An ISRO landmark

With the successful launch of PSLV-C3 on October 22, ISRO demonstrates its capacity to place in orbit multiple satellites from a single vehicle at highly competitive commercial rates.

WHEN the Polar Satellite Vehicle-Continuation 3 (PSLV-C3) rose from its launch pad at Sriharikota in Andhra Pradesh at 10-23 a.m. on October 22 and later injected three satellites into orbit one after another with precision, the event confirmed India's strength in three areas: the Indian Space Research Organisation's (ISRO) capability to launch multiple satellites from a single vehicle; its highly competitive commercial rates for launching satellites; and national security.

The three satellites are ISRO's 1,110- kg Technology Experiment Satellite (TES), Germany's BIRD (Bispectral and Infrared Remote Detection) weighing 92 kg and Belgium's PROBA (Project for Onboard Autonomy) weighing 94 kg. Remote-sensing satellites, or earth observation spacecraft, they are essentially meant to demonstrate advanced technologies. ISRO received a fee of about $1 million each for launching BIRD and PROBA. The PSLC-C2 flight in May 1999 had also injected into orbit three satellites: ISRO's Oceansat, South Korea's KITSAT and Germany's TUBSAT. ISRO made a tidy sum for orbiting KITSAT and TUBSAT.

The PSLV-C3 launch marks the fifth consecutive success in launching the vehicle. The PSLV has become a workhorse in India's space programme. According to officials of Antrix Corporation Limited, the commercial enterprise of ISRO, the string of successes has demonstrated that the PSLV is a reliable and cost-effective vehicle. They are confident that it will have a niche for launching medium- and small-sized satellites in the sun-synchronous orbit or the low-earth orbit.

The defence implications stem from TES' sophisticated cameras, which can take pictures of the earth with a resolution as high as one metre. This is the first time that India has orbited a satellite which can take such pictures, which can spot structures and even vehicles. The decision to go in for a one-metre regime was reportedly taken after the Army failed to detect the Pakistani intrusion in Kargil in 1998. TES can detect troop movements.

In a flawless flight that lasted about 27 minutes, PSLV-C3 first injected TES into orbit 970 seconds after lift-off. BIRD winged out about 40 seconds later. The fourth stage of the PSLV burned for another 10 minutes before PROBA went knifing into orbit, 1,658 seconds after the blast-off. While the previous PSLV flight lasted about 19 minutes, the present one lasted about 27 minutes.

All the three satellites were in fine fettle. The solar panels of TES were deployed and the power required was generated by them. First-level checks on BIRD and PROBA showed that their health was satisfactory.

ISRO Chairman Dr. K. Kasturirangan called it an extraordinarily successful flight. "The PSLV has shown its reliability in repeatedly successful launches... Not many versions of this class of vehicle are available in the world today," he said.

PSLV-C3 is a four-stage vehicle, with four strap-on booster motors strung around the first stage. It is 44.4 metres tall and its lift-off weight is 294 tonnes. While the strap-on motors and the first and third stages use solid propellants, the second and fourth stages use liquid propellants. The three satellites were housed in the equipment bay, which, with its array of electronic gadgets, forms the brain of the vehicle. The mission's uniqueness lay in that while TES and BIRD were launched in one orbit, PROBA was launched in a higher orbit because the Belgians asked for it. While TES and BIRD were injected into a circular orbit at an altitude of 568 km, PROBA was deployed in a highly elliptical orbit with a perigee of 568 km and an apogee of 638 km. "That is why the mission lasted 1,658 seconds, 500 seconds more than it did last time. It gives us confidence that we can undertake more complex missions," said S. Ramakrishnan, Mission Director, PSLV-C3.

A major manoeuvre was required to inject PROBA into a higher orbit. This was accomplished by firing small rockets called reaction control thrusters on board the fourth stage. Ramakrishnan said the satellites were ejected after suitable re-orientation of the equipment bay to avoid any collision between the satellites and the fourth stage.

According to K. Ramachandran, Vehicle Director, the PSLV's five successful flights demonstrated the country's capability in the development, design and manufacture of launch vehicles. "I am 100 per cent satisfied with its design. The vehicle is amenable to speedy manufacture," he said.

The launch on October 22 was kept under wraps because of security considerations after the September 11 terrorist attacks in New York and Washington, and the threat issued to India by Al Qaeda, the terrorist organisation of Osama bin Laden. Brajesh Mishra, National Security Adviser and Principal Secretary to Prime Minister A.B. Vajpayee, was present at the Mission Control Centre at Sriharikota during the launch.

Low-altitude clouds on the previous day made way for glorious weather on the day of launch. The countdown had no hold at all. The first stage core motor and four strap-on motors ignited first, and the remaining two strap-on motors came alive 25 seconds after lift-off. The separation of the burnt-out first stage and the strap-on motors; the second stage ignition; the jettisoning of the giant heat shield, which protected the three spacecraft from searing heat during the launch; the third stage ignition and separation; the fourth stage ignition and cut off, and the injection of satellites went exactly according to plan.

In the assessment of R.V. Perumal, Mission Director, Geo-synchronous Satellite Launch Vehicles (GSLV), D. Narayana Moorthi, Director, Launch Vehicles' Programme Office, ISRO Headquarters, Bangalore, and Dr. K. Sudhakara Rao, Vehicle Director of the GSLV flight in April last, the latest success demonstrated the "basic robustness" of the PSLV and ISRO's capability to achieve a repeatable performance. Perumal said, "We were particularly innovative this time because PROBA required boosting the orbit after injecting the main satellite. We could do it easily because we improvised the vehicle to do more functions than what we originally planned for. From that angle we are happy about the launch vehicle's reliability and its ability to adapt to mission requirements."

TES carries a state-of-the-art camera, with the latest technology in optical, detection and processing systems. "It will revolutionise remote-sensing technology. The satellite was built within 24 months at ISRO satellite centre, Bangalore," said M. Krishnaswamy, Satellite Director. It was basically meant to test the altitude and orbit control systems onboard and the systems for stabilising and orienting it. It has a new type of antenna called X-phased antenna for data transmission and a positioning system to know its exact location.

BIRD, an extended version of TUBSAT flown in the previous PSLV mission, would detect forest fires, latent volcanoes and industrial hazards.

PROBA could be used to monitor environmental hazards and security aspects and to predict earthquakes, claimed Piet Holbrouck, Director-General, VERHAERT, the Belgian company that built the satellite. "In the security area, PROBA can be used to pinpoint certain locations, especially if you know where to look," he said.

The PSLV-C3 success has boosted ISRO's hopes of cornering a slice of the big market for launching satellites. Prof. U.R. Rao, former Chairman of ISRO, said: "The rocket is absolutely reliable. We should be able to get many more customers now." K.R. Sridhara Murthi, Executive Director, Antrix Corporation, said the PSLV met a felt need for orbiting medium-sized satellites in the sun-synchronous orbit and the low-earth orbit. He expected the demand for launching satellites to boom in the next four years. Antrix Corporation was discussing with a number of parties the possibility of launching their satellites from SHAR.

There were four areas where ISRO has positioned its marketing interest. The first of the three are launching foreign satellites, supplying sub-systems for satellites fabricated abroad and providing services for tracking and checking the health of satellites from Master Control Facility in Hassan, Karnataka. Fourthly, ISRO leases transponders aboard its INSAT; nine of INSAT-2E's transponders were leased to INTELSAT for a handsome amount.

Was TES "a spy satellite"? Replying to this, Dr. Kasturirangan explained: "All earth observation satellites look at the earth. Whether you call it earth observation or spying, it is a matter of interpretation. All I can say is that... we have built this particular payload, which is used for imaging, as a forerunner to an advanced imaging system of a high-resolution type."

The one-metre-resolution pictures taken by Ikonos of the United States show buildings, structures, vehicles, a flooded area or small fields. It is a question of how the images are used. Kasturirangan took the stand that ISRO was not a user but a builder of satellites. One-metre-, five-metre- or 30-metre- resolution images could be used for defence. "Somehow the feeling has grown in our country that if it is a one-metre picture, it is a spy satellite. TES is an earth observation satellite. How it is used, is for the user to decide," Dr. Kasturirangan said. He asserted that TES is primarily for civilian use. There was a policy on how the high resolution data should be used consistent with the country's security considerations, he said.

Sriharikota will have a busy schedule in the coming years. Either METSAT (Meteorological Satellite) or Resourcesat will be orbited next year by a PSLV. METSAT will probably go up before March 2002. The second developmental flight of GSLV-D2 will also take place next year, according to R.V. Perumal. (GSLV-D2 too will employ a Russian cryogenic engine. The GSLVs will orbit satellites at a height of 36,000 km above the earth for communication purposes.)

K. Narayana, Director, SHAR, said that the professionalism of SHAR personnel came to the fore when they readied the spaceport's facilities for the PSLV-C3 launch just six months after GSLV-D1 had lifted off from there on April 18. To cater to the increased frequency of flights, a second launch pad is under construction. After the completion of civil works in four months, the installation of equipment will begin. "By the end of 2002 we must be in a position to realise the second launch pad. A flight can take place from it in the first quarter of 2003," Narayana said.

Several satellites are now being fabricated at the ISRO Satellite Centre, Bangalore. They include METSAT, Resourcesat, Cartosat-1, Cartosat-2, INSAT-3A and INSAT-3E. The launch of INSAT-3C, which has been delayed because of the Ariane 5 failure, will take place from Kourou, French Guiana, in December or January.

Resourcesat is the next-generation remote-sensing satellite after the IRS series. According to Dr.P.S. Goel, Director, ISRO Satellite Centre, Resourcesat is unique in that it has a multispectral resolution capability of 5.8 m. It has an advanced camera, that is, highly improved widefield sensors. Building this satellite has been a complex task and has taken more time than expected. Testing the optics alone took six to nine months. Cartosat is for mapping. Cartosat-1's pictures will have a resolution of 2.5 m while those of its successor will have a resolution of 1 m.

Indigenous development of the cryogenic engine has picked up speed. The validation tests on this engine will be done at Mahendragiri in Tamil Nadu in three months. ISRO plans to make a number of these engines to demonstrate its ground qualification. "Operational-ising a cryogenic rocket engine and its associated stage takes considerable time. The third or fourth flight of the GSLV will demonstrate this capability," said N. Vedachalam, Director, Liquid Propulsion Systems Centre.