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ITC Changes

Changes and bugs (coded red, or black if fixed) within the Integration Time Calculator are listed below. See the main ITC page for a list of the most recent changes.

  • 24 May 2007 - Added LGS support for NIRI. Merged NIRI and NIRI+Altair. Added support for NIFS + P2. Minor form changes.
  • 24 May 2006 - Fixed bug with minimum emission line width that affected all the instruments. Also added HK notch filter for NIRI.
  • 28 February 2006 - NIFS added to the list of available ITC's. Added support for Michelle Polarimetry in the imaging mode. New filters added for GMOS South.
  • 23 June 2005 - All v4.0 ITC running on new server for improved calculation speed. New near-IR and mid-IR background files and updated throughputs provide improved match to observed performance. Background and atmospheric transmissions models are high resolution for Michelle echelle. Michelle spectroscopy re-enabled. Background and atmospheric transmissions models are high resolution for GNIRS R=18000. T-ReCS re-enabled.
  • 2 March 2005 - Gemini North ITCs (GMOS North, NIRI including Altair, Michelle) now default to silver (primary and secondary) mirror coating
  • 29 August 2003 - Added Altair + NIRI ITC, implemented as a modification to the NIRI ITC.
  • 25 June 2003 - Updated T-ReCS "extra low frequency noise" parameter with on-telescope measured performance, better by a factor of 2.
  • 17 April 2003 - major changes to T-ReCS ITC. Detector properties now correspond to pre-ship AT performance which shows significantly elevated "extra low frequency noise" (ELFN). Updated filter list and filter transmission profiles. Added spectroscopy options (gratings, slits).
  • 17 April 2003 - added image quality data at 1.2um when using PWFS to improve interpolation accuracy. See the observing condition constraints for details.
  • 5 March 2003 [fixed in v3.0] - the GMOS South ITC output incorrectly reports that it is using the GMOS North CCD properties. It is actually using the correct file. 
  • 4 March 2003 - updates for semester 03B Call for Proposals. Added GMOS-S (currently assumes same optical properties as uses same files as GMOS-N but with blue-optimised detectors). NIRI (v3.1) spectroscopy internal background degraded to take account of grism scattering, predominantly at L but also some performance degradation at K and M). 
  • 4 September 2002 - new releases for all instruments and added Michelle (all v3.0). Revised image quality percentiles (was [20%, 50%, 80%, any] to [20%, 70%, 85%, any]). New graphics package.
  • 11 March 2002 - new releases for NIRI, GMOS, T-ReCS and AcqCam (all v2.0). Changes include: revised 80%-ile image quality and 70%-ile, 90%-ile and "any" cloud cover constraints, GMOS multiple IFU elements, upload of user-defined input spectra, plus many other changes. See the v2.0 release notes for details.  
  • 26 Oct 2001 - corrected GMOS R400 grating dispersion to 0.0673nm/pixel (was 0.0852nm/pixel)
  • 13 Sept 2001 [fixed 19 Sept 2001] - when GMOS spectral binning of 2 or 4 is selected, the wavelength range is not calculated correctly
  • 12 Sept 2001 - updated releases of NIRI (v1.2) and GMOS (v1.1) ITCs. Both include ASCII output spectra; GMOS includes first IFU implementation and R831 grating. First release of T-ReCS ITC (v1.0). 
  • 11 Sept 2001 [fixed 12 Sept 2001] - found in testing T-ReCS ITC that thermal emission from telescope was not being correctly applied. Will also have affected NIRI thermal (4 and 5um) calculations.
  • 28 Aug 2001 [fixed 1 Sept 2001] - in calculation of flux in 'peak' pixel for uniform surface brightness emission, flux is not updated when source brightness is changed although total signal in sq arcsec is calculated correctly (all ITCs).
  • 8 Aug 2001 - GMOS fixed-optics throughput file updated after initial on-telescope tests; slightly less throughput at blue wavelengths
  • 14 Mar 2001 - rarely, if the wavelength of the emission line SED is given to 3 decimal places the ITC returns "null"; the workaround is to specify with a precision of only 2 d.p. or change the wavelength slightly
  • 2 Mar 2001 - update of NIRI ITC for 2001B Call for Proposals; release of GMOS and AcqCam ITCs.
  • 19 Feb 2001 - when the noise from the source flux is larger than the background, the ITC issues the warning "not background limited", even when the background noise still exceeds dark and readout noise. Whilst strictly true, the ITC should note that the observation is source noise limited.
  • 16 Nov 2000 [fixed 21 Feb 2001] - in NIRI ITC, 'forward' calculation of total S/N does not given the same results as the 'reverse' calculation of integration time. Forward calculation actually gives the correct result. 
  • 30 Aug 2000 - first public release of NIRI ITC.
  • 24 May 2007 - Added LGS support for NIRI. Merged NIRI and NIRI+Altair. Added support for NIFS + P2. Minor form changes.
  • 24 May 2006 - Fixed bug with minimum emission line width that affected all the instruments. Also added HK notch filter for NIRI.
  • 28 February 2006 - NIFS added to the list of available ITC's. Added support for Michelle Polarimetry in the imaging mode. New filters added for GMOS South.
  • 23 June 2005 - All v4.0 ITC running on new server for improved calculation speed. New near-IR and mid-IR background files and updated throughputs provide improved match to observed performance. Background and atmospheric transmissions models are high resolution for Michelle echelle. Michelle spectroscopy re-enabled. Background and atmospheric transmissions models are high resolution for GNIRS R=18000. T-ReCS re-enabled.
  • 2 March 2005 - Gemini North ITCs (GMOS North, NIRI including Altair, Michelle) now default to silver (primary and secondary) mirror coating
  • 29 August 2003 - Added Altair + NIRI ITC, implemented as a modification to the NIRI ITC.
  • 25 June 2003 - Updated T-ReCS "extra low frequency noise" parameter with on-telescope measured performance, better by a factor of 2.
  • 17 April 2003 - major changes to T-ReCS ITC. Detector properties now correspond to pre-ship AT performance which shows significantly elevated "extra low frequency noise" (ELFN). Updated filter list and filter transmission profiles. Added spectroscopy options (gratings, slits).
  • 17 April 2003 - added image quality data at 1.2um when using PWFS to improve interpolation accuracy. See the observing condition constraints for details.
  • 5 March 2003 [fixed in v3.0] - the GMOS South ITC output incorrectly reports that it is using the GMOS North CCD properties. It is actually using the correct file. 
  • 4 March 2003 - updates for semester 03B Call for Proposals. Added GMOS-S (currently assumes same optical properties as uses same files as GMOS-N but with blue-optimised detectors). NIRI (v3.1) spectroscopy internal background degraded to take account of grism scattering, predominantly at L but also some performance degradation at K and M). 
  • 4 September 2002 - new releases for all instruments and added Michelle (all v3.0). Revised image quality percentiles (was [20%, 50%, 80%, any] to [20%, 70%, 85%, any]). New graphics package.
  • 11 March 2002 - new releases for NIRI, GMOS, T-ReCS and AcqCam (all v2.0). Changes include: revised 80%-ile image quality and 70%-ile, 90%-ile and "any" cloud cover constraints, GMOS multiple IFU elements, upload of user-defined input spectra, plus many other changes. See the v2.0 release notes for details.  
  • 26 Oct 2001 - corrected GMOS R400 grating dispersion to 0.0673nm/pixel (was 0.0852nm/pixel)
  • 13 Sept 2001 [fixed 19 Sept 2001] - when GMOS spectral binning of 2 or 4 is selected, the wavelength range is not calculated correctly
  • 12 Sept 2001 - updated releases of NIRI (v1.2) and GMOS (v1.1) ITCs. Both include ASCII output spectra; GMOS includes first IFU implementation and R831 grating. First release of T-ReCS ITC (v1.0). 
  • 11 Sept 2001 [fixed 12 Sept 2001] - found in testing T-ReCS ITC that thermal emission from telescope was not being correctly applied. Will also have affected NIRI thermal (4 and 5um) calculations.
  • 28 Aug 2001 [fixed 1 Sept 2001] - in calculation of flux in 'peak' pixel for uniform surface brightness emission, flux is not updated when source brightness is changed although total signal in sq arcsec is calculated correctly (all ITCs).
  • 8 Aug 2001 - GMOS fixed-optics throughput file updated after initial on-telescope tests; slightly less throughput at blue wavelengths
  • 14 Mar 2001 - rarely, if the wavelength of the emission line SED is given to 3 decimal places the ITC returns "null"; the workaround is to specify with a precision of only 2 d.p. or change the wavelength slightly
  • 2 Mar 2001 - update of NIRI ITC for 2001B Call for Proposals; release of GMOS and AcqCam ITCs.
  • 19 Feb 2001 - when the noise from the source flux is larger than the background, the ITC issues the warning "not background limited", even when the background noise still exceeds dark and readout noise. Whilst strictly true, the ITC should note that the observation is source noise limited.
  • 16 Nov 2000 [fixed 21 Feb 2001] - in NIRI ITC, 'forward' calculation of total S/N does not given the same results as the 'reverse' calculation of integration time. Forward calculation actually gives the correct result. 
  • 30 Aug 2000 - first public release of NIRI ITC.
  • [teaser] =>

    Changes and bugs (coded red, or black if fixed) within the Integration Time Calculator are listed below. See the main ITC page for a list of the most recent changes.

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