EDUSAT Placed in Near-Geosynchronous Orbit; Antennas Deployed

EDUSAT Placed in Near-Geosynchronous Orbit; Antennas Deployed
September 26, 2004


In the third and final orbit-raising operation conducted at 8.21 am (IST)
on September 24, 2004, from Master Control Facility (MCF), Hassan, EDUSAT
was placed in near Geosynchronous Orbit (GSO). The manoeuvre was completed
by firing the Liquid Apogee Motor (LAM) on board the satellite for a
duration of 2 min 15 secs. With this operation, the satellite has achieved
an orbital period of 23 hours and 46 minutes and is continuously within the
radio visibility of MCF. The spacecraft is now located at 61 deg East
longitude, and drifting towards its orbital slot of 74 deg E, at a rate of
2.54 deg per day. It will reach its first In-Orbit Test slot by October 2,
2004.

After the completion of the third apogee motor firing, the East side antenna
of EDUSAT was also deployed at 10:30 am (IST) successfully on September 24,
2004. This antenna is intended for transmitting and receiving Ku-band
signals with multiple Spot beams coverage.

Three-axes stabilisation of the satellite and its West side antenna
deployment were carried out yesterday (September 25, 2004) at 7:00 am and
2:15 pm respectively. West side antenna is intended for transmitting and
receiving Extended C-band signals. Besides the two deployable antennas, the
satellite has one body-mounted antenna meant for transmitting and receiving
Ku-band signals with National coverage beam.

In 3-axes stabilised mode, EDUSAT is locked onto earth continuously through
its optical sensors and maintains proper orientation to look at the earth in
a stable manner. The Momentum Wheels on-board the satellite spinning at 4500
revolutions per minute provide gyroscopic stiffness and maintain three axis
stabilisation.

It may be noted that EDUSAT was launched by GSLV on September 20, 2004 into
a Geosynchronous Transfer Orbit (GTO) of 180 km perigee (nearest point to
Earth) and 36,000 km apogee (farthest point to Earth) with an orbital
inclination of 19.3 degree with respect to the equatorial plane.
Subsequently, LAM was fired in three stages to take EDUSAT to its present
near geosynchronous orbit with an inclination of almost zero degree with
respect to the equator. The LAM was fired for a total duration of 94
minutes. A total velocity of 1.66 km per second was added by LAM at the
apogee point of the orbit to take the satellite from GTO to near GSO.

EDUSAT had 1128 kg of propellants at the time of its injection into GTO by
GSLV. After orbit raising operations, it now has 300 kg of propellants
remaining which is sufficient to maintain the satellite in its orbit and
control its orientation during its design life of 7 years.

The communication transponders of EDUSAT will be tested during the next
three weeks and EDUSAT is expected to be ready for use in two months time.




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Jacques :-)

www.spacepatches.info