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Using Quasars to Measure the Earth: A Brief History of VLBI

Looking Down a Well: A Brief History of Geodesy



  • Quasarville: The town that never moves NASA Explains Why June 30 Will Get Extra Second 06/23/2015 The day will officially be a bit longer than usual on Tuesday, June 30, 2015, because an extra second, or "leap" second, will be added. "Earth's rotation is gradually slowing down a bit, so leap seconds are a way to account for that," said Daniel MacMillan of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

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  • World map depicting locations of GNSS sites Real-Time GNSS Data and Products now available through the CDDIS 04/10/2015 The CDDIS staff is pleased to announce that its real-time caster is now operational, supporting the International GNSS Service (IGS) Real-Time Service (RTS). The IGS RTS, based on a cooperative global infrastructure of stations, data centers, and analysis centers, provides GNSS orbit and clock corrections that enable precise point positioning (PPP) and related applications, such as time synchronization and disaster monitoring at global scales. The CDDIS caster utilizes the NTRIP (Networked Transport of RTCM via Internet Protocol) software to disseminate these real-time streams to registered users.

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  • 19th ILRS Workshop logo 19th International Workshop on Laser Ranging a great success 11/18/2014 The 19th International Laser Ranging Workshop was hosted by NASA GSFC from October 27-31, 2014 in Annapolis, Maryland. October 31 marks the 50th anniversary of the first successful Satellite Laser Ranging (SLR) measurement which occurred at the Goddard Geophysical and Astronomical Observatory (GGAO) in 1964. The theme for this workshop, "Celebrating 50 Years of SLR: Remembering the Past and Planning for the Future" allowed the community to look back on its many accomplishments and to present plans for future advances in SLR technology and science.

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  • Staff Profile: 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.

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  • Staff Profile: 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.

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  • Staff Profile: 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.

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  • Staff Profile: 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.

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