MEETING HIGH BANDWIDTH SCIENCE AND EXPERIMENT TELEMETRY REQUIREMENTS OVER A LOW BANDWIDTH COMMUNICATION LINK VARIABLE TELEMETRY PROTOCOL

摘要

NASA's Small Spacecraft Technology Initiative (SSTI) is developing two light weight, "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 goals of the program are: (1) increase the capabilities of small spacecraft, (2) reduce the cost and development time of space missions, (3) demonstrate new designs and qualification methods, (4) integrate small instrumentation technology, and (5) promote commercial technology applications.rnUnder a prime contract issued by NASA to CTA INCORPORATED, the SSTI Clark program used an integrated product development team (IPDT) with government, industry and university members. CTA Space Systems is team leader, with NASA, Lockheed Martin Astronautics, and USAF membership. The Clark spacecraft will demonstrate 36 advanced technologies across all its subsystems. Lockheed Martin Astronautics provides electrical power, command and data handling, and structures and mechanisms subsystems. CTA Space Systems provides attitude determination and control, communications, integration and test , ground systems, mission planning and operations, and commercialization of the advanced technologies.rnNearly two dozen government, industry and university suppliers contribute to the program including EarthWatch, Incorporated, provider of the 3 meter panchromatic/15 meter multispectral imaging payload; North Carolina State University with the μMAPS payload; NASA Goddard Space Flight Center with the X-Ray Spectrometer; and IsComp Systems, Incorporated with thernAtmospheric Tomography experiment. Astro Aerospace Corporation provides the lightweight concentrator solar array and Eagle Pitcher Industries, Inc. the single pressure vessel Nickel/Hydrogen battery. These members are representative of a very strong and productive SSTI Clark program team.rnThe science instruments and several of the advanced technology demonstrations each require periods of high bandwidth telemetry. These requirements can not 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.rnThis paper will discuss the software implemented in the Command and Data Handling (C&DH) subsystem for the collection, storage and flow control of telemetry in a multi-processor 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.rnSpecial recognition goes to the following CTA personnel who assisted in the development and integration of these concepts: Steve Farrell, Dennis Jiraud, Mark Martin, Colin Pape and Paul Pendell.