Correction of uncommanded mode changes in a spacecraft subsystem

Details Correction of uncommanded mode changes in a spacecraft subsystem Correction of uncommanded mode changes in a spacecraft subsystem

1997-02-10

1998-10-13

Beausoliel, Jr., Robert W.

Communications: directive radio wave systems and devices (e.g.,

Clutter elimination

Mti

39518508, 342354, 342355, 244164, 701 3, 701 4, 701 13, H04B 7185, G06F 1100, G06F 1114, B64G 124

Patent

active

058225153

ABSTRACT:
In a spacecraft having devices which are operative in plural modes, particularly an earth sensor operative in a north hemispherical inhibit mode, a south hemispherical inhibit mode, and a normal mode, a watchdog circuit* is employed to detect the presence of a mode command issued to the device. The command may be issued by a station on the earth, and communicated via a telemetry link to the spacecraft. The watchdog circuit may be part of a central processing unit (CPU) with a computer on board the spacecraft, the computer serving to perform various data processing operations for the mission of the spacecraft. The watchdog circuit stores the mode command and then repeats the command during a succession of repetitions. Thereby, in the event that the device, particularly the earth sensor, is momentarily disabled by an electrostatic discharge (ESD) event, wherein digital control circuitry of the earth sensor may shift the sensor to a different mode of operation, the next repetition of the mode command from the watchdog circuit reinstates the desired mode of operation. The watchdog circuit and the CPU are radiation hardened and may be enclosed by a Faraday shield to render them substantially impervious to the radiation.

REFERENCES:
patent: 5062592 (1991-11-01), Kishimoto
patent: 5556058 (1996-09-01), Bender
patent: 5563794 (1996-10-01), Cosner et al.
patent: 5587714 (1996-12-01), Chu et al.

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