Bandwidth Coefficients



Note: the following information is intended for the IRAC instrument team only. If you are not such a person, you should not be reading this. No guarantees are made as to the applicability of this information to the real IRAC.



The following are the coefficients for the EBWC module. They are based on decay constants sent to me by Lori Allen, and were derived by examining cosmic ray hits in a dark frame. We will be re-deriving these constants in flight from measurements of stars. The jumps from one row to another (_col) namelist entries are based on an 11.4us read time for each pixel in a row, and an additional 8.6us for the jump from one row to another, as based on a memo sent to me by Bill Forrest.

About the "up" constants: it is not obvious how to measure the attack time without foreknowledge of the target source. Since we expect the attack constant to be much shorter than the decay constant, it will typically be at the level of 0.01%, which is sufficiently close to zero that I have zeroed these constants. In any case, this effect manifests itself as an aparrent decrease in signal level which is proportional to the unattenuated signal level. Thus, it will appear to be a readout-channel dependent gain term, and hence is corrected for by the flat-field. Thus, these constants actually should be set to zero.

Channel 1
Readout 0123
Kup 0000
Kup_col0000
Kdown 1.58e-32.17e-32.33e-31.64e-3
Kdown_col 1.2e-52.1e-52.4e-51.3e-5

Channel 2
Readout 0123
Kup 0000
Kup_col0000
Kdown 1.71e-33.63e-31.06e-31.11e-3
Kdown_col 1.4e-55.2e-56.0e-66.6e-6

Channel 3
Readout 0123
Kup 0000
Kup_col0000
Kdown 3.19e-31.04e-23.30e-32.09e-3
Kdown_col 4.2e-53.3e-44.4e-52.0e-5

Channel 4
Readout 0123
Kup 0000
Kup_col0000
Kdown 3.74e-33.74e-33.74e-33.74e-3
Kdown_col 5.5e-55.5e-55.5e-55.5e-5


Here are the namelists for channels 1, 2, 3, and 4.

Jason Surace (2/21/01)