As the s/c approaches Mars will it focus the camera and other instruments on the planet before MOI burn to (e/i)nsure some science return from the mission ?
Quote from: seshagirib on 08/31/2014 04:30 pmAs the s/c approaches Mars will it focus the camera and other instruments on the planet before MOI burn to (e/i)nsure some science return from the mission ?I read in media that ISRO is planning to take pictures after MOI maneuver completes.
"Since the engine has been idle for more than 300 days, we may have to test fire it," Isro chairman K Radhakrishnan told TOI. There is some uncertainty over a couple of valves and parts malfunctioning because of the corrosive fuel. After firing for the trans—Mars Injection, the primary fuel channel has been disabled to prevent leaks. The planned test—firing will be carried out using a secondary channel which will remain open for the actual firing on September 24 to remain in the Martian orbit. The test is not without handicaps. Since the spacecraft is moving at a speed of more than 22km per second, test—firing for a mere five seconds can take it away from the trajectory by more than 100km. This deviation will have to be factored in while carrying out the final orbit—capture manoeuvre around Mars.
“We are going to have the MOI on the September 24 morning. The engine firing is planned to start at 7.18 a.m. and last 28 minutes,” ISRO Chairman K. Radhakrishnan told The Hindu.
The ultimate moment, according to Dr. Radhakrishnan, will be “when we get the message at 8.15 that morning that the orbiter has captured the Mars orbit. Theoretically, that fructifies the objective of this mission. But today, our job is to gear up for the orbit insertion.”The spacecraft enters the Martian range of influence on September 22. ‘The action’ starts two days later when it would be about 700 km from the planet. First, at 6.50 a.m., the spacecraft will be turned or re-oriented. The most crucial act is to fire the engines on it to slow the spacecraft from a velocity of 22 km a second to 1.5 km a second. ISRO plans to fire all nine ‘guns’ on board: the main ‘LAM’ or liquid engine and eight small thrusters.
The most crucial act is to fire the engines on it to slow the spacecraft from a velocity of 22 km a second to 1.5 km a second.
QuoteThe most crucial act is to fire the engines on it to slow the spacecraft from a velocity of 22 km a second to 1.5 km a second.That's a delta-V change of 20.5 km/s! Surely there's a mixup somewhere. Mars orbit insertion is more like 2.5 km/s delta-V.
On September 22, about 48 hours prior to its crucial orbit insertion, the Mars Orbiter Mission's (MOM) 440N liquid apogee motor (LAM) will be test-fired for five seconds. The engine's test-firing will result in the spacecraft deviating from its trajectory, which will be corrected later. Isro chairman K Radhakrishnan told TOI on Friday that should there be a problem with the motor, the space agency will resort to its 'Plan B' for the Mars orbit insertion. This backup plan involves firing of the eight 22 Newton thrusters for the insertion.
I have trouble understanding a fundamental aspect of a Mars Orbit Insertion. Doesn't a spacecraft arriving on a Hohmann transfer ellipse really need a prograde (not retrograde) burn to match the heliocentric velocity of Mars? Isn't it at apohelion, and thus needing a "kick" to circularize its heliocentric trajectory?
A good overview of MOM's science instruments from Aviation Week: http://awin.aviationweek.com/portals/awin/Interactives/AWST/mom/mom.htmlBTW maybe the thread can have a better title like "Indian Mars Orbiter Mission - Launch and Mission updates"?
Can you take us through the chain of events scheduled from now to September 24? Also what is going to be the crucial challenge?On September 14th, we will be uploading the sequence of commands in the spacecraft with time tagging. It will be followed by test firing and then on the crucial day (September 24) at 8.15 a.m we will be able to say the Mission is successful.The crucial challenge will be restarting the 440N main liquid engine, the single main engine which has been sitting idle for 300 days, since the Trans-Martian Insertion Burn was performed. This is the longest interval between LAM firings ever - the engine is usually employed on Geostationary Satellites that use it over a period of days or weeks to achieve their planned orbit.On the ground we did testing of a similar liquid engine to see its restart characteristic, this was done well before the MOM launch. It was positive. In the recent days also again we have done ground testing and it was also successful.
Do you have plan B, if there is a problem in restarting the engine?Yes. Using the small eight 22 N thrusters for attitude control or orientation, which will not give you this original target though. It will be salvaging of the mission. But what we have tried to ensure before hand is to build in the necessary facilities for ensuring restart and also confirmation.At the time of MOI if you find it didn't restart, then we will loose that opportunity to operate the contingency, since it has to start early considering they are small thrusters and it takes longer duration.In Plan A it is 440N plus, with the eight thrusters, to be fired in the given duration. But if the main engine does not fire, then we have to do the entire job by the small thrusters but then you have to fire them for longer duration and if you have to get the correct ellipse around Mars, you have to start firing early. There must also be enough fuel for that purpose.
Quote from: antriksh on 09/02/2014 01:57 amQuote from: seshagirib on 08/31/2014 04:30 pmAs the s/c approaches Mars will it focus the camera and other instruments on the planet before MOI burn to (e/i)nsure some science return from the mission ?I read in media that ISRO is planning to take pictures after MOI maneuver completes.antariksh: do you have any pointers to the media reports? -Thanks
Events to followSeptember 24: At 6.57 am, Final phase of operation will start. Reorientation of the spacecraft should commence and it has to stabilise.At 7.15 am: Liquid engine firing would start and in the nominal operation that should be for about 24 seconds. Then once the desired velocity is achieved, the computer will give the command to cut the firing based on the accelerometer, which is onboard the spacecraft.Signal will take 12.5 minutes to reach here. That means Isro will know only after 12.5 minutes what is happening at the space.At 8.15 am, Isro could confirm whether the operation is successful.Later on the day: Colour camera will also be operated on the same date.
K. Radhakrishnan, Chairman, Indian Space Research Organisation (ISRO), said, “Commands will be loaded into the Mars spacecraft on Sunday for its insertion into the Martian orbit.” Since the spacecraft is on its course to Mars, there would be no trajectory correction manoeuvre of the spacecraft, originally scheduled on the same day. “We are doing a re-start of the 440 Newton engine for four seconds at 2 p.m. on September 22. We are doing that re-start to confirm [that the engine will erupt into life on September 24],” he said
This mission is essentially a technology mission. It is to demonstrate our ability to orbit a spacecraft around Mars and the five scientific instruments we have put in are secondary ones.
Quote from: Galactic Penguin SST on 09/08/2014 11:11 amA good overview of MOM's science instruments from Aviation Week: http://awin.aviationweek.com/portals/awin/Interactives/AWST/mom/mom.htmlBTW maybe the thread can have a better title like "Indian Mars Orbiter Mission - Launch and Mission updates"? Interestingly the camera slide says that it will be used to image the sattelites Phobos and Diemos.This is the first time I am seeing any mention of plans to study the sattelites. Hope they also have (revised) oppurtunistic plans for looking at the comet too.
The tri-colour MCC gives images and information about the surface features and composition of Martian surface. They are useful to monitor the dynamic events and weather of Mars. MCC will also be used for probing the two satellites of Mars — Phobos and Deimos, ISRO officials said
Does anyone have a link to the pork-chop plots for the MOI burn, and/or the entire mission?
... why did they include something like a Mars Colour Camera, instead of an experimental ion engine (in addition to the LAM)?