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At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

From remotely sensed solar-induced chlorophyll fluorescence to ecosystem structure, function, and service: Part I—Harnessing theory

Solar-induced chlorophyll fluorescence (SIF) is a remotely sensed optical signal emitted during the light reactions of photosynthesis. The past two decades have witnessed an explosion in availability of SIF data at increasingly higher spatial and temporal resolutions, sparking applications in diverse research sectors (e.g., ecology, agriculture, hydrology, climate, and socioeconomics). These applications must deal with complexities caused by tremendous variations in scale and the impacts of interacting and superimposing plant physiology and three-dimensional vegetation structure on the emission and scattering of SIF. At present, these complexities have not been overcome. To advance future research, the two companion reviews aim to (1) develop an analytical framework for inferring terrestrial vegetation structures and function that are tied to SIF emission, (2) synthesize progress and identify challenges in SIF research via the lens of multi-sector applications, and (3) map out actionable solutions to tackle these challenges and offer our vision for research priorities over the next 5-10 years based on the proposed analytical framework. This paper is the first of the two companion reviews, and theory oriented. It introduces a theoretically rigorous yet practically applicable analytical framework. Guided by this framework, we offer theoretical perspectives on three overarching questions: (1) The forward (mechanism) question—How are the dynamics of SIF affected by terrestrial ecosystem structure and function? (2) The inference question: What aspects of terrestrial ecosystem structure, function, and service can be reliably inferred from remotely sensed SIF and how? (3) The innovation question: What innovations are needed to realize the full potential of SIF remote sensing for real-world applications under climate change? In conclusion, the analytical framework elucidates that process complexity must be appreciated in inferring ecosystem structure and function from the observed SIF; this framework can serve as a diagnosis and inference tool for versatile applications across diverse spatial and temporal scales.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2011

Estar to SMOS: Development of Interferometric Radiometry for Remote Sensing from Space

ESTAR is an L-band radiometer that employs synthesis (interferometry) to obtain resolution in the across track dimension. It was designed as an aircraft prototype to demonstrate the technology of aperture synthesis for remote sensing of the earth from space. ESTAR was successful in several soil moisture and ocean salinity remote sensing experiments and demonstrated the potential of aperture synthesis for remote sensing. Among the lessons learned during the development of ESTAR are the scene dependence of calibration, that RFI is a problem, and the robustness of noise injection for the zero spacing radiometer. ESTAR was the first step in a path toward realizing aperture synthesis technology in space (e.g. SMOS). ESTAR was followed by a new instrument, 2D-STAR, which employs synthesis in both dimensions. 2D-STAR was tested in 2002 and participated in the SMEX field campaigns in 2003 and 2004.

LeVine, David M.↗
NASA NTRS2016

Validation of Ocean Color Remote Sensing Reflectance Using Autonomous Floats

The use of autonomous proling oats for observational estimates of radiometric quantities in the ocean is explored, and the use of this platform for validation of satellite-based estimates of remote sensing reectance in the ocean is examined. This effort includes comparing quantities estimated from oat and satellite data at nominal wavelengths of 412, 443, 488, and 555 nm, and examining sources and magnitudes of uncertainty in the oat estimates. This study had 65 occurrences of coincident high-quality observations from oats and MODIS Aqua and 15 occurrences of coincident high-quality observations oats and Visible Infrared Imaging Radi-ometer Suite (VIIRS). The oat estimates of remote sensing reectance are similar to the satellite estimates, with disagreement of a few percent in most wavelengths. The variability of the oatsatellite comparisons is similar to the variability of in situsatellite comparisons using a validation dataset from the Marine Optical Buoy (MOBY). This, combined with the agreement of oat-based and satellite-based quantities, suggests that oats are likely a good platform for validation of satellite-based estimates of remote sensing reectance.

In Situ Oceanic Observations↗
DOE OSTI2023

Seeing the Disturbed Forest for the Trees: Remote Sensing Is Underutilized to Quantify Critical Zone Response to Unprecedented Disturbance

Understanding the severity and extent of near surface critical zone (CZ) disturbances and their ecosystem response is a pressing concern in the face of increasing human and natural disturbances. Predicting disturbance severity and recovery in a changing climate requires comprehensive understanding of ecosystem feedbacks among vegetation and the surrounding environment, including climate, hydrology, geomorphology, and biogeochemistry. Field surveys and satellite remote sensing have limited ability to effectively capture the spatial and temporal variability of disturbance and CZ properties. Technological advances in remote sensing using new sensors and new platforms have improved observations of changes in vegetation canopy structure and productivity; however, integrating measures of forest disturbance from various sensing platforms is complex. By connecting the potential for remote sensing technologies to observe different CZ disturbance vectors, we show that lower severity disturbance and slower vegetation recovery are more difficult to quantify. Case studies in montane forests from the western United States highlight new opportunities, including evaluating post-disturbance forest recovery at multiple scales, shedding light on understory vegetation regrowth, detecting specific physiological responses, and refining ecohydrological modeling. Learning from regional CZ disturbance case studies, we propose future directions to synthesize fragmented findings with (a) new data analysis using new or existing sensors, (b) data fusion across multiple sensors and platforms, (c) increasing the value of ground-based observations, (d) disturbance modeling, and (e) synthesis to improve understanding of disturbance.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2020

The Spectrum Outlook for Earth Remote Sensing Post WRC-19

Every three to four years the International Telecommunication Union (ITU), a specialized agency of the United Nations, holds a treaty level meeting known as the World Radiocommunication Conference (WRC) to set international regulations on the use of the radio frequency spectrum. These regulations include protections for critical remote sensing bands. This paper presents the background information on, and the outcomes of, WRC-19. It also provides an examination of the potential regulatory actions that could impact the remote sensing community at the next WRC slated to be held in 2023. Lastly, the paper discusses the need for coordinated, intercalibrated interference monitoring and reporting within the remote sensing community.

radio frequency interference↗
NASA NTRS1971

A survey of multispectral remote sensing techniques for earth resources applications.

Remote sensing for earth resources applications has as its objective the collection and interpretation of information on all environmentally significant features of the atmosphere, oceans, and land surfaces. This information is most effectively gathered by airborne and satellite borne imaging systems. These systems operate at a variety of wavelengths extending from the visual spectrum, through the infrared and into the centimeter wavelengths of the microwave band. A comparison is made of the signal characteristics at these spectrum regions. In particular, the ability of microwave radiometric imaging to augment visual and infrared imaging is discussed. Recent developments in electronically scanned microwave radiometric sensors are described, together with methods of optimizing microwave data display. Results achieved with integrated display systems for both microwave and optical data are presented, together with projections for future applications.-

Pascalar, H. G.↗
NASA NTRS1973

Application of remote sensing in forestry

The use of remote sensing techniques in forestry studies is investigated. In particular, inventory, monitoring, detection, and management are discussed. Data show that infrared imagery appears to be the best technique for forestry studies. Data also show that color photographs are more easily interpreted than black and white ones.

Lauer, D. T.↗
NASA NTRS1975

Microwave remote sensing of soil water content

Microwave remote sensing of soils to determine water content was considered. A layered water balance model was developed for determining soil water content in the upper zone (top 30 cm), while soil moisture at greater depths and near the surface during the diurnal cycle was studied using experimental measurements. Soil temperature was investigated by means of a simulation model. Based on both models, moisture and temperature profiles of a hypothetical soil were generated and used to compute microwave soil parameters for a clear summer day. The results suggest that, (1) soil moisture in the upper zone can be predicted on a daily basis for 1 cm depth increments, (2) soil temperature presents no problem if surface temperature can be measured with infrared radiometers, and (3) the microwave response of a bare soil is determined primarily by the moisture at and near the surface. An algorithm is proposed for monitoring large areas which combines the water balance and microwave methods.

Cihlar, J.↗
NASA NTRS1976

Remote sensing for control of tsetse flies

Remotely sensed information is discussed which has potential for aiding in the control or eradication of tsetse flies. Data are available from earth resources meteorological, and manned satellites, from airborne sensors, and possibly from data collection platforms. A new zone discrimination technique, based on data from meteorological satellites may also allow the identification of zones hospitable to one or another species of tsetse. For background, a review is presented of the vegetation of Tanzania and Zanzibar, and illustrations presented of automatic processing of data from these areas. In addition, a review is presented of the applicability of temperature data to tsetse areas.

Giddings, L. E.↗
NASA NTRS1977

Application of remote sensing for planning purposes

Types of remotely sensed data are many and varied but, all are primarily dependent on the sensor platform and the kind of sensing system used. A sensor platform is the type of aircraft or satellite to which a sensing system is attached; each platform has its own inherent advantages and disadvantages. Selected attributes of several current or recently used platforms are outlined. Though sensing systems are highly varied, they may be divided into various operational categories such as cameras, electromechanical scanners, and radars.

Hughes, T. H.↗
NASA NTRS1979

Possible methods for distinguishing icebergs from ships by aerial remote sensing

The simplest methods for aerial remote sensing which are least affected by atmospheric opacities are summarized. Radar is preferred for targets off the flight path, and microwave radiometry for targets along the flight path. Radar methods are classified by ability to resolve targets. Techniques which do not require target resolution are preferred. Among these techniques, polarization methods appear most promising, specifically those which differentiate the expected relatively greater depolarization by icebergs from that by ships or which detect doubly-reversed circular polarization.

Howes, W. L.↗
NASA NTRS1981

NASA remote sensing programs: Overview

In the Earth remote sensing area, NASA's three functions are to understand the basic mechanics and behavior of the Earth, evaluate what resources are available (in the way of minerals, and hydrocarbons on a general scale), and to arrange a scheme for managing our national assets. The capabilities offered by LANDSAT D and technology improvements needed are discussed. The French SPOT system, its orbits, possibilities for stereo imagery, and levels of preprocessing and processing with several degrees of radiometric and geometric corrections are examined. Progress in the AgRISTARS project is mentioned as well as future R & D programs in the use of fluorescence, microwave measurements, and synthetic aperture radar. Other areas of endeaver include studying man environment interactions and Earth radiation budgets, and the establishment of data systems programs.

Raney, W. P.↗
NASA NTRS1981

USDA/federal user of LANDSAT remote sensing

Developed and potential uses of remote sensing in crop condition and acreage assessment, renewable resources inventories, conservation practices, and water and forest management applications are described. Operational approaches, the adaptation of procedures to needs, and the agency's concern about data continuity and cost are discussed as well as support for future technology development for enhanced sensing capability. The use of improved camera systems for soil mapping and conservation monitoring from space shuttle, and of aerospace radar to improve soil moisture monitoring are mentioned.

Allen, R.↗