PHASE: Operations SUBSYSTEM: Instrument

Criticality: Use caution under advisement of EOF personnel

Frequency: eclipse season; as needed for contingencies

Duration (Approx.): ~2 minutes

Constraints: Yes - see below

This procedure describes the instrument turn-off procedure TI_ioff. The only foreseeable time in which the instrument will be powered off will be the eclipse season and for contingencies. This procedure will gracefully shut down the instrument by stopping any sequences that may be active, returning mechanisms to their home positions, powering off the DPU and NEB.

The procedure TI_ioff will perform the following:

- stop all science sequences

- turn off the camera

- reset and initialize all mechanisms to home positions - TI_me_init

- centers the focus mechanism - TI_focus_center

- powers off all mechanisms

- ensures the decontamination heaters are off

- powers off operational heaters

- disables instrument safing actions

- powers off the DPU

- powers off the NEB

- ensures the instrument survival heaters are on

It would be dangerous to simply turn off the DPU or NEB without resetting the shutter (TI_me_init). If the shutter were to be left open, it is possible to damage the CCD by overexposure to the sun.