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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. -- --------------------------- Jacques :-) www.spacepatches.info |
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