downlink

Overview ¶

Example: Telemetry from a spacecraft to a ground station

This example demonstrates a complete CCSDS telemetry chain:

Spacecraft Side:
  1. Generate telemetry data as Space Packets (SPP)
  2. Frame packets into TM Transfer Frames (TMDL)
  3. Wrap frames as CADUs (ASM + optional randomization)
  4. Transmit over a simulated RF link

Ground Station Side:
  1. Receive CADUs from the RF link
  2. Unwrap to extract TM Transfer Frames
  3. Demultiplex virtual channels
  4. Extract original Space Packets from frames

The spacecraft uses two virtual channels:

• VC0 (priority 3): Housekeeping telemetry (APID 100)
• VC1 (priority 1): Science payload data (APID 200)