• An Object-Oriented System for Telemetry Data Management

      Tolat, Viral V.; Stanford University (International Foundation for Telemetering, 1992-10)
      In this paper we describe an object-oriented software system for realtime telemetry data management and display. The system has also been designed to be used as the primary means of data management during post-mission activities. The software system consists of three parts: the data interface library, the data format specification and the display applications. The data interface library contains a set of object definitions and procedures to provide uniform access to heterogeneous data streams. The data format specification is used by the data interface library to extract data from the raw data stream. The display applications use the data interface library to access the data and present it to the user. Currently, the interface between the data format specification and the data interface library is implemented procedurally and is modeled after a device driver. Each format is assigned a unique id and then accessed via that id. A data stream may be accessed by any number of different format specifications. A future implementation will separate the data format specification into a separate process with a message or RPC based interface. Therefore the data may be kept on remote systems and accessed in a transparent fashion. In addition, this model will support operation in distributed heterogeneous computing environments. This system handles multiple simultaneous data streams and applications can access data from different streams relatively transparently. This is possible since data variables (objects) to be displayed are specified by a syntax that contains the specification of both the data streams and the format to use. In addition, the concept of a primary stream is introduced to allow the user to scroll through one data stream and have the other streams follow. Synchronization between streams is based on time information in the data streams. Several applications have been written including various stripchart displays a tabular display and some other custom displays. A data analysis application similar to the UNIX program "awk" is currently under development. It will provide the user with the ability to extract data, i.e., report generation, for display or further analysis in an object-oriented manner.
    • A Software Architecture for Realtime Data Acquisition, Instrument Control and Command Processing

      Tolat, Viral V.; Stanford University (International Foundation for Telemetering, 1992-10)
      In this paper we describe the flight software for the SETS (Shuttle Electrodynamic Tethered System) experiment. The SETS experiment will fly as part of the TSS-1 (Tethered Satellite System) experiment on STS-46 currently scheduled for July 1992. The software consists of two major components: the SETSOS (SETS Operating System) and the SETS Application. The SETSOS is a UNIX-like operating system developed especially for realtime data acquisition, instrument control and command processing. The SETSOS, like all operating systems, provides resource management for application programs. It is UNIX-like in that access to resources is provided through a standard set of UNIX system calls. The SETSOS also implements the standard UNIX I/O model and a hierarchical file system. In addition to providing access to physical devices, the SETSOS provides support for two virtual devices: a packet-based data device and a command device. The packet-based data device is used by applications to place data into the telemetry stream. The command device is used to manage commands from the command uplink as well as other sources including other applications and other processors. The SETS Application is the primary program which runs under the SETSOS to handle data acquisition, instrument control and command processing. It executes as 5 separate processes, each performing a special task. The tasks include housekeeping data acquisition, limit checking, timeline management, and command processing. The processes communicate via shared memory. Time critical processing is coordinated by using signals and interrupts. In addition to a description of the software, we will discuss the relative merits and tradeoffs of using such a system design for command processing and data acquisition.