Photometric calibration

Photometric calibration corrects the observed flux for attenuation from the atmosphere, filters, optics, and detector quantum efficiency.

Photometric calibration uses the Forward Global Calibration Method (FGCM; Burke et al. 2018).

For a description of the photometric calibration steps, refer to the “Rubin Baseline Calibration Plan” (sitcomtn-086.lsst.io).

The steps of photometric calibration include:

• chromatic corrections

• observed passbands

• instrumental response (quantum efficiency)

• opacity of the optical system

• chromatic throughput

• reference flux flats

• atmospheric response

Overview

Bright, isolated stars with signal-to-noise greater than 10 that are detected in post-ISR images, and associated with the global absolute reference catalog refered to as The Monster catalog, are input into the FGCM solution. The FGCM model constrains the atmospheric parameters per night, as well as the absolute throughput.