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Stewart, W. N.

Publications and source records attributed to Stewart, W. N..

3 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Application of an onboard processor to the OAO C spacecraft

The design of a stored program computer for spacecraft use and its application on the fourth Orbiting Astronomical Observatory (OAO) is reported. The computer is a medium scale, parallel machine with a memory capacity of 16384 words of 18 bits each. It possesses a comprehensive instruction repertoire and operates on 45 W of power (including the dc-to-dc converter). The machine operates at a 500-kHz rate and executes an add instruction in 10 microseconds. Its primary functions on OAO C will be auxiliary command storage, spacecraft monitoring and malfunction reporting, data compression and status summary, and possible performance of emergency corrective action for certain anomalous situations.

Stewart, W. N.↗
NASA NTRS1971

The Advanced On-board Processor (AOP)

The goal of the Advanced On-Board Processor (AOP) development program is to design, build, and flight qualify a highly reliable, moderately priced, digital computer for application on a variety of spacecraft. Included in this development program is the preparation of a complete support software package which consists of an assembler, simulator, loader, system diagnostic, operational executive, and many useful subroutines. The AOP hardware/software system is an extension of the On-Board Processor (OBP) which was developed for general purpose use on earth orbiting spacecraft with its initial application being on-board the fourth Orbiting Astronomical Observatory (OAO-C). Although the OBP possesses the significant features that are required for space application, however, when operating at 100% duty cycle the OBP is too power-consuming for use on many smaller spacecraft. Computer volume will be minimized by implementing the processor and input/output portions of the machine with large scale integrated circuits. Power consumption will be reduced through the use of plated wire and, in some cases, semiconductor memory elements.

Hartenstein, R. G.↗