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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 MNRAS

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.

The MOHAVE-2009 campaign brought together diverse instrumentation for measuring atmospheric water vapor. We report on the participation of the ALVICE (Atmospheric Laboratory for Validation, Interagency Collaboration and Education) mobile laboratory in the MOHAVE-2009 campaign. In appendices we also report on the performance of the corrected Vaisala RS92 radiosonde measurements during the campaign, on a new radiosonde based calibration algorithm that reduces the influence of atmospheric variability on the derived calibration constant, and on other results of the ALVICE deployment. The MOHAVE-2009 campaign permitted the Raman lidar systems participating to discover and address measurement biases in the upper troposphere and lower stratosphere. The ALVICE lidar system was found to possess a wet bias which was attributed to fluorescence of insect material that was deposited on the telescope early in the mission. Other sources of wet biases are discussed and data from other Raman lidar systems are investigated, revealing that wet biases in upper tropospheric (UT) and lower stratospheric (LS) water vapor measurements appear to be quite common in Raman lidar systems. Lower stratospheric climatology of water vapor is investigated both as a means to check for the existence of these wet biases in Raman lidar data and as a source of correction for the bias. A correction technique is derived and applied to the ALVICE lidar water vapor profiles. Good agreement is found between corrected ALVICE lidar measurments and those of RS92, frost point hygrometer and total column water. The correction is offered as a general method to both quality control Raman water vapor lidar data and to correct those data that have signal-dependent bias. The influence of the correction is shown to be small at regions in the upper troposphere where recent work indicates detection of trends in atmospheric water vapor may be most robust. The correction shown here holds promise for permitting useful upper tropospheric water vapor profiles to be consistently measured by Raman lidar within NDACC (Network for the Detection of Atmospheric Composition Change) and elsewhere, despite the prevalence of instrumental and atmospheric effects that can contaminate the very low signal to noise measurements in the UT.

MIPAS observations of temperature, water vapor, and ozone in October 2009 as derived with the scientific level-2 processor run by Karlsruhe Institute of Technology (KIT), Institute for Meteorology and Climate Research (IMK) and CSIC, Instituto de Astrofısica de Andalucıa (IAA) and retrieved from version 4.67 level-1b data have been compared to co-located field campaign observations obtained during the MOHAVE-2009 campaign at the Table Mountain Facility near Pasadena, California in October 2009. The MIPAS measurements were validated regarding any potential biases of the profiles, and with respect to their precision estimates. The MOHAVE-2009 measurement campaign provided measurements of atmospheric profiles of temperature, water vapor/relative humidity, and ozone from the ground to the mesosphere by a suite of instruments including radiosondes, ozonesondes, frost point hygrometers, lidars, microwave radiometers and Fourier transform infrared (FTIR) spectrometers. For MIPAS temperatures (version V4O_T_204), no significant bias was detected in the middle stratosphere; between 22 km and the tropopause MIPAS temperatures were found to be biased low by up to 2 K, while below the tropopause, they were found to be too high by the same amount. These findings confirm earlier comparisons of MIPAS temperatures to ECMWF data which revealed similar differences. Above 12 km up to 45 km, MIPAS water vapor (version V4O_H2O_203) is well within 10% of the data of all correlative instruments. The well-known dry bias of MIPAS water vapor above 50 km due to neglect of non-LTE effects in the current retrievals has been confirmed. Some instruments indicate that MIPAS water vapor might be biased high by 20 to 40% around 10 km (or 5 km below the tropopause), but a consistent picture from all comparisons could not be derived. MIPAS ozone (version V4O_O3_202) has a high bias of up to +0.9 ppmv around 37 km which is due to a non-identified continuum like radiance contribution. No further significant biases have been detected. Cross-comparison to co-located observations of other satellite instruments (Aura/MLS, ACE-FTS, AIRS) is provided as well.

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.

The Sodankyla Total Column Ozone Intercomparison (SAUNA) campaign took place at the Finnish Meteorological Institute Arctic Research Center (FMI-ARC) at Sodankyla, Finland (67.37 N) in two separate phases during early spring 2006, and winter 2007. These campaigns has several goals: to determine and improve the accuracy of total column ozone measurements during periods of low solar zenith angle and high total column ozone; to determine the effect of ozone profile shape on the total column retrieval; and to make validate satellite ozone measurements under these same conditions. The GSFC Stratospheric Ozone Lidar (STROZ), which makes profile measurements of ozone temperature, aerosols and water vapor participated in both phases of the campaign. During the deployments, more than 30 profile measurements were made by the lidar instrument, along with Dobson, Brewer, DOAS, ozonesonde, and satellite measurements. The presentation will concentrate on STROZ lidar results from the second phase of the campaign and comparisons with other instruments will be discussed. This will include both ground-based and satellite comparisons.

Three NASA-funded field campaigns have been hosted at the Howard University Research Campus in Beltsville, MD. In each of the years 2006, 2007 and 2008, WAVES field campaigns have coordinated ozonesonde launches, lidar operations and other measurements with A-train satellite overpasses for the purposes of satellite validation. The unique mix of measurement systems, physical location and the interagency, international group of researchers and students has permitted other objectives, such as mesoscale meteorological studies, to be addressed as well. We review the goals and accomplishments of the three WAVES missions with the emphasis on the nonsatellite validation component of WAVES, as the satellite validation activities have been reported elsewhere.

As part of the NDSC, the GSFC mobile Ozone Lidar instrument has participated in numerous validation campaigns around the world. During all of these campaigns, ozonesondes were flown as part of the intercomparisons. This poster summarizes the results of these campaigns, and indicates that there are some biases between the sonde and lidar measurements.

This paper reports the results of a balloon flight of the Solar Disk Sextant (SDS) on 1992 September 30. This was the first flight in which the SDS used a wedge assembly fabricated by molecular contact in order to eliminate the wedge angle variations observed in previous flights. The instrument performed as designed. The main results obtained are values of the solar diameter for a number of discrete heliocentric latitudes, and the solar oblateness. The accuracy of the diameter values is better than 0.2 sec whereas the precision is approximately 1-2 mas. The equatorial solar diameter, at 1 AU, was 1919.06 sec +/- 0.12 sec, and the oblateness epsilon = 8.63 +/- 0.88 x 10(exp -6).

Preliminary results of a balloon flight on October 11, 1991, of the solar disk sextant (SDS) experiment are reported. The SDS is an instrument which measures the solar diameter at different orientations with respect to the solar polar axis. Fitting straight lines through two fixed-angle data sets with time as the independent variable yields slopes of (7.1 +/ - 1.5) x 10 exp -3 and (6.7 +/- 1.6) x 10 exp -3/mas s, consistent with the value of 6.47 x 10 exp -3/mas s expected from the earth's approach to the sun due to the orbital motion toward perihelion. Upon the instrument's rotation on its axis a sinusoidal component of the diameter measurement was observed in each rotation cycle, with a variable amplitude of about 150 mas. The present result is epsilon of (5.6 +/- 6.3) x 10 exp -6, about 30 deg offset from the polar-equator position. The absolute diameter obtained by means of the FFT definition is found to be 1919.269 +/- 0.240 arcsec or 1919.131 +/- 0.240 arcsec, depending on the orientation mode of the measurement.

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.

The effect on solar models of several types of slow, spherically symmetric perturbations, acting at various depths within the convective envelope, are calculated. Results are presented on perturbations of the efficiency of convective energy transport (alpha perturbations) and on changes in the nongas component of pressure (beta perturbations). The effects of magnetic fields concentrated near the interface between the radiative core and the convective envelope are explored. It is found that the response and relaxation diagnostics depend both on the type of perturbation and on the depth at which the perturbation is applied. In addition to the general depth dependence, model behavior is sensitive to the presence of major ionization zones near the perturbed layer. The time dependence of the solar model behavior is characterized by an initial hydrostatic reaction followed by a thermal readjustment on a time scale of about 100 years, and finally relaxation to a new thermal equilibrium on a Kelvin time scale.

The response of solar models to perturbations of the efficiency of convective energy transport is studied. Such perturbations primarily affect the shallow superadiabatic layer of the convective envelope. Independent of the details of the perturbation scheme, the resulting change in the solar radius is always very small compared to the change in luminosity. This appears to be true for any physical mechanism of solar variability which operates in the outer layers of the convection zone. Changes of the solar radius have been inferred from historical observations of solar eclipses in 1715 and 1925. Considering the constraints on concurrent luminosity changes, this type of solar variability must be indicative of changes in the solar structure at substantial depths below the superadiabatic layer of the convective envelope.

Thermal perturbations of the solar convection zone can be modeled (to the first order) by perturbing the mixing length parameter alpha (equal to the ratio of the mixing length to the pressure scale height) used in the standard mixing length theory of convection. Results of such an analysis are presented and discussed in relation to recent work by others.

An investigation of thermal perturbations of the solar convective zone via changes in the mixing length parameter were carried out, with a view toward understanding the possible solar radius and luminosity changes cited in the literature. The results show that: (a) a single perturbation of alpha is probably not the cause of the solar radius change and (b) the parameter W = d lambda nR./d lambda nL. can not be characterized by a single value, as implied in recent work.