UNAVCO Facility personnel traveled to Goddard's Geophysical and Astronomical Observatory (GGAO) located in Greenbelt, Maryland in order to setup two temporary GPS campaign systems over known marks as construction was commencing on the area that will be home to the next generation VLBI antenna. A Space Geodetic Proposal, which has been funded, includes funds to install two deep drill braced monuments at the observatory. These funds will not be available until February 2011 at the earliest, at which time the new permanent monuments can be installed. The reference frame station GODE/GODZ sits approximately 50 feet away from an area of trees that is being cleared to make room for the new VLBI antenna. In order to preserve the reference frame coordinate, a tie must be made so that an offset can be determined. Due to the close proximity of the new VLBI dish, which will overshadow GODE once installed, it became a top priority to get some temporary GPS systems logging data on some known marks within the observatory. Most of the details were worked out while onsite.
One campaign system was installed on an observation pier within the facility and is located between where the new VLBI dish will be installed, and where one of the new GPS monuments will be installed. This system consists of a Topcon choke ring antenna and Topcon NetG3A. Data is logged to a mini pc which is being housed in building 204. This system will continue logging data throughout the construction phase of the VLBI dish and the deep drill braced monuments. Data from this system will be used to solve for an offset from the old monument (GODE) to the new monument once installation of the new monument is complete. Figure 1 shows an aerial view of the GGAO Facility and where the two temporary systems are setup, denoted by the names PIER and TECH. The blue circle denotes the area where one of the deep drill braced monuments will be installed next year. The location of the second monument has yet to be decided and discussions are ongoing. The yellow area denotes where construction is currently underway and where the next generation VLBI antenna will be installed.
The second system that was setup consists of a Tech2000 mast, Zephyr antenna, and Trimble NetRS receiver. The original plan was to setup the Tech2000 over a known mark temporarily, but then move it once the concrete pad for the new VLBI dish has been poured and the markers were inset. But that plan has since changed and Honeywell setup 2 temporary battery powered systems on 2 markers which were installed in the concrete pad. These systems will collect data for at least 48 hours. In theory, there will be data available from 4 temporary systems for a short duration, and two systems will provide data for close to a year.
Data from both systems are being logged to a mini-pc via the second Ethernet port on the computer. The Acrosser system uses an 8Gb compact flashcard as the hard drive and utilizes an APC SmartUPS 750 XL which will keep the system running for approximately 12 hours should there be a loss of power at the site. The computer was not initially installed on the local network pending a security scan and the acquisition of a static IP address. The flashcard was recently swapped out for one containing a newer version of the OS installed (FC12). Data is now being streamed directly to JPL. A web cam was setup so that all interested parties can see the progression of construction.
Figure 1 - Aerial Map of GGAO Facility showing location of the two temporary systems
Figure 2 - Pillar monument outfitted with Topcon choke which will continue logging data until after the new permanent monuments have been installed.
Figure 3 - Tech2000 mast setup with Trimble Zephyr antenna.
Last modified: 2020-01-28 22:54:21 America/Denver