ISRO's MOM enters Martian Gravitational Sphere of Influence

[RPK]

CHENNAI: Cruising towards its historic rendezvous with the red planet, India's Mars Orbiter Mission (MOM) today entered the Mars Gravitational Sphere of Influence ahead of its scheduled Orbit Insertion on September 24.

"Our navigators' calculations show that MOM has entered the Gravitational Sphere of Influence of Mars," ISRO said on its social networking site, adding, the spacecraft was within 5.4 lakh km radius of the Mars' Gravitational Sphere of Influence.

After being launched from ISRO's spaceport of Sriharikota on November 5 last year, the MOM had left Earth's orbit on December 1 and began its historic voyage to put India on the list of elite nations, which has sent a mission to Mars.

"MOM has entered the Mars Gravitational Sphere of Influence this morning and we will perform certain procedures on the mission today. The fourth trajectory correction manoeuvre and test firing of Main Liquid Engine will be test fired for 3.968 seconds," " an ISRO official told PTI.

Now that the spacecraft has entered the Mars' influence, its velocity has to be controlled so that it does not escape the Mars' influence, he said, adding, the spacecraft is scheduled to enter the Mars Orbit Insertion at 7.30 AM IST on September 24.

The crucial fourth trajectory correction manoeuvre and test fire of the main liquid engine on the spacecraft is scheduled for 2.30 PM today.

he MOM, India's first interplanetary mission, was launched by India's workhorse Polar Satellite Launch Vehicle from the spaceport of Sriharikota in Andhra Pradesh.

Read more at:
ISRO's MOM enters Martian Gravitational Sphere of Influence - The Economic Times

 

[Skull and Bones]

Apt song for the hour, kudos to the scientists for making this feat possible.

 

[Nova2]

Another 45mins to go before liquid engines are fired for 4 seconds. Wish'em luck

 

[kaykay]

Oh yeah. We are very close to success. Let's hope for the best.

 

[anant_s]

The mission has gone with a copybook precession. Best of Luck ISRO!

 

[anant_s]

How this is being done

Two spacecraft are preparing to insert themselves into orbit around Mars in the next seven days to continue the exploration of our neighboring planet in the Solar System.

NASA who has been to Mars before, both in orbit and on the surface, is gearing up for the orbital insertion of its MAVEN Spacecraft on Monday (UTC) to mark the start of a detailed survey of the Martian atmosphere and the processes ongoing therein. The Indian Space Research Organization hopes to achieve one of its greatest achievements to date by sending its MOM spacecraft into orbit next Wednesday.

The Mars Orbiter Mission is set for its critical Mars Orbit Insertion Burn early on September 24, UTC, in the morning hours Indian Standard Time. This is the final hurdle for MOM to overcome to achieve a big milestone for the Indian Space Research Organization. One of the main objectives of MOM was to demonstrate that it was possible for ISRO to send a spacecraft to Mars and be successful in operating it through the different mission phases.

Compared to NASA's MAVEN mission that purely dedicated to science, MOM sets out to fulfill a number of technical mission objectives with science being somewhat of a bonus. MOM serves as a pathfinder, being India’s first mission beyond the Moon which brings its own unique challenges such as the operation of a spacecraft with a significant communications delay. Technical demonstrations that are performed on this mission include spacecraft construction, orbital maneuvers and transfer orbit design, navigation in all mission phases, spacecraft operations and maintenance and the incorporation of mainly autonomous mission operations.
Many of these elements will be needed for the critical Mars Orbit Insertion Burn that will be performed in a fully autonomous mode by the spacecraft that already received the command sequences that will be executed next week. Command uplink took place on September 14/15 and the sequences were verified by September 16.

One of the biggest unknowns is the behavior of MOM's main engine, called LAM, the Liquid Apogee Motor due to its original use in Geostationary Satellites that utilized the engine over a period of weeks to raise their orbits and reach GEO. LAM was not designed to sit idle for nearly 300 days and then cleanly re-start. India's Chandrayaan-1 lunar orbiter used its engine several months into the mission and studies were performed to clear LAM for use in a Mars Mission.LAM provides 440 Newtons of thrust which equates to 44.87 Kilograms, using Unsymmetrical Dimethylhydrazine as fuel and Mixed Oxides of Nitrogen as oxidizer. The engine is capable of operating in a broad range of conditions in terms of oxidizer-to-fuel ratio, injection pressures, temperatures and voltages.

In order to increase the probability of success of the crucial MOI burn, LAM was outfitted with a second set of propellant lines from the tanks of the spacecraft including a fully independent set of valves and regulators. The primary propellant system was used for the orbit-raising maneuvers, the trans-Martian insertion burn and the first Trajectory Correction Maneuver. After that, the lines were isolated using pyro valves to prevent the corrosive propellant from creating leaks in the valves that would lead to a loss of precious fuel.

Ahead of the MOI maneuver, the second set of propellant lines is opened to feed the engine. In order to test the second set of lines and the engine itself, a short LAM firing is being implemented on September 22 as part the mission's fourth Trajectory Correction Maneuver. Although this maneuver could be performed more accurately with the vehicle's eight 22-Newton thrusters, ISRO decided to use LAM for this burn as it presents a final opportunity to test the engine ahead of the critical MOI burn two days later.
TCM-4 takes place at 9:00 UTC on Monday when the Mars Orbiter is already within the Martian Sphere of influence in which the Martian gravity pulls the spacecraft in, further accelerating it. The burn has originally been planned for September 14, but trajectory optimization and the desire to use LAM drove the decision to delay the burn to the 22nd.

LAM will ignite just briefly - TCM-4 has a planned duration of 3.968 seconds to supply a change in velocity of 2.142 meters per second, slightly tweaking MOM's trajectory, lowering the periapsis of the Mars Flyby Trajectory from 723 Kilometers to 515 Kilometers which optimizes the orbital insertion burn that is desired to take place around a low periapsis.

After the Trajectory Correction, teams will examine telemetry recorded by the spacecraft to assess the status of the Liquid Apogee Motor. Should any anomaly related to LAM's operation be detected, teams would still have a little more than 24 hours to modify burn parameters or operating parameters for the engine during the MOI burn to ensure a good orbital insertion.

At the time of MOM's orbital insertion, its signals will take 12 minutes and 28 seconds to travel to Earth for reception by NASA's Deep Space Network Stations in Canberra and Goldstone that will relay the data in real time to ISRO's station in Bangalore so that teams can monitor data as it comes in. However, much of MOM's maneuver takes place behind Mars, as seen from Earth which means that from a point four minutes into the MOI burn until three minutes after the scheduled end of the maneuver, teams on Earth will have no insight into the spacecraft's progress.
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.

MOM is targeting an insertion orbit of 423 by 80,000 Kilometers at an inclination of 150 degrees with an orbital period of more than three days.

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.

The thrust augmentation by the 22N thrusters was first tested in November 2013 and worked as planned with the thrusters continuing to fire after LAM cutoff to optimize MOM's trajectory as best as possible.

 

[thesolar65]

Not if but after successful, treat meri taraf se!!

Engine fired, but confirmation will be after 12 minutes of comm. delay.

 

[astra-2016]

engine test fire and trajectory correction was successful

 

[astra-2016]

View attachment 73901
The mission has gone with a copybook precession. Best of Luck ISRO!

Isro's scientists trajectory calculation considering the gravitation pull of multiple planets was so accurate that MOM did not required two TCMs.
aakhir Great Mathematician and astronomer Aryabhata ke vanshaj jo hai hum log