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ITC, Sensitivity and Overheads

The GSAOI Integration Time Calculator (ITC) can be used to determine limiting magnitudes, exposure times, S/N ratios, background levels, etc. for a wide range of source properties, observing conditions and GSAOI configurations. The ITC is divided into five sections: (1) Spatial profile and brightness of source; (2) Spectral distribution of source; (3) Instrument and telescope configuration; (4) Observing conditions; and (5) Details of observation. In the GSAOI ITC the Strehl ratio is an input parameter. The Strehl ratio is calculated using the MASCOT algorithm in the Observing Tool. See the section Defining the CANOPUS AO WFS Stars and GSAOI ODGW Stars in the GSAOI OT Details web page for details.

GSAOI ITC and Strehl ratio (2013 Dec 10)

In the new Observing Tool (2014 1.2.1) the average Strehl and error and the minimum and maximum Strehl delivered by the Mascot algorithm, and visualized at the bottom of the OT Position Editor (see GSAOI OT Details page), take into account the Image Quality Conditions requested (Strehl ratios and maps for IQ=20%-ile, IQ=70%-ile and IQ=85%-ile conditions). The Strehl provided by the OT are based on the Strehl values measured for different seeing conditions listed in Table 1 of the GeMS Performance web page. For the GSAOI ITC, you can use either the Strehl values provided by the OT or the Strehl values listed in the GeMS Performance web page (Table 1).

Bug in the ITC (2012 September 10)

A bug has been reported in the GSAOI ITC when the "Photometry in software aperture that gives 'optimum' S/N ratio" option in the "Analysis Method" section is used with the "Extended Source with Uniform Surface Brightness" option in the "Spatial profile and brightness" section. Until the problem is fixed, the "Photometry in sofware aperture of diameter 2 arcsec" option has to be used to estimate the exposure time and the signal-to-noise for an "Extended Source with Uniform Surface Brightness". See the Analysis Methods web page for detailed information about the "optimum" aperture used in the case of a uniform surface brightness source.

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