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Last modified: 23 November 2021


Bugs: mkgarf

Table of Contents



Warnings related to missing SUM_2X2, OCLKPAIR, FEP_CCD, or ORC_MODE keywords

Users trying to run this tool with old versions of data products, those created with ASCDSVER less than version 8.4.2, may see warnings like

FITSIO status = 202: keyword not found in header
*** ERROR: *** Unable to get the value of `SUM_2X2' in /data/acisf04425_000N003_evt1.fits

Users should consult the Watch Out page for more information on this topic an information on how to upgrade their data products.

*** WARNING: The ARF was computed to be zero at all the specified energies.
             This is probably due to an incorrect source position

There are some cases where this is expected to happen, e.g, a mask truncates the order or the chip was turned off.

However, if you get this error for all orders and chips, then something is wrong. There are a few possible situations:

  1. An incorrect source position was input to the sourcepixelx and sourcepixely parameters. Confirm that the source position is correct, and re-run the tool if it's not.

  2. You are attempting to create a gARF for an order that does not fall on that plate, e.g. a positive order on HRC-S3. Refer to the Analysis Guide for Chandra High Resolution Spectroscopy for more information.

*** Warning: CYCLE not found or invalid in /tmp/imap_3.fits --- assuming 'P'

The CIAO response tools will issue this warning if the CYCLE keyword is missing from the file header. The CYCLE keyword is needed in alternating mode observations (also referred to as interleaved mode) to indicate which frame time was used in the file. If you are not working with interleaved data, you can ignore the warning.

The What is the CYCLE keyword? FAQ explains further about this keyword.

Bugs fixed in CIAO 4.14

The following is a list of bugs that were fixed in the CIAO 4.14 software release.

Failure to include "frame store shadow" bad pixels

The ardlib default BPMASK does not include the new Fame Store Shadow bit (bit 17). For sources located at the bottom edges of detector this can result in an overestimate of the effective area.

More details can be found on the Caveats about ACIS Frame Store Shadow Bad Pixels page.

Incorrect Vignetting calibrations

The azimuthal angle (angle measured around the optical axis) used to compute the vignetting correction component of the effective area is incorrect. The vignetting correction varies azimuthally about the optical axis. The amplitude of the variation is a function of off-axis angle and is energy dependent; but typically varies up to a few percent.