Using Quasars to Measure the Earth: A History of VLBI
VLBI, or Very Long Baseline Interferometry, is a technique that uses multiple radio telescopes to very precisely measure the Earth's orientation. It was originally invented back in the 1960s to take better pictures of quasars, but scientists soon found out that if you threw the process in reverse, you could measure how the ground beneath the telescopes moves around, how long days really are, and how the Earth wobbles on its axis as it revolves around the sun!
NASA Pinning Down "Here" Better Than Ever
NASA is helping to lead an international effort to upgrade the four systems that supply crucial location information in pinpointing where "here" is.
Time-lapse video of VLBI2010 Installation at GGAO
Time lapse video showing the construction of the VLBI2010 antenna at NASA Goddard Geophysical and Astronomical Observatory GGAO, September 15 through October 12, 2010.
Earth Orientation Animations
When you think of the Earth’s orientation, you’d probably imagine something like a globe, where it always rotates around an axis, called the spin axis, defined by the north and south poles. And while this generally makes sense, in reality, the Earth’s orientation is constantly changing very slightly, and this change can be described in three ways. Learn more about how the Earth's orientation changes by watching these animations.
Satellite Laser Ranging (SLR) and Pi
Satellite Laser Ranging (SLR) and Pi? Check out this podcast to learn how SLR is using pi to determine the effective reflective surface area of retroreflectors!
Global Space Geodesy Network
High-resolution photographic images of space geodetic systems installed around the world.
VLBI2010 Installation at GGAO
Installation of VLBI2010 at the Goddard Geophysical and Astronomical Observatory (GGAO) facility in Greenbelt, MD.
NGSLR Installation at GGAO
Installation of NGSLR at the Goddard Geophysical and Astronomical Observatory (GGAO) facility in Greenbelt, MD.
Installation of Drilled-Brace Monument at GGAO
Installation of Drilled-Brace Monument at the Goddard Geophysical and Astronomical Observatory (GGAO) facility in Greenbelt, MD.
SGP Summer Interns - 2012
The Space Geodesy Project hosted several interns from universities around the country.
Stephen Merkowitz, Project Manager
Project manager Stephen Merkowitz talks about his work with NASA's Space Geodesy Project, including a brief overview of the four fundamental techniques of space geodesy: GPS, VLBI, SLR, and DORIS.
Jan McGarry, Mathematician
Mathematician Jan McGarry discusses the science and history of Satellite Laser Ranging (SLR), her role in developing the Next Generation Satellite Laser Ranging system, and her career at NASA's Goddard Space Flight Center.
Chopo Ma, Space Geodesist
Space geodesist Chopo Ma explains the science of Very Long Baseline Interferometry (VLBI): using radio emissions from distant galaxies to create a precise reference frame for the Earth.
Carey Noll, Computer Scientist
Computer scientist Carey Noll talks about her job as manager of the Crustal Dynamics Data Information System (CDDIS), the applications of her work for various space geodesy techniques such as GPS, and her career at NASA's Goddard Space Flight Center.