TSC / CCS / MCS

Test - Integrate - Control

Support for Deduced Parameters

Support for deduced parameters has been added to the TC chain, in addition to the telemetry chain.
Deduced parameters (PTC=11) are mainly useful to exchange dynamic telemetry and telecommands with a spacecraft, where the parameter ID and value are explicitly carried in pairs in the packet.

For some time, deduced parameters have been permitted in variable telemetry packets (see VPD table)

This is useful in the situation where the spacecraft has a large onboard data pool containing many parameters, and we want to exchange only an explicit small subset of these parameters without defining fixed packets for them. The principle is that we do not know in advance which parameters are being exchanged: this is explicit in the telemetry or telecommand packet from the on-board parameter ID’s.

The MIB contains a mapping from the telemetry parameter name to its (optional) onboard parameter ID in the PCF_PID field.

When a telecommand contains a deduced parameter, the default value sent in the telecommand is based on the last preceding TC parameter of type Parameter ID (CPC_CATEG=P) in the same nested group of TC parameters; normally these would be pairs of parameter ID, value, but that is not mandatory.