The first developmental flight of Geo-synchronous Satellite
Launch Vehicle, GSLV-D1, was successfully carried out on April 18, 2001 from
SHAR Centre, Sriharikota. The flight was primarily intended to validate the
vehicle design and evaluate flight performance parameters. This objective was
met when the experimental satellite, GSAT-1, was successfully placed in the
geo-synchronous transfer orbit as planned. For the first time, validation of
Geo-synchronous launch Mission from SHAR with associated acquisition of signals
at satellite injection and carrying out the orbit raising maneuvers through a
network of international stations, coordinated and controlled by INSAT Master
Control Facility, Hassan, has been achieved.
The preliminary analysis of the flight data indicates that GSLV has performed
well in flight validating the design and functioning of all the vehicle
subsystems in flight, the integration procedures including the safe handling of
large quantities of liquid and cryogenic propellants, the navigation and
control, the flight sequence like ignition of various stages, separation of
spent stages, the heatshield and the spacecraft, besides the coordinated
working of a network of ground stations to track and monitor the vehicle in
It may be recalled that the first attempt to launch GSLV on March 28, 2001 was
aborted one second before the lift-off by the Automatic Launch Processing
System (ALS) after it detected that one of the liquid propulsion strap-on
boosters did not develop the required thrust. Based on the detailed analysis of
the data during the first three seconds of operation of the four strap-on
motors, it was established that the reason for one of the strap-on boosters not
developing the required thrust was due to a defective plumbing in the oxidiser
flow line of the engine, which had escaped detection during testing. This
resulted in reduced flow of oxidiser to the engine. The anomalous engine was
replaced with a standby engine for the relaunch on April 18, 2001. The
successful flight of GSLV-D1 has validated the analysis and the solution
adopted for the relaunch.
The GSLV flight test opportunity was also used to place an experimental
satellite, GSAT-1, in the geo-stationary orbit to prove new spacecraft elements
and conduct a few communication experiments. GSAT-1 was placed in an orbit of
181 km perigee (nearest point to earth) and 32,051 km apogee (farthest point to
earth) with an inclination of 19.2 degree with respect to equatorial plane. The
satellite was injected with a velocity that was 99.4 percent of the intended
10.2 kilometre per second. But this minor shortfall of 0.6 % in the overall
velocity resulted in reduction of orbital apogee of the satellite. The perigee
of 181 km and inclination of 19.2 deg were close to targeted values.
This minor deficiency in the apogee altitude was correctable and, in fact, was
corrected during the orbit manoeuvres of the satellite since such contingencies
are provided for in the mission planning. Through a series of six orbit
maneuvers conducted between April 19 and April 23, 2001, the satellite orbit
has now been raised close to near-geo-synchronous height with an apogee of
35,665 kilometer, perigee of 33,806 kilometer and inclination of 0.997 degree.
All deployments operations like those of antenna reflector, solar array and the
solar sail have been successfully completed. Further, the satellite has been
put in 3-axis stabilisation mode using momentum wheels.
Several new communication satellite technologies have been evaluated using
GSAT-1. These include: (i) Fast Recovery Star Sensor (FRSS) which provides
enhanced accuracies of measuring satellite orientation and for quick earth-lock
recovery in case of loss of lock, (ii) a new earth sensor using pyro electric
detectors, (iii) a new technique of using 22 Newton thrusters in a combination
of four as an alternate strategy for orbit raising, (iv) a new technology for
thermal control of satellites using heat pipes (v) new technique of power
management through charger arrays for improving the overall efficiency of power
systems and (vi) optimal orbit raising using perigee firing strategy.
During the orbit raising operations of the satellite, consumption of propellant
was much more than planned resulting in a shortage of about 10 kg to achieve
the geo-stationary orbit. The satellite is presently in a drift orbit with an
orbital period of 23 hr 2 minutes.
In conclusion, (i) GSLV-D1 launch vehicle has fulfilled all its intended
objectives and injected the GSAT-1 spacecraft into the Geo-synchronous transfer
orbit (ii) the shortfall of 0.6% in final velocity of injection was correctable
and was corrected using satellite propulsion (iii) several new technologies for
the spacecraft have already been evaluated. The satellite will be kept under
observation for further operations.