A Solid State Data Recorder for Spacecraft Telemetry Applications

Abstract

A Solid State Data Recorder (SSDR) has been developed which offers a high reliability alternative to tape recorders in many spacecraft telemetry applications. The storage medium used in this recorder was ferrimagnetic garnet films supporting nonvolatile magnetic "bubble" domains. This technology is very flexible and permits a recorder design which can simplify much of the interface with the telemetry system. The recorder was designed using modular construction consisting of a Digital Control Unit (DCU), Power Supply, and two Memory Modules. The Digital Control Unit (DCU) is made up of four independent microprocessor controlled data channels, configuration control, and a telemetry and test interface. The configuration can be programed so that the SSDR can operate as a 1, 2, or 4 serial channel recorder, or a single 8-bit parallel channel configuration. Each channel has a complete command set and can operate independently of the other channels. Details of the system organization and operational characteristics are presented. The Memory Module was designed with 32 magnetic assemblies, or cells, each containing 16 serial 102.4K bit magnetic "bubble" memory chips. Sense and operator electronics, and field coil drive electronics are also located in the memory module. A prototype SSDR has been fabricated. This prototype is designed for 10⁸ bits of storage but was populated with 128 chips for a 1.3 x 10⁷ bit capacity. Preliminary tests indicate satisfactory operation. Results of these tests are presented and variations with designed characteristics discussed.