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[IGSMAIL-233] Goddard FLINN GPS on the air
- Subject: [IGSMAIL-233] Goddard FLINN GPS on the air
- From: T. Clark
- Date: 3 APR 1993 17:00:57
IGS Electronic Mail 3-APR-1993 17:00:57 Message Number 233
***********************************************************************
From: T. Clark
Subj: Goddard FLINN GPS on the air
-------------------------------------
Today, April 2, 1993 we began GPS observations from the NASA/Goddard FLINN
site using a TurboRogue (s/n 129). The site is still being developed
and we have no telephone yet, so data will be hand-carried on floppy
disks for posting to the community.
The Goddard site is at GGAO, the Goddard Geophysical and Astronomical
Observatory. Many of you know the site under its old name GORF (Goddard
Optical Research Facility) -- we changed the name to reflect the multi-
disciplinary nature of the site. But old habits die slowly and the GORF
name is still frequently used.
Data should start appearing early next week on CDDIS. We solicit comments
and feedback on its quality.
---------------------------------------------
SITE INFORMATION:
Over the past several months, we have been developing new capabilities
at GORF=GGAO. A previously unused area at the site has been earmarked
for the radio geodetic activities. The MV-3 VLBI system will be moved
to a new location (SGP 7108) in a couple of weeks, and two GPS monuments
(JPL 4006 = GODE and JPL 4005 = GODW ) have been fabricated (GOD stands
for GODdard and E/W stands for East/West).
The new GODE pier is a fairly conventional FLINN monument -- a concrete
cylinder going down about 4M in depth -- differing from the standard
design (i.e. Santiago) only in the diameter (30 inches vs. 18 inches) of the
concrete. The larger diameter was chosen to further suppress the
"back-side" antenna radiation to minimize multipath. The GODE pier is about
50 cm above ground level. It has been outfitted with a standard Rogue
Dorn-Margolin antenna with the back of the choke ring 6.14 cm
above the marker reference plate, using standard mounting hardware
and stainless steel plate supplied by JPL.
The GODW monument is not yet in use -- it is intended to test some ideas I
have on how to suppress multipath; the reference point and stainless steel
plate are only a few cm high. Yet to be installed is an absorber pad
made of ordinary asphault surrounding the monument (rather like the
situation at Yaragadee).
The two new sites were chosen to provide a nearly optimum horizon mask.
Both GODE and GODW can observe down to about 10 degrees elevation in most
directions. The TurboRogue was showing good lock this afternoon on
satellites as low as 6 degrees elevation.
Detailed site descriptions for the GORF=GGAO site are in the CDP
(now SGP = Space Geodesy Project) site catalog. For details, contact
Mark Bryant (bryant @ cddis.gsfc.nasa.gov).
---------------------------------------------
GEODETIC CONTROL INFORMATION:
The new GPS and VLBI monuments have been surveyed into the extensive
existing GORF=GGAO network of monuments using conventional techniques
by Vaughn Nelson and the crew at AlliedSignal (formerly called Bendix).
Vaughn then adjusted the entire network using HAVAGO and provided the
following data. I have chosen to report on only a subset of the HAVAGO
adjustment for sites I deem relevant. I have included the major monuments
currently in active geodetic use, including the North and South GEOS
piers that at a part of the US FGCC (Federal Geodetic Control Commission)
test range.
********** GORF 1993 HAVAGO ADJUSTMENT ************
IERS LAT = W.LONG=
"OFFICIAL" 40451 39deg + 76deg +
MARKER DOMES Comment 01min + 49min + HEIGHT
NAME ## SS.SSSSS SS.SSSSS METERS
-------------------- ---- ------- -------- -------- ------
CDP 7102 M102 MV-3 VLBI 14.36504 41.05487 19.206
CDP 7103 M103 14.59254 41.05272 19.198
CDP 7105 M105 MOB-7 SLR 14.14893 39.69092 20.441
CDP 7106 M113 48" SLR 17.32755 42.22103 20.601
CDP 7125 M114 12.94027 38.80242 19.756
CDP 7920 (7125-B) M117 12.89761 38.97513 19.758
CDP 7918 M120 14.55636 40.22590 19.956
NORTH GEOS 1979 M110 GORF FGCC 15.40525 38.95255 20.215
SOUTH GEOS PIER 1976 (none) also FGCC 12.60829 38.93431 20.114
GODDARD 1962 (none) 14.74859 40.57937 19.279
GODDARD 2 (none) 15.78174 39.86318 18.529
GORF 1989 (none) 12.75846 39.67755 19.598
JPL 4006 (GODE GPS) NEW GPS EAST 18.18985 36.57690 15.756
JPL 4005 (GODW GPS) NEW GPS WEST 17.99260 37.50555 15.489
SGP 7108-1993 NEW VLBI MV-3 18.90468 35.54401 14.993
In the following, the columns labeled "NAD 83" HAVAGO represent the data from
the HAVAGO adjustment. A quick conversion to ITRF 91 has been made by adjusting
the NAD 83 coordinates by the [XYZ] offsets between the HAVAGO output and the
ITRF 91 position of the MV-3 VLBI system on marker 7102 as given on page 85
of the ITRF 91 report (IERS Technical note 12 by Boucher, Altamimi and Duhem),
X=+1130686.684, Y=-4831353.012 and Z=+3994110.909 meters.
--------- NAD 83 HAVAGO -------- -- HAVAGO SHIFTED TO ITRF 91 --
"OFFICIAL" -- RELATIVE TO CDP 7102 VLBI --
MARKER -- X -- -- Y -- -- Z -- -- X -- -- Y -- -- Z --
NAME +1130000+ -4831000+ +3994000+ +1130000+ -4831000+ +3994000+
-------------------- ------- ------- ------- ------- ------- -------
CDP 7102 687.018 -354.478 111.041 686.684 -353.012 110.909
CDP 7103 686.061 -350.159 116.487 685.727 -348.693 116.355
CDP 7105 720.141 -352.021 106.641 719.807 -350.555 106.509
CDP 7106 646.843 -305.920 182.897 646.509 -304.454 182.765
CDP 7125 746.179 -369.482 77.252 745.845 -368.016 77.120
CDP 7920 (7125-B) 742.322 -371.236 76.231 741.988 -369.770 76.099
CDP 7918 705.722 -346.885 116.097 705.388 -345.419 115.965
NORTH GEOS 1979 731.837 -324.052 136.598 731.503 -322.586 136.466
SOUTH GEOS PIER 1976 744.622 -376.751 69.524 744.288 -375.285 69.392
GODDARD 1962 696.472 -344.676 120.277 696.138 -343.210 120.145
GODDARD 2 708.543 -320.651 144.557 708.209 -319.185 144.425
GORF 1989 726.457 -377.596 72.797 726.123 -376.130 72.665
JPL 4006 (GODE GPS) 774.371 -255.013 200.506 774.037 -253.547 200.374
JPL 4005 (GODW GPS) 753.445 -263.631 195.611 753.111 -262.165 195.479
SGP 7108-1993 795.266 -235.260 217.151 794.932 -233.794 217.019
---------------------------------------------
SOME ADDITIONAL COMMENTS:
It is my intent that the GORF=GGAO VLBI and GPS facility will support a
number of R&D programs as well as contributing operational data to the
community. The GODE/GODW monument pair is intended to support an
ongoing research program of mine to alleviate and calibrate multipath
biases.
We also intend that the GORF=GGAO facility will host new receivers for
A/B comparisons. The first of these tests will be to operate the Turbo-
Rogue and a new Trimble 4000SSE receiver from the same antenna and with
identical observing profiles. The UNAVCO receiver comparisons were very
interesting to evaluate the manufacturer's receiver+antenna performance.
However antennas can be replaced, and we don't have a good feeling for
the receiver vs. receiver performance. To make such data available to
the community, the GODE antenna has been outfitted with a high-isolation
signal splitter so that multiple receivers can be operated simulteously.
Subsequent tests (after the MV-3 system moves to its new marker) will
also eliminate the manufacturer' internal crystal oscillator from the
equation by operating the receivers from the VLBI Hydrogen Maser standard.
When we have multiple receivers operating from the same antenna, we hit
a problem in the naming of the RINEX files. Unless there is a loud
scream from the community, here is what I propose to do:
The files from the GORF=GGAO site will be named
GODmDDDn.YYt
following the 8-dot-3 MessDOS compatibility rule. The "m" field will
be used to denote a specific monument ( GODE/GODW for the two dedicated
marker, GODN when a receiver is on the North GEOS FGCC pier, etcetera).
The "n" field will be the normal [0-9] sequence for the "prime" Turbo-
Rogue if multiple files are collected in a day (rarely does the sequence
number differ from zero). If another breed of receiver is sharing the
same antenna, the "n" field will be an alphabetic character to distinguish
it from the "prime" data (i.e. "T" for a Trimble, "A" for Ashtech, etcetera).
[Note -- Tom Herring predicted you would scream about this scheme and
noted that many groups reject all data except for "0". If you have a
better idea, we can be flexible. Carey Noll and I scratched our heads
long and hard over this seemingly minor point]
The two main people who will oversee the GORF=GGAO operations are Chuck
Kodak and Mark Bryant. Chuck can be reached at mv3 @ cddis.gsfc.nasa.gov
and Mark at bryant @ cddis.gsfc.nasa.gov . I will not be able to do much
myself for the next several months -- I leave this weekend for a 3-4
month sabbatical at Onsala. During that time, E-mail will reach me
at tac @ oso.chalmers.se
Regards, Tom Clark