PSLV-C3 Mission

PSLV-C3 is the sixth flight of ISRO’s Polar Satellite Launch Vehicle. In this mission, PSLV-C3 will launch three satellites

• TES (Technology Experiment Satellite) of India weighing 1108 kg,
• PROBA (PRoject for On Board Autonomy) of Belgium weighing 94 kg
• BIRD (Bispectral and Infrared Remote Detection) of Germany weighing 92 kg.

This is the second time that PSLV is launching three satellites simultaneously; in the previous launch in May 1999, PSLV had launched Indian IRS-P4, German DLR-TUBSAT and Korean KITSAT-3. While TES and BIRD will be placed in a 568 km sun-synchronous orbit, the third satellite, PROBA, will be placed in an elliptical orbit of 568 x 638 km, which will be achieved by firing the Reaction Control Thrusters of the fourth stage of PSLV-C3. As all other Indian satellite launch vehicles, PSLV-C3, is launched from Satish Dhawan Space Centre, SHAR on the east coast of India.

About PSLV

PSLV was developed to place 1000 kg class Indian remote sensing satellites into Polar Sun Synchronous Orbit (SSO). Since the first successful flight conducted inOctober 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 3500 kg satellites into 400 km Low Earth Orbit and 1000 kg satellites into Geo-synchronous Transfer Orbit (GTO).

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 677 kN thrust.

The second stage employs the 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 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 Kevlar epoxy 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 + Mixed Oxides of Nitrogen), each of these engines generates a maximum thrust of 7.4 kN.

The metallic bulbous heat-shield of PSLV, 3.2 m in diameter, is of isogrid construction and protects the spacecraft during the atmospheric regime of the flight. PSLV control system includes

• First stage: Secondary Injection Thrust Vector Control (SITVC) for pitch and yaw, reactioncontrol thrusters for roll and SITVC in two strap-on motors for roll control augmentation,
• Secondstage: Engine gimbal for pitch and yaw and, hot gas reaction control for roll,
• Third stage: flexnozzle for pitch and yaw and PS-4 RCS for roll and
• Fourth stage: Engine gimbal for pitch, yawand roll and, on-off RCS for control during the coast phase.

An Inertial Navigation and Guidance System (IGS) in the Vehicle Equipment Bay (VEB) guides the vehicle from lift-off to spacecraft injection.

The vehicle is also provided with instrumentation to monitor vehicle performance during flight. S-Band PCM telemetry systems and C-Band transponders cater to these requirements. The tracking system provide real time information for flight safety and preliminary orbit determination.