W

Pointing

025 deg accuracy

Telescope axis anywhere 1 arcmln accuracy 30 arcsec stability in 1 hr 10 deg/min slew rate

Data fĂ­ate (selectable)

64 Mb data storage capability

Orbit

Geosynchronous, 2.5 deg inclined

540 km circular, 22.75 deg inclined

Reliability

0.267 at 5 yrs

0.81 at 1 yr

Fig. 10-3. Mission Parameters for FLTSATCOM and HEAO-B. Note that loaded weight is mass in kg; this use continues throughout the example.

Fig. 10-3. Mission Parameters for FLTSATCOM and HEAO-B. Note that loaded weight is mass in kg; this use continues throughout the example.

providing UHF communications between ground stations and mobile users. The communications payload equipment consists of receivers, processors, transmitters, and antennas. Its mission of global communications requires full-Earth antenna coverage. The antennas are body-fixed and oriented to point toward nadir. The orbit has a 24-hour period (geosynchronous) and initially is inclined 25 deg to the equator. There is no active inclination control. The launch vehicle is an Atlas-Centaur to inject the spacecraft into an elliptic transfer orbit At apogee, a solid kick motor injects the spacecraft into geosynchronous orbit The spacecraft uses the Air Force Satellite Control Network for command and control.

The mission of HEAO-B was X-ray astronomy. Its payload consisted of 5 X-ray instruments mounted within a telescope assembly. The mission required the telescope

TABLE 10-32. FLTSATCOM and HEAO-B Requirements and Constraints (See Table 10-3).

Spacecraft

Mission

Payload

Orbit

Environment

Launch System

Ground System

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