COVER STORY

Support systems on the ground

Having taken control of INSAT-2E, the Master Control Facility near Hassan works to park the satellite in its orbit and manage and monitor its operations.

T.S. SUBRAMANIAN
in Hassan

On March 30, four days before the launch of INSAT-2E, the air was one of tense expectation at the Mission Control Facility (MCF) of the Indian Space Research Organisation (ISRO) near Hassan, 220 km from Bangalore. The MCF is the nerve-centre that manages INSAT-2E right from its injection into orbit through its entire life in space.

Dr. S. Rangarajan, Director of the MCF and also the INSAT programme, said that all systems at the MCF were geared for the launch. "There is a lot of excitement in the air," he said.

Early on April 3, the day of the launch, the tension was palpable: several hundred experts from ISRO and the user agencies of INSAT-2E sat before their computer consoles and watched the countdown for the Ariane 4 lift-off. Eight minutes after the satellite was injected into the geostationary transfer orbit, the MCF "acquired" the spacecraft for the first time.

It is from the MCF that commands are given to fire the liquid apogee motors on board INSAT-2E in order to raise it in stages from the geostationary transfer orbit to the geostationary orbit proper at an altitude of 36,000 km. It is from the MCF that commands are given to the satellite to switch on the batteries aboard the spacecraft; deploy its solar panels, solar array and antenna; and switch on its telecommunications and meteorological payloads. It is from here that commands are sent to orient the satellite in the correct longitude and nudge it into its final parking slot. It is the MCF that receives signals from the satellite which show how its sub-systems are working. In sum, the MCF is responsible for operationalising INSAT-2E and monitoring its health.

A few hours after the launch, D. Ravindranath, Group Director, Telemetry, Tracking and Command Network, MCF, told Frontline: "The satellite is healthy. All systems are working normally. Twenty-nine minutes after lift-off we got the first AOS (acquisition of spacecraft)." Ravindranath said that the rehearsal for the apogee motor firing took place after the first AOS and that it went off well.

HASSAN is situated close to the grand temples built by Hoysala kings at Belur and Halebid, and the MCF is located in picturesque surroundings on an area of 17.2 hectares. The site was chosen, Rangarajan said, "because it suited us geographically, geologically and logistically." The Karnataka Government offered the land. According to S. Krishnamurthy, Director, Publications, ISRO, the site was relatively calm and free of noise and encountered less terrestrial transmission than some other sites proposed. "Even if the signal from the satellite is weak, we should be able to pick it up. There should be no interference."

T.L.PRABHAKAR
An array of full-motion antennae and limited-motion antennae at the Master Control Facility in Hassan, which controls, commands and tracks INSAT-2E.

Rangarajan said that INSAT-2E, which weighed 2,550 kg, was the heaviest satellite built so far by ISRO. Its projected life-span, 12 years, is the longest for a satellite in the INSAT series. The Space Applications Centre (SAC) in Ahmedabad designed and made the communications and the meteorological payloads of INSAT-2E. The ISRO Satellite Centre (ISAC) in Bangalore made the bus systems and the power systems. The Liquid Propulsion Systems Centre in Thiruvananthapuram made the propulsion systems, liquid apogee motors and control systems. The ISAC integrated the entire satellite.

Rangarajan said that INSAT-2E cost between Rs.200 and Rs.220 crores to build. The total investment, including the cost of the satellite, payment to Arianespace and the insurance premium, was Rs.550 crores. When fully deployed, the satellite would measure 25 metres - about the height of an eight-storey building - from end to end, including the long boom and the sail on top.

THERE are three state-of-the-art facilities at the heart of the MCF. They are the Spacecraft Control Centre, the Mission Control Centre and the earth stations, namely, an array of antennae to beam commands to the satellite, receive signals from it and track it.

All operations of the satellite, including on-orbit operations, are controlled from the Spacecraft Control Centre. Ravindranath said: "All commands to the satellite are given from here."

The Mission Control Centre is, according to Krishnamurthy, "the focal point for all operations". It is from here that all designers of the sub-systems of the satellite remain in touch with Mission Director M. Annadurai. Should anything go wrong with any of the sub-systems of the satellite, instructions for corrections go out from here. The Mission Control Centre also receives telemetry from the satellite, that is, signals which provide information on its health. The designers keep track of the data coming in in respect of the sub-systems they designed, including the inertial systems, control systems, propulsion systems and sensors. They keep tabs on the temperature, heat and other parameters of the sub-systems.

K. Suriyanarayan Sharma, mission head, said that if there was any deviation from the range of limits in respect of the sensor parameters, an alarm was sounded and the designer concerned got in touch with the Mission Director and coordinated action was taken.

The earth stations - the array of antennae - provide the link between the satellite and the MCF. At the MCF, there are three full-motion and about a dozen limited-motion antennae. The full-motion antennae can be turned around 360° and in elevation can be lifted from zero° to 90°.

According to Ravindranath, the full-motion antennae serve three purposes: they receive signals from the satellite, send commands to the satellite, and help determine where the satellite is in orbit, which is called tracking through ranging.

After INSAT-2E goes into the final slot, the limited-motion antennae are sufficient to control and monitor the satellite.

T.L.PRABHAKAR
A view of the Mission Control Centre, where the health status of all sub-systems on the satellite is monitored and corrective measures are taken.

For the INSAT-2E mission, a full-motion antenna 11 metres in diameter serves as the prime station: it will be the first to receive the signal from INSAT-2E, and it is from this station that commands are sent to the satellite. Data received from the satellite are transmitted to the Spacecraft Control Centre.

B.V. Kanade, Group Director, MCF, said that after the payloads were switched on, the users would start using INSAT-2E for telecommunications and meteorological purposes.

Ravindranath said that one more full-motion antenna and another limited-motion antenna were being built at the MCF to cater to INSAT-3B, which would be launched from Kourou later this year.

Rangarajan said that the MCF could handle the operations of 12 INSAT-class spacecraft at a time. The MCF would fully support the indigenously built GSAT, to be launched by the Geostationary Satellite Launch Vehicle (GSLV) from Sriharikota by the end of this year or in early 2000. The MCF Director said: "Hassan will take care of all our spacecraft in geostationary orbit. Expansion goes on parallelly." He said that of the Rs.16 crores that was spent a year on the MCF, 40 per cent went towards augmentation of the facilities.

INSAT-2E is expected to last 12 years in space. The other second-generation INSATs had a projected life-span of seven years each. Rangarajan said that the life of a satellite was determined not only by the amount of propellant on board but by the status of other systems. "If the batteries are off, you cannot run the show in the transponders or any of the sub-systems. Reliability of the bus, payloads and propellant availability decides the mission life," he said.

The MCF has made big money for Anterix Corporation, the commercial arm of ISRO. Its Director said the MCF did the orbit-raising for a LockheedMartin satellite and payloads testing for two PanAm satellites, PAS 4 and PAS 7. "We got $150-200 million for each of these satellites. We trained recruits for Arabsat in Riyadh. The training was a success. We have got very good manpower at the MCF," Rangarajan said.