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Calibrations

Baseline Calibrations

For all queue observations, a set of standard calibrations (the "baseline calibrations") will be taken by Gemini Staff to ensure the long-term utility of data in the archive. The baseline calibration set varies from instrument to instrument and from mode to mode.

Applicants should not include time for baseline calibrations in their proposals. If additional calibrations are deemed necessary by applicants, for example to achieve a precision beyond that achievable via the baseline set, then these must be included explicitly as part of the Phase I proposal and Phase II science program.

Baseline calibration data may be shared between programs and will be distributed to the users as part of their dataset. Any time used between the hours of nautical sunset and sunrise to obtain baseline calibrations will not be explicitly charged to the program but will be charged to the partner country whose NTAC recommended time (i.e. it is part of the time accounting used to balance partner usage). The time will be charged in proportion to the number of programs that receive the calibration data. Any time required for additional calibrations requested by the PI will be charged to that particular program.

ALL Phase II (OT) files must include observations for all necessary calibrations. This includes the baseline calibrations as well as any additional requested calibrations.

Measurement Type	BLC¹	Notes
Bad pixel mask	yes	Derived each semester from flat, bias and dark images. May be derived more often if changes in the CCD are found.
Calibration unit flat field	yes	GCAL flats are taken nightly before or after each program for each echelle grating setting (i.e. without moving the grating).
Bias	yes	Bias images are taken every night in the readout modes and binning used for the science observations.
Dark	yes	Darks will not be taken for science exposures unless specifically requested by the PI and included in the Phase II program.
Wavelength Calibration	yes	ThAr arc lamp measurements are taken nightly before or after each program for each echelle grating (i.e. without moving the grating).
Telluric standard star	yes	Appropriate telluric standards should be chosen by the PI and included in the Phase II program: one before and one after each observation. When the observation is executed in the queue, the astronomer will select one of the two for the baseline calibration. The PI will not be charged for one telluric standard for each observation. The PI should take care to select a star of appropriate spectral type and brightness at an airmass that will match the science target.
Absolute Flux Calibration		Not included as part of baseline calibration set
Atmospheric extinction		Not included as part of baseline calibration set
Special standards		Radial velocity, rotational and spectral standards are not included as part of baseline calibration set

¹BLC : "yes" indicates the observation is considered part of the baseline calibration set.

Exposure Times

Calibration Type	GCAL Configuration
Calibration Type	Lamp	Filter	Diffuser	Exposure Time
Flat	QH	none	visible	100s
ThAr Arc	ThAr	none	visible	150s

Last update September 6, 2005; Steven Margheim