The Gaia mission is described, focussing on those technical aspects that are necessary to understand the details of its external (absolute) flux calibration. On board Gaia there will be two spectrophotometers, the blue one (BP) and the red one (RP) covering the range 330-1050 nm, and the white light (G-band) imager dedicated to astrometry. Given the fact that Gaia's focal plane will constitute 105 CCDs and the sources will cross the the focal plane at constant speed, at different positions in each of the foreseen passages (on average 70-80, but up to 350) in the mission lifetime, the "simple" problem of calibrating the integrated BP/RP and G-band magnitudes and the low resolution BP/RP spectra flux turns into a very delicate and complicated issue, including CTI effects, LSF variations across the focal plane and with time, CCD gating to avoid saturation and the like. The calibration model requires a carefully selected set of '200 Spectrophotometric Standard Stars (SPSS) with a nominal precision of a few %, with respect to Vega.
Hubble after SM4. Preparing JWST
- Pub Date:
- July 2010
- Astrophysics - Instrumentation and Methods for Astrophysics;
- Astrophysics - Galaxy Astrophysics
- 22 pages, 12 (very low resolution) figures, submitted to ASPC in "HST Calibration Workshop", Baltimore