1,315 research outputs found

    Precision Column CO2 Measurement from Space Using Broad Band LIDAR

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    In order to better understand the budget of carbon dioxide in the Earth's atmosphere it is necessary to develop a global high precision understanding of the carbon dioxide column. To uncover the missing sink" that is responsible for the large discrepancies in the budget as we presently understand it, calculation has indicated that measurement accuracy of 1 ppm is necessary. Because typical column average CO2 has now reached 380 ppm this represents a precision on the order of 0.25% for these column measurements. No species has ever been measured from space at such a precision. In recognition of the importance of understanding the CO2 budget to evaluate its impact on global warming the National Research Council in its decadal survey report to NASA recommended planning for a laser based total CO2 mapping mission in the near future. The extreme measurement accuracy requirements on this mission places very strong constraints on the laser system used for the measurement. This work presents an overview of the characteristics necessary in a laser system used to make this measurement. Consideration is given to the temperature dependence, pressure broadening, and pressure shift of the CO2 lines themselves and how these impact the laser system characteristics. We are examining the possibility of making precise measurements of atmospheric carbon dioxide using a broad band source of radiation. This means that many of the difficulties in wavelength control can be treated in the detector portion of the system rather than the laser source. It also greatly reduces the number of individual lasers required to make a measurement. Simplifications such as these are extremely desirable for systems designed to operate from space

    Spacelab 3 Mission Science Review

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    Papers and abstracts of the presentations made at the symposium are given as the scientific report for the Spacelab 3 mission. Spacelab 3, the second flight of the National Aeronautics and Space Administration's (NASA) orbital laboratory, signified a new era of research in space. The primary objective of the mission was to conduct applications, science, and technology experiments requiring the low-gravity environment of Earth orbit and stable vehicle attitude over an extended period (e.g., 6 days) with emphasis on materials processing. The mission was launched on April 29, 1985, aboard the Space Shuttle Challenger which landed a week later on May 6. The multidisciplinary payload included 15 investigations in five scientific fields: material science, fluid dynamics, life sciences, astrophysics, and atmospheric science

    The bridge volcanic LIdar-BILLI: A review of data collection and processing techniques in the Italian most hazardous volcanic areas

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    Volcanologists have demonstrated that carbon dioxide (CO2) fluxes are precursors of volcanic eruptions. Controlling volcanic gases and, in particular, the CO2 flux, is technically challenging, but we can retrieve useful information from magmatic/geological process studies for the mitigation of volcanic hazards including air traffic security. Existing techniques used to probe volcanic gas fluxes have severe limitations such as the requirement of near-vent in situ measurements, which is unsafe for operators and deleterious for equipment. In order to overcome these limitations, a novel range-resolved DIAL-Lidar (Differential Absorption Light Detection and Ranging) has been developed as part of the ERC (European Research Council) Project "BRIDGE", for sensitive, remote, and safe real-time CO2 observations. Here, we report on data collection, processing techniques, and the most significant findings of the experimental campaigns carried out at the most hazardous volcanic areas in Italy: Pozzuoli Solfatara (Phlegraen Fields), Stromboli, and Mt. Etna. The BrIdge voLcanic LIdar-BILLI has successfully obtained accurate measurements of in-plume CO2 concentration and flux. In addition, wind velocity has also been retrieved. It has been shown that the measurements of CO2 concentration performed by BILLI are comparable to those carried out by volcanologists with other standard techniques, heralding a new era in the observation of long-term volcanic gases

    Interpreting contemporary trends in atmospheric methane

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    Atmospheric methane plays a major role in controlling climate, yet contemporary methane trends (1982–2017) have defied explanation with numerous, often conflicting, hypotheses proposed in the literature. Specifically, atmospheric observations of methane from 1982 to 2017 have exhibited periods of both increasing concentrations (from 1982 to 2000 and from 2007 to 2017) and stabilization (from 2000 to 2007). Explanations for the increases and stabilization have invoked changes in tropical wetlands, livestock, fossil fuels, biomass burning, and the methane sink. Contradictions in these hypotheses arise because our current observational network cannot unambiguously link recent methane variations to specific sources. This raises some fundamental questions: (i) What do we know about sources, sinks, and underlying processes driving observed trends in atmospheric methane? (ii) How will global methane respond to changes in anthropogenic emissions? And (iii), What future observations could help resolve changes in the methane budget? To address these questions, we discuss potential drivers of atmospheric methane abundances over the last four decades in light of various observational constraints as well as process-based knowledge. While uncertainties in the methane budget exist, they should not detract from the potential of methane emissions mitigation strategies. We show that net-zero cost emission reductions can lead to a declining atmospheric burden, but can take three decades to stabilize. Moving forward, we make recommendations for observations to better constrain contemporary trends in atmospheric methane and to provide mitigation support

    Scientific and technical challenges in remote sensing of plant canopy reflectance and fluorescence

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    State-of-the-art optical remote sensing of vegetation canopies is reviewed here to stimulate support from laboratory and field plant research. This overview of recent satellite spectral sensors and the methods used to retrieve remotely quantitative biophysical and biochemical characteristics of vegetation canopies shows that there have been substantial advances in optical remote sensing over the past few decades. Nevertheless, adaptation and transfer of currently available fluorometric methods aboard air- and space-borne platforms can help to eliminate errors and uncertainties in recent remote sensing data interpretation. With this perspective, red and blue-green fluorescence emission as measured in the laboratory and field is reviewed. Remotely sensed plant fluorescence signals have the potential to facilitate a better understanding of vegetation photosynthetic dynamics and primary production on a large scale. The review summarizes several scientific challenges that still need to be resolved to achieve operational fluorescence based remote sensing approache

    Remote Measurements of Volcanic Gases Using Thermal Infrared Hyperspectral Imaging.

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    Ph.D. Thesis. University of Hawaiʻi at Mānoa 2018

    The Main Belt Comets and ice in the Solar System

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    We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies
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