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Friday, Dec 22, 2006
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PSLV to put recoverable satellite into orbit

T.S. Subramanian

To carry four satellites; launch slated around January 10

— Photo: ISRO

The recoverable satellite called Space Capsule Recovery Experiment undergoing tests.

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CHENNAI: Preparations are going on "smoothly" for the launch of four satellites from a single Polar Satellite Launch Vehicle named PSLV-C7 from Sriharikota around January 10, 2007. What is novel about this mission is that the Indian Space Research Organisation (ISRO) will orbit for the first time a recoverable satellite called the Space Capsule Recovery Experiment (SRE). After the SRE stays in orbit for a week or so, it will splash down 140 km east of Sriharikota island in the Bay of Bengal and recovered by the Navy.

This SRE, which weighs about 615 kg, is a technological forerunner to ISRO mastering the re-entry technology and building re-usable launch vehicles. A host of new technologies such as deceleration and flotation systems will be tested when the SRE descends from its orbit. Its three parachutes will open one after another when it is five km above the waters of the Bay of Bengal and commands given to drop down.

Multi-mission flight

B.N. Suresh, Director, Vikram Sarabhai Space Centre, Thiruvananthapuram, called the PSLV-C7 flight "a multi-mission." He said, "We will put four satellites in four different orbits. We have to put them in appropriate slots." The four satellites are: ISRO's Cartosat-II which weighs 665 kg; the cone-shaped SRE; the 56-kg LAPAN-Tubsat developed by Indonesia and the Technical University of Berlin; and the six-kg micro-satellite called Pehuen from Argentina.

The four stages of the PSLV-C7 have been stacked up in the first launch pad at SHAR. The four satellites will be married up (repeat married up) to the rocket in a few days.

"All tests are proceeding smoothly. So far we have faced no problem," said the VSSC Director.

"The launch of the SRE will really be a new experience for us," said Dr. Suresh. It would be a forerunner to ISRO mastering the re-entry and recovery technologies. "Both are important for our Re-usable Launch Vehicle," Dr. Suresh said. The SRE would stay in obit for a week. But it could stay longer for a month.

According to A. Subramonian, Project Director, SRE, VSSC, the SRE's payloads, during its stay in orbit, will perform two experiments. One relates to the growth of crystals and the other is a bio-mimetic experiment for studying the growth of minerals in micro-gravity environment.

According to ISRO engineers, after the SRE stays in orbit for about a week, it will be de-orbited and brought back to the earth in precisely planned manoeuvres. It will thus provide them valuable experience in navigation, guidance and control during the re-entry phase. The SRE has a thermal protection system which prevents it from burning up when it knives into the earth's atmosphere and searing heat is generated. After re-entry, about five km above the sea level, the three parachutes in the SRE will open up sequentially at predicted altitudes and the SRE will splash down.

Cartographic applications will get a boost from the images sent by the camera on board Cartosat-II. The images will be used in preparing maps for planning towns and cities, and at cadastral level. The images will have a one-metre resolution.

The LAPAN-Tubsat is a technology demonstrator for earth observation.

Pehuen satellite is to gain experience in building satellites and operating them.

The PSLV is 44.4 metres tall and weighs 295 tonnes. The PSLV, in its missions in 1999 and 2001, had orbited three satellites each. This is the first time that the PSLV will put in orbit four satellites.

While the VSSC is the key centre for building the rocket, ISRO Satellite Centre, Bangalore, is the lead centre for building Cartosat-II.

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