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		OVLBI EARTH STATION MEMO SERIES

			 L. R. D'Addario
			   27 May 1990


	I propose to establish an informal series of numbered
memoranda on the subject of earth station design for the support of
Orbiting Very Long Baseline Interferometry.  The series is motivated
by the existence of projects at several places, including the NRAO,
to develop such stations in support of the upcoming RADIOASTRON and
VSOP missions.  The present document is the first of the series. 

	Topics to be covered include:  radio communication links to
OVLBI spacecraft; phase transfer methods and performance; wideband
data encoding and decoding; data recording; earth station antennas;
measurements for orbit determination; interfaces to other parts
of an OVLBI system, including correlators; and any related matters. 

	Memo series of this type have been used in many other
projects at the NRAO, and have been very successful in providing a
way to organize information and allow for its rapid and widespread
dissemination.  For those who are not familiar with the concept, the
basic ideas are as follows.  Any interested person may write and
submit a technical memo on a subject relevent to the series.  A
central distribution point is established to receive contributions,
assign each a sequence number, enter it into an index, and send
copies to those who have asked to be on a mailing list.  The
contributions are not reviewed by anyone, and therefore have no
official status whatsoever; they can, and often do, contain
preliminary ideas and opinions.  The numbered memos can then be
referred to in future work, and since most people actively working
on a given project will have copies, there is a common, written
basis for discussions.  Of course, this is no substitute for formal
documentation of actual design decisions. 

	For the present series, the distribution point will be at 
the NRAO in Charlottesville.  Contributions and requests to be on 
the mailing list should be sent to:
		Ms. Cathy Burgess
		NRAO
		2015 Ivy Road
		Charlottesville, VA 22903
		phone:  804/296-0334   fax:  804/296-0324
		email:  CBURGESS@NRAO.EDU,  6654::CBURGESS
Two mailing lists will be maintained:  the first will receive the 
full text of each memo as soon as it is released, and the second 
will receive only periodic printouts of the index (monthly or 
quarterly, depending on the volume of contributions).  The index 
will include title, author, date, a one-sentence summary (if 
provided by the author), and some status codes (e.g., we will 
attempt to flag obsolete memos).  With each distribution of the
index, a form will be provided for ordering the full text of
				-2- 


individual memos.  To keep the paper and postage costs reasonable,
we strongly urge that requests to be on the first list be limited to
those who are actively involved in earth station development. 

	Contributions and requests to be on a mailing list will be
accepted from anyone, at any institution, worldwide.  The only 
guidelines are that the memos should be closely related to the 
subject of the series, and should kept reasonably brief.  Copies of 
papers or data published elsewhere should not be included, but 
references should be given.  Voluminous information (like long 
listings) that might be of value to only a few readers should be 
omitted, but instructions for finding that information should be 
given.  

	Submission of contributions in machine-readable form is 
encouraged.  Files should be ASCII only, but might be TeX input 
files if only standard macro packages are invoked.  Transmission on 
floppy disk or via network transfer is possible.  We will attempt to 
arrange for these memos to be available on-line through the 
networks.