Table of ACIS bad columns, pixels and grades

This table was provided by Y. Maeda and Y.Tsuboi, June 2000, and is based on study of data obtained in Sept-Oct 1999. New bad data may have emerged later in the mission. The list is designed to accompany a standard filtering of ASCA grades 02346, and does not include any search for bad events in the spectroscopic array chips S0-S2 or S4-S5 (i.e. CCD 4-6 and 8-9).

Chips Column (ChipX) Bad Flight Grade Origin Group
0123456789 512 104 Particle events which hit in the frame store area Group 1
0123456789 513 208 Particle events which hit in the frame store area Group 1
0123456789 256, 512, 768 8 Particle events which hit in the serial resister Group 1
0123456789 257, 513, 769 16 Particle events which hit in the serial resister Group 1
7 512 2, 64 ? Group 1
7 513 2, 64 ? Group 1
0 70, 74 all Nearby hot column (71,72,73) Group 2
1 302, 305, 408, 410 all Nearby hot column (303, 304, 409) Group 2
2 none Nearby hot column Group 2
3 none Nearby hot column Group 2
6 none Nearby hot column Group 2
0 3, 81, 1010, 1015 all Flickering pixel in the frame store area Group 3
1 none Flickering pixel in the frame store area Group 3
2 134, 559, 571, 1018 all Flickering pixel in the frame store area Group 3
3 none Flickering pixel in the frame store area Group 3
6 58, 585, 683 all Flickering pixel in the frame store area Group 3

Y.M. and Y.T. believe that Group 1 events will always be present, and are seen in all energy bands. Group 2 events are probably always present, but may be dependent on CCD temperature. Group 3 events seem to be present only in the soft band (roughly <1 keV), and may be highly dependent on CCD temperature and observation date. Groups 2 and 3 events can be identified in long exposures and may not be scientifically important in short exposures. The Group 1 filter also removes some good X-ray events (e.g. Flight grades 8 & 16 events) in the hard band of front-side illuminated chips, but the loss is probably not scientifically important.