Evaluation of EarthRadar unexploded ordnance testing at Fort A.P.Hill, Virginia

Previously, K. Bakhtar and E. Sagal [ibid. vol. 17, pp. 4-11, 2002] made remarkable claims for the performance of the Bakhtar Associates ground-penetrating radar (GPR) in detecting and classifying buried unexploded ordnance (UXO). In this article, we report the results of the series of blind tests on the EarthRadar carried out during the Fall of 2000 and Spring of 2001, which led to very different conclusions regarding the radar's performance. The contents of this article are excerpted from the final report on the testing, prepared by the Institute for Defense Analyses     

EXOSAT observations of NGC 1399 and NGC 1404: Two elliptical galaxies in the center of the Fornax cluster

Imaging X-ray observations of the Fornax cluster of galaxies centered on NGC 1399 and NGC 1404 are presented. NGC 1399 and NGC 1404, which are separated by about 10 arc minutes, are found to have an unusually high ratio of x-ray to optical flux. We consider the possibility that the x-radiation is produced by hot gas in the cores of the galaxies. Weak X-ray emission is also detected from a point almost exactly mid-way between NGC 1399 and NGC 1404. The combined emission from the galaxies is insufficient by over an order of magnitude to account for the the low-energy X-ray emission detected from this region by the HEAO-l satellite. It is suggested that the bulk of the HEAO-1 source is diffuse gas associated with the cluster as a whole, rather than individual galaxies.     

Two new hot white dwarfs in a region of exceptionally low hi density

We report the discovery of two hot white dwarfs which have the lowest line-of-sight neutral hydrogen column densities yet measured. The stars were found independently by the ROSAT EUV, Montreal-Cambridge-Tololo, and Edinburgh-Cape surveys. Follow-up observations made using the Voyager 2 ultraviolet spectrometer reveal strong continua shortward of the 912Å Lyman limit from which we deduce that the neutral hydrogen column densities are 1.3 × 10¹⁷ and 2.0 × 10¹⁷ atoms cm⁻².     

The university of wyoming's small scientific balloon program

Over 500 small scientific balloons have been launched by the University of Wyoming's Atmospheric physics Group from 26 locations over the globe in a study of stratospheric aerosol physics and chemistry which began in 1971. These flights have led to a basic understanding of the evolution of sulfurous gases, injected into the stratosphere by major volcanic eruptions, into sulfuric acid aerosol droplets. The recent use of new, thin film balloon technology, to reduce cost and simplify launch techniques, has been a major advantage to the program.     

Stratospheric dust and its relationship to the meteoric influx

A review of measurements sensitive to dust in the stratosphere is presented with special emphasis on the data obtained during the last 10 years. The measurements made by indirect techniques such as light scattering tend to show more stratospheric dust than the measurements obtained by direct sampling techniques, although this interpretation is somewhat complicated by the injection of dust from the Bali eruption in 1963. The discrepancy is interpreted as indicating that the stratospheric dust smaller than a few microns diameter is volital. Recent direct experimental evidence of the author supports this conclusion.The size distribution of stratospheric dust is presented as a composite of the results of several observers. A natural break in the distribution at a size of about 5 diameter is interpreted as indicating that the smaller dust is terrestrial in origin, while the larger dust is meteoric in origin. Other evidence is presented to support this conclusion. A comparison with particle flux measurements at 100 km and higher indicates that the meteoric component of the stratospheric dust is ablation products rather than single particles that have survived entry into the atmosphere. It is also argued that the small particles accounting for the high flux as measured by rocket and satellite microphone techniques are not present in the stratosphere.     

UAVSAR: New NASA Airborne SAR System for Research

NASA's Jet Propulsion Laboratory is currently building a reconfigurable, polarimetric L-band synthetic aperture radar (SAR), specifically designed to acquire airborne repeat track SAR data for differential interferometric measurements. Differential interferometry can provide key deformation measurements, important for studies of earthquakes, volcanoes, and other dynamically changing phenomena. Using precision real-time GPS and a sensor controlled flight management system, the system will be able to fly pre-defined paths with great precision. The expected performance of the flight control system will constrain the flight path to be within a 10 m diameter tube about the desired flight track. The radar will be designed to be operable on a Unpiloted Arial Vehicle (UAV) but will initially be demonstrated on a NASA Gulfstream III. The radar will be fully polarimetric, with a range bandwidth of 80 MHz (2 m range resolution), and will support a 16 km range swath. The antenna will be electronically steered along track to assure that the antenna beam can be directed independently, regardless of the wind direction and speed. Other features supported by the antenna include elevation monopulse and pulse-to-pulse re-steering capabilities that will enable some novel modes of operation. The system will nominally operate at 45,000 feet (13,800 m). The program began as an Instrument Incubator Project (IIP) funded by NASA Earth Science and Technology Office (ESTO).     

New EXOSAT results from the intermediate polar V1223 SGR

We report new results obtained from the EXOSAT AO- 1 observation of the intermediate polar V1223 Sgr. The detection of a 12.4 minute period in the medium energy X-ray flux with an associated hardness ratio variation has been previously reported in Osborne et al. (1984a). Further work has revealed: a narrow dip at the phase zero in the folded medium energy light curve; 30% modulation in the low energy X-ray (3000 Lexan) flux; a count rate ratio from 3 filters which allow the presence of a bright low temperature blackbody component (kT = .05 –. 40 KeV); and a phase resolved ME spectrum which must have two or more components when the source is bright. New optical ephemerides show that the X-ray and optical pulses are in phase at an orbital phase of = 0.31.Affiliated to the Astrophysics Division, Space Science Dept., ESA