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| Mechanical Subsystem | Aluminum honeycomb side panels (8), forward and aft panels, payload deck, and interior shear walls; two central load-bearing aluminum cylinders (forward and aft) |
| Mass | 494 kg |
| Dimensions |
Width = 2.25 m (7.4 ft) Height = 1.52 m (4.99 ft) |
| Thermal Subsystem | Heat pipes in payload deck connected to radiators on spacecraft side panels; MLI blankets; thermostat- and CIDP/PDU-controlled electrical resistance heaters for payload and spacecraft operations and survival |
| Command & Data Handling Subsystem | System Control Unit (SCU) consisting of RAD6000 flight computer plus modules for I/O, mass memory, command & telemetry, communications & memory, and power suppy; VME backplane; 4.096 Gbits DRAM in mass memory module; Mil-Std-1553B interfaces to other observatory systems |
| Communications Subsystem | S-band transponder; 1 medium-gain helix antenna; 2 low-gain omni-directional antennas; uplink data rate: 2 kbps; downlink data rate: 44 kbps (real-time mode); 2.28 Mbps (stored data playback mode) |
| Attitude Determination & Control Subsystem | Spin-stabilized; closed-loop spin-rate control |
| Sensors | Adcole 44690 sun sensor; Lockheed Martin ATC AST-201R autonomous star tracker; MEDA TAM-2A 3-axis magnetometer |
| Actuator | 1 Ithaco magnetic torque rod |
| Electrical Power Subsystem | Direct energy transfer; microprocessor-controlled power distribution unit (PDU) performs power distribution and battery charge control functions; Mil-Std-1553B interface with SCU |
| Solar Arrays | Body-mounted dual-junction gallium-arsenide solar cell arrays |
| Battery | 21 amp-hour Super NiCd battery; operating range: 22-34 Vdc |
spacecraft | science payload | launch vehicle