The Smart Panoramic Optical Sensor Head (SPOSH)—A camera for observations of transient luminous events on planetary night sides

We have developed a camera dedicated to imaging faint transient noctilucent phenomena, such as aurorae, electric discharges, meteors or impact flashes, on dark planetary hemispheres. The Smart Panoramic Optical Sensor Head (SPOSH) is equipped with a back-illuminated 1024×1024 CCD chip E2V 47-20 with up to 90% quantum efficiency and has a custom-made optical system of high light-gathering power with a wide field of view of 120°×120°. Images can be obtained over extended periods at high rate to make monitoring for transient events possible. To reduce the data transmission rate, only those images (or relevant portions thereof) that contain events are returned to the user. The camera has a sophisticated processing unit prepared to interface with a spacecraft system, for image processing and event detection at rates of up to 3 images per second at full resolution. While software optimized for detection of any noctilucent phenomenon can be implemented, the software is currently optimized for the detection of meteors. Over the past years, we have routinely carried out outdoor tests with 4 camera breadboard units that demonstrate that the camera has excellent radiometric performance and geometric resolution at low light levels over its large field of view. The camera has been demonstrated to capture meteors of magnitudes as faint as +6^m moving at angular speeds of 5°/s. The camera opens up new science opportunities for planetary missions.     

Non-thermal primeval fireball?

The possible significance of a large cosmic sub-millimeter electromagnetic radiation background is considered. It is shown that in some scalar-tensor cosmological models such an effect could be primeval, that is, the result of processes occurring at an epoch earlier than we now can attempt to compute. The radiation background due to electron pair annihilation in a scalar-tensor model also is considered. It is shown that, while this effect could very substantially increase the far infrared background, it cannot make a spectrum that would be consistent with all the available tentative measurements.Research supported in part by the National Science Foundation.     

Some Astronomical Aspects of the Study of Lunar Regolith

This article provides some astronomical background for a systematic study of the lunar regolith. The Moon, like other atmosphere-less bodies, is the subject to all kinds of cosmic radiation, which are imprinted in the lunar surface. Therefore, the study of the lunar regolith for signs of cosmic radiation can assist to trace the history of changes in these emissions over time. Mostly changes in the solar wind and galactic cosmic rays are very interesting at time intervals from a few tens of millions of years to several billion years. The paper develops the idea of paleoregolith, the possible location of which can be seen on the slopes of some craters (Euler, Bessel) in images obtained by camera of LRO spacecraft (LROC). Because of the complexities of placing a spacecraft on the slopes of craters, some other possible locations of paleoregolith are offered to consideration. To study the recent history of the evolution of the Moon and the inner planets (up to 200 million years) the stored information in impact and volcanic melts, which are widely represented in the LROC images, should be considered.     

A Search for Water Ice at the Lunar Poles with Clementine Images

Optical and near-IR signatures of water ice on the Moon's surface were sought in the permanently shadowed regions near its poles. Significant amounts of multiply-scattered radiation partly illuminate primary shadows cast by craters and other features. If there is water ice in the permanently shadowed regions of the Moon's surface, its spectral signature should appear in this multiply-scattered light. This investigation can be done most effectively with observations obtained by spacecraft, because most selenocentric positions occupied by the Earth will also be occupied by the Sun at some point in time, and because the lunar poles are seen only obliquely to a terrestrial observer. Images obtained by Clementine are particularly well-suited to this task, because the spacecraft's polar orbit allowed images of the poles to be acquired on nearly every orbit, resulting in literally thousands of images taken within a few degrees of each pole, and because the filters on the ultraviolet-visual camera (UVVIS) and the near infrared camera (NIR) occur at major absorption bands or within important continuum features of water ice. Approximately 5800 images obtained by the UVVIS camera and 1800 images obtained by the NIR camera were calibrated and combined into coadded mosaics to create multispectral maps of the lunar poles with the highest possible signal-to-noise. Unfortunately, analysis of our UVVIS mosaics indicates that any possible signal from multiply-scattered light in primary shadows was overwhelmed by instrumental stray light. For the NIR camera, we were able to determine the normalized reflectance of several regions that were identified by Margot et al. (1999, Science284, 1658-1660) as permanent shadows. We have identified one permanently shadowed crater with a 1.5-μm band spectral signature indicative of between 2.5 and 21% fractional coverage of H₂O frost. However, the same region shows a 2.0 μm spectral signature that is inconsistent with the presence of any water.     

The near infrared camera on the W.M. Keck telescope

The near infrared camera (NIRC) was used for a science demonstration run on the Keck telescope during 16–24 March 1993. The camera used a 256×256 InSb array manufactured by Santa Barbara Research Corporation. Observations were obtained using narrowband and broad band filters from 1 to 2.4 microns, and grisms with a spectral resolution of 0.6 percent in the J, H and K atmospheric windows. The instrument was fully background limited over the entire wavelength range. The sky background was quite low, reaching 14.3 mag/square arc sec in the broadband K _s filter. The image quality of the camera + telescope was excellent, being seeing limited in the range 0.5–0.9.The science demonstration observations of the NIRC on the Keck Telescope included observations of the most distant galaxy known, 4C41.17 at a redshift z=3.8 and the most luminous object known, the IRAS source FSC10214+4724 at a redshift z=2.29. Observations of the radio galaxy address the problem of the alignment effect in high redshift radio galaxies as well as the environments of such systems. FSC10214+4724 appears to be a merging galaxy that is at least 5×10⁸ years old.Based on observations obtained at the W.M.Keck Observatory, which is operated jointly by the California Institute of Technology and the University of CaliforniaThe W.M. Keck Observatory is operated as a scientific partnership between the California Institute of Technology and the University of California. It was made possible by the generous gift of the W.M. Keck foundation and the support of its president, Howard Keck.     

Gamma rays from halos around stars and the Sun

Inverse Compton (IC) scattering by relativistic electrons produces a major component of the diffuse emission from the Galaxy. The photon fields involved are the cosmic microwave background and the interstellar radiation field (ISRF) from stars and dust. Calculations of the inverse Compton distribution have usually assumed a smooth ISRF, but in fact a large part of the Galactic luminosity comes from the most luminous stars, which are rare. Therefore we expect the ISRF, and hence the inverse Compton emission, to be clumpy at some level, which could be detectable by instruments such as GLAST. Even individual nearby luminous stars could be detectable assuming just the normal cosmic-ray electron spectrum. We present the basic formalism required and give possible candidate stars to be detected and make predictions for GLAST. Then we apply the formalism to the OB associations and the Sun, showing that the IC emission produced is not negligible compared to the sensitivity of current or coming detectors. We estimate that the gamma-ray flux from the halo around the Sun contributes to the diffuse background emission at the few percent level.     

Photometric correction of Mercury's global color mosaic

During the third flyby of Mercury by the MESSENGER spacecraft, a dedicated disk-integrated photometric sequence was acquired with the wide-angle multispectral camera to observe Mercury's global photometric behavior in 11 spectral filters over as broad a range of phase angle as possible within the geometric constraints of the flyby. Extraction of disk-integrated measurements from images acquired during this sequence required careful accounting for scattered light and residual background effects. The photometric model fit to these measurements is shown to fit observed radiances at phase angles below 110°, possibly except where both solar incidence and emission angles are high (>70°). The complexity of the scattered light at wavelengths greater than 828 nm contributes to a less accurate photometric correction at these wavelengths. The model is used to correct the global imaging data set acquired at a variety of geometries to a common geometry of incidence angle=30°, emission angle=0°, and phase angle=30°, yielding a relatively seamless mosaic. The results here will be used to correct image mosaics of Mercury acquired in orbit.     

The Sunyaev–Zel'dovich effect contribution to WMAP: a cross-correlation between WMAP and ROSAT

We cross-correlate WMAP and ROSAT diffuse X-ray background maps and look for common features in both data sets. We use the power spectrum of the product maps and the cross-power spectrum to highlight a possible correlation. The power spectrum of the product maps does not detect any correlation and the cross-power spectrum does not show any significant deviation from zero. We explore different explanations for this lack of correlation. A universe with a low value of  σ₈  could naturally explain the lack of correlation. We also discuss the systematic effects that can affect this result, in particular the subtraction of some cluster signal from the ROSAT diffuse maps, which could significantly suppress the correlation signal. These systematic effects considerably reduce the significance of our constraints on the cosmological model. When we include the systematic effects, we find a weaker constraint on  σ₈  , allowing models with values as large as  σ₈= 1  (for  Ω_m= 0.3  ) to be consistent with the lack of correlation. To illustrate the capabilities of the method with future high-quality data, we show how from the correlation signal it should be possible to predict the level of contamination of the Sunyaev–Zel'dovich effect on the power spectrum of the cosmic microwave background. Within the systematic errors, we find evidence that this contribution is negligible for WMAP and is expected to be small in experiments like ACBAR or CBI, but can be important for future high-resolution experiments.     

Obstacles facing the venus radar mapper - The implications of gestalt formation in stereo-radargrammetry

The question of adapting to radar images the existing hardware that form topographic maps through stereo-photogrammetric models, is examined in principle. Such hardware utilizes a human/ computer hybrid. Although the problem of brightness differentials between corresponding landmarks can be dealt with pseudo-photoclinometrically, the main problem is whether the perspective in a radar image can be conceived to mimic that of a photographic image obtained by a suitably positioned camera. This conception is found to be possible, providing the characteristic relief subtends to a very small angle at the radar and at the fictitious camera. The photogrammetric model parameters must be determined a priori.     

C ring fine structures revealed in the thermal infrared

We analyze data sets obtained with the Composite Infrared Spectrometer (CIRS) onboard the Cassini spacecraft after the Saturn Orbit Insertion (SOI). Using the mid-IR interferometer's FP3 channel (600-1100 cm⁻¹), we derive radial temperature profiles for the C ring with a spatial resolution never achieved before. For the first time, the C ring's plateaus and ringlets can be clearly separated from the optically thinner background and their thermal behavior is studied separately for different viewing geometries. In particular, thermal phase curves derived for the plateaus reveal an interesting surge near 0° phase, not observed in the background. We show that mutual shadowing in the plateaus can explain the existence of the surge but is not sufficient to model the phase curves in detail. By analogy with thermal emission of asteroid surfaces we discuss the possible influence of small scale and large scale roughness of the ring structure itself. Because infrared emissivity cannot be derived without being deconvolved from the ‘structural’ filling factor, we examine temperature and filling factors measurements at opposition where the filling factor is most constrained. The occurrence of higher temperatures in the plateaus than in the background near opposition likely arises from enhanced mutual heating between particles, multiple scattering and surface roughness combined with a higher single-scattering albedo.     

Comet Hale—Bopp Shells Expansion: A CCD Study

Using a CCD camera attached to the 0.335 m and 0.20 m reflectors of S.A.S. Observatory (Novara, Italy), we followed the linear jets and shells of comet Hale–Bopp between May 1996 and May 1997. In addition to confirming the model of Sekanina and Bohenhardt (1997), the study of the linear jets provided indications concerning the orientation of the comet's axis of rotation over time. The study of the shells revealed that the speed at which they move away from the nucleus was not constant. A periodic variation of the shell expansion velocity may not be excluded : if so, a possible precessional effect on the axis of rotation of the comet's nucleus could explain this behavior. This revised version was published online in July 2006 with corrections to the Cover Date.     

Video observation of meteors at Yunnan Observatory

In the last 20 years, with the development of the CCD and image intensifiers, the use of small flexible video meteor observation systems has gradually increased, with the prospect that one day video observation will replace the visual observation and ordinary photographic observations. In this paper we report on the research and development of the No.1 meteor-comet video camera system of Yunnan Observatory and some preliminary observed results. The system consists of 5 changeable modules; it has a 36° large-field camera dedicated to the observation of meteors, with which a magnitude 6 star can be recorded on a single frame with an accuracy of about 0.2 mag. We also present a comparison of the video camera system with the traditional photographic system, and outline the merits, possible improvements and future development of the video system.     

Earth Radioactivity Measurements with a Deep Ocean Anti-neutrino Observatory

We consider the detector size, location, depth, background, and radio-purity required of a mid-Pacific deep-ocean instrument to accomplish the twin goals of making a definitive measurement of the electron anti-neutrino flux due to uranium and thorium decays from Earth’s mantle and core, and of testing the hypothesis for a natural nuclear reactor at the core of Earth. We take the experience with the KamLAND detector in Japan as our baseline for sensitivity and background estimates. We conclude that an instrument adequate to accomplish these tasks should have an exposure of at least 10 kilotonne-years (kT-y), should be placed at least at 4 km depth, may be located close to the Hawaiian Islands (no significant background from them), and should aim for KamLAND radio-purity levels, except for radon where it should be improved by a factor of at least 100. With an exposure of 10 kT-y we should achieve a 25% measurement of the flux of U/Th neutrinos from the mantle plus core. Exposure at multiple ocean locations for testing lateral heterogeneity is possible.     

Dark matter and fundamental physics with the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) is a project for a next-generation observatory for very high energy (GeV–TeV) ground-based gamma-ray astronomy, currently in its design phase, and foreseen to be operative a few years from now. Several tens of telescopes of 2–3 different sizes, distributed over a large area, will allow for a sensitivity about a factor 10 better than current instruments such as H.E.S.S, MAGIC and VERITAS, an energy coverage from a few tens of GeV to several tens of TeV, and a field of view of up to 10°. In the following study, we investigate the prospects for CTA to study several science questions that can profoundly influence our current knowledge of fundamental physics. Based on conservative assumptions for the performance of the different CTA telescope configurations currently under discussion, we employ a Monte Carlo based approach to evaluate the prospects for detection and characterisation of new physics with the array.First, we discuss CTA prospects for cold dark matter searches, following different observational strategies: in dwarf satellite galaxies of the Milky Way, which are virtually void of astrophysical background and have a relatively well known dark matter density; in the region close to the Galactic Centre, where the dark matter density is expected to be large while the astrophysical background due to the Galactic Centre can be excluded; and in clusters of galaxies, where the intrinsic flux may be boosted significantly by the large number of halo substructures. The possible search for spatial signatures, facilitated by the larger field of view of CTA, is also discussed. Next we consider searches for axion-like particles which, besides being possible candidates for dark matter may also explain the unexpectedly low absorption by extragalactic background light of gamma-rays from very distant blazars. We establish the axion mass range CTA could probe through observation of long-lasting flares in distant sources. Simulated light-curves of flaring sources are also used to determine the sensitivity to violations of Lorentz invariance by detection of the possible delay between the arrival times of photons at different energies. Finally, we mention searches for other exotic physics with CTA.     

The JPL deep-well mid-infrared array camera

We describe the development of a mid-infrared camera intended for use at the Palomar 5-m telescope and at the NASA Infrared Telescope Facility. The camera is based on Rockwell's HF-16 128×128 Si:As BIB array. This array is unusual in that it has a well depth of approximately 30 million electrons; this will allow the use of traditional broadband astronomical filters (N and Q) while keeping a reasonable field-of-view. Measured array performance indicates that it has a read noise of 1100 electrons and shows non-linearities of <1% up to 65% of full well. In this paper, we discuss the array and its operating characteristics and we give a brief overview of the camera design.National Research Council research associate at JPLSummer Undergraduate Research Fellow at JPL     

Particle creation in pre-big-bang cosmology

We present some phenomenological aspects of the pre-big-bang cosmological model inspired by the duality properties of string theory. In particular, assuming the spatial sections of the homogeneous background geometry to be isotropic, we discuss the quantum production of perturbations of the background fields (gravitons, dilatons, moduli fields), as well as the production of particles which do not contribute to the background, which we call “seeds”. As such we consider the cases of electromagnetic and axionic seeds. We also discuss their possible observational consequences, for example, we study whether they can provide the origin of primordial galactic magnetic fields, and whether they can generate the initial fluctuations leading to the formation of large-scale structure and the measured cosmic microwave background anisotropies. We finally analyze axion and photon production in four dimensional anisotropic pre-big-bang cosmological models.     

Monte Carlo studies of medium-size telescope designs for the Cherenkov Telescope Array

We present studies for optimizing the next generation of ground-based imaging atmospheric Cherenkov telescopes (IACTs). Results focus on mid-sized telescopes (MSTs) for CTA, detecting very high energy gamma rays in the energy range from a few hundred GeV to a few tens of TeV. We describe a novel, flexible detector Monte Carlo package, FAST (FAst Simulation for imaging air cherenkov Telescopes), that we use to simulate different array and telescope designs. The simulation is somewhat simplified to allow for efficient exploration over a large telescope design parameter space. We investigate a wide range of telescope performance parameters including optical resolution, camera pixel size, and light collection area. In order to ensure a comparison of the arrays at their maximum sensitivity, we analyze the simulations with the most sensitive techniques used in the field, such as maximum likelihood template reconstruction and boosted decision trees for background rejection. Choosing telescope design parameters representative of the proposed Davies–Cotton (DC) and Schwarzchild–Couder (SC) MST designs, we compare the performance of the arrays by examining the gamma-ray angular resolution and differential point-source sensitivity. We further investigate the array performance under a wide range of conditions, determining the impact of the number of telescopes, telescope separation, night sky background, and geomagnetic field. We find a 30–40% improvement in the gamma-ray angular resolution at all energies when comparing arrays with an equal number of SC and DC telescopes, significantly enhancing point-source sensitivity in the MST energy range. We attribute the increase in point-source sensitivity to the improved optical point-spread function and smaller pixel size of the SC telescope design.     

Speckle observations with PISCO in Merate: IV. Astrometric measurements of visual binaries in 2005

We present relative astrometric measurements of visual binaries made during the second semester of 2005, with the speckle camera PISCO at the 102 cm Zeiss telescope of Brera Astronomical Observatory, in Merate. Our sample contains orbital couples as well as binaries whose motion is still uncertain. The purpose of this long term program is to improve the accuracy of the orbits and determine the masses of the components. We performed 130 new observations of 120 objects, with most of the angular separations in the range 0″.1–4″, and with an average accuracy of 0″.01. Most of the position angles could be determined without the usual 180. ambiguity with the application of triple‐correlation techniques, and their mean error is 0°8. We have found a possible new triple system: ADS 11077. The measurements of the closest binaries were made with a new data reduction procedure, based on model fitting of the background of the auto‐correlations. As this procedure proved to be very efficient, we have re‐processed the old observations of close binaries made with PISCO in Merate since 2004. We thus improved 20 measurements already published and obtained 7 new measurements for observations that were previously reported as “unresolved”. We finally present revised orbits for ADS 684, MCA 55Aac (in the Beta 1 Cyg–Albireo multiple system) and ADS 14783 for which the previously published orbits led to large residuals with our measurements and for which the new observations made since their computation allowed a significant improvement of those old orbits. The sum of the masses that we derived for those systems are consistent with the spectral type of the stars and the dynamic parallaxes are in good agreement with the parallaxes measured by Hipparcos. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A possible satellite of (146) Lucina

This paper reports on an observation of the appulse of (146) Lucina with AGK3 + 17° 1309 made on April 18, 1982, at the Meudon Observatory in France. During this observation a secondary event occurred and was recorded. A Nocticon camera mounted on the 1-m telescope and video equipment was used. This equipment is well adapted to these observations primarily because astrometric and photometric reductions are possible. Furthermore no diaphragm is necessary in contrast to classical photometry, and this reduces the possibility of generating artifacts. The Meudon observation is described. Observational data from other sites have been collected, and have confirmed that the short extinction observed at Meudon was not due to the asteroid itself. A possible interpretation is the existence of a faint satellite in the neighborhood of (146) Lucina. The observation leads to a diameter of at least 5.7 km and a projected distance of 1600 km from the primary.