PSLV LAUNCHES RESOURCESAT-1

In its eighth flight conducted from Satish Dhawan Space Centre (SDSC) SHAR, Sriharikota on October 17, 2003, ISRO's Polar Satellite Launch Vehicle, PSLV-C5, successfully launched the Indian remote sensing satellite, RESOURCESAT-1 (IRS-P6) into an 821km high polar Sun Synchronous Orbit (SSO). The inclination of orbit was 98.76 deg with respect to the equator. The 1,360 kg RESOURCESAT-1 is the most advanced and heaviest remote sensing satellite launched by ISRO so far. PSLV forms an important component of the end-to-end system for natural resource planning and management.

PSLV-C5 lifted off from SDSC SHAR, Sriharikota exactly at the opening of the launch window at 10:22 am with the ignition of the core first stage and four strap-on motors. The remaining two strap-on motors of the first stage were ignited at 25 sec after lift-off. After going through the planned flight events including the separation of the ground-lit strap-on motors, separation of air-lit strap-on motors and first stage, ignition of the second stage, separation of the payload fairing after the vehicle had cleared the dense atmosphere, second stage separation, third stage ignition, third stage separation, fourth stage ignition and fourth stage cut-off, RESOUCESAT-1 was injected into orbit 1080 seconds after lift-off. It was separated after suitable reorientation of the fourth stage-equipment bay combination to avoid any collision with the satellite.

PSLV was originally designed and developed by ISRO to place 1,000 kg class Indian Remote Sensing satellites into polar Sun Synchronous Orbit (SSO). Since its first successful flight in October 1994, the capability of PSLV was continuously enhanced in the past nine years from 850 kg to the present 1,400 kg into an 820 km high Sun Synchronous Orbit. PSLV has also demonstrated multiple satellite launch capability. So far, it has launched seven Indian satellites as well as four small satellites for international customers.

The improvement in the payload capability of PSLV over successive flights was achieved through several means — increase in the propellant loading of the first stage solid propellant motor and second and fourth stage liquid propellant motors, improvement in the performance of the third stage motor by optimizing motor case and enhanced propellant loading and employing a carbon composite payload adapter. The sequence of firing of the strap-on motors was also changed from two ground-lit and four air-lit to the present four ground-lit and two air-lit sequence.

Specifically, in PSLV-C5, the metallic third stage adapter was replaced by the one built with carbon composites. Also, the liquid propellant second stage was operated at a higher chamber pressure for better performance.

In PSLV-C5 configuration, the 44.4 metre tall, 294 tonne PSLV had four stages using solid and liquid propulsion systems alternately.  The first stage was one of the largest solid propellant boosters in the world and carried 138 tonne of Hydroxyl Terminated Poly Butadiene (HTPB) propellant. The maraging steel motor case has a diameter of 2.8 m. The booster was designed for a maximum thrust of about 4,762 kN. Six strap-on motors, four of which were ignited on the ground, augmented the first stage thrust. Each of those solid propellant strap-on motors carried nine tonne of solid propellant and was capable of producing 645 kN thrust.