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Overheads

Overheads

The nominal GPI acquisition time is 15 minutes. This time is expected to apply to both coronagraphic and non-coronagraphic modes when the target is a bright (V <~9), single star, and should be added into your overall time estimate.  Fainter targets, or targets in very crowded fields requiring the use of finder charts, may require longer acquisitions.  Please note that the field of view is very small; so accurate positions and proper motions will be essential for efficient acquisitions. 

The following will be included as baseline calibrations (for baseline telluric standard frequency, see the IR Calibrations page). You do not need to account for these in your total requested time:

 

  • PSF standards (normally NOT needed as the PSF can be constructed from the satellite spots)
  • Telluric cancellation standards (taken as calibrations every run)
  • Polarization standards (taken as calibrations every run)

OT Time-line and time calculation

Currently there is a bug in the OT and thus the time for an observation is wrong. It also uses 10 minutes for the estimate for the acquisition which is not correct. The wall-clock time is for each observation:

  • Wall-clock time = ( ( requested exposure time + 3.0s) * Coadds ) + 15s (readout and transfer) 

This means that the overheads for a 1.5s exposure is significant, instead of a nominal 15s + readout it ends up 45s + readout. Please take this in mind when deciding on exposure times and allocated time for the program.