The LES-8/9 Telemetry System: Pt I, Flight System Design and Performance

Abstract

LES-8 and LES-9 are two experimental communication satellites designed and built for the Air Force by the M.I.T. Lincoln Laboratory. The on-board telemetry systems were designed not only to monitor the spacecraft on orbit but also to provide significant test support capability during subsystem development and spacecraft integration and test. Each system is configured in a distributed form, with remote Telemetry Input Converters (TICs) located in various subsystems communicating with a central Telemetry Output and Control (TOC). Salient features include 1) modular design of TICs permitting tailoring to specific subsystem requirements, 2) accurate analog measurement capability (.025% of full scale) over 140EC ambient temperature (-60°C to +80°C), 3) cross-checking of analog-to-digital converters via a high stability (50 microvolts) stepped calibration source, 4) flexible word allocation permitting late freezing of formats, 5) digital organization with individual parity check on each word, 6) sub multiplexing capability, 7) dual speed operation at 100 bps and 10-Kbps, and 8) downlink capability via a variety of rf links. Descriptions of overall operation and performance along with design considerations in critical areas are covered in detail.