Earth Survey Applications Division

Accomplishments of research and data analysis conducted to study physical parameters and processes inside the Earth and on the Earth's surface, to define techniques and systems for remotely sensing the processes and measuring the parameters of scientific and applications interest, and the transfer of promising operational applications techniques to the user community of Earth resources monitors, managers, and decision makers are described. Research areas covered include: geobotany, magnetic field modeling, crustal studies, crustal dynamics, sea surface topography, land resources, remote sensing of vegetation and soils, and hydrological sciences. Major accomplishments include: production of global maps of magnetic anomalies using Magsat data; computation of the global mean sea surface using GEOS-3 and Seasat altimetry data; delineation of the effects of topography on the interpretation of remotely-sensed data; application of snowmelt runoff models to water resources management; and mapping of snow depth over wheat growing areas using Nimbus microwave data

Design of pilot channel tracking loop Systems for high sensitivity Galileo receivers

Global Navigation Satellite Systems (GNSS) have been in the center stage of the recent technological upheaval that has been initiated by the rise of smartphones in the last decade. This is clearly reflected in the development of many applications based on GNSS technology as well as the emergence of multi-constellation GNSS with the launch of the first Galileo satellites at the end of the year 2011. GNSS does not only guarantee global positioning, navigation and timing services but also extends to applications in banking, agriculture, mapping, surveying, archaeology, seismology, commerce, ionosphere scintillation monitoring, remote sensing (soil moisture, ocean salinity, type of surface), wind speed monitoring, ocean surface monitoring, altimetry and many others. In the last decade, Location Based Services (LBS) have increased significant market demand where GNSS has been coupled with technologies based on terrestrial communication links in order to meet strict positioning accuracy requirements. In these conditions, relying on GNSS technology alone, raises a few challenges for signal synchronization even before positioning attempts and are mainly due to a considerable signal attenuation as it propagates through construction material and into indoor environments. Ionosphere scintillation induces a similar challenge where in addition to amplitude fading, the carrier phase and frequency suffer from indeterministic fluctuations. This research activity is devoted to explore and design the elements constituting pilot channel scalar tracking loop systems, specifically tailored to Galileo signals. It is expected that running such systems with extended integration intervals offers robust synchronization of the incoming signal which is heavily affected by external indeterministic fluctuations. In some conditions, it is desired to follow these fluctuations as in ionosphere scintillation monitoring while in other instances it is mainly desired to filter them out as noise to guarantee positioning capabilities. This is the objective of this research study which applies for both indoor environments and ionosphere scintillation affected signals. Towards this endeavor, a comprehensive theoretical study of the carrier and code tracking loops elements is undertaken, and particular attention is directed to the following aspects: • carrier frequency and phase discriminators and the relative optimum integration time • Galileo specific code discriminators and code tracking architecture especially tailored to Composite Binary Offset Carrier (CBOC) modulated signals. • optimum loop filters designed in the digital domain for different types of phase input signals • local signal generation using a numerically controlled oscillator and loop filter estimates • front-end filter bandlimiting effects on the tracking performance. This design is further tested with simulated Galileo signals with and without ionosphere scintillation as well as raw Galileo signals in an equatorial region during March 2013. Tracking performance comparison is carried out between the customized Galileo receiver developed in this research activity and an ionosphere scintillation dedicated professional GNSS receiver, the Septentrio PolaRxS PRO R receiver

Earth Resources: A continuing bibliography with indexes, Issue 4

This bibliography lists 651 reports, articles, and other documents introduced into the NASA scientific and technical information system between October 1974 and December 1974. Emphasis is placed on the use of remote sensing and geophysical instrumentation in spacecraft and aircraft to survey and inventory natural resources and urban areas. Subject matter is grouped according to agriculture and forestry, environmental changes and cultural resources, geodesy and cartography, geology and mineral resources, hydrology and water management, data processing and distribution systems, instrumentation and sensors, and economic analysis

Earth Resources: A continuing bibliography, with indexes, issue 31

This bibliography lists 505 reports, articles, and other documents introduced into the NASA scientific and technical information system. Emphasis is placed on the use of remote sensing and geophysical instrumentation in spacecraft and aircraft to survey and inventory natural resources and urban areas. Subject matter is grouped according to agriculture and forestry, environmental changes and cultural resources, geodesy and cartography, geology and mineral resources, hydrology and water management, data processing and distribution systems, instrumentation and sensors, and economic analysis

Research and Technology Objectives and Plans Summary (RTOPS)

This publication represents the NASA research and technology program for FY88. It is a compilation of the Summary portions of each of the RTOPs (Research and Technology Objectives and Plans) used for management review and control of research currently in progress throughout NASA. The RTOP Summary is designed to facilitate communication and coordination among concerned technical personnel in government, in industry, and in universities. The first section containing citations and abstracts of the RTOPs is followed by four indexes: Subject, Technical Monitor, Responsible NASA Organization, and RTOP Number

Advanced GNSS-R instruments for altimetric and scatterometric applications

This work is the result of more than eight years during a bachelor thesis, a master thesis, and the Ph.D. thesis dedicated to the development of the Microwave Interferometric Reflectometer (MIR) instrument. It summarizes all the knowledge acquired during this time, and describes the MIR instrument as detailed as possible. MIR is a Global Navigation Satellite System - Reflectometer (GNSS-R), that is, an instrument that uses Global Navigation Satellite System (GNSS) signals scattered on the Earth's surface to retrieve geophysical parameters. These signals are received below the noise level, but since they have been spread in the frequency domain using spread-spectrum techniques, and in particular using the so-called Pseudo Random Noise (PRN) codes, it is still possible to retrieve them because of the large correlation gain achieved. In GNSS-R, two main techniques are used for this purpose: the conventional technique cGNSS-R and the interferometric one iGNSS-R, each with its pros and cons. In the former technique, the reflected signal is cross-correlated against a locally generated clean-replica of the transmitted signal. In the latter technique the reflected signal is cross-correlated with the direct one. Nowadays multiple GNSS systems coexist, transmitting narrow and wide, open and private signals. A comparison between systems, signals, and techniques in fair conditions is necessary. The MIR instrument has been designed as an airborne instrument for that purpose: the instrument has two arrays, an up-looking one, and a down-looking one, each with 19 dual-band antennas in a hexagonal distribution. The instrument is able to form 2 beams at each frequency band (L1/E1, and L5/E5A), which are pointing continuously to the desired satellites taking into account their position, as well as the instrument's position and attitude. The data is sampled and stored for later post-processing. Last but not least, MIR is auto-calibrated using similar signals to the ones transmitted by the GNSS satellites. During the instrument development, the Distance Measurement Equipment/TACtical Air Navigation (DME/TACAN) signals from the Barcelona airport threatened to disrupt the interferometric technique. These signals were also studied, and it was concluded that the use of a mitigation systems were as strongly recommended. The interferometric technique was also affected by the unwanted contribution of other satellites. The impact of these contributions was studied using real data gathered during this Ph.D. thesis. During these 8 years, the instrument was designed, built, tested, and calibrated. A field campaign was carried out in Australia between May 2018 and June 2018 to determine the instrument's accuracy in sensing soil moisture and sea altimetry. This work describes each of these steps in detail and aims to be helpful for those who decide to continue the legacy of this instrument.Este trabajo es el resultado de más de 8 años de doctorado dedicados al desarrollo del instrumento Microwave Interferometric Reflectometer (MIR). Esta tesis resume todo el conocimiento adquirido durante este tiempo, y describe el MIR lo más detalladamente posible. El MIR es un Reflectómetro de señales de Sistemas Globales de Navegación por Satélite (GNSS-R), es decir, es un instrumento que usa señales de GNSS reflejadas en la superficie de la tierra para obtener parámetros geofísicos. Estas señales son recibidas bajo el nivel de ruido, pero dado que han sido ensanchadas en el dominio frecuencial usando técnicas de espectro ensanchado, y en particular usando códigos Pseudo Random Noise (PRN), es todavía posible recibirlas debido a la elevada ganancia de correlación. En GNSS-R existen dos técnicas para este propósito: la convencional (cGNSS-R), y la interferométrica (iGNSS-R), cada una con sus pros y sus contras. En la primera se calcula la correlación cruzada de la señal reflejada y de una réplica generada del código transmitido. En la segunda técnica se calcula la correlación cruzada de la señal reflejada y de la señal directa. Hoy en día muchos sistemas GNSS coexisten, transmitiendo señales de distintos anchos de banda, algunas públicas y otras privadas. Una comparación entre sistemas, señales, y técnicas en condiciones justas es necesaria. El MIR es un instrumento aerotransportado diseñado como para ese propósito: el instrumento tiene dos arrays de antenas, uno apuntando al cielo, y otro apuntando al suelo, cada uno con 19 antenas doble banda en una distribución hexagonal. El instrumento puede formar 2 haces en cada banda frecuencial (L1/E1 y L5/E5A) que apuntan continuamente a los satélites deseados teniendo en cuenta su posición, y la posición y actitud del instrumento. Los datos son guardados para ser procesados posteriormente. Por último pero no menos importante, el MIR se calibra usando señales similares a las transmitidas por los satélites de GNSS. Durante el desarrollo del instrumento, señales del sistema Distance Measuremt Equi Distance Measurement Equipment/TACtical Air Navigation (DME/TACAN) del aeropuerto de Barcelona mostraron ser una amenaza para la técnica interferométrica. Estas señales fueron estudiadas y se concluyó que era encarecidamente recomendado el uso de sistemas de mitigación de interferencias. La técnica interferométrica también se ve afectada por las contribuciones no deseadas de otros satélites, llamado cross-talk. El impacto del cross-talk fue estudiado usando datos reales tomados durante esta tesis doctoral. A lo largo de estos 8 años el instrumento ha sido diseñado, construido, testeado y calibrado. Una campaña de medidas fue llevada a cabo en Australia entre Mayo de 2018 y Junio de 2018 para determinar la capacidad del instrumento para estimar la humedad del terreno y la altura del mar. Este documento describe cada uno de estos pasos al detalle y espera resultar útil para aquellos que decidan continuar con el legado de este instrumento.Postprint (published version

SEASAT-A scientific contributions

SEASAT-A planned instrument complement and capabilities are reported together with an estimate of expected scientific contributions from satellite oceanic measurements

Geodetic Mass Balance of Svalbard glaciers : 1936 - 2004

Glaciers and ice masses are very important components of the earth system both in terms of global water storage and as climate indicators. The amount of water tied up in glaciers and ice caps is equivalent to about 69 meters of sea-level (Church and others, 2001). Recent predictions from global climate models indicate the arctic will experience enhanced changes as compared to the lower latitudes linked to the rise of greenhouse gases in the next 100 years (ACIA report, 2005). Svalbard glaciers and ice masses may therefore experience a rapid response to a change in climate (Hagen and others, 2003a). It is thus beneficial to document both present and the long term past glacier fluctuations to increase the comprehension of climatic changes. Svalbard is a high arctic archipelago, located in a climatically sensitive area at the northern extremity of the warm North Atlantic ocean current. Approximately 36000 km2 is covered by glaciers consisting of ice caps, tidewater, outlet, and smaller cirque and piedmont glaciers (Hagen and others, 1993). In this study, a 54 year geodetic balance of Svalbard glaciers is derived by comparing the oldest topographic map series of Svalbard (1936/38) to modern digital elevation models (DEM) from 1990. The errors of the older maps are assessed where precision is limited, but accuracy is sufficient for glacier studies. Elevation changes are analyzed for 7 regions in Svalbard (~5000 km2), where significant thinning was found at glacier fronts, and elevation increases in the upper parts of the accumulation areas. All regions experience volume losses and negative geodetic balances, although regional variability exists relating to both climate and topography. Many surges are apparent within the elevation change maps. Estimated volume change for the regions is -1.59±0.07 km3a-1 (ice eq.) for a geodetic annual balance of -0.30 m a-1 (w. eq.), and the glaciated area has decreased by 16% in the 54 year time interval. For recent balance estimations, differential GPS (2004) and laser altimetry (1996 & 2002) measurements are compared to the 1990 DEM over four glaciers in northwest Svalbard, and along two 60 km profiles in southern Svalbard. For both regions, the rate of frontal thinning has increased dramatically. The annual geodetic balances have become twice as negative for two smaller glaciers, Midtre and Austre Lovenbreen, while becoming more than three times more negative on the larger Kongsvegen. In southern Svalbard, while the glacier fronts are thinning faster in these recent measurements, complex dynamic behavior is occurring at higher altitudes, which complicate the elevation change signal. A number of dynamical events occurred in Wedel Jarlsberg Land between 1990 and 1996. The glaciers of Svalbard are losing ice volume at a faster rate more recently which can be attributed to a changing climate. The large scale synoptic patterns in atmospheric and oceanic circulation, and possibly temporal changes associate with them, is leading to increased thinning at the glacier fronts and slight increases at higher altitudes. Climate change is not only affecting glacier surface change in the form of temperature, but also in the form of precipitation. These changes progress through the glacier creating complicated dynamic patterns. Nonetheless, the present glacial-climate signal is that of increased volume loss

Research and Technology Objectives and Plans Summary (RTOPS)

This publication represents the NASA research and technology program for FY89. It is a compilation of the Summary portions of each of the RTOPs (Research and Technology Objectives and Plans) used for management review and control of research currently in progress throughout NASA. The RTOP Summary is designed to facilitate communication and coordination among concerned technical personnel in government, in industry, and in universities. The first section containing citations and abstracts of the RTOPs is followed by four indexes: Subject, Technical Monitor, Responsible NASA Organization, and RTOP Number

Earth Resources: A continuing bibliography with indexes, issue 2

Reports, articles, and other documents announced between April and June 1974 in Scientific and Technical Aerospace Reports (STAR), and International Aerospace Abstracts (IAA) are cited. Documents related to the identification and evaluation by means of sensors in spacecraft and aircraft of vegetation, minerals, and other natural resources, and the techniques and potentialities of surveying and keeping up-to-date inventories of such riches are included along with studies of such natural phenomena as earthquakes, volcanoes, ocean currents, and magnetic fields; and such cultural phenomena as cities, transportation networks, and irrigation systems. The components and use of remote sensing and geophysical instrumentation, their subsystems, observational procedures, signature and analyses and interpretive techniques for gathering data are, described. All reports generated under NASA's Earth Resources Survey Program for the time period covered are included