A photometric model (i.e. flat fields and sky-‐subtraction methodology) is in place which produces relative magnitudes between bright stars that are reproducible to <0.02 mag RMS on different exposures taken (a) at different times during a cloudless night (b) on different cloudless nights up to 3 weeks apart. [This is essentially a test of whether we can construct a flat field that describes system response to light and remains stable. DECAM TG-‐12. DECam TO-‐8 covers pupil ghosts, TD-‐10 is QE gradients]
- Observation of rich stellar density field during photometric conditions for model construction. Dither pattern?
- Use overlapping DES survey data to test model. Need repeated observations separated by 3 weeks.
- Need single epoch catalogs with astrometric solution <1"
- During Commissioning
- Use observation of dithered, dense stellar field to derive large scale variations of the stellar photometric response
- During Science Verification
- Test model on DES survey data with repeated observations on same night.
- Relative photometry of bright stars < 0.02 mag RMS
If the requirement is not met we may need to refine model or reexamine flat-fielding and sky subtraction methods.