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Integration Time Calculator

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The OT includes an interface to the on-line Integration Time Calculators (ITCs). The ITC tabs are found in the Base Sequence Component, to the right of the Timeline tab (see figure below). Instruments which only support imaging (i.e. GSAOI) will only show an Imaging tab, and instruments that only support spectroscopy will only have a Spectroscopy tab. Instruments which can do both will have both tabs, although depending on the observation, only one may be populated.


The ITC uses the spatial profile and spectral energy distribution defined in the Target Source Parameters section. If either is undefined the ITC will return an error.

When using an Extended Uniform Source spatial profile, the source magnitude will be interpreted as magnitudes per square arcsecond.


The top-left of the ITC tabs include drop-down menus to select the observing conditions to be used for the ITC calculations. These default to the values specified in the "Observing Conditions" component, but may be modified to see how the predicted results will change under better or worse conditions. Values different than the approved conditions are indicated in red.

Analysis Method

The top-right of the ITC tabs allows specifying the target and sky aperture sizes. The target aperture defaults to "Auto" which should yield the best S/N. See the ITC Documentation for additional information.

Configuration Table

The bottom of the ITC Imaging tab, and the middle of the ITC Spectroscopy tab shows a table of input and output values, with one line for each unique instrument configuration in the observation. If a target has multiple magnitude bands specified (in the Target Environment), the ITC will chose the Source Mag as the one closest in wavelength to the science wavelength. The Source Fraction is calculated based on the size of the offsets; offsets larger than half the field of view are counted as off-source. The Peak counts estimate the peak pixel value (in electrons), used for predicting saturation. The S/N is listed for a Single exposure, as well as the Total for when all the data from a single configuration are combined.


The bottom of the ITC Spectroscopy tab will also show graphs of signal and background, and signal/noise ratio as a function of wavelength. The graph ranges may be configured by setting the User Limits at the top of the graphs, or by drawing a box on the graph, moving from left to right, to zoom in on a portion of the graph. Drag from right to left to return to the default zoom level.

ITC Spectroscopy