Spacecraft design description

The vehicle design description provides information on a.o.:

  • How the S/C vehicle looks
  • What payload(s) it carries
  • What the payload(s) does (do) and its (their) functional characteristics
  • The S/C bus, what it does and its functional characteristics
  • Mass and size properties
  • Lifetime
  • Series size
  • Cost (development, production)
  • Reliability
  • Availability
  • Development time
  • Etc.

An example vehicle design description is given hereafter.

Advanced communications technology satellite (ACTS) design description

NASA's ACTS has been especially develop to allow testing of new communications technology applications. First some overall spacecraft data are given. Second some important subsystem data are given. All information is taken from acts.grc.nasa.gov/technology/spacecraft/specs.asp and is reproduded here for the purpose of illustrating a spacecraft specification overview.

Spacecraft data

  • Type of satellite: 3-Axis Stabilized Communications Technology Satellite
  • Application: Testbed of New Communications Technology Applications available to U.S. Experimenters in the Ka-band spectrum
  • Payload: Advanced communications technology, including several large (2-3 m diameter) antennae
  • Launch Vehicle: Space shuttle Transportation System/Transfer orbit Stage (TOS)
  • Orbit (position): Geosynchronous, Equatorial, 100° West
  • Design Life: 4 years
  • Total Mass: 1472 kg
  • Envelope (deployed configuration): About 15 x 10 x 5 m (47,1 x 29,9 x 15,2 ft)
  • Reliability: Not available
  • Cost: Not available

Figure 1 shows the ACTS in its deployed configuration. The figure clearly shows the importance of the large communications antennae and the solar array for the vehicle envelope.


Figure 1: ACTS deployed configuration
ACTS Subsystems data

Details of the ACTS subsystems are given below, whereas Figure 2 shows an exploded view of the spacecraft.

Electrical Power Distribution

  • Solar Array Output: 1418 Watts (4 Years)
  • Battery System: 2 NiCd batteries of 19 AH each. No payload operations during eclipse
  • Power Bus: 35.5 (+/- 0.5) Volts with full array illumination

Structure and Thermal

  • Structure: length: 2.0 m; width: 2.1 m, depth: 1.9 m
  • Solar Array: with yoke, 14.3 m tip-to-tip
  • Antenna Assembly: Height 2.95 m above antenna panel; width: 9.1 m deployed
  • Thermal: Passive and active temperature control: Blankets, heaters

Propulsion and Orbit Control

  • Design: Blowdown Hydrazine system with redundant thrusters and four tanks
  • Propellant: 263 kg
  • Thrusters: 16 (0.9, 2.2, and 4.5 N)
  • Stationkeeping: +/- 0.05°

Attitude Control

  • Transfer Orbit Control: Autonomous nutation control during spin. Initial pointing provided by TOS stage
  • On-Orbit Control: 3-Axis stabilized via Earth and Sun sensor and momentum wheel. Autotrack ref. used during Communications experiment periods
  • Pointing Accuracy: 0.025° pitch and roll, 0.15° yaw using autotrack. 0.1° pitch and roll, 0.25° yaw using Earth sensor
  • Offset Pointing Control: +/- 6° pitch, +/- 2° roll

Command, Telemetry and Tracking (Ranging)

  • Command, Telemetry and Tracking Frequency: Ka-Band; C-Band backup and transfer orbit
  • Command Rate: 100 pps frequency shift keying for bus functions; 5000 pps SGLS for payload
  • Command Capacity: 379 low rate discretes; 3 serial low rate data streams; 256 high rate discretes; 3 serial high rate data streams
  • Telemetry Format: 8 bits/word; 256 words/minor frame; 25 minor frames/major frame; 1024 bps
  • Telemetry Capacity: 312 bilevel, 364 analog and 6 serial words; dwell capability on any word
  • Tracking Tones:4, from 35.4 Hz to 27.777 kHz

Figure 2: Exploded view of ACTS

The exploded view clearly illustrates some of the more important (internal) configuration items, like the apogee kick motor and the propellant tanks.
 
 

 

© 2012 TU Delft

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