PGS: Space Geodesy Project

The April, 2014, meeting of the Potomac Geophysical Society will be held April 17th at the Fort Myer Officers’ Club in Arlington, VA ( in the Glassed-in room in the Fife and Drum (main dining room).

Abstract: NASA’s Space Geodesy Project, Stephen M. Merkowitz, NASA Goddard Space Flight Center, Greenbelt, MD: NASA’s Space Geodesy Project (SGP) recently completed a prototype core site as the basis for a next generation Space Geodetic Network that is part of NASA’s contribution to the Global Geodetic Observing System (GGOS). This system is designed to produce the higher quality data required to establish and maintain the Terrestrial Reference Frame and provide information essential for fully realizing the measurement potential of the current and future generation of Earth Observing spacecraft. The prototype core site is at NASA’s Geophysical and Astronomical Observatory at Goddard Space Flight Center and includes co-located, state of-the-art, systems from all four space geodetic observing techniques: Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). A system for monitoring of the “ties” between these four systems is an integral part of the core site development concept and this specific prototype. When fully implemented, this upgraded global network will benefit in addition to the ITRF, all other network products (e.g. precision orbit determination, local & regional deformation, astrometry, etc.) that will also be improved by at least an order of magnitude, with concomitant benefits to the supported and tracked missions, science projects, and engineering applications. This presentation will summarize the results of the prototype site demonstration and provide the motivation and plans for NASA’s next generation geodetic network.

Biography:  Stephen Merkowitz is a scientist and project manager at NASA Goddard Space Flight Center. His research interests include: fundamental tests of General Relativity, lunar and interplanetary laser ranging, and space geodesy. He received his PhD in Physics from Louisiana State University working on gravitational wave antennas, and continued this research for two years in Frascati, Italy on a National Institute for Nuclear Physics (INFN) fellowship. In 1998 he became a Research Associate at the University of Washington where he performed experimental tests of General Relativity and measurements of Newton’s gravitational constant (which remains the most precise measurement of “big G” to date). In 2000, he moved to NASA Goddard to serve as Deputy Project Scientist for the LISA Project, a space based gravitational wave mission. In 2009, Merkowitz went on a yearlong detail to the Executive Office of the President covering Physical Science and Engineering for the Office of Science and Technology Policy, followed by a detail at NASA Headquarters as Assistant Director of the Astrophysics Division. He returned to Goddard in 2011 and now manages NASA’s Space Geodesy Project and is Principal Investigator for the Global Positioning System Laser Retroreflector Array.

Meeting Room and Dining Arrangements: We now meet in the glassed-in room at the back of the main dining room—The Fife and Drum. We order individually from the Club menu, which has a nice variety of dinner offerings. We pay a single bill (I pay it with my Officers Club credit card), so we collect at least $25 from each diner with the agreement, that if one orders more than $20 in food and drink, he adds the amount over $20 to his contribution. The $5 overcharge goes to the Room Fee, Tax, Gratuity, and the Speaker’s Dinner. We collect on the Honor System. We did this throughout the last year, and it worked well. This room change and use of the menu have greatly reduced the loss that we have incurred in the past for having fewer than 20 people dining, and the change has preserved the viability of using the Officers Club for our meetings.

Reception at 6:00. Order Dinner at 7:00. Talk at 8:30 PM. Please note that the meal orders will be taken at 7:00. Allow 15 minutes for security entering Ft. Myer as all civilian vehicles are searched. To ensure access to and from Fort Myer use the Hatfield Gate, open 24 hours a day ( Reservations are not necessary, however, we need a head count, so, if you wish to attend dinner ($25), please inform Bob Fraser at 540-888-3001540-888-3001 or via E-mail at you wish, please feel free to attend the talk without dinner. Non-members and guests are welcome. Visit the PGS web site at for new meeting announcements, etc. Please send changes of address or email


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