PPS File Names

The names of the files produced by emchain and epchain are of the form[*] PnnnnnnnnnnXXsMMMccccDDDD*.FIT where

- the observation number
is the name of the instrument (M1 for MOS1, M2 for MOS2, or PN for the pn)[*].
a single character, either S or U denoting either a “scheduled” or an “unscheduled” observation segment.
- the observation segment number
- a character string denoting what type of file it is
- four digit encoding the data subset number and other information.

The “S” or “U” together with the three digits of MMM form the subexposure number. The “S” segments were the scheduled subexposures, while the “U” segments were the subexposures that may have occureed due to an unexpected interuption to the scheduled exposure. Note that while the subexposure numbers for scheduled observations are unique, the subexposure numbers for unscheduled observations may not be; the segments mos1U001 and mos2U001 would likely be simultaneous.