Variation of the Diameter of the Sun as Measured by the Solar Disk Sextant (SDS)

The balloon-borne Solar Disk Sextant (SDS) experiment has measured the angular size of the Sun on seven occasions spanning the years 1992 to 2011. The solar half-diameter -- observed in a 100-nm wide passband centred at 615 nm -- is found to vary over that period by up to 200 mas, while the typical estimated uncertainty of each measure is 20 mas. The diameter variation is not in phase with the solar activity cycle; thus, the measured diameter variation cannot be explained as an observational artefact of surface activity. Other possible instrument-related explanations for the observed variation are considered but found unlikely, leading us to conclude that the variation is real. The SDS is described here in detail, as is the complete analysis procedure necessary to calibrate the instrument and allow comparison of diameter measures across decades.Comment: 41 pages; appendix and 2 figures added plus some changes in text based on referee's comments; to appear in MNRA

STROZ Lidar Results at the MOHAVE III Campaign, October, 2009, Table Mountain, CA

During October, 2009 the GSFC STROZ Lidar participated in a campaign at the JPL Table Mountain Facility (Wrightwood, CA, 2285 m Elevation) to measure vertical profiles of water vapor from near the ground to the lower stratosphere. On eleven nights, water vapor, aerosol, temperature and ozone profiles were measured by the STROZ lidar, two other similar lidars, frost-point hygrometer sondes, and ground-based microwave instruments made measurements. Results from these measurements and an evaluation of the performance of the STROZ lidar during the campaign will be presented in this paper. The STROZ lidar was able to measure water vapor up to 13-14 km ASL during the campaign. We will present results from all the STROZ data products and comparisons with other instruments made. Implications for instrumental changes will be discussed

A New Differential Absorption Lidar to Measure Sub-Hourly Fluctuation of Tropospheric Ozone Profiles in the Baltimore - Washington D.C. Region

Tropospheric ozone profiles have been retrieved from the new ground based National Aeronautics and Space Administration (NASA) Goddard Space Flight Center TROPospheric OZone DIfferential Absorption Lidar (GSFC TROPOZ DIAL) in Greenbelt, MD (38.99 N, 76.84 W, 57 meters ASL) from 400 m to 12 km AGL. Current atmospheric satellite instruments cannot peer through the optically thick stratospheric ozone layer to remotely sense boundary layer tropospheric ozone. In order to monitor this lower ozone more effectively, the Tropospheric Ozone Lidar Network (TOLNet) has been developed, which currently consists of five stations across the US. The GSFC TROPOZ DIAL is based on the Differential Absorption Lidar (DIAL) technique, which currently detects two wavelengths, 289 and 299 nm. Ozone is absorbed more strongly at 289 nm than at 299 nm. The DIAL technique exploits this difference between the returned backscatter signals to obtain the ozone number density as a function of altitude. The transmitted wavelengths are generated by focusing the output of a quadrupled Nd:YAG laser beam (266 nm) into a pair of Raman cells, filled with high pressure hydrogen and deuterium. Stimulated Raman Scattering (SRS) within the focus generates a significant fraction of the pump energy at the first Stokes shift. With the knowledge of the ozone absorption coefficient at these two wavelengths, the range resolved number density can be derived. An interesting atmospheric case study involving the Stratospheric-Tropospheric Exchange (STE) of ozone is shown to emphasize the regional importance of this instrument as well as assessing the validation and calibration of data. The retrieval yields an uncertainty of 16-19 percent from 0-1.5 km, 10-18 percent from 1.5-3 km, and 11-25 percent from 3 km to 12 km. There are currently surface ozone measurements hourly and ozonesonde launches occasionally, but this system will be the first to make routine tropospheric ozone profile measurements in the Baltimore-Washington DC area

Deployable-erectable trade study for space station truss structures

The results of a trade study on truss structures for constructing the space station are presented. Although this study was conducted for the reference gravity gradient space station, the results are generally applicable to other configurations. The four truss approaches for constructing the space station considered in this paper were the 9 foot single fold deployable, the 15 foot erectable, the 10 foot double fold tetrahedral, and the 15 foot PACTRUSS. The primary rational for considering a 9 foot single-fold deployable truss (9 foot is the largest uncollapsed cross-section that will fit in the Shuttle cargo bay) is that of ease of initial on-orbit construction and preintegration of utility lines and subsystems. The primary rational for considering the 15 foot erectable truss is that the truss bay size will accommodate Shuttle size payloads and growth of the initial station in any dimension is a simple extension of the initial construction process. The primary rational for considering the double-fold 10 foot tetrahedral truss is that a relatively large amount of truss structure can be deployed from a single Shuttle flight to provide a large number of nodal attachments which present a pegboard for attaching a wide variety of payloads. The 15 foot double-fold PACTRUSS was developed to incorporate the best features of the erectable truss and the tetrahedral truss

Equivalent Fixed-Points in the Effective Average Action Formalism

Starting from a modified version of Polchinski's equation, Morris' fixed-point equation for the effective average action is derived. Since an expression for the line of equivalent fixed-points associated with every critical fixed-point is known in the former case, this link allows us to find, for the first time, the analogous expression in the latter case.Comment: 30 pages; v2: 29 pages - major improvements to section 3; v3: published in J. Phys. A - minor change

The influence of the physical environment on self-recovery after disasters in Nepal and the Philippines

Following a disaster, the majority of families rebuild their homes themselves. In this paper, we consider how the physical environment influences such ‘self-recovery’ by investigating disasters in the Philippines (typhoons Haiyan in 2013 and Haima in 2016) and Nepal (the Gorkha earthquake - 2015). Despite the many differences in the disaster contexts, there are some common barriers to self-recovery (and building back better) in a substantially changed and dynamic multi-hazard, post-disaster environment. These are related to changes in water supply (shortage or surplus), impacts of post-disaster geohazard events on infrastructure (particularly affecting transport) and the availability of technical advice. People face a broad spectrum of challenges as they recover and tackling these ‘geo-barriers’ may help to create a more enabling environment for self-recovery. The findings point to what needs to be in place to support self-recovery in dynamic physical environments, including geoscience information and advice, and restoration of infrastructure damaged by natural hazard events. Further research is necessary to understand the issues this raises for the shelter and geoscience communities, particularly around availability of geoscience expertise, capacity and information at a local scale.<br/

Self-recovery from disasters: an interdisciplinary perspective

This working paper presents the findings from a pilot research project that investigated how disaster-affected households in low- and middle-income countries rebuild their homes in situations where little or no support is available from humanitarian agencies. The project was an interdisciplinary collaboration involving social scientists, geoscientists, structural engineers and humanitarian practitioners. The work was broad in scope. It investigated households’ self-recovery trajectories and the wide range of technical, environmental, institutional and socioeconomic factors influencing them over time. It also considered how safer construction practices can be more effectively integrated into humanitarian shelter responses

The influence of the physical environment on self-recovery after disasters in Nepal and the Philippines

Following a disaster, the majority of families rebuild their homes themselves. In this paper, we consider how the physical environment influences such ‘self-recovery’ by investigating disasters in the Philippines (typhoons Haiyan in 2013 and Haima in 2016) and Nepal (the Gorkha earthquake - 2015). Despite the many differences in the disaster contexts, there are some common barriers to self-recovery (and building back better) in a substantially changed and dynamic multi-hazard, post-disaster environment. These are related to changes in water supply (shortage or surplus), impacts of post-disaster geohazard events on infrastructure (particularly affecting transport) and the availability of technical advice. People face a broad spectrum of challenges as they recover and tackling these ‘geo-barriers’ may help to create a more enabling environment for self-recovery. The findings point to what needs to be in place to support self-recovery in dynamic physical environments, including geoscience information and advice, and restoration of infrastructure damaged by natural hazard events. Further research is necessary to understand the issues this raises for the shelter and geoscience communities, particularly around availability of geoscience expertise, capacity and information at a local scale