After today's successful Ariane 5 mission
that placed INSAT 3A into orbit from Kourou, ISRO chairman Dr. Kasturirangan
and Arianespace CEO Jean-Yves Le Gall announced the signing of launch
contracts for two more payloads - the INSAT 4A and 4B spacecraft.
These are the 12th and 13th Isro satellites to be booked on the European
launcher. Since the launch of the Apple experimental satellite in
1981 on Flight L03, Arianespace has orbited ten Indian satellites.
Arianespace is slated to launch another ISRO payload, the INSAT 3E
satellite, later this year.
Designed, built and integrated by Isro, the INSAT 4A and INSAT 4B
satellites each weigh about 3,200 kg at liftoff. INSAT 4A and INSAT
4B are dedicated to telecommunications, with 12 Ku band and 12 C-band
transponders each. Their coverage zone is the Indian sub-continent.
Meanwhile, the 160th flight of Ariane, carrying Isro's 2,950 kg INSAT-3A
and GALAXI-XII of US, lifted off at 4.22 am IST from Kourou, French
Guyana. INSAT-3A was injected into a Geosynchronous Transfer Orbit
(GTO), 30 minutes after the lift-off in 3-axis stabilized mode, with
a perigee (nearest point to earth) of 859 km and an apogee (farthest
point to earth) of 36,055 km and an inclination of 1.99 deg. with
respect to the equator. The satellite is at present going round the
earth with an orbital period of about 10 hours 47 minutes, according
to the agency.
The Master Control Facility (MCF) at Hassan in Karnataka acquired
the telemetry signal from INSAT-3A at 04.52 am IST. The initial health
checks on the satellite indicate that the performance of the satellite
is normal. First operations on the satellite were carried out by issuing
commands from the MCF. The outermost panel of the stowed solar array
of INSAT-3A was oriented towards the Sun to start generating the electrical
power required by the satellite. Subsequently, the earth viewing face
was oriented towards the earth and calibration of the gyros on board
the satellite was carried out.
INSAT-3A is being tracked, monitored and controlled from MCF. During
the initial phase of INSAT-3A operations, MCF also utilises INMARSAT
Organisation's ground stations at Beijing (China), Fucino (Italy)
and Lake Cowichan (Canada). The satellite's orbit is being precisely
determined by continuous ranging from the participating Telemetry,
Tracking and Command (TTC) ground stations.
In the coming days, orbit raising operations of INSAT-3A will be carried
out by firing its 440 Newton Liquid Apogee Motor (LAM) in stages till
the satellite attains its final geostationary orbit, which is about
36,000 km above the equator. The satellite has about 1.6 tonne of
propellant (Mono-Methyl Hydrazine - MMH fuel and Mixed Oxides of Nitrogen
- MON-3 oxidiser) for orbit raising operations as well as for station
keeping and in-orbit attitude control. The on-orbit propellant availability
will enable maintaining the satellite for operational services for
a period of 12 years.
When the satellite reaches near-geostationary orbit, deployment of
its solar panels and the two antennas as well as the solar sail will
be carried out and the satellite put in its final 3-axis stabilised
mode. This will be followed by trim manoeuvres to take the satellite
to its designated orbital slot. The payloads will be subsequently
checked out before the commissioning of the satellite.
INSAT-3A will be positioned at 93.5 deg East longitude in the geostationary
orbit. |
