Telemetry Handling on the Space Station Data Management System

Abstract

Traditional space telemetry has generally been handled as asynchronous data stream fed into a time division multiplexed channel on a point-to-point radio frequency (RF) link between space and ground. The data handling concepts emerging for the Space Station challenge each of these precepts. According to current concepts, telemetry data on the Space Station will be packetized. It will be transported asynchronously through onboard networks. The space-to-ground link will not be time division multiplexed, but rather will have flexibly managed virtual channels, and finally, the routing of telemetry data must potentially traverse multiple ground distribution networks. Appropriately, the communication standards for handling telemetry are changing to support the highly networked Space Station environment. While a companion paper (1. W. Marker, "Telemetry Formats for the Space Station RF Links") examines the emerging telemetry concepts and formats for the RF link, this paper focuses on the impact of telemetry handling on the design of the onboard networks that are part of the Data Management System (DMS). The DMS will provide the connectivity between most telemetry sources and the onboard node for transmission to the ground. By far the bulk of data transported by DMS will be telemetry, however, not all telemetry will place the same demands on the communication system and DMS must also satisfy a rich array of services in support of distributed Space Station operations. These services include file transfer, data base access, application messaging and several others. The DMS communications architecture, which will follow the International Standards Organization (ISO) Reference Model, must support both the high throughput needed for telemetry transport, as well as the rich services needed for distributed computer systems. This paper discusses an architectural approach to satisfying the dual set of requirements and discusses several of the functionality vs. performance trade-offs that must be made in developing an optimized mechanism for handling telemetry data in the DMS.