Posts Tagged ‘MOI’

MOM orbit exactly as planned with a flawless MOI

September 24, 2014

ISRO can feel very satisfied. The MOI was flawless. The tracking indicates that the MOM has achieved an orbit of 421.7 km / 76993.6 km compared to the planned 423 km / 80,000 km. Not bad after a 10 month journey of some 680 million km. The inclination of orbit with respect to the equatorial plane of Mars is 150º and exactly as planned. 

The first colour pictures of Mars from MOM are expected within a day or two.

Now for a manned, fast, free-return, fly-by of Mars in 2018?

ISRO: India’s Mars Orbiter Spacecraft successfully entered into an orbit around planet Mars today morning (September 24, 2014) by firing its 440 Newton Liquid Apogee Motor (LAM) along with eight smaller liquid engines. This Liquid Engines firing operation which began at 07:17:32 Hrs IST lasted for 1388.67 seconds which changed the velocity of the spacecraft by 1099 metre/sec. With this operation, the spacecraft entered into an elliptical orbit around Mars. 

The events related to Mars Orbit Insertion progressed satisfactorily and the spacecraft performance was normal. The Spacecraft is now circling Mars in an orbit whose nearest point to Mars (periapsis) is at 421.7 km and farthest point (apoapsis) at 76,993.6 km. The inclination of orbit with respect to the equatorial plane of Mars is 150 degree, as intended. In this orbit, the spacecraft takes 72 hours 51 minutes 51 seconds to go round the Mars once.

Spaceflight101Launched back on November 5, 2013 atop a Polar Satellite Launch Vehicle, the Mars Orbiter was constrained by the performance of India’s workhorse launcher that required the spacecraft to take the scenic route – first entering an elliptical Earth orbit that the spacecraft raised by making six engine burns before firing its main engine, the Liquid Apogee Motor, a seventh time to depart Earth and enter a path to Mars on November 30. ….. 

The Mars Orbit Insertion Burn had a planned change in velocity of 1,098.7 meters per second with an anticipated burn time of 24 minutes and 14 seconds. However, engine shutdown was triggered by the navigation system when accelerometers sensed that the proper delta-v was achieved, dynamically adjusting for actual engine performance by extending of shortening the burn slightly. 

For MOM, the sun came up 19.5 minutes into its burn, but Earth was not coming into view until three minutes after the scheduled end of the Mars Orbit Insertion burn. The spacecraft was programmed to start the re-orientation back to its comm attitude one minute after shutdown, followed five minutes later by the re-activation of the communications system when MOM was visible from Earth again.
The Mars Orbit Insertion Burn had a planned change in velocity of 1,098.7 meters per second with an anticipated burn time of 24 minutes and 14 seconds. However, engine shutdown was triggered by the navigation system when accelerometers sensed that the proper delta-v was achieved, dynamically adjusting for actual engine performance by extending of shortening the burn slightly. 
For MOM, the sun came up 19.5 minutes into its burn, but Earth was not coming into view until three minutes after the scheduled end of the Mars Orbit Insertion burn. The spacecraft was programmed to start the re-orientation back to its comm attitude one minute after shutdown, followed five minutes later by the re-activation of the communications system when MOM was visible from Earth again.
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Culmination nears for India’s Mars Orbiter Mission

September 23, 2014

In 8 hours – if everything goes as planned – the MOM would have been inserted into Mars orbit of 423 km at periareion and 80,000 Kilometers at apoareion  at an inclination of 150 degrees and with an orbital period of a little more than three days. Though a number of experiments are planned, the most important objectives of the mission – to demonstrate technology and capability – will largely have been accomplished on getting into orbit.

Frugal engineering and with a cost of about 10% of that of NASA’s MAVEN will have taken ISRO’s MOM into Mars orbit – and at the first attempt.

But the next few hours will be tense and nervous not only for ISRO mission staff but for the many millions of Indians who will be following the live webcast at http://webcast.isro.gov.in/. The critical operations will take place while the MOM spacecraft is occluded on the far side of Mars and when signals will be taking over 12 minutes to reach earth.

Spaceflight101: 

The critical Mars Orbit Insertion Burn Sequence will begin three hours ahead of the planned maneuver time when the spacecraft automatically switches over to its Medium Gain Antenna for communications since the High Gain Antenna will be pointing away from Earth during the retrograde burn.
21 minutes ahead of ignition, the spacecraft will begin the re-orientation to the proper attitude for the burn, pointing LAM to the direction of travel. The re-orientation is accomplished using the vehicle’s Reaction Wheels. Five minutes and 13 seconds ahead of the burn, the spacecraft passes into darkness – for the first time since leaving Earth last year. In advance, MOM will fully charge its battery to be in a safe configuration for the eclipse.
Three minutes ahead of the burn, the vehicle’s eight 22-Newton thrusters are enabled to start providing attitude control which they will continue to do throughout the main engine burn, keeping MOM pointing forward. Ignition of the Liquid Apogee Motor is planned at 1:47:32 UTC on Wednesday, September 24, 7:17 Indian Standard Time. The Mars Orbit Insertion burn has a planned duration of 24 minutes and 14 seconds, slowing the spacecraft down by 1,098.7 meters per second to be captured in an elliptical orbit around Mars. During the burn, the engines will consume 249.5 Kilograms of propellant leaving only about 40 Kilograms of propellant for the rest of the mission.
Should something go wrong during the burn, MOM is programmed to react appropriately in order to achieve a stable orbit around Mars – even if that means to spend all the vehicle’s propellant to do so. In the event the Liquid Apogee Motor is not ignited or its burn is cut short, MOM would automatically switch to the 22-Newton thrusters to supply as much delta-v as possible. Due to their lower thrust, the 22N thrusters would need to fire much longer than LAM along a greater stretch around the periapsis pass which will increase propellant consumption and leave MOM in a higher orbit.
MOI timeline

Graphic ISRO (via spaceflight101)


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