The Hindu : Front Page : After runaway success, a major technological task begins for ISRO

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Thursday, Jan 11, 2007
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After runaway success, a major technological task begins for ISRO

T.S. Subramanian

After SRE stays in orbit for 11 days, it will be de-orbited and brought back to the earth in a sequential manner

SRIHARIKOTA: Although the PSLV-C7 launch was a runaway success with the injection of four satellites into orbit on Wednesday, the job of A. Subramonian has just begun. For, he is the Project Director of India's first recoverable satellite called the Space Capsule Recovery Experiment (SRE), one of the four satellites put in orbit.

"Right now, I feel that my job has just started. I am looking forward to January 22 morning when the SRE will be recovered," Mr. Subramonian said.

After the 555-kg SRE stays in orbit for 11 days, it will be de-orbited and brought back to the earth in a sequential manner. It is coated with thermal tiles to prevent it from burning up when it re-enters the earth's atmosphere. After it re-enters the atmosphere, about 5 km above the Bay of Bengal, three parachutes in the SRE will open up one after another. First, the pilot chute will pull out the drogue chute, which will deploy, and then the main chute will deploy. The main chute will slow down the descent of the SRE and it will ultimately splash down into the Bay of Bengal, about 140 km east of the Sriharikota island. A floatation system will keep it afloat. Dye markers will make it visible. The Coast Guard will recover it.

"There are a lot of technological challenges" in bringing back an orbiting satellite because "we are doing it for the first time," said G. Madhavan Nair, ISRO Chairman. It should be de-orbited in the right direction; it should be given the right incremental velocity. It should re-enter the atmosphere without burning up.

Dual Launch Adopter

The PSLV-C7 used for the first time a device called Dual Launch Adopter (DLA) to launch four satellites. It also used for the first time a video-imaging system on board to take pictures of the separation of the first three satellites from the fourth stage of the rocket.

According to George Koshy, Vehicle Director, the PSLV-C7 used a video-imaging system to take pictures of the separation of the Cartosat-2, the Peheunsat-1 and the SRE from the PSLV's fourth stage. No picture was taken of the injection of the LAPAN-TUBSAT into orbit.

N. Narayanamoorthy, Mission Director, PSLV-C7, said: "... The mission management to inject four bodies into precise orbit without any collision is a big design achievement in itself ... We are wonderfully happy."

After the 680-kg Cartosat-2 flew out first, the "vehicle was re-oriented" and out flew the six-kg Peheunsat-I, said Mr. Nair. There was one more manoeuvre of the vehicle and the SRE was injected into orbit. The vehicle was again tilted at an angle and the 56-kg LAPAN-TUBSAT flew out.

Precision system

All the four satellites were launched on the dot at the right height and inclination. Each of the four satellites was put into a circular orbit of 637 km above the earth while the predicted orbit was 635 km above the earth.

The inclination achieved was 97.9 degrees while the target was 97.91 degrees, a deviation of 0.01 degree. "This shows the precision of our rocket system and the functioning of the on-board computer," the ISRO Chairman said.

According to M. Krishnaswamy, Project Director, Cartosat-2, the satellite's images could be used in town and rural planning. With its one-metre resolution, at the cadastral level, the boundaries of each land area could be easily identified.

"This will be useful in tax assessment," Mr. Krishnaswamy said. The actual plan of houses up to one-metre accuracy could be found out, which would again be useful in tax assessment. The Cartosat-2 images would also be useful in road and drainage alignment, and studying the passage of communication lines.

The LAPAN-TUBSAT is an earth observation satellite. The Pehuensat-1 is to learn the art of building satellites.

It cost the ISRO Rs. 80 crore to build PSLV-C7, Rs. 180 crore for the Cartosat-2 and Rs. 30 crore for the SRE.

About $8,000-$10,000 a kg would be charged for orbiting the LAPAN-TUBSAT and the Pehuensat-1.

According to R.V. Perumal, Director, Liquid Propulsion Systems Centre, ISRO, a GSLV bearing an indigenous cryogenic stage will be launched either by the end of this year or the beginning of next year.

Chandrayaan-I, India's mission to the moon, would take place in the beginning of 2008. "We have a long way to go" for India's manned mission, said Mr. Nair. It would take eight years to send an Indian into space.

The Ariane vehicle will launch the INSAT-4B from the Kourou island in French Guiana by the middle of this year. The PSLV-C8 will lift off from SHAR in March or April to orbit Italy's Agile satellite and the ISRO's Advanced Avionics Mission Module.

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