Date: 12/06/2014 The second Trajectory Correction Manoeuvre (TCM-2) of India's Mars Orbiter Spacecraft was successfully performed on June 11, 2014 at 1630 hrs IST. TCM-2 was performed by firing the spacecraft’s 22 Newton thrusters for a duration of 16 seconds.At present, the radio distance between the Spacecraft and the Earth is 102 million km. A radio signal from the Earth to the Spacecraft now takes about 340 seconds. The spacecraft so far has traveled a distance of 466 million km as part of its total Journey of 680 million km.ISRO is continuously monitoring Mars Orbiter Spacecraft using Indian Deep Space Network (IDSN). The spacecraft and its five scientific instruments are in good health.
Still, I think this will probably the longest period between LAM burns... when it does the orbital insertion. Unless an INSAT adjusted its orbit fairly drastically late in its life, or reboosted. Anyone aware of such an occurrence?
The final Mars Orbit Injection (MOI) is achieved by a braking or de-boost manoeuvre of about 1.1 km (a negative Δv) at the periapsis (closest approach to Mars) of the hyperbolic MTT. This, in fact, is the largest incremental (albeit negative) velocity, which means the MOI will demand the longest retro firing of LAM and it will have to deliver after lying idle for 300 days. Together, with the incremental velocity of 1.5 km/s given up to trans-Mars injection, the magnitude of the cumulative incremental velocity required of LAM is thus 2.6 km/s. The spacecraft will enter the Martian orbit in September 2014.
The LAM that will be used in this mission, both for orbit raising and MOI, is the same 440 Newton thruster that is used in geostationary satellite launches by ISRO. The first operation of orbit raisings is limited to the first one week. But MOI is only after 300 plus days of MTT. Once the valves get wetted by the propellant, they can swell a little bit and the performance will come down. They may also begin to leak. So the strategy that has been adopted is to close this path after orbit raisings, isolate the engine by operating pyro valves and open additional flow lines and valves when restarting the engine 10 months later to take care of the problem. The engine has been tested for its performance for a given number of days after use.
“In Chandrayaan-1 the engine was qualified for 30 days. Now we are talking of 300 days,” pointed out Radhakrishnan. “The performance deterioration in propulsion efficiency, which means specific impulse, is about 2 per cent. So we know it a priori. When you finally want to calculate how much the engine should fire to impart a given retro boost to capture a Martian orbit, this information is important but not very crucial at the same time because it is done in the closed loop mode. It will be looking at the accelerometers and then adjusting automatically. Also, the trans-Martian injection being very complex, you may miss this capture. We have kept fuel for one more try,” he added
follow-on" mission to the Red Planet between 2017 and 2020 having a lot of scientific content. the final decision will depend upon the success of the Mars Orbiter Mission (MOM) orbit insertion on September 24, 2014
India plans another Mars mission in 2017-20Quotefollow-on" mission to the Red Planet between 2017 and 2020 having a lot of scientific content. the final decision will depend upon the success of the Mars Orbiter Mission (MOM) orbit insertion on September 24, 2014http://timesofindia.indiatimes.com/india/India-plans-another-Mars-mission-in-2017-20/articleshow/38565995.cms
ISRO on Thursday said, "The mission officials have just ruled out the need for a trajectory correction manoeuvre, originally planned for August. This means MOM needs only three out of four TCMs originally planned for the entire heliocentric journey."
"It is currently about 163 million kilometers away from Mars. It is travelling at a speed of 1.2 million kilometers per day. It is on schedule and on target. Originally we were planning to have a corrective manoeuvre on August 19. But in the current situation, we don't think it is necessary. So the next (trajectory) correction is scheduled for September 14 and on September 24, the orbiter is supposed to reach Mars and perform the manoeuvre to orbit the red planet,"
"We have 290 kilograms of fuel left, and we will require about 240 kilograms for the manoeuvre to enter the Mars orbit. The process will involve reducing the velocity of the spacecraft and allowing it to get captured by Mars' (gravity),"
he said adding that all the commands will be fed in to the spacecraft three days in advance (before the manoeuvre on September 24) and the manoeuvre is expected to happen using the autonomous features of the spacecraft at 7:30 am on September 24.
After the spacecraft is captured in the Mars' orbit, we will encounter the Siding Spring comet that will engulf Mars in October
The MOM will be using the instruments onboard to observe the Siding Spring's passage and its effects on the Martian atmosphere which is much thinner that compared to Earth.
Will ISRO test fire the LAM ( for a short duration ) prior to the actual MOI burn to check out and calibrate the LAM?
The spacecraft is travelling at a speed of 22km/second. The challenge before Isro would be to reduce this drastically to 1.6km/second, so that the rules of gravity around Mars are employable and the spacecraft is sucked into the desired orbit.To achieve this, the space agency must fire its LAM engine, which would have remained idle for 299 days by September 24. Not only will the engine have to be fired but it has to be done after changing the orientation completely."Right now MOM is travelling in one direction, if we just fire the engine, it will only add to the velocity. So we will have to re-orient it to look the opposite direction and then fire the engine. What this does is it will push the spacecraft in the opposite direction and thereby reduce velocity," a senior scientist said.
Quote from: seshagirib on 08/20/2014 08:51 amWill ISRO test fire the LAM ( for a short duration ) prior to the actual MOI burn to check out and calibrate the LAM?I guess not. The original plan was to use all the redundant lines for the fuel during MOI, but a similar test in the earth orbit didnt work. Apparently, each line works individually but not in parallel. My guess, they will program it to open other line if one fails to produce required deceleration during MOI. BTW, MOI will happen behind mars (just like chandrayaan 1), so any guesses how long we will have to wait for a confirmation?
Quote from: antriksh on 08/21/2014 02:13 amQuote from: seshagirib on 08/20/2014 08:51 amWill ISRO test fire the LAM ( for a short duration ) prior to the actual MOI burn to check out and calibrate the LAM?I guess not. The original plan was to use all the redundant lines for the fuel during MOI, but a similar test in the earth orbit didnt work. Apparently, each line works individually but not in parallel. My guess, they will program it to open other line if one fails to produce required deceleration during MOI. BTW, MOI will happen behind mars (just like chandrayaan 1), so any guesses how long we will have to wait for a confirmation?Maybe ( just guessing ) - if the LAM has issues in both the modes ( primary lines and redundant lines ) the MOI software could try to put the MOM in some kind of orbit around Mars using the attitude thrusters. This will buy time to try and fix the LAM issues.
"On Sept 24, the manoeuvring of the spacecraft will begin around 7.30 a.m. The spacecraft's speed will be reduced from the current speed so that the Mars Orbiter enters the Martian orbit. Whether the spacecraft has entered the Martian orbit or not will be known around 8.30 or 9 a.m."
Quote from: seshagirib on 08/20/2014 08:51 amWill ISRO test fire the LAM ( for a short duration ) prior to the actual MOI burn to check out and calibrate the LAM?I guess not. The original plan was to use all the redundant lines for the fuel during MOI, but a similar test in the earth orbit didnt work.
Here are some interesting snippets:QuoteThe final Mars Orbit Injection (MOI) is achieved by a braking or de-boost manoeuvre of about 1.1 km (sic: it should be 1.1 km/s) (a negative Δv) at the periapsis (closest approach to Mars) of the hyperbolic MTT. This, in fact, is the largest incremental (albeit negative) velocity, which means the MOI will demand the longest retro firing of LAM and it will have to deliver after lying idle for 300 days.QuoteOnce the valves get wetted by the propellant, they can swell a little bit and the performance will come down. They may also begin to leak. So the strategy that has been adopted is to close this path after orbit raisings, isolate the engine by operating pyro valves and open additional flow lines and valves when restarting the engine 10 months later to take care of the problem. The engine has been tested for its performance for a given number of days after use.
The final Mars Orbit Injection (MOI) is achieved by a braking or de-boost manoeuvre of about 1.1 km (sic: it should be 1.1 km/s) (a negative Δv) at the periapsis (closest approach to Mars) of the hyperbolic MTT. This, in fact, is the largest incremental (albeit negative) velocity, which means the MOI will demand the longest retro firing of LAM and it will have to deliver after lying idle for 300 days.
Once the valves get wetted by the propellant, they can swell a little bit and the performance will come down. They may also begin to leak. So the strategy that has been adopted is to close this path after orbit raisings, isolate the engine by operating pyro valves and open additional flow lines and valves when restarting the engine 10 months later to take care of the problem. The engine has been tested for its performance for a given number of days after use.