity.This is being used as the PSLV cannot give a sufficient velocity to escape the Earths orbit and enter the Transmartian Hohman's transfer orbit.Thus the gravity slingshot maneuvers of the earth(Gravity assists) are being used to increase the velocity of the satellite for the final transmartian burn to get a sufficent delta V to enter the transfer Orbit. In the last burn the Perigee velocity was around 10.44 Kms/sec and it has to cross now around 11.2 Kms/sec to allow it to escape earth and enter the transmartian transfer orbit. This was also used by Chandrayaan 1 mission to get into the translunar injection,(5th burn is succesful)

Prasanna: 11/15/2013 07:47 CST

ISRO ave the following details The fifth orbit raising manoeuvre of Mars Orbiter Spacecraft, starting at 01:27 hrs(IST) on Nov 16, 2013, with a burn Time of 243.5 seconds has been successfully completed.The observed change in Apogee is from 118642km to 192874km. The ISRO facebook page gave us continuous live updates during the 5th burn done on NOv 16 1.27 AM IST and we were all having a nail biting time especially when the so called "real time tracking websites(which actually do not do real time tracking) showed junk values at the perigee !! I was hopin to see a new Blog post by Emily but did not see one ;(

Prasanna: 11/15/2013 07:49 CST

This shows the achieved orbit https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-frc3/1471186_1397479530489987_1908402753_n.png

prasanna: 11/20/2013 10:38 CST

First picture form Mars Color camera https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-ash4/p480x480/1472810_1399270930310847_502934609_n.jpg

shrirang: 11/24/2013 09:06 CST

To start an engine to gain speed is the easiest part, the ability to apply the brake during the Mars Orbit Insertion is an important part when the MOM reach it final destination. Despite checking during prelaunch session on earth .The same needs to be done before the MOM leave earth orbit. As the firing session didnt complete no fuel was lost & the engine was fired twice after the 4th round mean the engine is in perfect working condition (b)"logic for thrust augmentation by the attitude control thrusters ( needed in mars orbit) was being tested " was an intended test to check the Satellite progammed logic in near earth orbit rather then at MARS

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