Mangalyaan : ISRO's Mars Orbiter Mission

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby SSridhar » 11 Nov 2013 13:29

kvraghavaiah wrote:Cant the arrival time at Mars be adjusted by slightly changing the direction of the route from earth to mars in the final firing (so that MOM path intersects the Mars orbit a bit early or later based on its direction adjusted)

While certain course corrections (indeed, three planned) will be made because of various factors, the path that is chosen is the best in terms of energy efficiency. Anything else could cause more energy to be expended with consequent shortening in mission life or even failure to reach Mars. The sixth firing which imparts the escape velocity to MOM takes advantage of the gravitational pull of the sun to make the MOM reach the Mars Sphere of Influence at the right time and the right place. Remember that an almost similar amount of energy needs to be spent, as in escaping the earth, by the MOM to de-boost and remain in a Martian orbit after reaching there. Fuel needs to be preserved.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby manoba » 11 Nov 2013 15:14

ISRO's Press Release on 11 Nov MOM's Orbit Raising Manoeuvre.

Plus, details about previous three orbit-raising operations.

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.

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.


http://www.isro.gov.in/pressrelease/scr ... Nov11_2013

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby prashanth » 11 Nov 2013 15:16

Mars mission: After glitch, Isro plans supplementary orbit-raising operation tomorrow

The Indian Space Research Organization (Isro) has come up with an explanation on the Mars Orbiter Mission's fourth orbit-raising operation that could not take the apogee of the spacecraft to the intended one lakh km.

"In the fourth orbit-raising operation conducted this morning (November 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," Isro said.

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.

Isro said during the fourth orbit-raising operations held today (November 11, 2013), the redundancies built-in for the propulsion system were exercised, namely, (a) energizing 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 energized 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," Isro explained. {Do they mean that the spacecraft was propelled by thrusters instead of LAM?}

While this parallel mode of operating the two coils is not possible for subsequent operations, they could be operated independently in sequence, Isro said.
Last edited by prashanth on 11 Nov 2013 15:28, edited 4 times in total.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby SSSalvi » 11 Nov 2013 15:20

@sarvana
Latest orbital vectors ( after 3rd Orbit Raising Maneuver ) is available at

http://www.celestrak.com/NORAD/elements/tle-new.txt

Elements post 4th ORM have yet to appear.. maybe tonight ( US daytime )..

I am following it religiously ..

Have all 4 sets

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby saumitra_j » 11 Nov 2013 15:26

From the ISRO website:
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.

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.

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.

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

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby rahulm » 11 Nov 2013 16:47

The report states that the thrusters fired and the incremental velocity reduced - (don't know if this is cause and effect).

I don't understand - if the use case of the primary and secondary solenoid coil being energised together were gamed,then was the fuel flow cut off to the LAM an expected outcome and if so did ISRO not plan for this during orbit raising maneuver? IOW, why the surpise if this was planned?

If the thrusters fired for attitude control as a consequence of the LAM shutting down then, if my understanding is correct, almost certainly this will have an impact on the fuel available for the mission.

Many years ago in a GSAT, thrusters were used in lieu of the LAM to try and recover a satellite after differing flow rates in 2 fuel tanks resulted in the satellite's centre of gravity being shifted. ISRO used thrusters to try and reach the satellite to geo orbit.

I am not a space guru - so will defer to gyani's

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby prashanth » 11 Nov 2013 17:33

saumitra_j wrote:I don't understand - if the use case of the primary and secondary solenoid coil being energised together were gamed,then was the fuel flow cut off to the LAM an expected outcome and if so did ISRO not plan for this during orbit raising maneuver? IOW, why the surpise if this was planned?


We will have to wait until 5 AM tomorrow to see if the solenoid valves work fine. I cannot imagine why they risked operating the two valves simultaneously. Last thing we want at this stage is jammed valves that don't let through fuel to the motor.
On second thoughts, may be they tried to operate the redundant (secondary) valve for the fourth manouver but forgot to override the primary valve (automated procedure). Either way, this incident makes one uneasy. Let's hope for the best.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby kvraghavaiah » 11 Nov 2013 17:58

One testing done after deployment... Small mistake. Let us be optimistic that supplimentary firing succeeds. They said..satellite's health is normal.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby harbans » 11 Nov 2013 18:39

They possibly realized that parallel operating of primary and redundant coils is not possible to be tested later and so went on to test it in this maneuver. The software which controls the attitude control thrusters would have a time lag that prevented complete augmentation of incremental velocity. So while they tested all controls including the redundancies, they would need a next normal thrust augmentation to fire it to the correct elliptic. My take.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby saumitra_j » 11 Nov 2013 19:00

But what were they trying to achieve by energising both the valves togethger? Higher fuel flow rates and hence higher thrusts? What was the purpose of this step? Wish isro was a little more verbose for mango abduls like me....

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby PratikDas » 11 Nov 2013 19:24

saumitra_j wrote:But what were they trying to achieve by energising both the valves togethger? Higher fuel flow rates and hence higher thrusts? What was the purpose of this step? Wish isro was a little more verbose for mango abduls like me....


The ISRO press release does clearly refer to the coils as primary and redundant, not primary and secondary. If more thrust was achievable by activating both coils and if this higher thrust was a necessary component for getting Mangalyaan to Mars, then the redundant coil would not really be a redundant coil, rather a secondary coil. So I don't think additional thrust was the goal, rather the goal might have been additional reliability in keeping the fuel line open by keeping both coils open simultaneously during a critical manoeuvre. The alternative would be to activate the redundant coil if the primary fails. The amount of time taken to activate the redundant coil in this case, including the time taken to detect the failure, might be a tad too long and too late for preventing overshoot or undershoot.

Perhaps not enough current was available to drive both solenoids and the onboard systems simultaneously?

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby member_23832 » 11 Nov 2013 20:28

ISRO press release says the Spacecraft is healthy, they energised both the primary and the redundant coils to increase the flow of propelleant to get the additional thrust probably in double quick time..??...but flow to the liquid engine stopped..is there any other valve apart from the above mentioned valves..??...since the LAM did'nt fire, the thrust level agumentation logic activated all the thrusters to achieve the required thrust. This was the back-up plan, but may be thrusters cannot achieve the same thrust level of LAM. I dont know how long the thrusters fired or how much fuel it consumed in this process.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby SaiK » 11 Nov 2013 21:13

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.

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


!? I assume redundant designs playing here to allow only one to be engaged. sounds like something not correct from the definitions of redundancy.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby negi » 11 Nov 2013 21:25

One cannot rule out the possibility of the word redundant being used instead of secondary erroneously (just verified it's ISRO release). It seems to me that the both Attitude control motor and the LAM share their fuel tanks and that is why when both were operated in simultaneous mode LAM froze but when operated individually they seem to work fine.
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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby PratikDas » 11 Nov 2013 21:25

SaiK ji, I have a feeling they were aiming for Hot Redundancy instead of Warm Redundancy as described here: Schneider Electric: Three Levels of Redundancy

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby rahulm » 12 Nov 2013 00:35

Others have questions too.Emily Lakdawala http://www.planetary.org/blogs/emily-lakdawalla/2013/11110806-mars-orbiter-mission-update.html

..., 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.


That's where I cam coming from. It's the fuel that concerns me.

I get the warm versus hot redundancy but wouldn't the system have interlocks to ensure that either the primary or the redundant valve works - not both together. An XOR situation?

Or Maybe they [ISRO] 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
This would be a nice outcome.


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

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:


However, from http://www.bbc.co.uk/news/science-environment-24900271
"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."
- So its a glitch but the PSLV's precision has provided a fuel buffer.

Unofficial confirmation about the glitch

http://blogs.wsj.com/indiarealtime/2013/11/11/first-hiccup-for-indias-mars-mission/
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. [So why test it?]"

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby harbans » 12 Nov 2013 00:53

I think they were testing the redundancy and this was the only time. What in their hurry to test the redundancies they 'forgot' that the thrusters would not augment completely what the LAM is supposed to do. Thus the planned orbit could not be achieved. Possibly they realized that only after starting the redundancy procedures. This is a very hurriedly patched mission..and it's highly possible they did not factor in the software limitations. Once they got it, they said Oh, Spacecrafts OK, no problems, 4 kg fuel is still saved from efficient orbit insertion..so no problems. And there is no problem as such, just a small scare to us jingo's. These 'silly' kind of things do happen when one performs checks on such kind of systems. In fact worse things happen in reality. It's a bit hard to put it up in publec. SO ISRO puts it up with some jargon. But as i earlier thought, it is just this. :D

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby SaiK » 12 Nov 2013 00:53

any news or links to support that ISRO tested out this firing both primary & redundant scenario on the ground?

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby ramana » 12 Nov 2013 01:19

rahulm, In the MOM brochure or th ISRO website do they give the thrusters thrust values. Obvioulsy it would be much less than the LAM thrust of 440N.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby rahulm » 12 Nov 2013 02:35

From my earlier post on page 8 of this thread, Magalyaan has 8 thrusters @ 22N each.

Craft also has 4 reaction control thrusters @ 5 Nms each.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby ramana » 12 Nov 2013 03:32

So if the LAM(440N) did not perform the thursters would be hard pressed to make it up being less than half of the total thurst (8x22N).

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Bade » 12 Nov 2013 03:48

SriKumar wrote: The inlined image above on altitudes (by indranilroy) suggests a 78,000 km apogee for 3rd boosted orbit, but per an ISRO conference on Oct. 30, i.e. prior to launch, quoted a number of 70,656 km. I think the 78,000 km number is suspect (or old number). 3rd boosted orbit looks good.
....

Thanks for that clarification. I did not see your reply earlier.

Ramana, as they claim they can still fire them in sequence (primary and secondary) if needed all is ok, no. If the fuel efficiency of the thrusters are the same as the LAM then they got the quantum of thrust for the fuel consumed (2kg ? as claimed), even if below the target impulse on schedule. So nothing lost from a fuel budget point of view.

Looking forward to today's results in a few hours.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby andy B » 12 Nov 2013 03:49

rahulm wrote:From my earlier post on page 8 of this thread, Magalyaan has 8 thrusters @ 22N each.

Craft also has 4 reaction control thrusters @ 5 Nms each.


saar if you are back in melb drop us a note please @ anand-83 at hawtmail dawt com thanks mods sorry about OT

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Bade » 12 Nov 2013 04:03

Everything is under control, says ISRO

‘No reason to panic’

An official involved in the building of the Mars spacecraft said, “Everything is safe and under control. There is no reason for panic.”

ISRO scientists explained to The Hindu that the 440-Newton engine onboard is equipped with a primary and a redundant electrical coil that enable the fuel and the oxidiser to flow through two valves of the spacecraft.

During the firing on Monday morning, the team was trying to use both the primary and the redundant coils together as part of a trial. However, there was no fuel flow in this mode and the orbiter could not pick up the required velocity or reach the desired higher orbit.

Meanwhile, the time slot for firing the engine had expired as the spacecraft had moved away.

A senior engineer involved in the process said, “Both the coils are working independently (but not if they are switched on together.) Tomorrow we will use the primary coil (as they did on November 7, 8 and 9.) It’s a very minor issue. We are confident that we will overcome it.”

He explained: “In the last three firings we operated only the primary coil. Today we wanted to conduct a trial. We first operated the primary coil and the redundant coil later, and both worked independently. We then switched on both together in the test firing today but the system did not work in that mode. So we went back to using them separately and they worked well.

The release said, “In the fourth orbit-raising operation conducted on November 11, the apogee (the farthest point to Earth) of the 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 m/second originally planned to raise the apogee to about 1,00,000 km). The spacecraft is in normal health. A supplementary orbit-raising operation is planned tomorrow (November 12) at 0500 hrs.”

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Vinod Ji » 12 Nov 2013 04:57

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. says ISRO's Mars Orbiter Mission face book page

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby sanjaykumar » 12 Nov 2013 05:11

Thank goodness.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby SaiK » 12 Nov 2013 05:40

nice to know that..

e A senior engineer involved in the process said, “Both the coils are working independently (but not if they are switched on together.) Tomorrow we will use the primary coil (as they did on November 7, 8 and 9.) It’s a very minor issue. We are confident that we will overcome it.”He explained: “In the last three firings we operated only the primary coil. Today we wanted to conduct a trial. We first operated the primary coil and the redundant coil later, and both worked independently. We then switched on both together in the test firing today but the system did not work in that mode. So we went back to using them separately and they worked well.”


makes sense! working as redundancy design I was thinking then [XOR].

PrathikDas, I am not sure if we could translate to hot, warm and cold here. May be, we have no details to dig, as to what levels of automation is there for redundant component to take over. Per the description here, it appears that the firing was done on cold mode onlee.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby manoba » 12 Nov 2013 07:14

Fourth supplementary orbit raising manoeuvre successful.

From ISRO's page.

Fourth supplementary orbit raising manoeuvre of Mars Orbiter Spacecraft, starting at 05:03:50 hrs(IST) on Nov 12, 2013, with a burn Time of 303.8 seconds has been successfully completed.The observed change in Apogee is from 78276km to 118642km.


From FB Page, it says, the velocity added is 124.9 m/s.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby SSridhar » 12 Nov 2013 07:27

India's Mars Mission: The Media Converts Science to a Soap Opera - Ajay Lele, The Space Review

He rebuts all the half-baked, motivated and Western-inspired arguments against this mission.

To Mars, with no ambiguity of purpose - Bijal 'Bee' Thakore, The Space Review

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby rahulm » 12 Nov 2013 08:03

The way I read this is:

Total velocity to be imparted in 4th burn was 130 m/s

Velocity added in 4th burn (lets call it 4a)was 35 m/s
velocity added in supplemental burn (lets call it 4b) was 124.9 m/s

Therefore, total velocity added = 44a+4b= 159.9 m/s unless, when ISRO says velocity added it means total velocity. although I doubt it.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Bade » 12 Nov 2013 08:10

^^^ Very likely so, as the Apogee for the new orbit after today's burn is much higher than what was planned for the initial 4th parking orbit.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby rahulm » 12 Nov 2013 08:38

Andy B, please check email.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Bade » 12 Nov 2013 08:59

Slightly larger orbital period for this parking orbit. Nothing ominous. No worries for sure.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby vina » 12 Nov 2013 09:22

pandyan wrote:what is the implication Bade saab?

The next burns be of shorter duration to impart lesser velocity than planned. Think of this. If X is the total velocity required on Dec 1 on the way to moon, each of that at the perigee is cumulative. So if you now have greater than what was planned in the 4th firings, the remaining two firings will be of lesser duration.

They would have calculated how much burn would be needed in the 4th burn 2nd attempt, when the first one hadn't fully met objective and compensated for that to reach the Dec 1 window.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby negi » 12 Nov 2013 09:26

Earlier this year I had read that Sun's magnetic field is going to flip in a few months ( it's a ~11 year cycle) not sure how it will affect the Mangalyan and it's instruments.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Indranil » 12 Nov 2013 10:13

Bade wrote:Slightly larger orbital period for this parking orbit. Nothing ominous. No worries for sure.


So I was right :).

indranilroy wrote:But it becomes very interesting now. Because of this unintended shorter orbit, the craft will reach its perigee a few hours earlier. If everything goes according to plan, then the injection into heliocentric orbit will also be a few hours earlier. Unless they make the 4th and/or 5th parking orbit slightly larger than what they had initially planned.


negi wrote:Earlier this year I had read that Sun's magnetic field is going to flip in a few months ( it's a ~11 year cycle) not sure how it will affect the Mangalyan and it's instruments.

I don't know about EMI, but there will be no change in the path, even if this happens.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby kvraghavaiah » 12 Nov 2013 11:41

negi wrote:Earlier this year I had read that Sun's magnetic field is going to flip in a few months ( it's a ~11 year cycle) not sure how it will affect the Mangalyan and it's instruments.


Magnetic field changes in Sun change only the level of exposure of MOM to charged particles slightly. It has practically little effect. Nothing to worry.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Pratyush » 12 Nov 2013 12:13

^^^

When launching the probe, won't the ISRO have factored the 11 year solar cycle?

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby Pratyush » 12 Nov 2013 12:20

Mars orbiter bounces back; raring to go at 1.18 lakh kilometres

It seems that the orbital issues have now been resolved.

"During the orbit-raising operations conducted since November 7, 2013, Isro has been testing and exercising the autonomy functions progressively. 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," Isro said.

The drawback means the planned simultaneous operation of two coils would not be possible anymore, but if the rest of the operations happen as planned, the spacecraft will reach the Martian orbit on September 24.


Can some one tell this lay man what is the meaning of the portion in bold.

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Re: Mangalyaan : ISRO's Mars Orbiter Mission

Postby chetak » 12 Nov 2013 12:34

Pratyush wrote:Mars orbiter bounces back; raring to go at 1.18 lakh kilometres

It seems that the orbital issues have now been resolved.

"During the orbit-raising operations conducted since November 7, 2013, Isro has been testing and exercising the autonomy functions progressively. 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," Isro said.

The drawback means the planned simultaneous operation of two coils would not be possible anymore, but if the rest of the operations happen as planned, the spacecraft will reach the Martian orbit on September 24.


Can some one tell this lay man what is the meaning of the portion in bold.



http://isro.gov.in/pressrelease/scripts ... Nov11_2013

ISRO reports that the spacecraft is in good health, and that only a small amount of fuel was wasted. Tonight they will again re-attempt to raise the orbit to the required height. Then after that there will be one more planned orbit-raising after a few days, and then the planned final engine burn on Dec 1 to fling the orbiter towards Mars.

The problem seems to have resulted from their attempt to perform various equipment checks as part of the orbit-raising maneuver. The spacecraft's main rocket motor has 2 fuel lines - a primary one and an extra one for backup - and the fuel flow through each is regulated by their respective solenoid valve. So to do a systems check while the rocket was operating, they opened the main fuel line / flow valve and this worked, then they switched to the backup fuel line / flow valve and this also worked, but when they tried to use both fuel lines / flow valves together at the same time, then this resulted in a stoppage of the fuel flow to the rocket motor and its shutoff.
The software's automatic thrust augmentation logic then triggered on its own to fire additional thrusters to compensate, however their weaker strength meant the resulting orbit achieved was only 78K km instead of 100K km.

So what they've then learned from this is that they cannot use both valves / fuel lines together at the same time. This may be due to a tank pressure limitation. Perhaps it can't supply the required pressure to push enough fuel through if both valves are open, instead of just either one alone.

If that's the case, then it's something that should have been tested and discovered on the ground first. I recall reading that ISRO did not build a duplicate mockup of the spacecraft for testing on the ground, but only tested using software simulations in order to save costs. Maybe this is something which would have turned up had they tested on a physical duplicate of the spacecraft. Being able to use both the main and backup fuel lines together is not absolutely essential, however it's what traditionally gets done during the deceleration at Mars, in order to guard against stoppage of fuel flow which would be fatal during this critical maneuver. At least by discovering the problem now, they can reconfigure a software workaround to switch to backup in the event of a fuel line problem.


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