INSAT-3B is the first of the five satellites was successfully launched under the INSAT-3 series. INSAT-3B carried 12 extended C-band transponders, three Ku-band transponders and S-band mobile satellite service payloads. The satellite is primarily intended for business communication, developmental communication and mobile communication. The launch of INSAT-3B has been advanced to precede that of INSAT-3A to cater to the immediate requirement of extended C-band capacity that was depleted due to INSAT-2D failure.
INSAT-3B was launched on the 128th flight of European launch vehicle, Ariane, from Kourou in French Guyana along with its co-passenger, a broadcast satellite, Asia Star, belonging to a US company, World Space. It will be collocated with INSAT-2E at 83° longitude. It may be noted that INSAT satellites now occupy four slots -- INSAT-2B and INSAT-2C are collocated at 93.5°E longitude, INSAT-1D and INSAT-2A are collocated at 74°E longitude and INSAT-2DT is located at 55°E longitude besides INSAT-2E at 83° E longitude.
INSAT-3B will weigh 2,070 kg at lift-off. It will have about 1100 kg of propellant (Mono-Methyl Hydrazine - MMH and Mixed Oxides of Nitrogen - MON-3) for raising it from the geo-synchronous transfer orbit to its final orbit as well as for station keeping and in-orbit attitude control for the duration of its designed life of 10 years. For the first time, an indigenously developed titanium propellant tank, with special propellant management device that ensures bubble-free propellant supply under zero-G environment, is being employed.
The satellite main body is a cuboid of 1.93 X 1.7 X 1.65 m and, with the two solar panels fully deployed in orbit, it will measure 14.7 m in length. The sun tracking, solar panels, with a total area of 23 sq m generate a 1.7 kW of power. A 24 Ah Ni-Cd battery supports the payload operations during eclipses. INSAT-3B, like all its predecessors in the INSAT series, is 3-axis body-stabilised using momentum/reaction wheels, earth sensors, sun sensors, inertial reference unit and magnetic torquers. It is equipped with unified bi-propellant thrusters. The satellite has two deployable antennas and three fixed antennas that carry out various transmit and receive functions. The antennas have a pointing accuracy of ±0.2° in pitch and roll axes and ±0.4° in yaw axis. The satellite uses passive thermal control system.
INSAT-3B communication payload provides 12 extended C-band channels, each having a bandwidth of 36 MHz. The Ku-band payload provides three channels, having a bandwidth of 77/72 MHz. The Mobile Satellite Service transponders operate in C/S band frequencies. Compared to INSAT-2C/2D, the power of extended C-band transponders on board INSAT-3B has been increased from 10 W to 15 W and that of Ku-band from 20 W to 55W.
INSAT-3B has undergone extensive qualification programmes to evaluate each spacecraft function under different environmental conditions that it may encounter. The satellite has undergone vibration, shock and acoustic tests to the level of expected launch environment and it has been tested in its orbital configuration in thermo-vacuum chamber. Deployment tests for solar arrays and antennas, antenna pattern tests, closed-loop functional tests for attitude control system, etc, have also been carried out.
The Ariane-505 rocket will inject INSAT-3B into a geo-synchronous transfer orbit of 560 km perigee and 35,865 km apogee with an inclination of 7° with respect to the equatorial plane. From this orbit, INSAT-3B will be taken to its final geo-stationary orbit at a height of about 35,800 km in the equatorial plane by firing, in stages, the 440 Newton thrust liquid apogee motor on board the satellite. The higher perigee height of 560 km at the time of injection by Ariane-5, compared to 200 km in earlier INSATs launched by Ariane-4, results in lesser propellant consumption for orbit raising operations -- an equivalent of the propellant required for six months of in-orbit operation. When the satellite is near geo-stationary orbit, deployment of two solar panels and the two antennas will be carried out and the satellite put in its final 3-axis stabilised mode. The payloads will be checked out before commissioning the satellite.
INSAT Master Control Facility (MCF) at Hassan in Karnataka will take control of INSAT-3B soon after its injection into orbit by Ariane and, subsequently, carry out all orbit manoeuvres, deployment of appendages, payload checks and the in-orbit operation of the satellite during its life. MCF, which is responsible for initial and in-orbit operation of all INSAT satellites, has a network of six Satellite Control Earth Stations (SCES); SCES-6, with a full motion 11 m diameter antenna and two 7.2 m diameter limited motion antenna has been commissioned to meet the requirement of INSAT-3 series of satellites. MCF has an advanced computer network with six servers and fifty client workstations exclusively dedicated to spacecraft mission operations. MCF also has an elaborate backup power system to ensure uninterrupted mission operations.
During the orbit raising phase of INSAT-3B, Telemetry, Tracking and Command (TTC) stations located at Perth (Australia), Fucino (Italy) and Lake Cowichan (Canada) will also support the TTC operations.
Once commissioned, INSAT-3B is expected to further boost the Very Small Aperture Terminal (VSAT) services that started less than five years ago and seen a rapid growth. Today, there are about 7,500 VSATs, serving about 300 corporates in about 400 locations. The major VSAT users include banking and financial institutions, stock markets, white goods sector, fast moving consumer goods sector and medium to heavy engineering companies. Several public and private sector units have established dedicated closed-user group networks for their in-house applications. At present seven transponders from INSAT-2B and INSAT-2C are being used for these applications and INSAT-3B will almost double the transponder capacity for these services. For the first-time Ku-band frequencies will also be used for VSAT services, which enables use of smaller ground terminals.
Communication Antenna Coverage
INSAT-3B will also be used to provide the first set of transponders for Swaran Jayanti Vidya Vikas Antariksh Upagraha Yojana (Vidya Vahini) which had been announced by the Prime Minister on August 15, 1998. These transponders will be used exclusively for interactive training and developmental communication and will be a further extension of the present Training and Developmental Communication Channel of INSAT that is being used by several agencies for interactive training and education. Tele-medicine is also expected to be introduced that will help in remote diagnostics and extension of super special hospital treatment to rural population.
INSAT-3B will provide Mobile Satellite Service (MSS) that has forward link channel in C X S band and return link in S X C band. MSS can support portable terminals and carry voice, fax or data. It also supports messaging service using reporting terminals.
With ISRO Satellite Centre (ISAC), Bangalore, as lead centre, INSAT-3B was realised with major contributions from Space Application Centre (SAC), Ahmedabad, Liquid Propulsion System Centre (LPSC) at Valiamala and Bangalore, Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram and ISRO Inertial Systems Unit (IISU), Thiruvananthapuram. Besides, several industries in both public and private sectors have contributed to the realisation of INSAT-3B.
