STANDARD SERVICES FOR THE CAPTURE, PROCESSING, AND DISTRIBUTION OF PACKETIZED TELEMETRY DATA

Abstract

The Information Processing Division (IPD) at the Goddard Space Flight Center (GSFC) has the primary responsibility for the data capture, short-term storage, quality assurance and accounting, pre-processing, and distribution of telemetry data from numerous National Aeronautics and Space Administration (NASA) spacecraft missions. This functional service is referred to as level 0 processing. Level 0 processing is differentiated from higher level processing in that the functions performed do not change the raw sensor or supporting data received and extracted from the telemetry streams (1). Error correction processing and the filling of data gaps to maintain continuity are included functions where applicable. Currently there are two basic forms of telemetry utilized by spacecraft missions supported by level 0 processing systems in the IPD; time division multiplexed and packetized. The basic processing services provided by these systems which are very similar have evolved over many years through experience with numerous spacecraft missions and differing user requirements. The goal of reducing the end-to-end information data system complexity and developmental and operational costs has led to the current extensive effort to standardize data formats utilized by spacecraft missions as well as the user services provided. It has been shown that the use of packetized telemetry will significantly reduce costs while enhancing service for future missions. Packet telemetry standards consistent with the international Consultative Committee for Space Data Standards (CCSDS) are being developed which will provide the basis for future mission data system implementations (2). The IPD has developed two facilities which provide level 0 processing for missions utilizing packetization; the Hubble Space Telescope (HST) Data Capture Facility (DCF) and the Packet Processor (Pacor). The HST DCF, a dedicated system, was the first to be developed and provided the basis for the development of the multimission Pacor DCF. The Pacor is currently capable of providing the processing for the Gamma Ray Observatory and other missions using non-standard packet formats and future missions using standard packet formats compatible with the CCSDS recommendations. Through the development of the packet processing systems, which included extensive working with users, standard level 0 processing functions and services evolved. It is felt that these functions and services form the basis for future implementations including those for the Space Station Freedom. This paper will detail these functions and services.