TSC / CCS / SCS

Test - Integrate - Control

PID_DFHSIZ population

For some missions it is now mandatory to populate PID_DFHSIZ.
In the current CCS5 release (27091) there are cases where PID_DFHSIZ is a mandatory MIB field (even though SCOS2000 treats it as optional).

Explanation: the system now chooses the onboard time format entirely using “P-Field”, setting or MIB field. This is needed to accommodate a variety of time codes.
However some missions add a padding byte (or bytes) at the end of the onboard time.
In these cases, the system now relies on PID_DFHSIZ.

In any case it is highly recommended to populate PID_DFHSIZ, because in CCS5, this enables TM packet simulation.
SCOS2000 will tolerate PID_DFHSIZ being populated, although only reads it when the packet is variable (VPD).

If populating this field would give you too much trouble, then it might be advisable to wait for the next CCS5 release: we are planning to adopt CCSDS-301-B4, which allows extension of the P-field to accommodate padding bytes.