Development of SEDS data system flight software

The Small Expendable-tether Deployer System (SEDS) is being built for a 1991 flight on a Delta launch vehicle. SEDS will deploy a 50 lb instrument satellite as an end mass at the end of a 20 km tether. The objective of the experiment is to test the SEDS design concept by demonstrating that the system will satisfactorily deploy the full 20 km tether without stopping prematurely, come to a smooth stop on application of the brake, and cut the tether at the proper time after it swings to the vertical. SEDS will also collect data that will be used to test the accuracy of tether dynamics models for this type of deployment. Radar tracking is planned. In addition, the SEDS on-board computer system will record, store, and continuously transmit data over the Delta II S-band telemetry channel. Initial testing of the software under simulated flight conditions was performed. These tests used both assembly language routines running on SEDS data systems and C-language routines on an IBM-PC. As the software now stands relatively few additions are needed before the entire set of flight software is complete.