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NASA NTRS1999

Multi-Wavelength Analysis of the March 26, 1991: Solar Flare

We have engaged in detailed multi-wavelength analysis of the March 26, 1991, solar flare in order to develop a method of diagnostics of the physical processes responsible for the efficient acceleration of charged particles to high energies and also for diagnostics of the photospheric response to the injection of the accelerated particles. Consideration of this particular flare is of special interest because to date it is the only flare in which the gamma-ray emission with energies of 20-1000 MeV was registered throughout the entire development of the event in the optical, radio and soft x-ray bands. individual registration by the GAMMA-1 telescope of the energy and precise time for each registered gamma-ray photon allowed the maximum detailed investigation of the energy spectrum and flux evolution during the flare.

Kurt, V. G.↗
NASA NTRS1999

Demonstration of An Image Rejection Mixer for High Frequency Applications (26-36 GHz)

A new high frequency image-rejection mixer was successfully tested in a 26-36 GHz band receiver. This paper briefly describes the motivation for implementation of an image rejection mixer in a receiver system, the basic operation of an image rejection mixer, and the development and testing of an image rejection mixer for a high frequency, cryogenic receiver system.

Bankston, Cheryl D.↗
NASA NTRS2000

Hurricane Bonnie Landfalling Observed from ER-2 Doppler Radar on 26 August 1998 During CAMEX-3

The NASA ER-2 and DC-8 aircraft collected remote sensing and in situ data sets from Hurricane Bonnie (23, 24, and 26 August 1998) during the Convection And Moisture Experimental-3 (CAMEX-3). Bonnie was an exceptional case where NASA and NOAA had five aircraft sampling both upper levels and lower altitudes. The ER-2 was instrumented with the ER-2 Doppler XBand radar (EDOP) and several radiometers ranging from visible to lower frequency microwaves. EDOP is a fixed dual-beam radar (nadir and forward-looking beams) which allows computation of both vertical and alongtrack horizontal winds. The hurricane secondary circulation is typically difficult to measure at upper levels due to aircraft altitude limitations and sensitivity of the lower altitude airborne radars. EDOP is in principle, well suited to measure these components of the wind. When ER-2 flies across the approximate center of the hurricane circulation, the along-track winds derived from EDOP, are approximately equal to the hurricane radial flow comprising the secondary circulation. Assuming that the hydrometeor fallspeeds can be approximated, the radial and vertical wind components of the secondary circulation can be measured. Since the hydrometeor motions can be estimated with more confidence in the higher altitude ice regions (i.e., graupel and mixed phase are complicated at lower altitudes), the derived radial and vertical winds have higher accuracy at upper levels. On the other hand, the reflectivities are extremely low at higher altitudes, resulting in fewer Doppler velocity estimates.

Heymsfield, G. M.↗
NASA NTRS2000

The Sulfur Dioxide Plume from the February 26, 2000 Eruption of Mt. Hekla, Iceland

The February 2000 fissure eruption of Mt. Hekla, Iceland was captured in sulfur dioxide data from the Earth Probe TOMS. A special algorithm is used to discriminate sulfur dioxide from ozone. The eruption began at 18:19 GMT on February 26, 2000 and was first viewed by TOMS at 09:55 GMT on February 27. The volcanic cloud at that time appeared as a very long and narrow arc extending west from the volcano in southern Iceland, then north across Greenland, and finally east towards Norway. The cloud altitude was reported from aircraft sightings and data to be above 10 km. The circulation of a ridge located north of Iceland produced the large arc shaped cloud. As the eruption is non-explosive the high altitude cloud contains little ash. Almost all the ash from the eruption fell out locally across Iceland. By February 29, the sulfur dioxide cloud had drifted eastward in a band along the Barents Sea coast of Norway and Russia. The analysis includes an assessment of the initial sulfur dioxide content and its rate of conversion to sulfate.

Krueger, Arlin J.↗
NASA NTRS2004

Warm Core Structure and Mid-Level Intrusion in Hurricane Bonnie (1998) During Landfalling on 26 August 1998

On 26 August 1998 during CAMEX-3, Hurricane Bonnie was overflown by the NASA ER-2 aircraft instrumented with the EDOP X-Band radar and other instrumentation. Bonnie was an asymmetric storm on this day with several prominent features during its brush with the East coast. One of these features was strong intrusion of dry air on the west side of the storm. During the interaction of this westerly shear with the storm, the precipitation band rotates cyclonically from northwest to the south of the storm center. In this paper, we examine the structure of this dry intrusion and its effect on the storm. The EDOP observations are analyzed along with dropsondes, flight-level observations (NASA DC-8 and NOAA P3), and satellite data. The most apparent feature of the EDOP observations are the strong shears in the interface between the western eyewall updraft, and the dry intrusion. Mammatus are formed along this interface reminiscent of convective rear inflows, and suggestive of intense drying of the air through subsidence. This observation as well as other aspects of the analysis are related to recent numerical simulations of Hurricane Bonnie.

Heymsfield, G. M.↗
NASA NTRS2004

Solar Control on Jupiter's Equatorial X-ray Emissions: 26-29 November 2003 XMM-Newton Observation

During November 26-29,2003 XMM-Newton observed X-ray emissions from Jupiter for 69 hours. The 0.7-2.0 keV X-ray disk of Jupiter is observed to be brightest at the subsolar point, and limb darkening is seen in the 0.2-2.0 keV and 0.7-2.0 keV images. We present simultaneous lightcurves of Jovian equatorial X-rays and solar X-rays measured by the GOES, SOHO/SEM, and TIMED/SEE satellites. The solar X-ray flares occurring on the Jupiter-facing side of the Sun are matched by corresponding features in the Jovian X- rays. These results support the hypothesis that X-ray emissions from Jovian low-latitudes are solar X-rays scattered and fluoresced from the planet's upper atmosphere, and confirm that the Sun directly controls the non-auroral X-rays fiom Jupiter's disk. Our study suggest that Jovian equatorial X-rays; during certain Jupiter phase, can be used to predict the occurrence of solar flare on the hemisphere of the Sun that is invisible to space weather satellites.

Bhardwaj, Anil↗
NASA NTRS2000

The Solar Wind Depletion (SWD) event of 26 April 1999: Triggering of an auroral pseudobreakup event

The interplanetary solar wind depletion (SWD) event of 26 April 1999 and its magnetospheric consequences are examined. The SWD event is characterized by a solar wind density decrease from [similar to] 3.0 to 0.7 cm(sup -3) leading to a solar wind ram pressure decrease from [similar to] 2.0 to 0.2 nPa. This SWD onset is followed by a dipolarization of nightside magnetospheric fields.

Megnetic fields auroral pseudobreakup↗
NASA NTRS2005

The 26 December 2004 tsunami source estimated from satellite radar altimetry and seismic waves

The 26 December 2004 Indian Ocean tsunami was the first earthquake tsunami of its magnitude to occur since the advent of both digital seismometry and satellite radar altimetry. Both have independently recorded the event from different physical aspects. The seismic data has then been used to estimate the earthquake fault parameters, and a three-dimensional ocean-general-circulation-model (OGCM) coupled with the fault information has been used to simulate the satellite-observed tsunami waves. Here we show that these two datasets consistently provide the tsunami source using independent methodologies of seismic waveform inversion and ocean modeling. Cross-examining the two independent results confirms that the slip function is the most important condition controlling the tsunami strength, while the geometry and the rupture velocity of the tectonic plane determine the spatial patterns of the tsunami.

ocean general circulation model (OGCM)↗
NASA NTRS2004

Aeroacoustic Study of a 26%-Scale Semispan Model of a Boeing 777 Wing in the NASA Ames 40- by 80-Foot Wind Tunnel

An acoustic and aerodynamic study was made of a 26%-scale unpowered Boeing 777 aircraft semispan model in the NASA Ames 40- by 80-Foot Wind Tunnel for the purpose of identifying and attenuating airframe noise sources. Simulated approach and landing configurations were evaluated at Mach numbers between 0.12 and 0.24. Cruise configurations were evaluated at Mach numbers between 0.24 and 0.33. The research team used two Ames phased-microphone arrays, a large fixed array and a small traversing array, mounted under the wing to locate and compare various noise sources in the wing high-lift system and landing gear. Numerous model modifications and noise alleviation devices were evaluated. Simultaneous with acoustic measurements, aerodynamic forces were recorded to document aircraft conditions and any performance changes caused by the geometric modifications. Numerous airframe noise sources were identified that might be important factors in the approach and landing noise of the full-scale aircraft. Several noise-control devices were applied to each noise source. The devices were chosen to manipulate and control, if possible, the flow around the various tips and through the various gaps of the high-lift system so as to minimize the noise generation. Fences, fairings, tip extensions, cove fillers, vortex generators, hole coverings, and boundary-layer trips were tested. In many cases, the noise-control devices eliminated noise from some sources at specific frequencies. When scaled to full-scale third-octave bands, typical noise reductions ranged from 1 to 10 dB without significant aerodynamic performance loss.

Horne, W. Clifton↗
NASA NTRS2006

GEOSAT Follow-On (GFO) Altimeter Document Series, Volume 8: GFO Altimeter Engineering Assessment Report Update:The First 109 Cycles Since Acceptance November 29, 2000 to December 26, 2005

The purpose of this document is to present and document GFO performance analyses and results. This is the fifth Assessment Report since the initial report. This report extends the performance assessment since acceptance to 26 December 2005. The initial GFO Altimeter Engineering Assessment Report, March 2001 (NASA/TM-2001-209984/Ver.1/Vol.1) covered the GFO performance from Launch to Acceptance (10 February 1998 to 29 November 2000). The second of the series covered the performance from Acceptance to the end of Cycle 20 (29 November 2000 to 21 November 2001). The third of the series covered the performance from Acceptance to the end of Cycle 42 (29 November 2000 to 30 November 2002). The fourth of the series covered the performance from Acceptance to the end of Cycle 64 (29 November 2000 to 17 December 2003). The fifth of the series covered performance from Acceptance to the end of Cycle 86 (29 November 2000 to 17 December 2004). Since launch, we have performed a variety of GFO performance studies; an accumulative index of those studies is provided in Appendix A.

Conger, A. M.↗
NASA NTRS1967

Performance of 26 Meter Diameter Ringsail Parachute in a Simulated Martian Environment

Inflation, drag, and stability characteristics of an 85.3-foot (26-meter) nominal diameter ringsail parachute deployed at a Mach number of 1.15 and at an altitude of 132,600 feet (40.42 kilometers) were obtained from the first flight test of the Planetary Entry Parachute Program. After deployment, the parachute inflated to the reefed condition. However, the canopy was unstable and produced low drag in the reefed condition. Upon disreefing and opening to full inflation, a slight instability in the canopy mouth was observed initially. After a short time, the fluctuations diminished and a stable configuration was attained. Results indicate a loss in drag during the fluctuation period prior to stable inflation. During descent, stability characteristics of the system were such that the average pitch-yaw angle from the local vertical was less than 10 degrees. Rolling motion between the payload and parachute canopy quickly damped to small amplitude.

Whitlock, Charles H.↗
NASA NTRS2011

Relation Between the 3D-Geometry of the Coronal Wave and Associated CME During the 26 April 2008 Event

We study the kinematical characteristics and 3D geometry of a large-scale coronal wave that occurred in association with the 26 April 2008 flare-CME event. The wave was observed with the EUVI instruments aboard both STEREO spacecraft (STEREO-A and STEREO-B) with a mean speed of approx 240 km/s. The wave is more pronounced in the eastern propagation direction, and is thus, better observable in STEREO-B images. From STEREO-B observations we derive two separate initiation centers for the wave, and their locations fit with the coronal dimming regions. Assuming a simple geometry of the wave we reconstruct its 3D nature from combined STEREO-A and STEREO-B observations. We find that the wave structure is asymmetric with an inclination toward East. The associated CME has a deprojected speed of approx 750 +/- 50 km/s, and it shows a non-radial outward motion toward the East with respect to the underlying source region location. Applying the forward fitting model developed by Thernisien, Howard, and Vourlidas we derive the CME flux rope position on the solar surface to be close to the dimming regions. We conclude that the expanding flanks of the CME most likely drive and shape the coronal wave.

CMEs↗
NASA NTRS2013

All-Particle Cosmic Ray Energy Spectrum Measured with 26 Icetop Stations

We report on a measurement of the cosmic ray energy spectrum with the IceTop air shower array, thesurface component of the IceCube Neutrino Observatory at the South Pole. The data used in this analysiswere taken between June and October, 2007, with 26 surface stations operational at that time, corresponding to about one third of the final array. The fiducial area used in this analysis was 0.122 square kilometers.The analysis investigated the energy spectrum from 1 to 100 PeV measured for three different zenithangle ranges between 0 and 46. Because of the isotropy of cosmic rays in this energy range the spectrafrom all zenith angle intervals have to agree. The cosmic-ray energy spectrum was determined under differentassumptions on the primary mass composition. Good agreement of spectra in the three zenithangle ranges was found for the assumption of pure proton and a simple two-component model. Forzenith angles theta less than 30 deg., where the mass dependence is smallest, the knee in the cosmic ray energy spectrumwas observed at about 4 PeV, with a spectral index above the knee of about -3.1. Moreover, an indicationof a flattening of the spectrum above 22 PeV was observed.

icetop↗
NASA NTRS2017

Medical Countermeasures for Radiation Induced Health Effects: Reports of an Interagency Panel Session Held at the NASA Human Research Program Investigator's Workshop, January 26, 2017

An Interagency Panel Session organized by the NASA Human Research Program Space Radiation Program Element (SRPE) was held during the NASA Human Research Program (HRP) Investigator’s Workshop (IWS) in Galveston, Texas on January 26, 2017 to identify complementary research areas that will advance the testing and development of medical countermeasures (MCM) in support of radioprotection and radiation mitigation on the ground and in space. There were several areas of common interest identified among the various participating agencies. This report provides a summary of the topics discussed by each agency along with potential areas of intersection for mutual collaboration opportunities. Common goals included repurposing of pharmaceuticals, neutraceuticals for use as radioprotectors and/or mitigators, low-dose/chronic exposure paradigms, late effects post-radiation exposure, mixed-field exposures of gamma-neutron, performance decrements, and methods to determine individual exposure levels.

Carnell, Lisa S.↗
NASA NTRS2019

Daily evaluation of 26 precipitation datasets using Stage-IV gauge-radar data for the CONUS

New precipitation (P) datasets are released regularly, following innovations in weather forecasting models, satellite retrieval methods, and multi-source merging techniques. Using the conterminous US as a case study, we evaluated the performance of 26 gridded (sub-)daily P datasets to obtain insight into the merit of these innovations. The evaluation was performed at a daily timescale for the period 2008–2017 using the Kling–Gupta efficiency (KGE), a performance metric combining correlation, bias, and variability. As a reference, we used the high-resolution (4 km) Stage-IV gauge-radar P dataset. Among the three KGE components, the P datasets performed worst overall in terms of correlation (related to event identification). In terms of improving KGE scores for these datasets, improved P totals (affecting the bias score) and improved distribution of P intensity (affecting the variability score) are of secondary importance. Among the 11 gauge-corrected P datasets, the best overall performance was obtained by MSWEP V2.2, underscoring the importance of applying daily gauge corrections and accounting for gauge reporting times. Several uncorrected P datasets outperformed gauge-corrected ones. Among the 15 uncorrected P datasets, the best performance was obtained by the ERA5-HRES fourth-generation reanalysis, reflecting the significant advances in earth system modeling during the last decade. The (re)analyses generally performed better in winter than in summer, while the opposite was the case for the satellite-based datasets. IMERGHH V05 performed substantially better than TMPA-3B42RT V7, attributable to the many improvements implemented in the IMERG satellite P retrieval algorithm. IMERGHH V05 outperformed ERA5-HRES in regions dominated by convective storms, while the opposite was observed in regions of complex terrain. The ERA5-EDA ensemble average exhibited higher correlations than the ERA5-HRES deterministic run, highlighting the value of ensemble modeling. The WRF regional convection-permitting climate model showed considerably more accurate P totals over the mountainous west and performed best among the uncorrected datasets in terms of variability, suggesting there is merit in using high-resolution models to obtain climatological P statistics. Our findings provide some guidance to choose the most suitable P dataset for a particular application.

Hylke E. Beck↗
NASA NTRS2022

TESS Eclipsing Binary Stars. I. Short-cadence Observations of 4584 Eclipsing Binaries in Sectors 1–26

In this paper we present a catalog of 4584 eclipsing binaries observed during the first two years (26 sectors) of the TESS survey. We discuss selection criteria for eclipsing binary candidates, detection of hitherto unknown eclipsing systems, determination of the ephemerides, the validation and triage process, and the derivation of heuristic estimates for the ephemerides. Instead of keeping to the widely used discrete classes, we propose a binary star morphology classification based on a dimensionality reduction algorithm. Finally, we present statistical properties of the sample, we qualitatively estimate completeness, and we discuss the results. The work presented here is organized and performed within the TESS Eclipsing Binary Working Group, an open group of professional and citizen scientists; we conclude by describing ongoing work and future goals for the group. The catalog is available from http://tessEBs.villanova.edu and from MAST.

Andrej Prša↗