State-of-the-Art Technology for Mexico
| Height stowed | 3.1 m (10 ft 1 in) |
|---|---|
| Width stowed | 2.7 m x 3.5 m (8 ft 9 in x 11 ft 7 in) |
| Solar arrays deployed | 21 m (68 ft 10 in) |
| Antennas deployed | 7.2 m (23 ft 5 in) |
| Weight Beginning of life |
1641 kg (3610 lb) |
When the Mexican government planned the implementation of a second-generation satellite system, it turned again to Hughes Space and Communications Company which today is Boeing Satellite Systems, Inc. The new pair of spacecraft is called Solidaridad, signifying the way satellite telecommunications are uniting the urban and remote parts of the country with one another and the rest of the world. These replace the two Hughes-built Morelos satellites, the first of which was retired in 1994 after nine years' service.
The Solidaridad contract was signed in May 1991. In selecting Hughes over two competitors, the Secretariat of Communications and Transportation cited technical excellence, lowest price, shortest delivery schedule, longest useful life, and best payload capacity. The spacecraft are operated by the government agency Telecomunicaciones de Mexico (Telecomm).
Hughes provided two Hughes 601 model high-power spacecraft, associated ground equipment, and training. The first satellite was launched Nov. 19, 1993, and the second was Oct. 7, 1994, both on Ariane 4 boosters from Kourou, French Guiana. The Solidaridad contract calls for a satellite life of 14 years.
The new satellites allow Telecomm to continue to provide such services as voice telephony, data communications, television relay, facsimile transmission, business networks, and educational TV broadcasts. A new feature is nationwide mobile services.
To accommodate the high power and capacity Telecomm demands of Solidaridad, the new spacecraft differ markedly from Morelos. The earlier satellites are Hughes' popular, cylindrical, spin-stabilized HS 376 design, weighing about 646 kg (1420 lb) and generating 950 watts. Solidaridad, in contrast, is a body-stabilized spacecraft. It consists of a cube-shaped center portion containing the electronic and propulsion systems, and, along the north-south axis, a pair of three-panel solar array wings that total almost 21 meters (68.8 feet) in length. Each spacecraft weighs about 1641 kg (3610 lb) at beginning of life on orbit. Its solar arrays provide 3300 watts, and a 27-cell nickel-hydrogen battery provides power during eclipse.
There are 16 active Ku-band transponders -- four times the existing capacity -- with 42.5-watt traveling-wave tube amplifiers. In addition, Solidaridad has one L-band channel for service to users traveling by land, sea, or air and in rural areas. This service has four 21-watt SSPAs linked in parallel.
All bands cover Mexico, and the C- and Ku-band coverage extends into the southwestern United States. In addition, spot beams in Ku-band reach such major U.S. cities as Chicago, Dallas, Houston, Los Angeles, Miami, New York, San Antonio, San Francisco, Tampa, and Washington, D.C. C-band coverage includes the Caribbean and Central and South America.
Tracking, telemetry, and command operations for the spacecraft are conducted at an existing station in Iztapalapa, a suburb about 10 miles southeast of Mexico City, and at an alternate control center at Hermosillo City, Sonora, in northwest Mexico. Hughes built the Iztapalapa station for the Morelos satellites, and enhanced the equipment and trained Mexican citizens for operation of the more complex Solidaridad system.
With the antennas deployed the spacecraft are 7.2 meters (23.5 feet) across. The C-band antenna is on the west side of the spacecraft and Ku-band on the east. Both are 2.4-meter by 1.8-meter (8-foot by 6-foot) oval X-wing antennas with two reflecting surfaces, one of which is sensitive to vertical polarization and the other to horizontal. A 26-element L-band cup dipole array covers the earth-facing side of the spacecraft.
Solidaridad's antennas and solar panels fold up alongside the body for launch, forming a cube 2.7 meters by 3.5 meters by 3.1 meters (8.8 feet by 11.6 feet by 10.1 feet). A flight-proven bipropellant propulsion system features an integral 490-Newton (110-lbf) Marquardt liquid apogee motor, plus twelve 22-Newton (5-lbf) thrusters for stationkeeping.
The three-axis, body-stabilized Hughes 601 -- now the Boeing 601 -- satellite was introduced in 1987 to meet anticipated requirements for high-power, multiple-payload satellites for such applications as direct television broadcasting, private business networks, and mobile communications.
The Solidaridad body is composed of two modules: the primary structure that carries all launch vehicle loads, contains the propulsion subsystem, and houses bus electronics and battery packs; and a structure of honeycomb shelves that hold the communications equipment and isothermal heat pipes. Such a modular approach allows work to proceed in parallel on the structures, thereby shortening the manufacturing schedule and test time.