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Cal-R1 » History » Version 1

Robert Armstrong, 07/30/2012 09:17 AM

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h1. Cal-R1
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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]
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h2. Prerequisites
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* Observation of rich stellar density field during photometric conditions for model construction.  Dither pattern?
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* Use overlapping DES survey data to test model.  Need repeated observations separated by 3 weeks.
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* Need single epoch catalogs with astrometric solution <1"
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h2. Procedure
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* During Commissioning
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** Use observation of dithered, dense stellar field to derive large scale variations of the stellar photometric response
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* During Science Verification
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** Test model on DES survey data with repeated observations on same night.
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h2. Verdict
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* Relative photometry of bright stars <  0.02 mag RMS
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h2. Consequences
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If the requirement is not met we may need to refine model or reexamine flat-fielding and sky subtraction methods.