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Success in very first attempt, a rare feat

T.S. Subramanian

Precise commands saw Chandrayaan-1 through

CHENNAI: The remarkable fact about the Indian Space Research Organisation (ISRO) precisely inserting Chandrayaan-1 into the lunar orbit on Saturday is that India did this tricky manoeuvre in its very first attempt. While it is true that Japan and China also put their Hiten and Chang’e-1 spacecraft into their lunar orbit in their first attempts in 1990 and 2007, the U.S., a technological powerhouse, floundered in its several initial attempts. In 1961, the U.S. attempted test flights of Ranger 1 and Ranger 2 to the Moon, its Ranger 3 in January 1962 missed the Moon by 36,793 km and Ranger 4 in April 1962 crashed in the lunar far side. Again, in October 1962, Ranger 5 missed the moon by 724 km.

ISRO technologists gathered at the Spacecraft Control Centre (SCC), the nerve-centre of Chandrayaan-1’s operations now, said “it was a feast to the eyes” to see Chandrayaan-1 go into a perfect lunar orbit of 7502 km by 504 km and that they could see on the plot-boards the deceleration of the spacecraft before it entered the lunar orbit.

B.N. Suresh, former Director, Vikram Sarabhai Space Centre, Thiruvananthapuram, said, “This is very unique because we have not done this manoeuvre earlier. Any mistake, the spacecraft would have run away from the Moon’s gravity. So it was a very crucial operation. It was a very critical manoeuvre. It went off excellently well. Everybody is happy.”

“Everything went as per plan,” said M. Annadurai, Project Director, Chandrayaan-1. Commands were given from the SCC at the ISRO Telemetry, Tracking and Command Network (ISTRAC), Bangalore, to reduce its velocity by 366.8 metres a second so that it was captured by the Moon’s gravity and it entered the lunar orbit. To achieve this feat, the top brass of ISRO including the Chandrayaan-1 had worked tirelessly for four years and a half, he said. “We feel that is not an achievement for ISRO alone, but for the entire country,” Mr. Annadurai said.

S. Ramakrishnan, Director (Projects), Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram, said: “We made precise calculations. The plot-boards showed that everything went as per predictions.” As Chandrayaan-1 approached the Moon, its gravity took over. At the precise moments, commands were radioed from the SCC to the spacecraft’s onboard engine so that Chandrayaan-1 velocity was reduced. Mr. Ramakrishnan said, “The precision with which this manoeuvre should be done is very important. Otherwise, Chandrayaan-1 will skip and go away. If you overfire the engine, the spacecraft will become sub-orbital and crash on the Moon. So the burn-duration of the motor firing to give the precise delta-velocity to the spacecraft is very important. It should be executed with precision and at the right moment. And it was successfully and safely put into lunar orbit.”

Dr. Suresh, who is also Director, Indian Institute of Space Science and Technology, Thiruvananthapuram, said the insertion of Chandrayaan-1 into the lunar orbit on Saturday was as perfect as the launch of the Polar Satellite Launch Vehicle (PSLV-C11) on October 22. On that day, the PSLV-C11 rose from its launch pad at Sriharikota at 6.22 a.m. and put the spacecraft into the initial orbit around the earth, with an apogee of 22,866 km and a perigee of 256 km.

After Chandrayaan-1 enters the final lunar orbit of 100 km by 100 km on November 15, its Moon Impact Probe (MIP) will be commanded to eject from the spacecraft and it will crashland on the moon’s surface. The MIP is painted with the flag on its sides. Chandrayaan-1’s Terrain Mapping Camera has already been switched and it has taken pictures of both the Earth and the Moon. After November 15, the remaining nine scientific instruments will be switched on, one after another.

Mr. Ramakrishnan said India’s success in its very first planetary mission would give it the confidence to plan more such missions. “We will command respect in the international community and we can be partners in such international programmes,” he said.

Full text of ISRO press release

Chandrayaan takes pictures of moon

Chandrayaan 1: In depth

Chandrayaan-1 gets closer to moon

How Chandrayaan-1 is raised to higher orbits

Chandrayaan-1 bound for Moon

Chandrayaan’s orbit raised

“ISRO can put an Indian into space before 2015”

Off to the Moon: Editorial

‘Once Chandrayaan goes near the moon, we will be there to track it’

Going boldly where others have gone before

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