The Hindu : Front Page : INSAT-4B orbit raised

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Wednesday, Mar 14, 2007
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INSAT-4B orbit raised

Special Correspondent

All systems functioning normally

CHENNAI: The first manoeuvre to raise the orbit of India's communication satellite, INSAT-4B, was successfully executed on Tuesday morning and, as a result, the orbit's perigee (nearest point to the earth) was raised from 250 km to 14, 244 km. Its apogee (farthest point from the earth) remains almost the same at 35,886 km.

An ISRO official called this manoeuvre "a critical one" and said the satellite's orbit was raised by giving commands to its liquid apogee motor to fire. The motor fired continuously for 93 minutes, beginning at 5.35 a.m.

The commands were given to it from ISRO's Master Control Facility (MCF) at Hassan in Karnataka. The MCF has a series of sophisticated antennae on its campus for tracking INSAT-4B, transmitting radio-commands to it and receiving information from it on its condition. The liquid apogee motor uses mono-methyl hydrazine as fuel. The oxidiser is mixed oxides of nitrogen. ISRO's Liquid Propulsion Systems Centre at Valiamala in Kerala built these liquid apogee motors.

In its new orbit called the intermediate orbit, the satellite takes about 15 hours and 21 minutes to go round the earth once, an ISRO press release said. All systems on board the satellite are functioning normally. More manoeuvres to raise the satellite's orbit will be performed in the coming days.

It will take about a week to slowly nudge the satellite into the vicinity of the geo-stationary orbit. Then commands will be given to it for its solar panels and antenna to spread out. Before the satellite is declared operational, its transponders will be thoroughly tested.

Ariane-5, launch vehicle of Arianespace, put INSAT-4B into orbit on Monday. The satellite has 24 transponders, which will boost the direct-to-home telecasting, especially for entertainment, in India. The ISRO Satellite Centre at Bangalore built INSAT-4B, which will have a life of 12 years.

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