The US company CTA Space Systems, of McLean, Virginia, is making its first venture into the lightweight geostationary orbit (GEO) communications satellite market. It is building the Indostar 1 satellite for PT Mediacitra of Indonesia.
This first direct broadcast satellite (DBS) dedicated to television transmissions for a single nation will be launched in May 1997 aboard an Ariane 4 booster. The $100 million contract, signed in December 1993, includes the satellite and launch. This represents the first use of CTA's three-axis stabilised Star spacecraft bus.
Direct-to-home digital TV
The Indostar will offer high-power S-band direct-to-home digital TV, providing quality transmissions using 0.7m-diameter receiving dishes costing $100-500, despite serving a region which receives heavy rain and experiences regular atmospheric scintillation . The S-band frequency penetrates rain and other interference better than do more traditional Ku-band and C-band DBS systems.
The Indostar has a state-of-the-art lightweight graphite composite structure designed by CTA and built by Composite Optics of San Diego. The Star spacecraft bus can support a GEO communications payload weighing 1,540kg and is capable of generating up to 3kW of electrical power in orbit. The Indostar 1 will weigh a total of 1,420kg at launch and 430kg on station, however. CTA's turnkey contract with PT Mediacitra also includes the provision of the ground control centre at extra cost.
The Indostar 1, equipped with a Thiokol Star 30C solid-propellant apogee kick motor to circularise the orbit at GEO from its initial, elliptical geostationary transfer orbit (GTO), will be placed in GEO at 106.1¹E. Mediacitra plans three more satellites to be launched into GEO positions at 115.1¹E, 105.9¹E and 114.9¹E. CTA is in the running for these - although the US giant, TRW, is building a similar GEO satellite, the Rocsat, for Taiwan, and another small company, Spectrum Astro, wants to market a similar spacecraft bus.
Each Indostar satellite will broadcast one analogue TV channel for low-cost educational, cultural and national-interest programmes, plus five digital video channels to subscribers. An L-band transponder will be added to the Insotar 2 and subsequent spacecraft to provide CD radio services to users with handsets costing about $100.
The Indostar contract is an important one for CTA Space Systems - part of the larger CTA Incorporated group of Rockville, Maryland which had a turnover of $217 million in 1995. The company has been associated with smaller, low-Earth orbit (LEO) satellites and, like Spectrum Astro, is keen to enter the GEO market, with smaller, more cost-effective communications satellites for specialist, customers.
CTA has built and operated over 20 small light Earth-observation "Lightsats" for mainly military and research customers, as well as providing spacecraft system design, hardware, software test and flight-operations support for NASA's Small Explorer, Space Shuttle Small Payloads and Spartan-Shuttle missions. The company has built over 20 satellite command and control systems, and also supplies meteorological satellite data, airborne and air-dropped remote-sensor and communications, information-technology systems.
CTA has provided five spacecraft buses to prime contractor TRW for the US Air Force Space and Missiles Systems Center's Space Test Programme (STEP). The STEP 0 and 2 were launched and operated successfully in 1994, satellites 1 and 3 were lost in launch failures and the STEP 4 is due for launch in 1997. These versatile 150kg-class spacecraft enable the US Air Force to fly new technologies and experiments, relatively rapidly, without any major redesign of the spacecraft bus for each mission.
CTA's first all-up satellite was the Global Low Orbiting Message Relay (GLOMR) craft, sponsored by the US Air Force and deployed by the Space Shuttle Challenger STS 51B in April 1985. The Special Experimental Communications Systems craft for digital store-and-forward communications was the first payload to fly an Orbital Sciences (OSC) Pegasus air-launched booster in 1990. There have been five further Pegasus launches of CTA-related craft, two of which failed. The STEP 0 launch is so far the only to be made by the OSC Taurus, in 1994.
Satellite successes
The Microsats were notable CTA successes. Launched aboard a Pegasus in 1991, these seven satellites were placed in equally spaced positions along an orbital plane in a 195 x 245km orbit (rather than the 425km circular orbit planned because of a partial failure of another Pegasus).
Another satellite, the US Air Force's Radiation Experiment Satellite (REX-2), was launched in 1996. The REX 2 was the 27th small satellite designed and built by CTA and was used to test the effects of atmospheric anomalies on radio transmissions. The REX was equipped with low -cost, lightweight reaction wheel assemblies built by CTA under licence from NASA. It was also the first satellite to use global-positioning-satellite (GPS) technology for attitude and control. The GPS equipment is being included on the NASA Clark and EarthWatch Early Bird remote-sensing Earth-observation satellites.
CTA also built the service module for the Commercial Experiment Transporter project (COMET) for Westinghouse. This fully integrated space transport and recovery system is now offered by EER Systems, under the new name Meteor, but the failure of the first Meteor to reach orbit when the EER Conestoga launcher exploded has placed the programme in doubt. CTA also featured in another launch failure, that of the first Lockheed Launch Vehicle in 1995, carrying the CTA Gemstar digital communications satellite.
Source: Flight International
