Figure 1: Mosaic of 32 images of HD50310.
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The data were processed with version 2.21 of the DAT, using the campaign G dark and illumination correction images. A centroid measurement was performed on roughly half the 32 DCEs, but cosmic rays and the B-side anomaly mentioned above precluded a good centroid measurement on all 32 images. The DCEs that were measured successfully were used to infer the dither position of the other DCEs, assuming that the CSMM repeated positions accurately (as shown in the 24µm data). The data were coadded in IRAF to make a mosaic, which was used to measure the flux from the source.
As expected, this task generated a total of 32 non-stimulator DCEs on the star. The images were mosaicked as described above, and the resulting image is shown in Figure 1. The radial profile is shown in Figure 2.
Figure 1: Mosaic of 32 images of
HD50310.
Figure 2: Radial profile of the star in
Figure 1.
I computed the total counts from the star in the mosaic, using an aperture 5 pixels in radius and a sky annulus 8 to 12 pixels in radius in IRAF's "imexam" task. The counts are 0.38 DN/s (ratioed to the stimulator). The median counts in the sky annuli are 0.020 DN/s. I computed an aperture correction for an aperture this size of 1.15, using a model PSF from Tiny Tim. The model PSF was generated using a 3000K blackbody as a source and the simulated image was 30 arcminutes in diameter. The model PSF was measured exactly as the calibrator star. The flux for the target star (HD50310) is 0.69 Jy at 70µm, so the ratio of DN/s to Jy is 0.38 * 1.15 / 0.69 = 0.63. The implied background level is 0.020 DN/s / 0.63 DN/s/Jy * 1e-6 MJy/Jy / (9.84/206265)² sr/pix = 13.9 MJy/sr, higher than the SPOT prediction of 6.3 MJy/sr for this date.
The flux calibration is delivered in this writeup. The calibration images and mosaic are available should they be needed.