Trouble with the Archive
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The archive initiative is an ongoing attempt to reorganize the data
produced by the VLA in its many years of operation; the data was
originally stored on 9 track tapes, the `archive process' takes that
data, converts it to a more modern format and rewrites it onto 8mm
exebyte tapes. The online database is composed of information that
gets written as each observation is updated from the old format
to the new.
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Much to our chagrin, in February 1998 we discovered that the
translation program was flawed. Specifically, all spectral line data
correlated in modes involving IFs B, C and D were mistranslated. A
second bug affected spectral line data with greater than 128 complex
frequency channels per baseline. These two bugs are cumulative and
affect about 20% of all spectral line data taken before 1988.
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The result is that all spectral line observations involving modes B, C
and D or with 256 or more complex frequency channels per baseline will
have to be re-archived. The data still exists on 9 track, nothing was
permanently lost by the bug, but it set us back a bit.
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Affected observations are noted in the catalog via a modification to
the `Tape' field. In unaffected observations the field is in the
format XHYYNNN (an `X', an `H', a two digit year code, and a three
digit tape number); affected observations are the same save that the
`X' has been replaced with an `*'.
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Modified on
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