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GNIRS Calibration Exposure Times

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The following tables provide proper GCAL configurations and exposure times for GCAL flats and arcs for GNIRS.

The values given cover a range of configurations, slit widths and wavelengths. If your particular configuration is not here, you may be able to extrapolate from similar settings. If not, please submit a query via the HelpDesk.

caution UPDATE May 2006: New GNIRS CAL sensitivities are now listed below following the installation of a new NIR color balance GCAL filter. Sufficient illumination of XD orders 3 - 9 (2.55 - 0.77 microns) is now achieved with 2 GCAL flat settings without saturating the lower orders. If your science needs to utilize XD order 10, then please specify this in a NOTE within your phase II, and let your contact scientist know. They will add a third flat field field step to the template sequence below.

caution UPDATE March 2005: New xenon (Xe) lamp REPLACES krypton (Kr) lamp to provide better wavelength calibration for R=18,000 observations.

Jump to instrument config:


  • Cross-dispersed, 32 l/mm grating (XD-32)
  • Cross-dispersed, 111 l/mm grating (XD-111)
  • IFU, 32 l/mm grating (IFU-32)
  • IFU, 111 l/mm grating (IFU-111)
  • Long slit, short camera, 32 l/mm grating (LS-S32)
  • Long slit, short camera, 111 l/mm grating (LS-S111)
  • Long slit, long camera, 111 l/mm grating (LS-L111)

Cross-Dispersed 32 l/mm, Short Camera (Long Camera not used with XD-32)
GNIRS Configuration GCAL Configuration
Filter Slit Width (arcsec) Lamp Filter Exposure Time (s) Coadds
XD 0.3, 0.45, 0.675 IR* NIR balance 1.5 8
XD 1.0, 3.0 IR* NIR balance 0.2 8
XD 0.3, 0.45, 0.675 QH** NIR balance 0.6 9
XD 1.0, 3.0 QH** NIR balance 0.2 9
XD 0.3, 0.45, 0.675, 1.0, 3.0 Ar none 0.2 20


;a name="XD111">Cross-Dispersed 111 l/mm, Short Camera (Long Camera not yet available with XD-111)
GNIRS Configuration GCAL Configuration
Filter Slit Width (arcsec) Lamp Filter Exposure Time (s) Coadds
XD 0.3, 0.45, 0.675 IR* NIR balance 4.0 4
XD 1.0, 3.0 IR* NIR balance 0.6 8
XD 0.3, 0.45, 0.675 QH** NIR balance 1.5 6
XD 1.0, 3.0 QH** NIR balance 0.2 8
XD 0.3, 0.45, 0.675, 1.0, 3.0 Ar none 0.2 20


* The IR lamp is a better flat field source for XD Order 3 (the first continuous order viewed from the left in the image display).

** The QH lamp now illuminates ALL the XD orders without saturating the array! There is an absorption feature due to the QH source present in the first order on the left as seen in the display (XD order 3). Use the IR lamp flat for this order only instead of the QH flat.

IFU 32 l/mm, Short Camera (Long Camera not used with IFU-32)
GNIRS Configuration GCAL Configuration
Filter Lamp Filter Exposure Time (s) Coadds
K IR NIR balance 4.0 2
H QH NIR balance 3.0 2
J QH NIR balance 10.0 3
K Ar none 10 2
H Ar none 2.5 2
J Ar none 1.2 2


IFU 111 l/mm, Short Camera (Long Camera not used for IFU 111)
GNIRS Configuration GCAL Configuration
Filter Lamp Filter Exposure Time (s) Coadds
K IR NIR balance 10.0 3
H QH NIR balance 7.0 2
J QH NIR balance 10.0 4
K Ar none 20 2
H Ar none 10 2
J Ar none 5.0 4


Long Slit 32 l/mm, Short Camera
GNIRS Configuration GCAL Configuration
Wavelength Slit Width (arcsec) Lamp Filter Exposure Time (s) Coadds
J 0.3, 0.45, 0.675 QH NIR balance 2.0 3
J 1.0, 3.0 QH NIR balance 0.6 3
H 0.3, 0.45, 0.675 QH NIR balance 0.6 4
H 1.0, 3.0 QH NIR balance 0.2 3
K 0.3, 0.45, 0.675 IR NIR balance 1.0 5
K 1.0, 3.0 IR NIR balance 0.2 5
L, M 0.3, 0.45, 0.675 blocked NIR balance 0.2 12
J 0.3, 0.45, 0.675, 1.0, 3.0 Ar none 0.6 2
H 0.3, 0.45, 0.675, 1.0, 3.0 Ar none 0.6 3
K 0.3, 0.45, 0.675, 1.0, 3.0 Ar none 4.0 3


Long Slit 111 l/mm, Short Camera
GNIRS Configuration GCAL Configuration
Wavelength Slit Width (arcsec) Lamp Filter Exposure Time (s) Coadds
J 0.3, 0.45, 0.675 QH NIR balance 5.0 3
J 1.0, 3.0 QH NIR balance 1.0 3
H 0.3, 0.45, 0.675 QH NIR balance 1.0 6
H 1.0, 3.0 QH NIR balance 0.2 6
K 0.3, 0.45, 0.675 IR NIR balance 2.5 6
K 1.0, 3.0 IR NIR balance 0.5 6
L, M 0.3, 0.45, 0.675 blocked NIR balance 0.4 12
J 0.3, 0.45, 0.675, 1.0, 3.0 Ar none 0.4 5
H 0.3, 0.45, 0.675, 1.0, 3.0 Ar none 0.6 5
K 0.3, 0.45, 0.675, 1.0, 3.0 Ar none 10.0 3


Long Slit 111 l/mm, Long Camera
GNIRS Configuration GCAL Configuration
Wavelength Slit Width (arcsec) Lamp Filter Exposure Time (s) Coadds
J 0.1, 0.2, 0.3 QH NIR balance 1.0 8
H 0.1, 0.2, 0.3 QH NIR balance 1.0 8
K 0.1, 0.2, 0.3 IR NIR balance 3.0 6
L 0.1, 0.2, 0.3 blocked none 10.0 6
M 0.1, 0.2, 0.3 blocked none 4.0 5
J 0.1, 0.2, 0.3 Ar, Xe* none 20 4
H 0.1, 0.2, 0.3 Ar, Xe* none 20 4
K 0.1, 0.2, 0.3 Ar, Xe* none 20 4

*Both Ar and Xe lamp exposures may be needed for sufficient calibration in some wavelength regions at this resolution. Check for availability of Ar and Xe emission lines here.


Last update July 28, 2006; Greg Doppmann