[IGEXMail-0003] Goddard IGEX site

["Dr Thomas A Clark (W3IWI)" <tac @ clark.net>]

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IGEX Electronic Mail    28-Aug-1998 06:38:09                   Message No 0003
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Author: "Dr Thomas A Clark (W3IWI)" <tac @ clark.net>
Subject: Goddard IGEX site 


This is to give you advanced notice that we will be contributing an 
additional dual-frequency GPS+GLONASS station for IGEX.  We had not
previously "registered" this with IGEX since we were not certain that we
could make it happen. Here are some details -- we will send the official 
participation form soon:


SITE:      NASA Goddard Space Flight Center, Greenbelt MD

SITE NAME: GODZ -- GODZ uses the same antenna as the GODE IGS station, so all
           station parameters will be the same as already in IGS database.
           [I'm typing this at home and don't have the NASA or DOMES numbers
           readily available.] 

ANTENNA:   GODE's AOA/JPL Dorn-Margolin Choke Ring equipped with 8-port
           high-isolation power splitter.

SITE NOTES: GODE/GODZ is collocated with VLBI, SLR & PRARE systems (but not 
           DORIS) at the NASA Goddard Geophysical & Astronomical Observatory 
           (GGAO). GGAO has a large number of geodetic monuments associated
           with the various geodetic systems at GGAO. The GODE name means
           GODdard East GPS marker. GODZ (Z meaning Z-18) is chosen to
           provide a unique site name for the Z-18 data. [Note -- for a few 
           days, I think we will have a second Z-18 occupying the GODW 
           (West) monument, 22 meters from GODE/GODZ, in case anyone wants
           to do dual-receiver short-baseline tests.]

Sponsors:  Joint activity of the NASA/GSFC Space Geodesy Program and Ashtech

Receiver:  Ashtech Z-18

Frequency Reference: Today it is running with the Z-18's internal crystal. 
           Next week it SHOULD be running with the same VLBI Hydrogen Maser 
           that runs the normal IGS GODE TurboRogue and MV-3 VLBI, and that 
           provides site-wide time/frequency reference for the various NASA 
           SLR systems at GGAO.

Status:    Mark Bryant (Ashtech), Chuck Kodak and I got GODZ running mid-day 
           Aug.27. Data is logged in real time to a Windows95 PC and the 
           entire operation can be run remotely. We should have the operation
           running smoothly next week and will provide the GODZ RINEX files
           directly to CDDIS. As soon as the data flow is established we
           will announce the availability of the Z-18 GPS+GLONASS data via
           IGEXMAIL.

Dramatis Personae: Tom Clark & Chuck Kodak (NASA/GSFC)
           Mark Bryant (Ashtech)



Two additional notes:
(1) We have run Carrol Alley's (Univ. of Maryland) 3S GLONASS/GPS receiver  
on the GODE antenna in the past. His receiver is currently at the factory 
being updated and Carrol has not indicated when it will be returned to him. 
I anticipate that if/when he does get it back, he will want us to connect
it the GODE antenna. So we MAY be able to contribute data from an additional 
receiver sometime during IGEX.

(2) Bruce Schupler and I made initial measurements on the standard D-M choke-
ring antenna (AOA TurboRogue version) in our new GSFC anechoic chamber over 
the entire GPS+GLONASS L1 & L2 frequency bands. Preliminary results (showed 
at the Spring AGU meeting) indicate that the phase center varies linearly
and smoothly with frequency, and that the antenna heights have ~85 microns/MHz
slope over the entire L2-to-L1 frequency range. We have additional anechoic 
chamber time scheduled in mid-Sept. to perform additional tests and verify 
the phase center slope.


Tom Clark
mailto://clark @ tomcat.gsfc.nasa.gov