CALDB Release Notes
Version: 2.24
CALDB effective date: 2003-09-23T14:00:00
SDP (Internal) Release ONLY

This CALDB version is to be released internally only, simultaneously with the
installation of DS 7.0.0 in Operations, which requires the three new files
included below. A later CALDB release with CIAO upgrades will include these
files in a public release.

I. Summary of Changes

A. SIM positions file version N0002
Location: $CALDB/data/chandra/sim/bcf/pos/
FILENAME: simD1999-07-22posN0009.fits

Description:
   The purpose of this change is to allow the obidet pipeline to 
    correctly update the sim_z_offset value in the actual obspar. 
    sim_z_offset is calculated according to 

    sim_z_offset = SIM_TRANS_Z - SIM_Z 

    where SIM_Z is the SIM translation stage position in the STF 
    coordinate system (derived from SIM telemetry), SIM_TRANS_Z is the 
    value from Table 1, recorded in the TRANS_Z_n columns of the SIM 
    position ARD, and sim_z_offset is the SIM translation stage 
    offset.  For historical reasons, the sim_z_offset recorded in the 
    ocat has the opposite sign for the SIM Z position when compared to 
    the CXC standard STF coordinate system.  To enable simple 
    comparison between the actual obspar values and the ocat (and also 
    all existing archived predicted obspars), we preserve this 
    reversal of sign for the sim_z_offset (only) here. 

Affects: OBIDET L0.5 pipeline. Does not affect CIAO in any way.


B. HRC Tapring Test Coefficients, version N0002

Location: $CALDB/data/chandra/hrc/bcf/tapring/
Filenames:
	hrciD1999-07-22tapringN0002.fits
	hrcsD1999-07-22tapringN0002.fits

Description:

HRC events processed on the lowest gain setting (AMP_SF=3) and which have an 
even number of amplifier tap values exceeding a
threshold are subject to the tap-ringing problem (see 
http://cxc.harvard.edu/contrib/juda/memos/ring_evt_id/event_id.html) for a
complete description of the problem). The problem is in determining when an 
even number of tap values are above threshold. At
present, this is done by examining the ratio of tap values AU1/AU2 or AV1/AV2. 
Whenever these ratios exceed a constant, the
event is corrected for tapringing. Values of the constants are contained in 
the current tapringtest files in CALDB.

In October, 2000, an HRC operating parameter that determined when event widths 
were labelled as "wide" was set to a value that
made it clear when events had an even number of tap values above threshold. 
This provided an independent, unambiguous means of
identifying events subject to tapringing. Examination of events observed after 
this date indicate that a better test for
identifying tapringing events prior to October, 2000 is a staright line, i.e., 
AU1 > A * AU2 + B, and similarly for the V axis.
Thus two constants are now needed for each axis. The new constants are 
contained in the new versions of the tapringtest CALDB files.

Affects: hrc_process_events (HRC L1 pipeline)

Note: Affect on CIAO in the near term is that reprocessing data with
CIAO 3.0.1 or earlier version will NOT include the new CALDB files OR the
new software. Any HRC data process with DS 7.0.0 or later, and then 
reprocessed with CIAO 3.0.1 hrc_process_events or earlier version, will remove 
the PSF enhancement that these new files and software provide. A future 
release of CIAO (expected December 2003) will include these new CALDB data and 
the software in hrc_process_events.