CHENNAI: With the 52-hour countdown having begun at 5.48 a.m. on January 8, everything is set for the launch of the Polar Satellite Launch Vehicle (PSLV-C7) at 9.23 a.m. on Wednesday from the beachside launch pad on the Sriharikota Island in Andhra Pradesh.

It is a multi-mission launch with the PSLV-C7 injecting four satellites into the orbit one after another. Two satellites belong to India and two are from abroad.

Countdown smooth

B.N. Suresh, Director, Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram, said: ``Everything is going on as planned. The countdown is progressing smoothly. All tests are over. If everything goes well, the vehicle will lift off at 9.23 a.m. on January 10.''

The highlight of the mission is that the Indian Space Research Organisation (ISRO) will launch for the first time a recoverable satellite called Space Capsule Recovery Experiment (SRE). After the SRE stays in orbit 635 km above the earth for 11 days, it will be brought back on the 12th day in a sequential operation with the ISRO beaming a series of commands from its ground stations. It will splash down with the help of parachutes in a pre-determined area in the Bay of Bengal, about 140 km east of the Sriharikota Island. Coast Guard personnel will recover it. The SRE can stay in orbit up to 30 days. During its stay, micro-gravity experiments will be done using its payloads.

New technologies

The SRE will help ISRO test a host of new technologies, including the re-entry and recovery technologies. The SRE is also a trial balloon to the ISRO building re-usable launch vehicles.

The three other satellites are ISRO's Cartosat-II; LAPAN-TUBSAT of Indonesia and the Technical University of Berlin; and Argentina's Pehuensat-I.

Another highlight of the mission is the use of a device called Dual Launch Adopter (DLA) as more than one large satellite is being put into the orbit by a single rocket. Although ISRO launched three satellites each during its PSLV flights in 1999 and 2001, it did not use a DLA then because two of the three satellites in those missions were small. But this time, Cartosat-II weighs 680 kg, SRE 550 kg, LAPAN-TUBSAT 56 kg and Pehuensat-I 6 kg.

The four satellites, seated on top of the fourth stage, will fly out in a sequence. All will go into a circular orbit 635 km above the earth. The first to fly out will be Cartosat-II. The next will be Pehuensat-I, followed by SRE and LAPAN-TUBSAT.

Slotted into orbit

Each time a satellite is slotted into orbit, the PSLV's fourth stage will be re-oriented, i.e., tilted at an angle so that the satellites do not collide with each other.

The fourth stage is re-oriented thus by firing small rockets on board. The PSLV is a four-stage vehicle.

Dr. Suresh said, ``After keeping it (SRE) in orbit for 11 days, we will bring it back to the earth on the 12th day.'' Two days before the SRE is de-orbited, ISRO will send commands to it to change its orbit from the circular to elliptical. ``This is done to basically ensure that we get daily repetitive visibility for 10 to 12 days so that we can send de-orbiting commands to it from the ground station'' at Sasketoon in Canada, he said.

Tirupati Special Correspondent reports:

ISRO Chairman G. Madhavan Nair said here on Monday that all sub-systems on board the launch vehicle were working satisfactorily. Barring unforeseen contingencies such as bad weather, the lift-off would take place as scheduled.

A 10-minute `narrow-window' was, however, provided for any possible last-minute manoeuvres, he said.

Answering a question, Mr. Nair said that as the Failure Analysis Committee had attributed the failure of the previous launch (GSLV) to a `defect in fabrication,' ISRO had meticulously ``revisited'' all the critical and crucial areas vis-a-vis the PSLV-C7 so as to ensure its successful launch.

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