A major critical operation of deploying the 14m long solar sail and boom on the
North face of INSAT-2E was successfully completed this morning (April 12,
1999). The deployment took place in two stages - first by firing an explosive
device to release the sail-boom assembly and later operating a motor for about
15 minutes to ensure a controlled deployment.
At the time of launch, the sail-boom assembly is kept compactly packed which
just occupies about 1/50th of its final deployed length. The boom is made of
ultra light-weight glass fibre structure weighing about 3.5 kg. The sail
measuring 2 m across and 5 m tall weights less than a kilogram.
INSAT-2E carries a meteorological payload, which requires the detector to be
maintained at an extremely low temperature. This precludes the use of solar
arrays symmetrically on both north and south faces. To counteract the torque
generated by the sun's radiation falling on the solar array on the south side,
the solar sail mounted on a boom is incorporated in the design of INSAT-2E on
the north side.
The sail and boom were indigenously designed, developed and manufactured at ISRO
Satellite Centre, Bangalore, followed by extensive testing in simulated
This deployment was preceded by turning on the momentum wheels onboard the
satellite, and running them up to a speed of 4800 revolutions per minute. The
momentum wheels are used for maintaining the precise orientation of the
satellite required for the communication and meteorological payloads. With
this, the satellite is in the 3-axis stabilised final configuration with earth
orientation, and the stage is set for turning on the payloads.