I have extracted the star magnitudes derived by the CXC aspect pipeline for 585 stars observed between Jan. 4, 2000 and Apr. 28, 2000. Repeat observations of the same star are not included. These magnitudes are taken from archived aspect level 1 "GSPROPS" (guide star properties) files. They have been calculated based on the summed pixel values in good images, meaning those images without any bad status flags or outlying centroid values.
The plots below show the magnitude error (observed magnitude - AGASC magnitude) versus three independent variables: color (B-V), AGASC magnitude, and time. In each case I also plot a line corresponding to zero error and a 0.8 mag error. The latter quantity corresponds roughly to the systematic error used in the MAY1000 and MAY1400 loads.
Nevertheless, the large number of failed ACQ and GUIDE star acquisitions for the MAY1000 and MAY1400 loads means something was happening. A more careful look at the frequency of failed acquisitions during this time period is a first step.
get_gs_fid.pl Drive arc5gl to get all gsprops and fidprops files gsprops_1.3.fits Star data using original gsprops ACA_MAG. Mix of 1.3 and 1.4 gsprops_1.4.fits Star data using AGASC 1.4 magnitudes (780 star points) gsprops_1.4_uniq.fits Same as gsprops_1.4.fits, but no repeated stars gsprops_all.fits Raw merge of all gsprops. Includes many repeats. mag_err.gif Plot of observed - catalog magnitudes mag_err.ps Plot of observed - catalog magnitudes mags.dat AGASC magnitudes for the 780 stars plot_mags.pro Make mag_err.ps plot