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CDDIS Bulletin - October 1989
Volume 5 No. 1
In this issue:
On the cover: Very Long Baseline
Array Sites
Recently several accounts have been established on the CDDIS MicroVAX
to support the Project's VLBI analysis group. These accounts have privileges
to access a large common data area where users can deposit experiment
schedules and log files. Electronic mail communication is also available
through these accounts. Below is a list of the VLBI user accounts on
CDDIS:
Account Responsible Account Responsible
Name Party Name Party
HAYSTACK Dr. Arthur Niell JPLVLBI Dr. Chad Edwards
USNO James Martin HATCREEK Al Masters
NGS Michael Morrison BENDIXVLBI Bruce Schupler
FBKS Steve Caskey NRL Dr. Jane Russell
HAWAII Clyde Cox KASHIMA Noriyuki Kawaguchi
MOJAVE Curt Mitchell ONSALA Dr. Gunnar Elgered
WESTFORD Dr. Alan Whitney HARTRAO Dr. George Nicolson
RICHMOND Dr. Alice Babcock MATERA Dr. Bartolomeo Pernice
GBANK George Grove NOTO Dr. Paolo Tomasi
VLBA Dr. Craig Walker MEDICINA Dr. Franco Mantovani
CFA Dr. Tomas Herring UBONN Dr. James Campbell
FTDAVIS J. D. Williams WETTZELL Richard Kilger The VLBI group schedules telescope resources months in advance
and then distributes plans for these experiments. Each station must
then send logs back to the VLBI group after completion of the experiment.
Prior to an electronic environment, these schedules and logs where
distributed via U.S. mail and TELEMAIL; today, however, file transfers
and mail on CDDIS has become an integral part of this distribution.
Figure 1 shows the local, GSFC VLBI computing
environment; Figure 2 presents how the above
nodes connect to CDDIS to exchange data and mail messages. The GSFC
VLBI group prefers to utilize TCP/IP protocol for data exchange because
of its vendor independence; some nodes, however, will continue to
use SPAN and dial-up methods to communicate until alternatives are
available. The CDDIS MicroVAX has network connections to both SPAN
and INTERnet, as well as dial-up lines. Therefore, the system acts
as a central repository for VLBI experiment information and message
exchange.
The CDDIS has recently received the SL7.1 polar motion and station
position solutions submitted to the IERS by the GSFC SLR analysis
group. The solution was generated by fitting thirty day arcs of LAGEOS
laser ranging normal point data from May 1976 through June 1987.
The CDDIS data base tables contain this information are:
PMOTIONIERS_SLRGSFC polar motion data submitted to the IERS
POSITIONSIERS_SLRGSFC station position data submitted to the IERS
This issue of the DIS Bulletin marks the four year anniversary
of the publication. The following pages list all articles included
in Volume 4 of this document, issue numbers 1 through 6.
This section is designed to give brief notices of special events
or problems encountered in recent months.
As reported in the last issue of the DIS Bulletin, the Bendix Data
Services group has recently begun the generation of test sets of
SLR normal points. To date, the CDDIS now has normal point data produced
from the A version of the January through April, 1989 full-rate data.
The Bendix Data Services Group has notified the CDDIS that the
TLRS-1 data previously released for 1988 will have to be recalled
and replaced because of a retroactive change in the calibration paths
and eccentricities at Cabo San Lucas, Mexico and Westford, MA. The
data from the Cabo San Lucas occupation is biased short by 13 mm.
The user may correct for this problem by adding 13 mm to all one-way
satellite ranges, or 867 picoseconds to all two-way time. The data
from the Westford occupation is biased long by 20 mm. The user may
subtract 20 mm or 1334 picoseconds two-way time to all one-way satellite
ranges or two-way time respectively. The table below lists the total
number of passes per month requiring correction:
No. of
Mon. Passes Site
May 13 Cabo San Lucas
Jun 33 Cabo San Lucas
Jul 3 Cabo San Lucas
Aug 2 Westford
Sep 51 Westford
Oct 9 Westford
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