Chennai, Jan 22
Ahead of its Mission to Moon next year, India Monday achieved an
important milestone in its space odyssey as it safely brought back
to earth the recovery satellite put into orbit by the Polar
Synchronised Launch Vehicle PSLV-C7 12 days ago.
On Jan 10, the PSLV-C7 had put the into space four satellites -
three communication satellites of India, Indonesia Argentina and the
Space Recovery Experiment-1 (SRE-1).
On Monday, the SRE-1 splashed down in the waters of the Bay of
Bengal at 9.47 a.m., about 140 km from where it had taken off into
space, the Sriharikota launch station in Andhra Pradesh.
Its re-entry is the first ISRO test of re-usable vehicles and
satellites before India launches its moon mission in February 2008.
ISRO scientists speaking from Bangalore on telephone said that it
was a milestone in India's space technology.
The SRE demonstrates the technology of an orbiting platform for
doing experiments in micro-gravity conditions.
The SRE was recovered by a Coast Guard ship, "Sarang", and brought
to the Ennore container port north of Chennai late in the evening
amid tight security and secrecy.
It was then sent back to the launching station, Sriharikota Space
Centre (SHAR) on the Sriharikota island off the Andhra Pradesh
coast, about 80 km north of here, by road for further studies on how
far Indian scientists had succeeded in the experiments they began on
this satellite.
"Its speed at the time of splashdown was about 40 km per hour, the
speed of a car," said an official of the Indian Space Research
Organisation (ISRO).
The re-entry of the satellite, orbiting 625 km above earth for 10
days, was guided by the Spacecraft Control Centre of ISRO's
Telemetry, Tracking and Command Centre (ISTRAC) at Bangalore.
The operation began Saturday when the SRE's height was reduced
gradually. To facilitate its return, the space capsule was then
shifted to an elliptical orbit.
The "de-boost operations" began at 9.00 a.m. Monday with the firing
of on-board rocket. After 17 minutes, the space capsule was
reoriented for its re-entry into the atmosphere, ISRO scientists
said.
At 9.37 a.m., the capsule returned to earth's atmosphere at an
altitude of 100 km, with a velocity of eight km per second (29,000
km per hour), ISRO said.
The SRE-1 descended rapidly and when it was just about five km
above, aerodynamic braking was used to reduce its velocity to 101
m/sec (363 km per hour).
A 'drogue parachute' on board reduced the velocity further to 170 km
per hour. Aerodynamic brakes helped the spacecraft to come down
gently.
At an altitude of just about two km above the sea, the main
parachute opened out, allowing the capsule to splash down at a
reduced velocity of about 43 km per hour at precisely 9.46 a.m.
A float on board got activated to keep the capsule afloat as soon as
it touched down.
Coast Guard vessels had kept vigil around the designated site all
night and the capsule was tracked through their radars when it
splashed down there.
A navy helicopter was immediately despatched to the spot marked by
green dye released by the capsule. It also had a transmitter that
broadcast its position to the Coast Guard ship continuously.
The Sarang carried on board heavy-duty cranes that lifted out of the
water the cone-shaped space capsule weighing about 550 kg.
The SRE has an aero-thermal protection system and ISRO is testing
basic technology for protective outer jackets for satellites and
vehicles, mission director N. Narayana Moorthy had told reporters.
The capsule was protected from the intense heat by the carbon
phenolic ablative material and silica tiles placed on its outer
surface.
The decision to test the re-entry and recovery technology was taken
after 80 scientists from across the country gave their unanimous
consent to sending a manned mission to space at a conference in
Bangalore in November at the instance of Prime Minister Manmohan
Singh.
Made of mild steel, the satellite's re-entry has also given ISRO
data on navigation, guidance and control, hypersonic
aero-thermodynamics, management of communication blackout,
deceleration and floatation system and recovery operations.
Only a handful of countries including the US, Russia and China have
successfully mastered re-entry technology.
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