MMA Memo Abstract Template
 

MMA Memo Abstract Template


# abstract.template -- MMA Memo Series Electronic Abstract Template
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# Comments are preceded by the "#" symbol.  Anything following a "#" is
# ignored.
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# The following entry is for internal use only.  Do not fill it in.
#Number:


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# Enter the MMA memo title in the following section
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#Title:
Precision Radiometry and the APHID 22~GHz Water Line Monitor

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# List the MMA memo authors in the order that they appear on the paper.
# Use a comma to separate the names of multiple authors.  List each author's
# affiliation in parenthesis following the name.
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#Authors:
A.I. Harris (Department of Astronomy, University of Maryland)

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# Enter the date that the memo was submitted in the format mm/dd/yy.
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#Date:
05/03/00

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# Enter a list of keywords which might be used to find this memo in an
# electronic search.  Multiple keywords should be separated by commas.
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#Keywords:
Phase correction, radiometers, water vapor radiometry, precision radiometry

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# Enter a plain ASCII abstract between here and the #END symbol
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#Abstract:
Fluctuating amounts of water vapor over an antenna in an
interferometer add phase shifts to the instrument, shifting the fringe
pattern on the sky to decrease signal correlation.  Optically thin
line radiation from the same water vapor that causes the decorrelation
can be accurately measured, however, allowing an estimate of the
column of water above individual antennas.  Knowledge of the water
column allows an equivalent but opposite phase to be inserted in the
data processing; this is the radio equivalent of adaptive optics.
This memo explores the instrumental requirements for a multi-channel
radiometer capable of measuring pathlength differences to 35\um, a
goal for interferometry at 1~mm wavelength.  An examination of linear
and nonlinear error sources shows that residual amplifier or detector
nonlinearity is likely to be the most significant instrumental limit
for atmospheric phase correction.

#END