Applications of satellite and marine geodesy to operations in the ocean environment

The requirements for marine and satellite geodesy technology are assessed with emphasis on the development of marine geodesy. Various programs and missions for identification of the satellite geodesy technology applicable to marine geodesy are analyzed along with national and international marine programs to identify the roles of satellite/marine geodesy techniques for meeting the objectives of the programs and other objectives of national interest effectively. The case for marine geodesy is developed based on the extraction of requirements documented by authoritative technical industrial people, professional geodesists, government agency personnel, and applicable technology reports

Interaction of marine geodesy, satellite technology and ocean physics

The possible applications of satellite technology in marine geodesy and geodetic related ocean physics were investigated. Four major problems were identified in the areas of geodesy and ocean physics: (1) geodetic positioning and control establishment; (2) sea surface topography and geoid determination; (3) geodetic applications to ocean physics; and (4) ground truth establishment. It was found that satellite technology can play a major role in their solution. For solution of the first problem, the use of satellite geodetic techniques, such as Doppler and C-band radar ranging, is demonstrated to fix the three-dimensional coordinates of marine geodetic control if multi-satellite passes are used. The second problem is shown to require the use of satellite altimetry, along with accurate knowledge of ocean-dynamics parameters such as sea state, ocean tides, and mean sea level. The use of both conventional and advanced satellite techniques appeared to be necessary to solve the third and fourth problems

Research program of the Geodynamics Branch

This report is the Fourth Annual Summary of the Research Program of the Geodynamics Branch. The branch is located within the Laboratory for Terrestrial Physics of the Space and Earth Sciences Directorate of the Goddard Space Flight Center. The research activities of the branch staff cover a broad spectrum of geoscience disciplines including: tectonophysics, space geodesy, geopotential field modeling, and dynamic oceanography. The NASA programs which are supported by the work described in this document include the Geodynamics and Ocean Programs, the Crustal Dynamics Project and the proposed Ocean Topography Experiment (TOPEX). The reports highlight the investigations conducted by the Geodynamics Branch staff during calendar year 1985. The individual papers are grouped into chapters on Crustal Movements and Solid Earth Dynamics, Gravity Field Modeling and Sensing Techniques, and Sea Surface Topography. Further information on the activities of the branch or the particular research efforts described herein can be obtained through the branch office or from individual staff members

The future of spaceborne altimetry. Oceans and climate change: A long-term strategy

The ocean circulation and polar ice sheet volumes provide important memory and control functions in the global climate. Their long term variations are unknown and need to be understood before meaningful appraisals of climate change can be made. Satellite altimetry is the only method for providing global information on the ocean circulation and ice sheet volume. A robust altimeter measurement program is planned which will initiate global observations of the ocean circulation and polar ice sheets. In order to provide useful data about the climate, these measurements must be continued with unbroken coverage into the next century. Herein, past results of the role of the ocean in the climate system is summarized, near term goals are outlined, and requirements and options are presented for future altimeter missions. There are three basic scientific objectives for the program: ocean circulation; polar ice sheets; and mean sea level change. The greatest scientific benefit will be achieved with a series of dedicated high precision altimeter spacecraft, for which the choice of orbit parameters and system accuracy are unencumbered by requirements of companion instruments

Analysis of Satellite-to-Satellite Tracking (SST) and altimetry data from GEOS-C

Radar altimetry and satellite-to-satellite (SST) range and range rate tracking measurements were used to infer the exterior gravitational field of the earth and the structure of the geoid from GEOS-C metric data. Under the SST analysis, a direct point-by-point estimate of gravity disturbance by means of a recursive filter with backward smoothing was attempted but had to be forsaken because of poor convergence. The adopted representation consists of a more or less uniform grid of discrete masses at a depth of approximately 400 km from the earth's surface. The layer is superimposed on a spherical harmonics model. The procedure for smoothing the altimetry and inferring the fine-structured gravity field over the Atlantic test area is described. The local disturbances are represented by means of a density layer. The altimeter height biases were first estimated by a least squares adjustment at orbital crossover points. After taking out the bias, long wavelength contributions from GEM-6 as well as a calibration correction were subtracted. The residual heights were then represented by a mass distribution beneath the earth's surface

Remote sensing for oceanography: Past, present, future

Oceanic dynamics was traditionally investigated by sampling from instruments in situ, yielding quantitative measurements that are intermittent in both space and time; the ocean is undersampled. The need to obtain proper sampling of the averaged quantities treated in analytical and numerical models is at present the most significant limitation on advances in physical oceanography. Within the past decade, many electromagnetic techniques for the study of the Earth and planets were applied to the study of the ocean. Now satellites promise nearly total coverage of the world's oceans using only a few days to a few weeks of observations. Both a review of the early and present techniques applied to satellite oceanography and a description of some future systems to be launched into orbit during the remainder of this century are presented. Both scientific and technologic capabilities are discussed

Shape of the ocean surface and implications for the Earth's interior: GEOS-3 results

A new set of 1 deg x 1 deg mean free air anomalies was used to construct a gravimetric geoid by Stokes' formula for the Indian Ocean. Utilizing such 1 deg x 1 deg geoid comparisons were made with GEOS-3 radar altimeter estimates of geoid height. Most commonly there were constant offsets and long wavelength discrepancies between the two data sets; there were many probable causes including radial orbit error, scale errors in the geoid, or bias errors in altitude determination. Across the Aleutian Trench the 1 deg x 1 deg gravimetric geoids did not measure the entire depth of the geoid anomaly due to averaging over 1 deg squares and subsequent aliasing of the data. After adjustment of GEOS-3 data to eliminate long wavelength discrepancies, agreement between the altimeter geoid and gravimetric geoid was between 1.7 and 2.7 meters in rms errors. For purposes of geological interpretation, techniques were developed to directly compute the geoid anomaly over models of density within the Earth. In observing the results from satellite altimetry it was possible to identify geoid anomalies over different geologic features in the ocean. Examples and significant results are reported

Altimetric system: Earth observing system. Volume 2h: Panel report

A rationale and recommendations for planning, implementing, and operating an altimetric system aboard the Earth observing system (Eos) spacecraft is provided. In keeping with the recommendations of the Eos Science and Mission Requirements Working Group, a complete altimetric system is defined that is capable of perpetuating the data set to be derived from TOPEX/Poseidon, enabling key scientific questions to be addressed. Since the scientific utility and technical maturity of spaceborne radar altimeters is well documented, the discussion is limited to highlighting those Eos-specific considerations that materially impact upon radar altimetric measurements

다중 인공위성 센서 및 기후 모델을 활용한 남극 얼음 질량 변화의 이해

학위논문(박사) -- 서울대학교대학원 : 사범대학 과학교육과(지구과학전공), 2021.8. 서기원.지난 수 십 년 간, 남극의 얼음 질량 변화에 대한 우리의 지식은 인공위성 관측과 지구 물리 모델링 기술의 발전에 의해 비약적으로 향상되어 왔다. 인공위성 관측은 진행중인 남극 얼음 질량 손실과 가속화를 설명할 수 있는 메커니즘들을 지속적으로 제안하고 있으며, 이들을 고려한 모델링은 미래에 진행될 남극 빙하 손실을 정량적으로 산출하고 있다. 현재의 관측과 모델링 모두는 남극의 얼음 배출이 향후에 점차 가속화 될 것이라고 예측하고 있다. 이러한 증가율이 지속된다면, 남극은 가까운 미래에 해수면 상승을 유발시키는 첫번째 기여자가 될 것이다. 남극에서 배출될 빙하의 질량을 정확하게 예측하기 위해서는 진행중인 얼음 질량 손실에 대한 지속적인 관찰과 함께, 그것의 원인 기작을 규명하는 일이 요구된다. 남극의 얼음 질량 변화는 각 빙하마다 비균질하게 발생하고 있으며, 개별 빙하의 동력학은 대기와 해양 순환, 그리고 고체 지구의 변동성 등 다양한 지구 시스템 구성 요소들의 영향을 받고 있다. 각 요소들이 얼음 질량 변화에 미치는 물리적 기작을 보다 정확히 이해하고, 미래 질량 변화 예측의 불확실성을 해소하기 위해서는 이들을 총 망라하는 다학제간 연구가 필요하다. 이러한 흐름의 일환으로, 본 학위 논문에서는 기후 모델들과 원격 탐사 데이터를 활용하여 남극의 얼음 질량 변화를 분석한 세 개의 연구들이 수행되었다. 첫번째 연구는 얼음 질량 변화와 강설량의 관계를 조사한 것으로, 지구 시스템 내의 기권과 빙권 간의 상호작용에 대해 다루고 있다. 조사 결과, 최근 수 십 년 간 발생한 남극의 강설은 얼음 질량 변화의 경년 변동성의 대부분을 설명하고 있었으며, 동 시기 진행된 남극 얼음 질량 손실의 가속화의 약 30%가 강설량 변화의 기여임을 발견하였다. 또한 추가적인 통계분석을 통해, 이러한 강설량 변화가 남반구 극진동 (Southern Annular Mode, SAM) 이라고 불리우는 남반구 고위도의 주기적 기후변화와 밀접한 관련이 있음도 발견하였다. 두 번째 연구에서는 남극 얼음 질량 변화 관측의 해상도를 높이고자 하였다. 이는 빙하 동력학 모델들의 초기 조건을 단일 빙하와 같은 작은 규모에서 효과적으로 제약하기 위한 목적이다. 해상도 증가를 위해, 인공위성 중력계와 고도계 관측 데이터를 융합하는 새로운 선형 역산법을 개발하였다. 역산법의 적용 결과, 남극 대륙 전체의 얼음 질량 변화 (2003-2016) 를 약 27km의 높은 공간 해상도와 함께 한 달의 짧은 샘플링 간격으로 확인할 수 있는 데이터를 산출하였다. 이 연구에서 만든 데이터는 인공위성 중력계나 고도계를 독립적으로 활용하는 것에 비해 더 높은 정확도를 가질 것이라 추측된다. 예를 들어, 새로운 데이터를 활용하여 계산한 남극의 빙하 별 질량 변화는 각 센서를 따로 활용하는 것에 비해, Input-Output 방법이라는 독립적인 관측 결과와 더 높은 유사성을 보이고 있다. 세 번째 연구에서는 남극 빙하 하부의 고체 지구가 유발하는 후빙기 반동 (Glacial Isostatic Adjustment, GIA) 효과를 추정하고자 하였다. 이는 현재의 기술로 관측이 불가능한 GIA 효과가 얼음 질량 관측에 미치는 불확실성를 경감시키기 위한 목적으로 수행되었다. GIA효과를 분리시키기 위해, 앞서 수행한 고해상도 질량 추산 데이터와 다수의 기후모델을 서로 비교하였다. 그 결과, 서남극 로스 빙붕 근처에 위치한 캠 빙류 (Kamb Ice Stream) 하부의 GIA 효과가 효과적으로 분리될 수 있었다. 계산 값을 선행 연구에서 개발된 후빙기 반동 모델들과 비교한 결과, 대부분의 모델들이 캠 빙류의 후빙기 반동을 과대추정하고 있음도 발견하였다. 현존하는 다수의 GIA 모델들에서 캠 빙류 하부의 후빙기 반동 효과가 남극에서 가장 높게 모의되고 있다는 사실을 감안할 때, 이 발견은 모델들의 불확실성을 재고한다는 점에서 남극 얼음 질량 변화에 대한 기존 관측 결과에 시사하는 바가 크다. 세 연구의 결과를 종합한 남극 빙하 배출량 추정과 그에 따른 해수면 상승 예측이 논문의 마지막 장에 제시되어 있다. 이 결과는 대기와 고체 지구의 변동성을 고려함과 동시에, 개별 빙하의 해수면 상승 기여도를 예측하였다는 점에서 이전의 연구들과 차별된다.Over the past few decades, understanding of ice mass changes in Antarctica has been greatly improved by advances in satellite observation and geophysical modeling techniques. Satellite observations have clearly shown evidence of ongoing Antarctic ice mass loss, and numerical models have quantitatively estimated future ice mass loss. Both observation and modeling have found that Antarctic ice mass loss is accelerating and this would continue in the future. Within this century, Antarctica is expected to be the most important contributor to sea-level rise. To accurately predict Antarctic ice mass loss, continuous Antarctic observation is required, and the cause of Antarctic ice mass loss should be understood. Ice mass variations over Antarctic glaciers are determined by many factors, and their magnitudes differ significantly from glaciers to glaciers. Understanding ice mass variations at individual glaciers are important to project future Antarctic ice mass losses and subsequent sea level rise. Because glacier mass balances are affected by different physical mechanisms associated with atmospheric and oceanic circulations and solid earth deformation, multidisciplinary studies have been required for the accurate understanding of the interaction between Antarctic Ice Sheet (AIS) and the entire Earth system. In this dissertation, three studies are carried out using multiple climate models and remote sensing data to understand the current status of glacier mass balance in AIS. The first study examines the role of precipitation in AIS ice mass changes, identifying the interaction between atmosphere and cryosphere. It is found that the precipitation accounts for most of the inter-annual ice mass variability in recent decades and about 30% of the acceleration in contemporary ice mass loss can be explained by precipitation decrease. EOF analysis suggests that such precipitation variability is closely related to periodic climate change in the high altitude of the Southern Hemisphere, named Southern Annular Mode (SAM). After removing effects associated with precipitation decrease, Antarctic ice mass loss associated with glacier dynamics can be obtained. The second study is to develop a new method to improve the spatial resolution of the Antarctic ice mass change by combining two different satellite observations. Antarctic ice mass change in higher resolution can be estimated by a new linear inversion technique using satellite altimetry and gravimetry observations together. The new method provides monthly ice mass changes (2003-2016) for all Antarctic glaciers with a spatial resolution of 27 km. The high-resolution ice mass data agree better with the ice mass change from the Input-Output method than data conventionally obtained either from gravimetry or altimetry satellite. The third study estimates the Glacial Isostatic Adjustment (GIA) effect beneath the Antarctic glaciers. This aims to minimize the GIA error in ice mass observations. By comparing the high-resolution mass estimates with multiple climate models, the GIA effect beneath the Kamb Ice Stream (which is located near the Ross Ice Shelf in West Antarctica) is estimated. The estimated GIA effect is then compared with many GIA models. It is found that most of the GIA models overestimate the GIA effect at the Kamb Ice Stream. Given that a number of models simulate the highest GIA rate beneath the Kamb Ice Stream within Antarctic glaciers, this finding has significant implications to improve the accuracy of Antarctic ice mass change by reducing the GIA uncertainty. Lastly, we aggregate the results of the three studies to project the future mass loss of Antarctic glaciers. This result is distinct from previous studies in that it provides glacial-scale projections of ice mass changes based on ice dynamic effects after removing effects of precipitation and solid earth deformation from glacial-scale ice mass observations.Chapter 1. Introduction 1 Chapter 2. Backgrounds 5 2.1 Satellite gravimetry 5 2.1.1 Overview & Principle 5 2.1.2 Estimation of surface mass densities from GRACE gravity data 6 2.1.3 Spatial filtering 8 2.2 Satellite altimetry 11 2.2.1 Overview & Principle 11 2.2.2 Laser & radar altimetry 12 2.2.3 Data types 13 2.3 Least squares inversion 14 2.3.1 Simple least squares for linear inverse problem 14 2.3.2 Application of least square inversion to GRACE data 16 Chapter 3. Surface mass balance contributions to Antarctic ice mass change investigated by climate models and GRACE gravity data 19 3.1 Introduction 19 3.2 Data & Methods 20 3.2.1 Precipitation models 20 3.2.2 EOF analysis of SMB 21 3.2.3 REOF analysis of SMB 21 3.3 AIS SMB from 1979 to 2017 23 3.4 Observation of AIS SMB 29 3.5 Implications of SMB to present-day ice mass loss in AIS 34 3.6 Conclusion 35 Chapter 4. Estimation of high-resolution Antarctic ice mass balance using satellite gravimetry and altimetry 38 4.1 Introduction 38 4.2 Data 39 4.2.1 GRACE gravity data 39 4.2.2 Satellite altimetry data 40 4.3 Methods 43 4.3.1 Forward Modeling (FM) solution 43 4.3.2 Joint estimation using constrained linear deconvolution 46 4.3.3 Uncertainties 50 4.3.3.1 Uncertainty of GRACE observation 52 4.3.3.2 Uncertainty of FM solution 52 4.3.3.3 Uncertainty of altimetry-based mass loads 54 4.3.3.4 Uncertainty of CLD solution 57 4.4 High resolution Antarctic ice mass loads 59 4.5 AIS glacier mass balance 62 4.6 Conclusion 66 Chapter 5. Estimation of GIA effect beneath the Antarctic Glacier using multiple remote sensing and climate models 68 5.1 Introduction 68 5.2 Data & Method 69 5.2.1 Method 69 5.2.2 Basin boundary 71 5.2.3 SMB models 73 5.2.4 Mass densities from GRACE data 73 5.2.5 Mass densities from satellite altimetry data 74 5.2.6 High-resolution GRACE data and its sensitivity to GIA estimates 75 5.3 Result & Discussion 77 5.3.1 Estimated mass rates 77 5.3.2 GIA mass rate beneath the KIS 80 5.4 Conclusion 81 Chapter 6. Sea-level projections 82 Chapter 7. Conclusion 86 Appendix: Glacial mass variability calculated by satellite gravimetry, altimetry, and their joint estimation 89 References 112 Abstract in Korean 122박

Development of a real time bistatic radar receiver using signals of opportunity

Passive bistatic radar remote sensing offers a novel method of monitoring the Earth\u27s surface by observing reflected signals of opportunity. The Global Positioning System (GPS) has been used as a source of signals for these observations and the scattering properties of GPS signals from rough surfaces are well understood. Recent work has extended GPS signal reflection observations and scattering models to include communications signals such as XM radio signals. However the communication signal reflectometry experiments to date have relied on collecting raw, high data-rate signals which are then post-processed after the end of the experiment. This thesis describes the development of a communication signal bistatic radar receiver which computes a real time correlation waveform, which can be used to retrieve measurements of the Earth\u27s surface. The real time bistatic receiver greatly reduces the quantity of data that must be stored to perform the remote sensing measurements, as well as offering immediate feedback. This expands the applications for the receiver to include space and bandwidth limited platforms such as aircraft and satellites. It also makes possible the adjustment of flight plans to the observed conditions. This real time receiver required the development of an FGPA based signal processor, along with the integration of commercial Satellite Digital Audio Radio System (SDARS) components. The resulting device was tested both in a lab environment as well on NOAA WP-3D and NASA WB-57 aircraft