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Unmanned satellites have now been used for almost a decade in useful earth-oriented applications; communication, navigation, geodetic survey, meteorology. In the coming 1970-1980 era, these applications are expected to increase in number and expand in scope; and to be augmented by additional applications having to do with the discovery and monitoring of the earth's natural resources, and of other phenomena of interest to man -- disasters, patterns of cultural development, oceanic traffic, and others. These latter tasks fall within the functional category of “observation” tasks wherein the principal role of a space system will be the collection of information, both by direct observation and by gathering data emitted from sensors deployed over the earth's surface. Eventually, these observation functions will be complemented by satellite-directed surface activity -- ships, aircraft, land vehicles.

Design review is becoming a basic requirement during the design and development of military systems. The main purpose of the design review is to increase the system's inherent and operational reliability. The major portion of this paper is the result of reliability's effort to comply with Paragraph 3.6 of NPC 250-1 Reliability Program Provisions for Space Contractors. The design review to be discussed is a reliability circuit design review with emphasis placed on what should be reviewed and the review techniques employed. The basic circuit design review prerequisites, component parts and their ratings, are discussed at the beginning of this paper. The remainder deals with the organization and reviewing of circuits. The review items include worst-case circuit performance, component applications, failure mode analysis, noise rejection, electrical stress, and the determination of component temperatures. Many examples are included to illustrate how each item was accomplished.