PSLV Launch Successful -
Places Three Satellites in Orbit

In its sixth flight conducted today (October 22, 2001) from SHAR Centre, Sriharikota, ISRO's Polar Satellite Launch Vehicle, PSLV-C3, successfully launched three satellites -- Technology Experiment Satellite (TES) of ISRO, BIRD of Germany and PROBA of Belgium - into their intended orbits. This is the second time that PSLV launched three satellites simultaneously; in the previous launch in May 1999 PSLV had launched India's IRS-P4 along with German DLR and Korean KITSAT-3.

While TES and BIRD (Bispectral and Infrared Remote Detection) satellites were placed in the 568 km sun-synchronous orbit, PROBA (Project for On Board Autonomy) was placed in an elliptical orbit with a perigee (nearest to earth) of 568 km and an apogee (farthest to the earth) of 638 km. The higher orbit for PROBA was achieved by firing the reaction control thrusters of PSLV-C3 fourth stage.

PSLV-C3 lifted off Sriharikota at 10.23 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, the air lit strap-on motors and first stage separation, the ignition of the second stage, separation of the heat shield after the vehicle had cleared the dense atmosphere, third stage ignition, third stage separation, third stage ignition, third stage separation, fourth stage ignition and fourth stage cut-off, the satellites were systematically injected into the orbit as per plan.

The first satellite to be ejected into the orbit was ISRO's TES at a height of 572 km after 970 seconds from lift-off. About 40 seconds later, the second satellite, BIRD, was separated from the fourth stage and equipment bay. Subsequently, the fourth stage reaction control thrusters of PSLV was fired to raise the orbit of the equipment bay along with the third satellite, PROBA, to a height of 590 km before the satellite was ejected, 1658 second from lift-off. The satellites were ejected after suitable reorientation of the equipment bay to avoid any collision between the satellites and the fourth stage-equipment bay
combination. All the three satellites have been placed in their intended polar sun-synchronous orbits.

About PSLV

It may be noted that PSLV was developed by ISRO to place 1000 kg class Indian remote sensing satellites into Polar Sun-synchronous Orbit (SSO). Since the first successful flight conducted in October 1994, the capability of PSLV has been enhanced from 805 kg to 1200 kg into 820 km SSO. PSLV also has the capability to launch 3,500-kg satellites into 400 km low earth orbit and 1000 kg satellites into Geo-synchronous Transfer Orbit.
In its present configuration, the 44.4 metre tall, 294 tonne PSLV has four stages using solid and liquid propulsion systems alternately. The first stage is one of the largest solid propellant boosters in the world and carries 138 tonne of Hydroxyl Terminated Poly Butadiene (HTPB) propellant. It has a diameter of 2.8 m. The motor case is made of maraging steel. The booster develops a maximum thrust of about 4,430 kN. Six strap-on motors, four of which are ignited on the ground, augment the first stage thrust. Each of these solid propellant strap-on motors, carries nine tonne of HTPB propellant and produces 667 kN thrust.

The second stage employs indigenously manufactured Vikas engine and carries 40 tonne of liquid propellant -- Unsymmetrical Di-Methyl Hydrazine (UDMH) as fuel and Nitrogen tetroxide (N2O4) as oxidiser. It generates a maximum thrust of about 724 kN.

The third stage uses 7 tonne of HTPB-based solid propellant and produces a maximum thrust of 324 kN. Its motor case is made of polyaramide (Kevlar) fibre. The fourth and the terminal stage of PSLV has a twin engine configuration using liquid propellant. With a propellant loading of 2 tonne (Mono-methyl hydrazine and Mixed Oxides of Nitrogen), each of these engines generates a maximum thrust of 7.4 kN.

The 3.2 m diameter metallic bulbous heat-shield of PSLV, is of isogrid construction and protects the spacecraft during the atmospheric regime of the flight. PSLV control system includes: a) First stage; Secondary Injection Thrust Vector Control (SITVC) for pitch and yaw, reaction control thrusters for roll and SITVC in two strap-on motors for roll control augmentation, b) Second stage; Engine gimbal for pitch and yaw and, hot gas reaction control for roll, c) Third stage; flex nozzle for pitch and yaw and PS-4 RCS for roll and d) Fourth stage; Engine gimbal for pitch, yaw and roll and, on-off RCS for control during the coast phase.
The inertial navigation system in the equipment bay, which is located on top of the fourth stage, guides the vehicle from lift-off to spacecraft injection into orbit. The vehicle is provided with instrumentation to monitor the vehicle performance during the flight. S-band PCM telemetry and C-band transponders cater to this requirement. The tracking system provides real-time information for flight safety and for preliminary orbit determination once the satellite is injected into orbit.

PSLV employs a large number of stage auxiliary systems for stage separation, heat-shield separation and jettisoning, etc.

Improvements in PSLV-C3

A few improvements had been carried out in the PSLV-C3 compared to PSLV-C2. They included introduction of lightweight fourth stage (PS4) tank for better vehicle performance and ball-lock separation system for the separation of auxiliary satellite, which has an interface that is compatible with the European Ariane vehicle.

PSLV-C3 Flight Profile

The flight profile for PSLV-C3 mission had been modified to place the three satellites in their specified orbits -- the Indian satellite, TES and the German satellite, BIRD, in a 568 km sun-synchronous orbit and the third satellite, the Belgian PROBA in a 568 x 638 km elliptical orbit - which require firing the reaction control thrusters of PSLV fourth stage for about 500 seconds after the separation of first two satellites. A Data Storage Unit (DSU), which stores the telemetry parameters and transmits in delayed mode had been introduced to take care of any break in the radio visibility between the vehicle and the ground stations located at Thiruvananthapuram and Mauritius as well as recording of the PROBA separation event. The PROBA separation related parameters were transmitted when the stage passed over the Lucknow ground station of ISRO.

Technology Experiment Satellite (TES)

The Technology Experiment Satellite, TES, weighing 1108 kg, is an experimental satellite to demonstrate and validate in orbit, technologies that could be used in the future satellites of ISRO. Some of the technologies that are planned to be demonstrated in TES are attitude and orbit control system, high-torque reaction wheels, new reaction control system employing optimised thrusters and a single propellant tank, light-weight spacecraft structure, solid state recorder, X-band phased array antenna, improved satellite positioning system, miniaturised TTC and power systems and, two-mirror-on-axis camera optics. TES will also carry a panchromatic camera for remote sensing experiments.

PROBA

PROBA (Project for On Board Autonomy) is a small satellite of Verhaert, Belgium weighing 94 kg. The payloads in the satellite include high-resolution camera with 115 mm diameter aperture and wide angle camera having aperture of 60 mm.

BIRD

BIRD (Bispectral and Infrared Remote Detection) is a small satellite of the German Space agency, DLR, weighing 92 kg. It is intended for testing small satellite technologies and a new generation of infrared sensors for the detection of hot spots like forest fires and volcanoes from space.
TES Functioning Well
Soon after its injection into orbit, the solar panels on board TES were deployed automatically to generate necessary electrical power for the satellite. Further in a series of operations conducted from the ISRO Telemetry, Tracking and Command (ISTRAC) stations at Bearslake in Russia and Lucknow in India, the satellite was put in three axis stabilised mode using the reaction wheels on board the satellite. The satellite health is being continuously monitored from the Spacecraft Control Centre at Bangalore along with the ISTRAC network of stations at Bangalore, Lucknow, Mauritious, Bearslake and Hyderabad. Further operations on the satellite like switching on the experimental camera on board and checking out the other hardware which are being tested in orbit will be commenced.
With the successful launch of three satellites simultaneously for the second time, ISRO's PSLV has proved itself as a promising vehicle with prospects for commercial launching of satellites even while serving its primary goal of launching Indian remote sensing satellites. PSLV is also proposed to be used for a geo-synchronous mission for launching the ISRO's METSAT. Thus, PSLV is poised to become a versatile launch vehicle in the coming years and, along with GSLV, make India self-supporting for its launch services in the near future.

  PSLV-C3 Salient Features

Overall length : 44.4 m
Lift-off weight : 294 t
No. of stages : 4
Payload : TES , BIRD, PROBA
Orbit (SSO) : 570 km