of launching communications satellites of the 4-ton class. Facilities The SDSC has two operational orbital launch pads. SHAR is ISRO's satellite launching base and additionally provides launch facilities for the full range of Rohini sounding rockets. The Vehicle Assembly, Static Test and Evaluation Complex (VAST, previously STEX) and the Solid Propellant Space Booster Plant (SPROB) are located at SHAR for casting and testing solid motors. The site also has a Telemetry, Tracking, Range Instrumentation, & Control centre for Range Operation (RO), Liquid Propellant Storage and Servicing Facilities (LSSF), the Management Service Group and Sriharikota Common Facilities. The PSLV launch complex was commissioned in 1990. It has a 3,450 tonne, 76.5 m high Mobile Service Tower (MST) which provides the SP-3 payload clean room. The Solid Propellant Space Booster Plant (SPROB) processes large size propellant grains for the satellite launch vehicles. The Vehicle Assembly & Launching Facility (VALF), Solid Motor Preparation & Environmental Testing Facility (SMP&ETF) tests and qualifies different types of solid motor for launch vehicles. The control centre at SHAR houses computers and data processing, closed circuit television, real-time tracking systems and meteorological observation equipment. It is linked to eight radars located at Sriharikota and the five stations of ISRO's Telemetry, Tracking & Command Network (ISTRAC). The propellant production plant produces composite solid propellant for rocket motors of ISRO using ammonium perchlorate (oxidiser), fine aluminium powder (fuel) and hydroxyl terminated polybutadiene (binder). The solid motors processed here include those for the first-stage booster motor of the Polar Satellite Launch Vehicle (PSLV) — a five segmented motor of diameter and length, weighing with a thrust level of . Rocket motors and their subsystems have to be rigorously tested and evaluated on ground before they are declared flight worthy. The facilities at SDSC are used for testing solid rocket motors, both at ambient conditions and simulated high altitude conditions. Besides these, there are facilities for conducting vibration, shock, constant acceleration and thermal/humidity tests. SDSC has infrastructure for launching satellites into low Earth orbit, polar orbit and geo-stationary transfer orbit. The launch complexes provide support for vehicle assembly, fueling, checkout and launch operations. The centre also has facilities for launching sounding rockets for atmospheric studies. The mobile service tower, launch pad, preparation facilities for different launch stages & spacecraft, storage, transfer and servicing facilities for liquid propellants, etc., are the principal parts of the PSLV/GSLV launch complex. For supporting the GSLV Mark