Monitoring and analysis of ACIS corner pixels by the instrument team. The corner pixel distribution is characterized by fitting a Gaussian to a histogram of corner pixel pulseheights. All events in all observations since the end of January 2000 are included.
Neither the centroid or the width of the fitted Gaussian has changed significantly since 2000. Small deviations in the width are correlated with changes in the particle background. The mean values for the Gaussian centroid and width are shown below along with data taken during thermal vac testing at Ball (-110C). In all but three cases the Gaussian centroid is within 0.05 ADU of zero. The two BI CCDs, S1 and S3, have higher centroids (+0.7 ADU) and S4 has a lower centroid (-0.7 ADU). The Gaussian sigmas range from 2.14 - 2.46 ADU.
| CCD | Flight | Ground | ||
|---|---|---|---|---|
| Centroid | Sigma | Centroid | Sigma | |
| I0 | +0.03 | 2.18 | -0.08 | 2.14 |
| I1 | +0.01 | 2.15 | +0.33 | 2.14 |
| I2 | -0.02 | 2.20 | +0.87 | 2.20 |
| I3 | -0.05 | 2.21 | +0.59 | 2.13 |
| S0 | -0.01 | 2.36 | -0.03 | 2.38 |
| S1 | +0.72 | 2.45 | +1.19 | 2.39 |
| S2 | +0.03 | 2.20 | +0.53 | 2.06 |
| S3 | +0.63 | 2.46 | +0.88 | 2.81 |
| S4 | -0.77 | 2.36 | +0.23 | 2.17 |
| S5 | +0.02 | 2.24 | +0.41 | 2.27 |
The data used to make these plots can be found here
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