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Date: Tue, 29 Feb 2000 10:44:05 -0800 (PST)
From: mel wright 456 <wright@creek2.berkeley.edu>
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MMA Memo Abstract Template
 

MMA Memo Abstract Template


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


#
# Enter the MMA memo title in the following section
#
#Title:
Atmospheric Noise in Single Dish Observations 


#
# 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.
#
#Authors:
Melvyn Wright (Radio Astronomy Laboratory, University of California, Berkeley)


#
# Enter the date that the memo was submitted in the format mm/dd/yy.
#
#Date:
02/29/00


#
# Enter a list of keywords which might be used to find this memo in an
# electronic search.  Multiple keywords should be separated by commas.
#
#Keywords:

Atmospheric Noise, Single Dish Observation.
#
# Enter a plain ASCII abstract between here and the #END symbol
# 
#Abstract:
Atmospheric noise and pointing fluctuations will severely impact the
signal-to-noise and image fidelity of ALMA observations.  Single dish
observations are required for extended sources.  For wideband total
power observations, the maximum integration time ~ 0.1 s in order
to keep atmospheric fluctuations less than the thermal noise. A gain
stability ~ 10^{-4} in 0.1 s is required.  For OTF mapping, the
noise is limited by the atmospheric fluctuations between the ON and OFF
positions.  For sources which are only a few beamwidths across,
OTF mapping is inefficient. The single dish capability of ALMA could be
improved by instrumenting a few antennas to scan the beam pattern,
either with  x-y nutating subreflectors, or better, with array
receivers.  A number of experiments are possible to check the
conclusions of atmospheric modeling. These could be done on existing
submillimeter telescopes such as the JCMT, and might impact the ALMA
design.

#END