The Chandra Snapshot creation is controlled by tlogr.pl. It takes tracelogs of real-time telemetry values output from ACORN and produces a text version, web version, and wml version of selected values, while doing some limit checking. Tlogr first checks for new telemetry. If any tracelogs have been updated in the past 3 minutes, we will produce an updated web page. If there is no new data flowing, we check the comm schedule to confirm that there should be no data, then update the radiation values (top line of snapshot) in the text version and exit. If data, should be flowing but is not, a flag is set. If no data is seen on neither the primary or redundant site after a certain amount of time an alert is sent. tlogr.pl controls the alert sending, while subroutine check_comm in snap.pm does the actual checking.

If data is flowing tlogr makes calls to procedures in snap.pm to collect the data into an associative array. There are some computations such as EPHIN rates to be performed next, see comps.pm. Then limits are checked by procedures defined by check_state.pm. We also incorporate the Chex.pm module from Tom Aldcroft to check configuration dependent values like SIM position, RA, Dec, and Roll. The parameter file snaps2.par defines which mnemonics are checked and how there are checked.

Finally, snap_format.pm contains the instructions to write output.

snap.cgi displays the web page. It collects the current data for the top line displayed (ACE, Alt., etc.) and reads in the stored archive of telemetry values (snarc* files). The cgi allows browsing to previous real-time epochs (back to three days).

The State of Health Pages operate on similar principles with 2 ACORN feeds and a tlogr for each page (Top, CCDM,PCAD,...). They create static web pages, overwriting the previous version. There is no cgi to access previous pages.

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