Command and Data Handling

The Command and Data Handling (C&DH) system is a combination of software and hardware that manages the subsystems of the UW Dawgstar satellite. By using a high speed data bus, the C&DH system

  • performs the transfer of data between satellite subsystems,
  • prepares telemetry for downlink,
  • distributes telemetry from uplink, and
  • performs system maintenance and self checks.

Due to its vital role in Dawgstar operations, the C&DH subsystem faces very strict performance requirements, and it also places demands on the other satellite subsystems. These requirements are listed below.

C&DH Component Temperature Range. C&DH electronics must be maintained in a temperature range of 40  to 85 C during operation.

Telemetry Storage. Since it will not be able to continuously send data to Earth, the nanosatellite will need onboard flight software to store telemetry data for later transmission to ground station(s).

Error Detection and Correction. The nanosatellite computer system will self check its system memory using Error Detection and Correction (EDAC) software and hardware.

Subsystem Interface (Digital and Analog). Subsystems will use an input/output (I/O) card cross-communications. Also, analog/digital (A/D) converters will be used for analog subsystem communications.

CPU Operating System. A CPU schedule will support the operating system, maximize power savings and manage CPU heat production. Protocols will handle the scheduling of limited computer memory space.

Health Monitor Reset Frequency. The flight software shall reset the processor watchdog timer every second.

Flight Software Restart Capability. The flight software shall be able to perform partial and total restarts.

Autonomous Health Monitoring. The flight software shall monitor subsystem health and take corrective actions when predetermined errors are found.

Satellite Telemetry Processing. The flight software must do on-board processing and downlink of collected telemetry data to the ground station(s).

Satellite Databus Type. The databus for the satellite must be standardized with protocols for information management. These protocols include prioritizing the most important information for a given situation.