India's Large Satellite Launcher Returns to Flight

by Stephen Clark

Date: 03 September 2007 Time: 12:14 AM ET

It was a day of redemption for India's space program Sunday, when the nation's most powerful rocket returned to the skies for the first time since a booster engine failure doomed a launch last year.

The Geosynchronous Satellite Launch Vehicle, making its fifth flight since debuting in 2001, blasted away from the Satish Dhawan Space Center on Sriharikota Island. Liftoff was at 1250 GMT (8:50 a.m. EDT), the exact time of sunset on India's east coast.

The 161-foot-tall rocket flew east over the Bay of Bengal on track to deposit the INSAT 4CR communications satellite into orbit.

The liftoff was delayed two hours due to a last-second technical problem that halted the countdown moments before launch.

The GSLV's cryogenic upper stage successfully deployed INSAT 4CR about 17 minutes after liftoff.

INSAT 4CR was released into an elliptical transfer orbit stretching from a low point of about 104 miles to a high point of 21,568 miles. The orbit's inclination was 20.7 degrees, according to the Indian Space Research Organization.

The apogee mark was 786 miles lower than pre-launch predictions, and the achieved inclination was one degree off the target of 21.7 degrees.

Despite the rocket's underperformance, Indian space officials declared the critical mission a success. They offered no explanation of the slightly low orbit.

ISRO officials also confirmed the payload unfurled its two solar panels a few minutes after spacecraft separation. The power-generating arrays stretch about 31 feet from tip to tip.

The three-stage rocket's last flight ended in disaster about one minute into another communications satellite delivery mission in July 2006. A committee appointed to analyze the failure determined a propellant regulator inside one of four liquid-fueled strap-on boosters malfunctioned, which allowed excess propellant to flow into the Vikas engine.

"The reason for this could be an inadvertent error in manufacturing, which escaped the subsequent inspection and acceptance test procedures," ISRO said in a statement.

The investigation board recommended revamped fabrication and acceptance guidelines, and ISRO implemented the improved procedures, according to a spokesman. ?

Pressures and temperatures inside the engine soared above operational limits, which led to the power plant's premature shutdown just moments after liftoff. The rocket's steering systems performed well until the launcher neared the speed of sound, and the GSLV veered out of control and broke apart about 55 seconds after liftoff.

The four strap-on engines burn hydrazine and nitrogen tetroxide during the first two-and-a-half minutes of launch. The boosters are clustered around a solid-fueled core stage.

INSAT 4CR was ordered as a replacement for INSAT 4C, which was lost in last year's launch accident.

The 4,696-pound satellite will raise its altitude and reduce its inclination in the next few weeks before parking itself in geostationary orbit 22,300 miles above the Indian Ocean.

Expected to operate for at least ten years, INSAT 4CR will specialize in direct-to-home television broadcasting, video picture transmission and digital satellite news gathering services. INSAT 4CR carries 12 Ku-band transponders that will reach across India.

INSAT 4CR is the 11th member of the INSAT fleet in service today. The INSAT series includes both communications and weather satellites.

India's next launch could be less than three weeks away, according to local media reports.

Workers at Sriharikota are busy preparing a Polar Satellite Launch Vehicle for launch later this month with an Israeli spy satellite called Polaris. The covert spacecraft will be the first Israeli satellite fitted with a cloud-piercing radar instrument, which can see objects on the ground through darkness and inclement weather.

Testing is also continuing on a new third stage engine for future GSLV launches. The GSLV currently uses a Russian-supplied cryogenic engine, but Indian engineers are working on an indigenous system for use on upcoming flights.

Engineers completed an eight-minute test firing of the new engine last month. The engine, which burns liquid hydrogen and liquid oxygen, will fire for about 12 minutes during a real launch.

An ISRO spokesman told Spaceflight Now the first flight of the new engine is scheduled for next March or April.

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