Meeting high bandwidth science and experiment telemetry requirements over a low bandwidth communication link: variable telemetry protocol

NASA's Small Spacecraft Technology Initiative (SSTI) is developing two "pathfinder" spacecraft, Lewis and Clark, to demonstrate a better, faster, cheaper approach to gain valuable space science and technology. SSTI is a two year to flight program. The science instruments and several of the advanced technology demonstrations each require periods of high bandwidth telemetry. These requirements cannot all be met simultaneously with a conventional fixed telemetry stream, given the relatively low bandwidth of the communication link. A Variable Telemetry Protocol (VTP) and associated flight and ground software have been developed for the SSTI Clark program to handle the temporal variation in telemetry bandwidth during the mission. The VTP protocol is capable of modifying the content and rate of the telemetry stream based on a simple ground command. This paper will discuss the software implemented in the Command and Data Handling subsystem for the collection, storage and flow control of telemetry in a multiprocessor environment. In addition, a relational database management system will be discussed which captures all required telemetry attributes and automatically generates flight code used to setup measurement storage, processing and monitoring functions. This database also contains a built-in communication link simulation to test telemetry configurations against the capability of the communication link and associated contact profile.