The CXC performs SDP, or "pipeline" processing, on all Chandra science data. This processing has several levels or stages. All data products from SDP undergo V&V.

The processing version is recorded in the header keyword "ASCDSVER". CIAO is designed for use with data with a processing version of R4CU5UPD8 or higher. Note that the version naming convention changed after version R4CU5UPD14 to the "DS" system, starting with DS 6.0.0.

This FAQ entry shows you how you can use CIAO to find out the processing version of your data.