 
For each day when a SWE/VEIS background measurement was made,
the record numbers of background measurement have been written to a file 
"yyyymmdd.bckrec".

Level zero CD's for each day between the hours 00:00:00 and 01:30:00
have been scanned for background measurements
using program lzscan.pro in WGGS tool package.

The first LZ data scanned in this way was 950725.
This was done on Sep 13, 1996. All background measurements prior to 950725 
already existed as of Sep 13, 1996 as .idlsav and .dat files.

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In order to make the averaged background counts arrays, 

avgcts(ndets, nsteps, nsectors), 

which are to be subtracted from measured counts, do this:

1. Use the WGGS analysis tool and display distribution function data 
for the day of interest. Then  click on "VEIS cts", then "Background/Rel gain"; choose the LZ record interval of the background measurement, 
sum counts over all spins in interval, find the average, avgcts,
and create .idlsav files.

2. Run backg_review.pro to make ( _prt ) listings of 
avgcts(ndets, nsteps, nsectors). Various avgcts arrays
may be compared with one another to look for changes in background over time.

3. Run backg.pro to create the binary .dat files of 
avgcts(ndets, nsteps, nsectors) to be used with analysis of levelzero data.
The procedure backg.pro also updates the ascii index "bdates" which associates
every date from WIND launch through 19961231 with the appropriate .dat file
of avgcts.

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LZ data scanned as of Aug 8, 1997:  up to and including 970419.

R. J. Fitzenreiter
