Calibration Nov 2004 update - Caltech

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Things to Avoid(Changing the Calibration)18-20 November 2004 GALEX Science Team Meeting
Flat Field Construction• The ground flat field map was constructed by moving point images aroundthe field and tracking their intensity.– The amount of data collected in ground calibration was only sufficient for a ~10’resolution map.– It can not capture the finer details of the instrument response, such as FUV gridwire shadows.– It worked remarkably well!• The flight flat field map was constructed by building stacks of images withsimilar exposure rotated to detector coordinates, and then determining themedian value for each “arrow” through the stack.– Captures much more detail than the ground map.– The new flat is scaled so that the original zero points (18.82 FUV Fand 20.08NUV) provide correct magnitudes.– But there is something else going on, because the scatter (about 7%) is notgreatly improved over the original.18-20 November 2004 GALEX Science Team Meeting
Page 1 and 2: GALEX GR1 Instrument Performance an
Page 4 and 5: Calibration Priorities for GR1• A
Page 6 and 7: FUV-X-DETDET-TO-SKY-480Ground MapFl
Page 8 and 9: Photometry for GR1• Our main goal
Page 10 and 11: Adding up the Light• For the GALE
Page 14 and 15: FUV Ground vs Flight ComparisonGrou
Page 16 and 17: GALEX Deep Field Analysis• Match
Page 18 and 19: GR1: dm vs m18-20 November 2004 GAL
Page 20 and 21: GR1: Thermal Variation?18-20 Novemb
Page 22 and 23: GR1: Flat Field Residuals for ~6000

Calibration Nov 2004 update - Caltech

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