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Calibration Access and Data Handbook

Description

This file contains a single extension, BADPIX, describing the locations and several characteristics of the pn CCD bad pixels. These are pixels which exhibit a signal in a high proportion of readout frames and/or anomalously high signals. Depending on operating mode, most of the bad pixel locations are uploaded and their signals blanked out by the on-board electronics. In addition, in order to reduce noise, several rows of pixels at the read-out end of the CCDs are similarly blanked out.

Keywords to describe the contents of the CCF:

BPT_CODE:

Code of the bad pixel table (BPT) version described in the CCF. Owing to the occurrence of new bad pixels and periods of operational changes, the number and location of blanked-out bad pixels included in the BPT has altered frequently from observation to observation. These changes are reflected in the corresponding CCFs. In view of the resulting large number of issues, a procedure has been implemented in the SAS to check whether the correct CCF is used for a given observation. This is done by correlating the uploaded BPT version, uniquely coded through the pn HK parameters F1629, F1630 and F1628, with the associated CCF header keyword BPT_CODE. A warning is issued if the two do not tally. The BPT coding has been implemented since revolution 293 and the corresponding BPT_CODE keyword will be present in EPN_BADPIX CCF issues as of 0093.

The CCF contains one table:

BADPIX:

This table is accessed by CAL_getBadPixelMap(), CAL_getBadPixelList() and CAL_pnCtiCorrect().

Attributes:

None.

Columns:

CCD_ID:

CCD index number (1-12).

NODE_ID:

Node ID (0 for pn).

RAWX:

Start of bad pixel region in RAWX (absolute coordinates on chip, thus independent of any windowing information).

RAWY:

Start of bad pixel region in RAWY (absolute coordinates on chip, thus independent of any windowing information).

YLENGTH:

Length of bad column ( ${\tt YLENGTH}=1$ indicates a single bad pixel).

DESCRIPTION:

Type of the bad pixel listed. A bad CCD pixel can be:

• dead: no signal is ever detected in this type of pixel. All pixels that are transferred through a dead pixel are dead as well. (Type value equals 'd' if up-linked, 'D' if stored in CCF only);
• hot: a pixel that contains a signal almost at every readout of the CCD. The charge content of such a pixel is nearly constant, and is dependent on the CCD bias and readout parameters. (Type value equals 'h' if up-linked, 'H' if stored in CCF only);
• flickering: the characteristics of flickering pixels depend on the CCD bias and readout parameters, as well as on the average charge that is transferred through them during readout. (Type value equals 'f' if up-linked, equals 'F' if stored in CCF only).

MODE_N/A:

Mode(s) for which bad pixels are not applicable.

N_SAT_IMP:

Hot pixel brightness.