Satellites to Deliver TV Direct to Home Viewers
| Height stowed | 12.6 ft (3.8 m) |
|---|---|
| Width stowed | 9.2 ft x 10.8 ft (2.8 m x 3.3 m) |
| Solar arrays deployed | 86 ft (26 m) |
| Antennas deployed | 23.3 ft (7.1 m) |
| Weight Beginning of life |
3800 lb (1727 kg) |
The spacecraft are 601 body-stabilized models ordered by DIRECTV, Inc., a unit of Hughes Electronics Corporation. DIRECTV-2 and DIRECTV-3 are collocated with DIRECTV-1 at 101 degrees West longitude and are used exclusively by DIRECTV. Collectively the three satellites have the capacity to deliver more than 200 channels of entertainment programming to subscribers that are equipped with DSSTM digital home receiving units, which feature an 18-inch dish.
To provide the high satellite power necessary for such small antennas, the DIRECTV-1 spacecraft has 16 transponders powered by 120-watt traveling-wave tube amplifiers (TWTAs). The TWTAs were reconfigured to provide eight channels with 240 watts of power on DIRECTV-2 and DIRECTV-3. The amplifiers are suitable for analog or digital signals, and are capable of transmitting high-definition television (HDTV) signals and compact disc-quality audio as well.
The satellites operate in the BSS portion of the Ku-band spectrum (12.2-12.7 GHz) and employ circular polarization. Depending on configuration of the transponders, they can deliver 48 to 53 dBW radiated power over the contiguous United States.
Each DIRECTV spacecraft measures 23.3 feet (7.1 meters) across with the two transmit antennas deployed, and 86 feet (26 meters) long from the tip of one four-panel solar array wing to the other. These arrays generate a combined 4300 watts of electrical power, backed up by a 32-cell nickel-hydrogen battery for uninterrupted power during eclipse. The spacecraft weigh around 3800 pounds (1727 kg) at beginning of life on orbit.
An innovative graphite antenna system makes its debut on the DIRECTV-1 spacecraft. The transmit and receive reflectors feature a specially contoured surface that requires only one, rather than multiple, feedhorns to provide an optimal signal. The composite material is so light that each 8-foot-diameter transmit antenna weighs less than 20 pounds. The antennas are aligned in a unified structure to provide a significant improvement in antenna pointing performance.
The Boeing 601 body is composed of two main modules. The bus module is the primary structure that carries launch vehicle loads and contains the propulsion, attitude control, and electrical power subsystems. The payload module is a honeycomb structure that contains the payload electronics, telemetry, command and ranging equipment, and the isothermal heat pipes. Reflectors, antenna feeds, and solar arrays mount directly to the primary module, and antenna configurations can be placed on three faces of the bus. Such a modular approach allows work to proceed in parallel, thereby shortening the manufacturing schedule and test time.
The operations control center for the DIRECTV satellites is in Long Beach, Calif.; telemetry and command terminals are in Castle Rock, Colo., and Spring Creek, N.Y. Uplink is from both the DIRECTV Castle Rock and Los Angeles broadcast centers.