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The Advanced Camera for Surveys is an imaging instrument on the Hubble Space Telescope, designed with separate wide-field, high-resolution and ultraviolet channels. Filters select spectral bands; dispersing elements also provide low-resolution spectroscopy. The different channels have different detectors and optical paths, so the instrument name alone does not specify the relevant wavelength coverage.^[ref]

For an exoplanet transit, a sequence of dispersed images can be divided into spectral channels, each yielding its own light curve. Comparing fitted exoplanet transit depths constructs an exoplanet transmission spectrum. Detector response and pointing variations must be calibrated along with the planetary signal. Historical observations should be interpreted using the channel and observing mode actually employed.