[daip] Question about BM162A

[Data Analysts]

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>From marscher at buast0.bu.edu Fri Feb  8 13:02 MST 2002
Date: Fri, 8 Feb 2002 15:02:47 -0500 (EST)
From: Alan Marscher <marscher at buast0.bu.edu>
To: analysts at zia.aoc.NRAO.EDU
Subject: Question about BM162A
Cc: jorstad at rjet.bu.edu
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Status: RO

Hi,

We're now busy reducing the batch of BM162 VLBA observations. In the first
one, BM162A (10 May 2001), we encountered a strange problem with the
frequencies. There are 3 frequency IDs in the data (there should be only 2).
Frequency 1 is 22 GHz, but 2 is also 22 GHz at times when
the .key schedule calls for 43 GHz. This occurs only for the
first hour of the observation (i.e., up to 24:00). After that,
the frequency suddenly switched to 43 GHz as the new day started.
This is assigned frequency ID 3.

What does this mean and why did it occur? What I suspect is that
there was a correlator coding of 22 GHz when in fact the
antenna receivers were set at 43 GHz. If so, can this be corrected
in AIPS by changing the header?

Thanks for checking this out. We won't get to BM162B until next
week, at which point I'll see whether it was only a one-time
problem.

Thanks,
Al


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