Barrier breaks, next moon steps tougher - Chandrayaan-1 moves into third orbit, goes farther than India's most distant satellites
New Delhi, Oct. 25: Obeying commands from Bangalore, a thrust-providing rocket on Chandrayaan-1 came to life at 5.48am today to propel the craft towards a realm of space where no Indian satellite had gone before.
The 16-minute firing of the liquid propellant-fuelled rocket engine moved the craft into a new orbit in which its most distant position from Earth, or apogee, is 74,715km, more than twice the distance between Earth and India’s farthest satellites.
The spacecraft, launched from Sriharikota on October 22, is now in the third of six planned orbits that will move it farther and farther from Earth until it moves close to the moon, about 384,000km from Earth, ready for injection into a lunar orbit.
“We’ve broken a barrier,” Indian Space Research Organisation (Isro) chairman G. Madhavan Nair said this evening, shortly after the spacecraft had reached its new apogee.
Until now, India’s most distant satellites had been the Insat series of weather, television and telecommunication satellites, parked in slots about 36,000km above the equator.
Claps broke out in the control room of India’s Deep Space Network (DSN) tracking station at Byalalu near Bangalore this morning after signals from the spacecraft indicated that it was safe in its new orbit.
“It’s exciting to do something for the first time,” said Srirangapatna Shivkumar, the head of Isro’s tracking network that had relayed the thrust rocket-firing command issued by engineers at Isro’s Spacecraft Control Centre, Bangalore.
“Everything worked flawlessly,” Shivkumar said.
Isro engineers told The Telegraph that shortly before the launch of Chandrayaan-1, they had decided to add two intermediate orbits to its journey.
The initial plan was to inject the spacecraft into three Earth orbits, each with a greater apogee — 22,800km, 37,000km and 74,000km — before it was guided into a fourth orbit that would take it close to the moon.
But mission engineers decided to add two orbits — with apogees of about 164,000km and 267,000km — instead of leaping directly from 74,000km to the final Earth orbit at 384,000km.
They believe this will give them more experience of the deep space environment where the gravitational tugs of the moon and the Sun become significant. “We’ll be able to make precise assessments of these gravitational influences,” Nair said.
“When we’re climbing stairs, it’s better to go a step at a time,” Mylswamy Annadurai, project director of Chandrayaan-1, said.
The next orbit-raising manoeuvres are expected to take place tomorrow, on October 29 and on November 3.
But engineers expect to encounter one of the most challenging tasks of the mission as the spacecraft approaches the moon. The thrust rocket will have to be fired to steer Chandrayaan-1 from its Earth-bound orbit into a new orbit around the moon.
“The orientation of the spacecraft, the timing of the firing, and the exact thrust delivered by the rocket will have to be co-ordinated with extreme precision,” Annadurai said.
The calculations are complex, but are based on textbook dynamics.
While preparing for the mission, Isro scientists had simulated the gravitational forces the spacecraft will experience and calculated the required thrust.
Once it enters a lunar orbit, the speed of Chandrayaan-1 will need to be reduced to bring it closer and closer until it reaches its target orbit of 100km.
Some early lunar missions from the US and Russia had missed the moon. In 1962, a US spacecraft, Ranger-3, had missed the moon by 36,000km. A Soviet-built spacecraft, Luna-6, was intended to land on the moon in 1965 but missed it by 160,000km.
“But technology has dramatically improved since that era. Space operations are a lot more precise now than in the 1960s,” one Isro engineer said.
Several scientists from US space agency Nasa -- some of them of Indian origin and some not – have rung up Isro looking for opportunities to work in future Indian space missions, a PTI report said quoting Annadurai.
Annadurai, according to the report from Bangalore, said he definitely saw a “small trend” of “reverse brain drain” following the successful Chandrayaan-1 launch.
“Some of my friends and juniors working there (Nasa) are looking for opportunities to work in Isro,” Annadurai said.
He said at least half-a-dozen scientists had approached him and he knew that “a good number of foreigners” too were looking to work with Isro.