Using Quasars to Measure the Earth: A History of VLBI

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.

Staff Profiles

Stepehn Merkowitz, Project Manager for the Space Geodesy Project

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

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.