Space

Embracing Mars

Print edition : October 17, 2014

The surface of Mars photographed by India’s Mars Orbiter Mission. The latitude and longitude values of this location on Mars are 3.67 degree S and 73.61 degree E respectively. Photo: REUTERS/PIB

Members of the Mission Operation Team and ISRO staff celebrate at ISRO’s Telemetry, Tracking and Command Network in Bangalore on September 24 after the successful entry of the spacecraft into a Mars orbit. Photo: K. MURALI_KUMAR

India celebrates the success of its maiden Mars mission.

A WAVE of excitement swept through the Mission Operations Complexes (MOX)-2 and MOX-1 at Peenya in Bangalore at 8 a.m. on September 24. S. Arunan, Project Director, Mars Orbiter Mission (MOM), Indian Space Research Organisation (ISRO), greeted his cheering colleagues with raised hands. Jubilant engineers and scientists flashed the V-sign and shook hands with one another.

Soon India exploded into celebration. Excited schoolchildren visiting the regional science centre and planetarium in Kozhikode, Kerala, celebrated the success with sweets. At the Indian Institute of Science, Bangalore, students formed themselves into ISRO’s logo. In Chennai, schoolchildren held aloft a poster that read: “MAR(VELLOU)S, Salute Our Scientists.” In New Delhi, the Indian staff of the United States Consulate proudly displayed a banner, “Congratulations, India.”

When ISRO Chairman K. Radhakrishnan received a call on his intercom in MOX-2 from V. Kesava Raju, Mission Director, MOM, at 8 a.m. that the huge antennas (with a diameter of 70 metres) in Canberra, Australia, and the Goldstone Deep Space Communication Complex, U.S., had received telemetry signals from India’s spacecraft to Mars, he calmly walked up to Prime Minister Narendra Modi to tell him about the success of India’s MOM. Modi greeted the ISRO Chairman with a hug. India had reached Mars. ISRO’s orbiter to Mars, after traversing 65 crore kilometres of “speedometer” or “road” distance through space from November 5, 2013, was successfully contained in an orbit around Mars at 7-41 a.m. on September 24. Radhakrishnan said: “We have done our best. India is great.”

“We are living our dream,” said Arunan, who attributed the success to the “dedication, focussed approach and meticulous planning” of the MOM team. Kesava Raju called it “a really great achievement for our country”. He said: “We took meticulous care at every stage of the spacecraft’s conceptualisation and configuration, the design of its equipment and subsystems and their realisation. Besides, there was teamwork and meticulous planning in building the spacecraft.”

Suspense was building up at MOX-2, the nerve centre of MOM operations, and MOX-1, from 3 a.m. on September 24. ISRO engineers sat in front of their computer consoles while big screens in front of them flashed the latest update on MOM. Three hours prior to T, the spacecraft started using its medium-gain antenna for communication with the earth. Then, the spacecraft’s forward rotation began. The manoeuvre was to reorient the Liquid Apogee Motor (LAM), also called 440 Newton engine, on the spacecraft. On the dot (that is, T), at 7-17 a.m., as the spacecraft neared Mars, the LAM and the eight small thrusters started firing simultaneously. The eight thrusters fired to control the spacecraft’s attitude so that it could communicate with the earth.

At 7-21 a.m. began the Mars occult—a phenomenon when the spacecraft goes behind Mars and communication with the spacecraft is lost. Thus, no telemetry information would be available from the spacecraft. At 7-33 a.m., applause broke out when MOX-2 received confirmation from the spacecraft that the LAM and the eight thrusters had started firing together. Their flawless firing lasted about 23 minutes as per the timeline and came to an end around 7-41 a.m. The simultaneous firing led to a reduction in the spacecraft’s velocity by 1.09 km a second and it started orbiting Mars.

India reached Mars in its debut attempt. The Soviet Union failed in its initial attempts in the early 1960s to put a spacecraft around Mars. The U.S.’ Mariner-3 failed in November 1964 to reach Mars. In 1998, Japan sent its Nozomi spacecraft to Mars, but the orbiter failed to make it. In 2003, the European Space Agency put the spacecraft called Mars Express into an orbit around the Red Planet, but its lander, called Beagle-2, crashed. A Chinese payload could not reach Mars in 2011 after the Russian mission called Phobos-Grunt, on which it was riding piggyback, failed. Phobos-Grunt’s main engine did not fire after lift-off.

India made it to Mars by executing with effortless ease the most crucial and complex manoeuvre of the mission, the Mars Orbit Insertion (MOI). The MOI had been the bane of several initial U.S. and Russian missions. What added to India’s success was that the LAM, which was hibernating aboard the spacecraft, ignited into life after a gap of 300 days. ISRO had subjected the LAM to a battery of tests on the ground, simulating deep-space conditions, to ensure that it woke up after its long slumber.

Soon after the MOI, the spacecraft settled in its orbit around Mars, with a periapsis (closest approach to Mars) of 421.7 km and an apoapsis (farthest point from the red planet) of 76,993 km. What was targeted was 423 km × 80,000 km.

The reverse manoeuvre of the spacecraft began at 7-42 a.m. to orient its antenna towards the earth to resume communication. The orbiter’s solar panel was oriented towards the sun to generate power. The Mars occult ended at 7-45 a.m.

Kesava Raju explained why it was necessary to reduce the spacecraft’s velocity by 1.09 km/s to enable the spacecraft’s entry into the Martian orbit. He said: “When we reach Mars, the spacecraft will have a velocity of 22.57 km/s, whereas Mars’ velocity is 25.71 km/s. It means the spacecraft is slower. When the spacecraft is under the influence of Mars’ gravity, it reaches the closest point to Mars. At that time, it will attain a velocity of 5.7 km/s. But we do not require 5.7 km/s for our spacecraft to reach the desired orbit. We require 4.6. So the orbiter’s velocity is reduced from 5.7 km/s to 4.6 km/s. The velocity decrement is 1.1 km/s.”

ISRO’s Plan A required that the LAM and the eight thrusters fire simultaneously. If the LAM failed to ignite, ISRO had a Plan B, in which only the eight thrusters would fire. This would take the orbiter to a different orbit around Mars. The planned orbit offered a vantage view for the five instruments on board India’s orbiter to study the Martian atmosphere, mineralogy, morphology, presence of methane, and so on. The Plan B orbit would not have been a stable one, Kesava Raju said. It would have a periapsis of 20,000 km and an apoapsis of eight lakh to nine lakh kilometres. “These parameters will vary from time to time. They are not stable. Still, they will be able to provide you some scope for observing Mars,” he said. Within a couple of hours of the spacecraft settling in the Martian orbit, ISRO switched on the Mars Colour Camera aboard it to take pictures of the red planet’s surface. The Indian Space Science Data Centre at Byalalu village, about 40 km from Bangalore, received five “frames” of the Mars’ surface taken by the camera.

Outstanding feats

The MOM demonstrated ISRO’s ability to navigate the orbiter through 66 crore km, covering the earthbound phase, its sun-centric phase and then the cruise towards Mars. Indeed, as Prime Minister Modi said, ISRO had taken “a route known to very few”. ISRO excelled in deep-space communication, too, with the orbiter through 300 days of its interplanetary voyage.

“Our ability to communicate over 224 million km of radio distance [that is, 66 crore km of ‘road distance’] was successfully demonstrated in this mission,” Arunan said. When a spacecraft voyages through deep space, it faces many uncertainties, but ISRO developed the capability to predict them. “The accuracy of our prediction comes from our communication system, which has worked to perfection. We were able to communicate about 224 million km of radio distance with our orbiter. Our ability to communicate can go up to 375 million km of radio distance,” Arunan said.

The third remarkable feature of MOM was the spacecraft’s “autonomy”. It would take more than 26 minutes for a radio signal from the ground to reach the orbit and return to the ground station. This made real-time rectification of a case of “misbehaviour” by any system on board the spacecraft impossible. So the spacecraft was vested with its own intelligence to manage crucial operations such as the MOI, detect faults, isolate them and rectify them, and conduct operations during periods when the spacecraft would not be visible from the earth.

“…We have sensors and transmitters on board the orbiter that can sense the failure and reconfigure the redundant system on the spacecraft on their own. The reconfiguration will take place autonomously in the orbiter,” said M. Annnadurai, Programme Director, Indian Remote-Sensing Satellites and Small Satellites Systems, ISRO ( Frontline, November 15, 2013).

Kesava Raju said: “In case of unexpected events, the spacecraft has to survive on its own. If the spacecraft’s attitude is not proper, we will not be able to communicate with it from the earth. So the eight thrusters should simultaneously burn with the LAM and orient the spacecraft’s attitude in such a way that we can contact it from the earth. All these manoeuvres should take place on [commands from on] board itself and they should happen automatically at the required time.” In Radhakrishnan’s assessment: “If one were to identify two important elements in the Mars orbiter, it is its autonomy and navigation towards Mars.”

Another feature that stood out in the MOM was ISRO’s ability to restart the LAM after the engine had remained dormant for 300 days. The LAM was last fired on December 1, 2013, to perform a tricky manoeuvre called trans-Mars injection when the orbiter was shot out of its earthbound orbit into its sun-centric phase and then began its 300-day voyage to Mars. On September 22, 2014, there was a brief firing of LAM for four seconds. This was a dress rehearsal for the prolonged simultaneous firing of the LAM and eight thrusters for 24 minutes on September 24, which led to the all-important MOI.

“We left no stone unturned to ensure” that the LAM fired after it remained dormant in space for 300 days, Arunan said. ISRO rocket engineers tested the LAM on the ground, simulating the thermodynamic conditions of its Mars spacecraft. A simultaneous firing of the LAM and eight thrusters was done. The Project Director said: “We conducted this test in operating conditions [of the spacecraft] as envisaged during the MOI manoeuvre. The test was successful. The engine performance was as per prediction…. So there was no concern about the simultaneous firing of the LAM engine and the eight 22 Newton engine.” This simultaneous firing was done at the ISRO Propulsion Complex (IPRC) at Mahendragiri, near Nagercoil, in Tamil Nadu.

In addition, ISRO’s propulsion specialists test-fired a LAM, kept on the ground for 450 days, simulating the same conditions that India’s Mars orbiter was undergoing in space. “We kept the LAM engine in a vacuum chamber for 450 days and when we fired it again, its performance was absolutely as predicted,” Arunan said. This test on the LAM was done just two weeks ahead of the crucial MOI on September 24.

What came to the fore in the MOM was ISRO’s youth power. Deepak Panda, who took part in the simulation of the attitude control done by the eight thrusters and in the development of the electronics needed for the spacecraft’s orbit control, is only 26. The LAM and the eight thrusters boasted a closed loop guidance scheme (CLGS). “If at all any error developed in the attitude control, the CLGS would nullify it,” said Panda. Rishabh Mishra developed the software for display on the big monitors in MOX-1 and 2. The display related to the telemetry data from the spacecraft.

Kamlesh Kumar Sharma, also in his 20s, could not hide his happiness. “I sent the first command to MOM [on November 15, 2013], after it went into its earthbound orbit. I sent the first command during the spacecraft’s trans-Mars insertion on December 1, 2013,” he said. Sharma described himself as “the prime controller during the spacecraft’s MOI” on D-day. “I was also the first to verify the good news that we received” that India’s spacecraft had entered the Martian orbit, he exulted.

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