Mission success

Print edition : January 26, 2007

After last year's failure of the GSLV flight, the success of the PSLV-C7 mission is all the more sweet for ISRO.

T.S. SUBRAMANIAN in Sriharikota

PSLV-C7, BEARING FOUR satellites, lifting off from the Satish Dhawan Space Centre at Sriharikota on January 10. It sucessfully put all the four satellites in orbit.-JOHN VINO/AFP

"LIKE individuals, organisations too have their emotions," said D. Narayana Moorthi, Visiting Scientist at the Indian Space Research Organisation (ISRO) and former Director, Launch Vehicle Programme Office, ISRO headquarters, Bangalore.

At the end of the 19-minute flight on January 10, when the Polar Satellite Launch Vehicle (PSLV-C7) mission turned out to be a huge success, having put four satellites, one after another, in orbit, there was an explosion of joy at the Satish Dhawan Space Centre at Sriharikota in Andhra Pradesh. Although this was the PSLV's ninth successful flight in a row and the vehicle had proved itself to be a workhorse, ISRO personnel had reason to be overjoyed. On July 10, 2006, ISRO's Geosynchronous Satellite Launch Vehicle (GSLV) had to be destroyed in mid-flight 55 seconds after its lift-off from Sriharikota because it had veered too much off its path. One of its four strap-on motors, powered by liquid propellants, did not build up enough thrust. The three previous GSLV flights were successful.

A day earlier, India had received another blow when the maiden launch of Agni-III ballistic missile of the Defence Research and Development Organisation (DRDO) failed after its heat-shield malfunctioned.

The GSLV failure shook ISRO deeply, and its scientists dredged up the strap-on motors from the depths of the Bay of Bengal to zero in on the reason for the failure. A 15-member Failure Analysis Committee, headed by K. Narayana, former Director, SDSC, reviewed the GSLV's performance from the lift-off to the moment when the debris fell into the sea. The primary cause of the failure was the sudden loss of thrust in the fourth strap-on stage at 0.2 seconds after the lift-off. The propellant regulator in the failed engine had a much higher discharge co-efficient in its closed condition because of a manufacturing defect.

What worried ISRO rocket engineers was that although the PSLV had proved its mettle with eight successful flights in a row until then, the liquid stage that failed in the GSLV flight was common to both the launch vehicles. In other words, the second liquid stage of the PSLV becomes one of the four strap-on liquid stages of the GSLV. So ISRO did not want to take chances with the PSLV-C7 flight.

Besides, ISRO was attempting a complicated mission with the PSLV-C7. It was a multi-mission: a single vehicle was to put four satellites in orbit. Although the PSLV, in its missions in 1999 and 2001, had deployed three satellites in orbit, this was a challenging mission because two of the four satellites were heavy. The PSLV had a new device called Dual Launch Adopter to put four satellites in orbit.

A CROWD WATCHES the launch at Sriharikota.-BABU/REUTERS

ISRO was staking its prestige on the PSLV-C7 mission on another count. It was orbiting for the first time a recoverable satellite called Space Capsule Recovery Experiment (SRE) - which was a technological challenge on many fronts. The SRE would provide ISRO personnel with "valuable experience" in mastering re-entry and recovery technologies, and in building a reusable launch vehicle. The SRE would be a forerunner to India's plans to send an astronaut into space in about 10 years from now.

After staying in orbit for 11 to 30 days about 635 km above the earth, the SRE would re-enter the earth's atmosphere without burning up. (When a spacecraft re-enters the earth's atmosphere, it burns up owing to the intense heat generated by friction). Then, about five km above the Bay of Bengal, three parachutes in the SRE would open up one after another with precision. The deployment of the second and third parachutes would slow down the descent of the SRE and it would have a soft touchdown in the waters of the Bay of Bengal about 140 km east of Sriharikota. A flotation system would keep it alive. Beacons on its board would signal its splashdown. Dye markers would make it visible and a Coast Guard vessel would recover it.

The SRE, which looks like a sphere-cone, is made of mild steel. It is 1.6 metres tall and its base diameter is two metres. Placed inside this capsule are the parachutes, pyro devices, avionics packages, telemetry and tracking systems, and two payloads for conducting experiments in micro-gravity.

The 555-kg SRE has been built jointly by the Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram, the ISRO Satellite Centre, Bangalore, and the Liquid Propulsion Systems Centre, among others.

The other three satellites that were to be put in orbit by the PSLV-C7 were ISRO's Cartosat-2; LAPAN-TUBSAT, jointly built by Indonesia and the Technical University of Berlin; and Pehuensat-1 of Argentina. The 680-kg Cartosat-2 is for mapping purposes. LAPAN-TUBSAT, which weighs 56 kg, is a remote-sensing satellite. The six-kg Pehuensat-1 is to learn the art of building satellites. Thus the success of the PSLV-C7 mission was keenly watched from abroad.

Although ISRO Chairman G. Madhavan Nair denied that the organisation was under pressure following the failure of the previous GSLV flight, the atmosphere was tense in the Mission Control Centre in the final hours of the 52-hour countdown to the lift-off at 9-23 a.m. The entire countdown proceeded without any hold, and the four-stage, 44-metre tall PSLV, which weighs 295 tonnes, lifted off majestically from its beachside launch-pad on the dot. All the stages ignited on time, jettisoned at precise moments, and the fourth stage injected the four satellites into orbit.

Madhavan Nair paid tributes to the ISRO community for bringing about this triumph "in about six months from the last debacle". The textbook mission showed "the precision with which the rocket systems, control systems, guidance systems, navigations systems and the on-board computer functioned... . The satellites were separated as per sequence."

The ISRO Chairman explained how it happened: "We had gone through a series of processes, checkouts, calibrations, quality checks and previews. At the end of it, we are happy that the processes that we adopt for such launch missions have worked out and all the sub-systems also have worked as per plan."

He praised the team led by John P. Zachariah, Deputy Director, VSSC, "which slogged here for two months to realise the vehicle". Dr. B.N. Suresh, Director, VSSC, which built the vehicle, said, "There will be four or five launches this year. This [success] has given a firm foundation to the launches planned this year."

According to D. Narayana Moorthi, there were self-driven reviews in ISRO, and success was achieved because of pressure not from outside but from inside. "The entire ISRO showed strength of character in identifying the problem in the GSLV in a fast mode, analysing it and completely reviewed the process of making the vehicle, including quality procedures and protocol." Narayana Moorthy, Koshy and Zachariah gave an account of how the success was achieved: once the problem in the GSLV was identified, VSSC's quality assessment teams put in all efforts to check every part in the PSLV-C7. They went into all possible defects. Extra care was taken to re-examine all the items, systems and sub-systems. The entire assembly and integration of the vehicle was meticulously done.

Although the PSLV was a proven vehicle, the internal length of the C-7 was 2.6 m more because of the use of the DLA for launching four satellites. This required a detailed analysis in vehicle dynamics and characterisation. To inject four bodies into orbit without any collision was in itself a big mission design achievement.

The attention now is on the SRE. The tentative date for its recovery is January 22. "Although the problem occurred in a stage common to both the GSLV and the PSLV, it was a challenge to build confidence in the teams. Thanks to the ISRO spirit of never-say-die, this success has been achieved. Till the SRE is recovered, the entire ISRO will be anxious," said Narayana Moorthy.

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