The requirements for a data acquisition system for launch vehicles are very similar to those intended for lower altitudes with a few exceptions. The most obvious is the more extreme environmental conditions which include the severe vibration and shock experienced on take-off, followed by a very sharp thermal shock. Launch vehicles also may need to dynamically adapt to changing configurations - for example when an instrumented stage is released. Additionally there is often difficulty in telemetering data during the initial launch stage from a vehicle that may not be recoverable, and therefore does not offer the option of an onboard recorder.
Addressing these challenges requires simple, rugged and flexible solutions. Recoverable DAUs should continue to record data while the ‘Master’ System should keep operating without the discarded DAUs. For PCM systems, cabling needs to be designed so that the ‘personality’ of affected DAUs changes as cables are severed. For Ethernet systems it is simply a case of a node/s leaving the network.
To transmit valuable data collected at launch, data should be stored during the take-off stage and transmitted after a predetermined time (e.g. 30s) once stable flight has been achieved. This must be automatic. Craft in orbit can utilize remote controlled recorders capable of ‘read while write’ functionality that sends data/perform other operations as required when dealing with limited transmission windows.
Flight Test Instrumentation is already designed to address similar issues, although modifications may be required, for example to meet increased vibration or temperature envelopes. Space qualified COTS ensures systems are qualified to meet the needs of the mission.