In-flight experiments are performed in several steps:
- Set-up of the insert and switch-on (crew participation)
- Initialization of experiment
- Thermal regulation
- Cycle of several elementary experiments
- Thermal regulation switched off
- Switch-off, removal and storage of the insert (crew participation)
Each elementary experiment iconsists of a "preparation phase" and a "measurement phase".
The preparation phase corresponds to the period necessary to create the right conditions to trigger the scientific phenomenon to be studied, depending on the type of experiment. This phase lasts several hours.
The measurement phase corresponds to the period where the scientific phenomenon to be studied takes place. The beginning of this phase which lasts several minutes, can not be precisely determined. With the information from the telemetry, the scientific user detects the beginning and sends commands to change the number, type and rate of the scientific data.
During this latter phase, the need for near-real-time telemetry is up to one image per second through the NTSC line and up to 1Mbps through the Ethernet link. In parallel, data can be stored onto the internal hard disk at a rate up to 12Mbps. These data must be downloaded before saturating the hard disk (400 GB). This could be done during the preparation phases when the telemetry rate is lower. Note that some of these data could be compressed, thus reducing the volume to be sent to the ground.
The rest of the time, the near-real-time telemetry is devoted to the control of the experiment. The rate is up to one image per minute through the NTSC line and up to 1 MB/min through the Ethernet link. The rate of scientific data stored onto the internal hard disk is up to 1 MB/min. Except during the initialization and measurement phases, very few telecommands are planned to be sent.
The figure above is an example of the thermal profile for a given area inside the insert and the expected TM/TC needs for the different steps.