• Laser ranging to the moon
    Laser Ranging to the Moon
    NGSLR, located at NASA GSFC's Goddard Geophysical and Astronomical
    Observatory (GGAO),is shown ranging to the Lunar Reconnaissance Orbiter (LRO)
    orbiting the Moon. The LRO Laser Ranging (LR) system enables the spacecraft
    to achieve its precision orbit determination requirement.
  • antenna
    GGAO VGOS
    VGOS, located at NASA GSFC's Goddard
    Geophysical and Astronomical Observatory
    (GGAO), is the next generation of
    geodetic VLBI systems currently
    under development.
  • Monument brace
    Drilled Brace Monument for GNSS Antenna
    The newly installed drilled brace monument for the
    Global Navigation Satellite System (GNSS) antenna at
    NASA GSFC's Goddard Geophysical and Astronomical
    Observatory (GGAO). The multi-GNSS-capable
    receiver will track signals from several GNSS including
    GPS, GLONASS, and Galileo.
  • DORIS
    DORIS Antenna
    The Doppler Orbitography and Radio-positioning Integrated
    by Satellite (DORIS) antenna located at NASA GSFC's Goddard
    Geophysical and Astronomical Observatory (GGAO) tracks
    satellites equipped with DORIS beacons; NGSLR can be seen
    in the background.

Latest Project news

09/14/2022
GTA#1 in the SGSLR dome at GGAO Gimbal and Telescope Assembly (GTA) #1 installed in the SGSLR shelter in late June 2022
The Gimbal with Mass Simulator was removed from the GGAO SGSLR facility in June 2022 and shipped back to Cobham. After the Factory Acceptance Test at Cobham in Lansdale, the Gimbal and Telescope Assembly (GTA) #1 was shipped to GGAO and installed in the SGSLR shelter in late June 2022. Preparations for the Site Acceptance Testing (SAT) were begun shortly after installation.

GTA#1 in the SGSLR dome at GGAO

GTA#1 in the SGSLR dome at GGAO.





Ny-Ålesund SGSLR dome hydraulic pump successfully replaced
09/14/2022
The Ny-Ålesund SGSLR dome hydraulic pump was successfully replaced in August 2022 by Baader Planetarium as warranty work. The original pump was replaced with one that has a larger motor and does not require a heating element. Continued testing post-installation indicates that this replacement pump is working well.

Shortest day in modern times
08/12/2022
round analog clockAs noted in social media and the press (for example, here), the Earth recently experienced its shortest day in modern history. The length of day (LOD) of June 29, 2022 was recorded with 1.59 ms shorter than a standard 24-hour day (86,400 SI seconds). While this is a record in the era of atomic clocks (since the 1960s), it is nothing out of the extraordinary. LOD fluctuates over time and there were local minima in recent years as well. What is surprising is the fact that the Earth was speeding up a bit. In general terms, the Earth is slowing down mostly due to tidal friction caused by the moon: tidal bulges slow down the rotation of the Earth. For that, leap seconds are inserted to account for the slowed rotation. The currently observed increased rotational speed may be attributed to different geophysical phenomena, by themselves or in combination, including post-glacial rebound effects following the melting of ice masses particularly in the polar regions (including both recent ice mass loss as well as the long-term loss since the Pleistocene), climatological impacts on global hydrology due to recent consecutive La Nina events and changes in the parameters of the Earth's Chandler wobble (see articles here and here). On geological time scales (millions of years), however, the Earth has seen much shorter days (minutes to hours). Also, pre-atomic clock era LOD derivations using telescopic data from lunar occultations of stars point at around 2 ms shorter days in the 1870s, though with a much larger uncertainty. Hence, June 29, 2022 was not the shortest day ever in the history of the Earth but the shortest day in recent modern times. Monitoring these changes in the Earth's rotation is a critical function of the NASA Space Geodesy Project and its international partners as the changes are often unpredictable and provide key information about the geophysical changes affecting the Earth system (solid Earth, hydrosphere and atmosphere) and support precise positioning, satellite navigation, and the definition and maintenance of the Terrestrial Reference Frame.

graph showing the length of day from 1980-2023

The time history of LOD from space geodesy measurements since 1975 are available from the IERS here.



The twelfth session of the United Nations Committee of Experts on Global Geospatial Information Management (UN-GGIM) was held August, 3-5 2022
08/02/2022
Un-GGIM logoThe twelfth session of the United Nations Committee of Experts on Global Geospatial Information Management (UN-GGIM) was held August, 3-5 2022 at the United Nations Headquarters in New York. The session brought together senior officials and executives from national geospatial information and statistical authorities within Member States, and international geospatial experts from across the globe. Several NASA personnel from the Space Geodesy Program participated in support of the UN-GGIM Subcommittee on Geodesy. Dr. Karen St. Germain, the Earth Science Division Director at NASA Headquarters, presented "the critical role that geodesy and the global observatories play in Earth observation" during the Forum on Global Geodetic Reference Frame for Sustainable Development. The recording of Dr. St. Germain's presentation is available here.

NASA Mirrors on ESA Pathfinder to Empower Space Geodesy
07/08/2022
laser ranging equipment at GGAO, MD, USANASA will supply the upcoming European Space Agency (ESA) Lunar Pathfinder mission with an array of laser retroreflectors, mirrored devices that reflect light back at its source. The retroreflectors will offer new opportunities for lunar science and space geodesy.

Read more on nasa.gov...

NASA Mirrors on ESA Pathfinder to Enhance Lunar Navigation
07/08/2022
satellite orbiting the moonNASA will supply the upcoming European Space Agency (ESA) Lunar Pathfinder satellite with an array of laser retroreflectors, mirrored devices that reflect light back at its source. The retroreflectors will validate navigation capabilities that will be critical to the Artemis missions and future lunar exploration.

Read more on nasa.gov...

The Space Geodesy Project completed the Factory Acceptance Testing (FAT) of SGSLR's Gimbal and Telescope Assembly Unit #1 (GTA#1)
06/27/2022
SGSLR's Gimbal and Telescope Assembly Unit #1 at GGAO, MD, USAThe Space Geodesy Project completed the Factory Acceptance Testing (FAT) of SGSLR's Gimbal and Telescope Assembly Unit #1 (GTA#1) in early June 2022 at the manufacturer's facility (Cobham Advanced Electronic Solutions in Lansdale PA). After passing the FAT Review GTA#1 was then shipped to GGAO on June 21st and installed in the SGSLR facility on June 22nd by the prime SGSLR contractor, KBR, Inc. KBR and Cobham are currently preparing the gimbal and optics to start the Site Acceptance Testing (SAT).

New Jackscrew Successfully Installed on GGAO VGOS Antenna
06/17/2022
VGOS antenna at GGAO, MD, USAA new jackscrew and gearbox assembly were installed on the 12m VGOS antenna system at NASA Goddard Geophysical Astronomical Observatory (GGAO) in Greenbelt, Maryland during the week of June 6 – 10, 2022. The GGAO site operations and engineering management team from Peraton, antenna repair technicians from Intertronics Solutions, Inc. (ISI) – Calian and heavy equipment operations personnel from United Rigging in Beltsville, Maryland supported the repair activities. Replacement of the jackscrew improves overall structural and motion integrity associated with antenna pointing requirements and promotes continuous VLBI scientific research contributions from the NASA/SGP network.

The Space Geodesy Project completes the installation of the dome, riser, and optical bench support structure for the new NASA Space Geodesy Satellite Laser Ranging (SGSLR) station at Ny-Ålesund, Svalbard
05/18/2022
Ny-Alesund stationThe Space Geodesy Project completed the installation of the dome, riser, and optical bench support structure for the new NASA Space Geodesy Satellite Laser Ranging (SGSLR) station at Ny-Ålesund, Svalbard. The installation was performed by members of the SGSLR KBR team and the dome manufacturer Baader Planetarium, along with support from the Norwegian Mapping Authority and King's Bay AS. The Norwegian Mapping Authority hosted a Geodesy Event at Ny-Ålesund for Norwegian and United Nations dignitaries to celebrate this milestone. Dr. Karen St. Germain (NASA Earth Science Division Director) gave a public lecture on "The critical role that geodesy and the global observatories play in Earth observation" at the event and Stephen Merkowitz (Space Geodesy Project Manager) served on a discussion panel. The Norwegians also produced a short video for the event: Geodesy at the top of the world.

First year of Apache Point Lunar Laser Ranging data released under NASA stewardship
02/11/2022
Apache Point Laser ranging stationIn 2021, the Apache Point Lunar Laser Ranging station became part of the NASA Space Geodesy Network with New Mexico State University responsible for the on-site day-to-day operations and maintenance of the system. Over the past year, the NASA team worked with the former APOLLO team to establish best practices regarding observation and reduction of raw data into normal points, including the development of a new quality control process to identify centimeter-level biases in lunar laser ranging data. The new process helps to eliminate erroneous normal points and systematic biases prior to data publication. NASA Postdoctoral Fellow Nicholas Colmenares (one of the primary members of the former APOLLO group) led the development of the data procedures and archival of the data in the new version 2 of the Consolidated Range Data (CRD) format. The full set of 2021 data is now available from the Crustal Dynamics Data Information System (CDDIS) at https://cddis.nasa.gov/Data_and_Derived_Products/SLR/Lunar_laser_ranging_data.html.



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Using Quasars to Measure the Earth: A Brief History of VLBI
Looking Down a Well: A Brief History of Geodesy