Search NASA⌕ Search

SEARCH · Search NASA

Results for “Space Geodesy”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Earthquakes and sea level - Space and terrestrial metrology on a changing planet

A review is presented of the stability and scale of crustal deformation metrology which has particular relevance to monitoring deformation associated with sea level and earthquakes. Developments in space geodesy and crustal deformation metrology in the last two decades have the potential to acquire a homogeneous global data set for monitoring relative horizontal and vertical motions of the earth's surface to within several millimeters. New tools discussed for forecasting sea level rise and damaging earthquakes include: very long baseline interferometry, satellite laser ranging, the principles of GPS geodesy, and new sea level sensors. Space geodesy permits a unified global basis for future metrology of the earth, and the continued availability of the GPS is currently fundamental to this unification.

Bilham, Roger↗
NASA NTRSDate not supplied

Satellite Laser Ranging at Brandal

Space Geodesy Satellite Laser Ranging (SGSLR) is a component of NASA’s Space Geodesy Project. It is an initiative to renew and expand NASA’s Geodetic Network. SGSLR at Ny-Ålesund is being developed, deployed, and integrated into the NASA Network by KBR Wyle, in partnership between NASA and Kartverket.

Evan Hoffman↗
NASA NTRSDate not supplied

Current Status and Plans for Test and Deployment of the First NASA SLR System

Over the last decade the Space Geodesy Project has been progressing toward the development and deployment of NASA’s next generation network of geodetic stations ( https://space-geodesy.nasa.gov ). The Satellite Laser Ranging (SLR) part of this effort is called Space Geodesy Satellite Laser Ranging (SGSLR). Significant progress has been made in the development of SGSLR’s nine subsystems, and many of these subsystems are completed or are nearing completion. The next major step will be the Integration and Testing (I&T) of all subsystems into the first SGSLR system which will start before the end of 2022. Verification testing (collocation) with NASA’s legacy operational SLR system, MOBLAS-7, is planned for early 2024. The first SGSLR system is being developed for Kartverket, also known as the Norwegian Mapping Authority (NMA). The system will be installed at Ny-Ålesund in Svalbard, Norway. The planned start of operations is early 2025. This presentation will give the current status of development, the testing and deployment plans, and the future of NASA’s SGSLR global network.

Satellite Laser Ranging↗
NASA NTRS2019

SLR Data: from Station to User

The ILRS provides laser ranging data and products on an operational basis to geodesy analysts as well as a broader scientific community. ILRS is one of four services within the International Association for Geodesy (IAG) supporting space geodesy. IAG established these services to facilitate international cooperation and scientific research: Networks, Data centers, Analysis groups. Services perform successful operations through cooperation of many international organizations, leveraging their respective resources to all levels of service functionality.

Noll, Carey↗
NASA NTRSDate not supplied

The Crustal Dynamics Data Information System (CDDIS) – SLR Updates

The Crustal Dynamics Data Information System (CDDIS), established in 1982, is NASA’s archive for space geodesy and geodynamics. Over decades, the CDDIS has grown and evolved alongside space geodesy communities, such as the DORIS, GNSS, SLR, and VLBI user communities. With this growth, different needs have becoming apparent for various sub-groups. Generally, the CDDIS ensures new updates and releases of data and products are made known to the general user community. In addition to this, inquiries on the frequency of data and product uses have become more common from various agencies. This poster provides an overview of these items.

Justine Woo↗
NASA NTRS2012

An Update on the CDDIS

The Crustal Dynamics Data Inforn1ation System (CoorS) supports data archiving and distribution activities for the space geodesy and geodynamics community. The main objectives of the system are to store space geodesy and geodynamics related data products in a central data bank, to maintain infom1ation about the archival of these data, and to disseminate these data and information in a timely mam1er to a global scientific research community. The archive consists of GNSS, laser ranging, VLBI, and OORIS data sets and products derived from these data. The coors is one of NASA's Earth Observing System Oata and Infom1ation System (EOSorS) distributed data centers; EOSOIS data centers serve a diverse user community and are tasked to provide facilities to search and access science data and products. The coors data system and its archive have become increasingly important to many national and international science communities, in pal1icular several of the operational services within the International Association of Geodesy (lAG) and its project the Global Geodetic Observing System (GGOS), including the International OORIS Service (IDS), the International GNSS Service (IGS), the International Laser Ranging Service (ILRS), the International VLBI Service for Geodesy and Astrometry (IVS), and the International Earth Rotation Service (IERS). The coors has recently expanded its archive to supp011 the IGS Multi-GNSS Experiment (MGEX). The archive now contains daily and hourly 3D-second and subhourly I-second data from an additional 35+ stations in RINEX V3 fOm1at. The coors will soon install an Ntrip broadcast relay to support the activities of the IGS Real-Time Pilot Project (RTPP) and the future Real-Time IGS Service. The coors has also developed a new web-based application to aid users in data discovery, both within the current community and beyond. To enable this data discovery application, the CDDIS is currently implementing modifications to the metadata extracted from incoming data and product files pushed to its archive. This poster will include background information about the system and its user communities, archive contents and updates, enhancements for data discovery, new system architecture, and future plans.

Noll, Carey↗
NASA NTRS2018

Important Changes to User Access at the NASA CDDIS

The Crustal Dynamics Data Information System (CDDIS) supports data archiving and distribution activities for the space geodesy and geodynamics community. The main objectives of the system are to make space geodesy and geodynamics related data and derived products available in a central archive, to maintain information about the archival of these data, to disseminate these data and information in a timely manner to a global scientific research community, and to provide user based tools for the exploration and use of the archive. Since its inception, the user community has utilized anonymous ftp for accessing and downloading files from the CDDIS archive. Although this protocol allows users to easily automate file downloads, many organizations, data systems, and users have already migrated from ftp or are actively pursuing a move away from the protocol due to problems from a system and security standpoint. Furthermore, U.S. Government agencies have become increasingly concerned about this legacy protocol and ensuring data integrity for the user community have begun recently to disallow the use of the ftp protocol. The CDDIS, operated by NASA GSFC, must therefore address these concerns and provide alternative methods for access to its archive for continued easy and automated download of its contents. This poster will discuss the upcoming changes at CDDIS and provide examples on transitioning from anonymous ftp.

Noll, Carey E.↗
NASA NTRS2018

NASA's Satellite Laser Ranging Systems for the 21st Century

For over 40 years, NASA’s global network of satellite laser ranging (SLR) stations has provided a significant percentage of the global orbital data used to define the International Terrestrial Reference Frame (ITRF). The current NASA legacy network is reaching its end-of-life and a new generation of systems must be ready to take its place. Scientific demands of sub-millimeter precision ranging and the ever-increasing number of tracking targets give aggressive performance requirements to this new generation of systems. Using lessons learned from the legacy systems and the successful development of a prototype station, a new network of SLR stations, called the Space Geodesy Satellite Laser Ranging (SGSLR) systems, is being developed. These will be the state-of-the-art SLR component of NASA’s Space Geodesy Project (SGP). Each of SGSLR’s nine subsystems has been designed to produce a robust, kilohertz laser ranging system with 24/7 operational capability and with minimal human intervention. SGSLR’s data must support the aggressive goals of the Global Geodetic Observing System (GGOS), which are 1 millimeter (mm) position accuracy and 0.1 mm per year stability of the ITRF. This paper will describe the major requirements and accompanying design of the new SGSLR systems, how the systems will be tested, and the expected system performance.

J. F. Mcgarry↗
NASA NTRSDate not supplied

Advances in Estimation of the Earth Orientation Parameters From Observation

Historically, a two-step procedure for estimation of Universal Time and polar motion from observations was adopted: night averages from individual observatories formed a raw non-equidistant time series that was edited for outliers, smoothed, and formed the final data product. This approach was by inertia used for processing modern space geodesy observations. I will present an alternative one-step approach and its application for processing a dataset of VLBI observations since 1990.0 through present. The essence of this approach is to represent the Earth orientation parameters in a form of an expansion into basic functions and estimate of the expansion coefficients directly from observations. A further extension of this approach is to assimilate not only space geodesy data, but atmospheric and ocean angular momentum from assimilation numerical weather models and their forecasts. That makes a smooth bridge between Earth rotation estimation and prediction. I will talk about my experience of running data analysis in such a way on a semi-operational basis, present results, and discuss advantages and disadvantages of this approach.

Leonid Petrov↗
NASA NTRS1985

Space-age geodesy - The NASA Crustal Dynamics Project

The NASA Crustal Dynamics Project (CDP) has deployed satellite laser ranging (SLR) systems and VLBI techniques for measurements of global and regional crustal motions and earth rotation parameters. The measurement programs for the years 1984 and 1983 are described, and some preliminary results are presented. A complete list of the fixed receiving stations in the CDP network is given.

Coates, R. J.↗
NASA NTRS1993

Expected orbit determination performance for the TOPEX/Poseidon mission

Each of the components required for the computation of precise orbits for the TOPEX/Poseidon (T/P) spacecraft - gravity field modeling, nonconservative force modeling, and satellite tracking technologies - is examined. The research conducted in the Space Geodesy Branch at Goddard Space Flight Center in preparation for meeting the 13-cm radial orbit accuracy requirement for the T/P mission is outlined. New developments in modeling the earth's gravitational field and modeling the complex nonconservative forces acting on T/P are highlighted. The T/P error budget is reviewed, and a prelaunch assessment of the predicted orbit determination accuracies is summarized.

Nerem, R. S.↗
NASA NTRS1994

Seismology and Space-Based Geodesy

The spatial and temporal distributions of strain accoumulation and release involved in various tectonic and earthquake processes can be inferred from high-precision geodetic measurements of the correcponding crustal deformation at the Earth's surface.

Global↗
NASA NTRS2002

Tides and Modern Geodesy

In modem high-precision geodesy, and especially in modem space geodesy, every measurement that one makes contains tidal signals. Generally these signals are considered noise and must somehow be eliminated. The stringent requirements of the latest space geodetic missions place severe demands on tidal models. On the other hand, these missions provide the strongest data for improving tidal models. In particular, TOPEX/POSEIDON altimetry and LAGEOS laser ranging have improved models to such an extent that new geophysical information about the ocean and the solid Earth are coming to light. Presumably GRACE intersatellite ranging data will also add to this information. This paper discusses several of these new geophysical results, with special emphasis given to the dissipation of tidal energy. Strong constraints have recently been placed on the partitioning of energy dissipation among the ocean, atmosphere, and solid earth and between the deep and shallow ocean. The dissipation in deep water is associated with internal tides and has potentially important implications for understanding the ocean's thermohaline circulation.

Ray, Richard D.↗
NASA NTRS2000

The Importance of Local Surveys for Tying Techniques Together

The synergistic benefits of combining observations from multiple space geodesy techniques located at a site are a main reason behind the proposal for the establishment of the International Space Geodetic and Gravimetric Network (ISGN). However, the full benefits of inter-comparison are only realized when the spatial relationships between the different space geodetic systems are accurately determined. These spatial relationships are best determined and documented by developing a local reference network of stable ground monuments and conducting periodic surveys to tie together the reference points (for example: the intersection of rotation axes of a VLBI antenna) of the space geodetic systems and the ground monument network. The data obtained from local surveys is vital to helping understand any systematic errors within an individual technique and to helping identify any local movement or deformation of the space geodetic systems over time.

Long, James L.↗
NASA NTRS2000

A Lifetime of Geodesy and Geophysics: In Rememberence of Bill Kaula

In the early 1960's the secrets that knowledge of the Earth's gravity field would eventually reveal about the processes that govern our planet were yet to be appreciated. It was the beginning of a new science known as space geodesy, which arose at a time when most efforts were devoted to understanding how to extract precise measurements of Earth structure and motions from an orbiting spacecraft. Bill Kaula was central to that beginning and showed the way for many who were to follow, both in time and in the development of approaches most likely to yield results. Bill laid out the theory, analyzed the data, and argued strenuously for a spacecraft mission devoted to measuring gravity to make it all come true in the way he knew it really could. That mission, GRACE, was a long time coming and Bill would not see its final staging, but his influence in making it happen was everywhere. With time, the concepts for measuring the static gravity field of the Earth and terrestrial planets became well advanced, although not universally agreed upon, and certainly not by Bill, who was always eager to argue and challenge traditional methods and thinking. The extension of space geodetic techniques to the planets and the development of new techniques to measure time variations in gravity have recently brought geodesy even closer to the geophysical processes that Bill sought to understand. This presentation will contain a little geodesy, a little history, and a little reminiscing about the leader in our field.

Smith, David E.↗
NASA NTRS2003

Three-Gorge Reservoir: A 'Controlled Experiment' for Calibration/Validation of Time-Variable Gravity Signals Detected from Space

With the advances of measurements, modern space geodesy has become a new type of remote sensing for the Earth dynamics, especially for mass transports in the geophysical fluids on large spatial scales. A case in point is the space gravity mission GRACE (Gravity Recovery And Climate Experiment) which has been in orbit collecting gravity data since early 2002. The data promise to be able to detect changes of water mass equivalent to sub-cm thickness on spatial scale of several hundred km every month or so. China s Three-Gorge Reservoir has already started the process of water impoundment in phases. By 2009,40 km3 of water will be stored behind one of the world s highest dams and spanning a section of middle Yangtze River about 600 km in length. For the GRACE observations, the Three-Gorge Reservoir would represent a geophysical controlled experiment , one that offers a unique opportunity to do detailed geophysical studies. -- Assuming a complete documentation of the water level and history of the water impoundment process and aided with a continual monitoring of the lithospheric loading response (such as in area gravity and deformation), one has at hand basically a classical forwardinverse modeling problem of surface loading, where the input and certain output are known. The invisible portion of the impounded water, i.e. underground storage, poses either added values as an observable or a complication as an unknown to be modeled. Wang (2000) has studied the possible loading effects on a local scale; we here aim for larger spatial scales upwards from several hundred km, with emphasis on the time-variable gravity signals that can be detected by GRACE and follow-on missions. Results using the Green s function approach on the PREM elastic Earth model indicate the geoid height variations reaching several millimeters on wavelengths of about a thousand kilometers. The corresponding vertical deformations have amplitude of a few centimeters. In terms of long-wavelength spherical harmonics, the induced geoid height variations are very close to the accuracy of GRACE- recoverable gravity field, while the low-degree (2 to 5) harmonics should be detectable. With a large regional time-variable gravity signal, the Three-Gorge experiment can serve as a useful calibration/verification for GRACE (including the elastic loading effects), and future gravity missions (especially for visco-elastic yielding as well as underground water variations).

Chao, Benjamin F.↗
NASA NTRS2003

Global navigation satellite sounding of the atmosphere and GNSS altimetry : prospects for geosciences

The vast illuminating power of the Global Positioning System (GPS), which transformed space geodesy in the 199Os, is now serving to probe the earth's fluid envelope in unique ways. Three distinct techniques have emerged: ground-based sensing of the integrated atmospheric moisture; space-based profiling of atmospheric refractivity, pressure, temperature, moisture, and other properties by active limb sounding; and surface (ocean and ice) altimetry and scatterometry with reflected signals detected from space. Ground-based GPS moisture sensing is already in provisional use for numerical weather prediction. Limb sounding, while less mature, offers a bevy of attractions, including high accuracy, stability, and vertical resolution; all-weather operation; and exceptionally low cost. GPS bistatic radar, r 'reflectometry,' is the least advanced but shows promise for a number of niche applications.

occultation↗