Table of Statistics
| Date | Mean (e-/s) | Peak (e-/s) | Mean near peak (e-/s) | N > 100 e-/s | N > 200 e-/s | N > 2000 e-/s | N > 3000 e-/s |
|---|---|---|---|---|---|---|---|
| 1999-Aug-11 | 11.9 | 9.7 | 10.2 | 3495 | 1778 | 4 | 3 |
| 2000-Nov-20 | 22.2 | 11.5 | 11.9 | 34097 | 18442 | 28 | 10 |
| 2001-Mar-01 | 23.9 | 12.5 | 12.9 | 37381 | 19962 | 27 | 13 |
| 2002-Feb-26 | 29.2 | 12.5 | 13.6 | 56671 | 29657 | 46 | 19 |
| 2002-May-17 | 29.8 | 12.2 | 13.6 | 59754 | 31238 | 52 | 21 |
| 2002-Aug-25 | 31.1 | 11.9 | 13.6 | 64023 | 33701 | 62 | 21 |
| 2002-Dec-04 | 31.7 | 11.9 | 13.6 | 66850 | 34954 | 64 | 21 |
| 2003-Apr-26 | 33.6 | 12.8 | 14.5 | 71418 | 36831 | 76 | 21 |
| 2003-Jul-14 | 19.6 | 7.6 | 7.8 | 44179 | 14708 | 21 | 5 |
| 2004-Jan-02 | 21.6 | 7.8 | 8.4 | 51338 | 17339 | 23 | 6 |
| 2004-Mar-24 | 23.2 | 8.5 | 9.4 | 54534 | 18700 | 29 | 8 |
| 2004-Jun-19 | 22.7 | 7.7 | 8.4 | 55605 | 18941 | 26 | 6 |
| 2004-Sep-09 | 23.1 | 7.6 | 8.4 | 57613 | 19715 | 29 | 8 |
| 2004-Dec-24 | 25.7 | 9.0 | 10.3 | 61944 | 21270 | 30 | 6 |
| 2005-Mar-11 | 26.7 | 8.4 | 10.2 | 66981 | 23434 | 35 | 8 |
| 2005-Jul-10 | 31.1 | 12.2 | 14.3 | 72427 | 25014 | 35 | 7 |
Histograms
| The linear-scale differential histogram generated by the standard dark current calibration and examination procedure. | Zooming in, an x-axis linear-scale differential histogram in that peak region of all of the calibrations since the CCD cooldown. |
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Evaluation of those Peak Values
Plot of all of the peaks with a line fit to all but the first and last points: here the pre-cooldown points are scaled by an estimated factor to arrive at a reasonable line.
The deviation of the position of the newest data point from an estimate based on the fit line seems to be well outside measurement uncertainty.
The plots of other features of the statistics information also show a shift.
The shift or deviation in this last dark current measurement extends to the number of warm and hot pixels, but not to the same extent; much smaller deviation from expected values in terms of sigma.
This plot includes a histogram of pixel differences in consecutive dark current calibrations since the CCD was cooled to -15C
And this plot contains similar information, except here are changes relative to the first dark current calibration after the cool-down instead of consecutive changes.
To see if there are any quadrant-specific effects, here is a plot of the dark current values for each of the quadrants.
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To look for patterns in the dark current accumulation, we've also looked at the position of pixels that have certain dark current values. This has been done for the current dark current calibration, 2005191, and the previous one, 2005070.
http://asc.harvard.edu/mta/ASPECT/dark_curr_shift/dist_2005191imd.html
http://asc.harvard.edu/mta/ASPECT/dark_curr_shift/dist_2005070imd.html
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Last modified:12/27/13