# 6.2.3 Estimation of Exposure Times

The exposure times for FLITECAM imaging observations should be estimated using the on-line exposure time calculator, SITE. SITE can be used to calculate the signal-to-noise ratio (S/N) for a given ''total integration time'', or to calculate the total integration time required to achieve a specified S/N. The format of the S/N values output by SITE depends on the source type. For Point Sources, the reported S/N is per resolution element, but for Extended Sources, it is the S/N per pixel. The total integration time used by SITE corresponds to the time actually spent integrating on-source without overheads. These integration times are used as input for SPT and for SSPOT, both of which will automatically calculate the necessary overheads.

The exposure times for FLITECAM grism mode spectroscopic observations should be estimated using the on-line exposure time calculator. This calculator can be used to calculate the signal-to-noise ratio (S/N) for a given ''total integration time'', to calculate the total integration time required to achieve a specified S/N, or to estimate the limiting flux for a desired S/N. For both imaging and spectroscopy modes, the estimated total integration time from the respective calculators should be used as the time for an observation in the SOFIA Proposal Tool (SPT). Remember, overheads should not be included, as SPT calculates them independently.