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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:
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.