Content Comparison

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The date used for this is:

1. if DATE-END exists, the DATE-END in the Red camera, or, if no Red data, the Green Camera

2. the time when the shutter was closed passed into the call to the FITSAssembly class

3. if neither of the above times exist, then the current timestamp when the final filename is needed

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Assembly

• After each observation, the FITS Assembler pulls images with the appropriate obsIDs from the separate subsystem interim directories

• These sub-FITS are then directly copied into the larger L0 FITS, in the correct order, with no modifications, as shown in this schematic:

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Keck and Lick Observatories rely on a postgres Postgres database that collects and records all keyword values and their time of broadcast. The keyheader program takes a timestamp and finds the last broadcast value for a given keyword at that timestamp. The program then turns that into a FITS header compatible output. A request for the kpfexpose.EXPOSE value becomes

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The final L0 assembler will take the kpfexpose.STARTTIME and kpfexpose.ENDTIME, offset each by a small time, and then search for the telemetry in the keyheader database around those times. Those are denoted as the time_beg and time_end in the FITSAssmeble FITSAssemble library. Some states will only be true between those times (shutters will only be open during an exposure for example) so a third time is searched which is just the average the start and end times.

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1. Create a blank primary header data unit which will become the final one

2. Read in each primary header from the sub-FITS, and move keywords to the L0 primary or to other FITS extensions as appropriate.

3. For each input file, compare the DATE-BEG and DATE-END values with those from kpfexpose.STARTTIME and kpfexpose.ENDTIME. If the kpfexpose values are significantly older than the values in the files, use the values in the files. These file values become time_beg and time_end used for queries

4. Use keyheader to make three queries. One at time_beg plus an offset, one at the average of time_beg and time_end which is called time_mid, and finally one at time_end plus an offset.

5. The comments are part of the keyheader configuration file and can include the dispatchers and dispatcher keywords that the data come from.

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Dispatcher Implementation

The dispatcher is provided by the service kpfassemble.