MEETING OF THE GBT SCIENTIFIC WORKING GROUP 

November 30, 1993  --  4 PM EDT

AGENDA

  1) Update on construction  (Bob Hall)
  2) Monitor and Control News (Mark Clark)
  3) Spectrometer Developments (Ray Escoffier; Rich Lacasse)
  4) Receiver Priorities for 1995 continued (Jay Lockman; Roger Norrod)
        a) A tertiary reflector
        b) Q-band design
        c) S-band priority
        d) S/X receiver


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	A recent memo of mine (dated Oct 28, 1993 but thoughtfully left 
unsigned) summarized the discussion at the last SWG meeting on receiver 
priorities.  This memo provoked some comment, which is summarized here 
since not all of it was sent to the SWG exploder.

On the question of the importance of a tertiary reflector for fast 
beam switching, Al Wootten notes that it is necessary for good 
continuum observations at high frequencies at which interesting science
is expected.  

Several people noted the importance of S-band for planetary radar, using
the GBT as the receiver and the upgraded Arecibo dish as the transmitter.
It is particularly important for the Saturn system.  Its importance for other
science is not so compelling.

There was a lot of comment about the need for dual S/X capability.  It is
currently used mostly for geodesy for which the GBT is not needed, 
but it is also used for astrometry on very weak sources such as stars.  
The choice of S/X for dual-frequency VLBI is historical and is not 
necessarily the correct choice.  It is, however, the only dual-frequency
system in common use around the world.  

--F.J. Lockman