Crowded-field image simulator for WSO-UV/ISSIS: first functional version developed by the Glendama team

We are developing a web-based interactive software to simulate crowded-field imaging with ISSIS on board the future WSO-UV. This new tool is aimed to prepare WSO-UV/ISSIS proposals to observe multicomponent targets and dense fields. For a given combination of UV channel, filters and exposure time, the user creates a set of point-like and extended sources (source model). This source model produces a final image, which takes into account a pixelated field of view, a realistic conversion between physical flux and counts per second, the convolution with the expected point spread function, a sky background and noise fluctuations. The current version of the simulator is available at the Glendama website, and it allows users to specify all relevant parameters of each point-like or extended source, drag-and-drop sources by using a mouse or a fingertip/stylus on a touchscreen, change the frame size or the brightness scale, etc.     

Ultraviolet Astronomy: Astrophysical Perspectives of the Spektr-UF Project (WSO-UV)

Astrophysics - The prospects for astronomical observations in the ultraviolet (UV) are discussed in a brief review and the areas in which UV astronomy is especially in demand are listed. Some...     

The Imaging and Slitless Spectroscopy Instrument for Surveys (ISSIS): expected radiometric performance,operation modes and data handling

ISSIS is the instrument for imaging and slitless spectroscopy on-board WSO-UV. In this article, a detailed comparison between ISSIS expected radiometric performance and other ultraviolet instruments is shown. In addition, we present preliminary information on the performance verification tests and on the foreseen procedures for in-flight operation and data handling.     

Final results from the space dust (SPADUS) instrument flown aboard the earth-orbiting ARGOS spacecraft

In this paper, we present the final report of the data obtained from the Space Dust (SPADUS) instrument on the Earth-orbiting Advanced Research and Global Observation Satellite (ARGOS). The University of Chicago's SPADUS instrument on the US Air Force's Advanced Research and Global Observation Satellite has been operating in a nearly polar orbit, at an altitude of approximately 850 km, since soon after its launch on day 54, 1999 (23 February) until termination of the SPADUS operations on day 248, 2001 (5 September).The instrument consists of a polyvinylidene fluoride (PVDF) dust trajectory system, which includes two planar arrays of PVDF sensors (a total of 16 sensors per array) separated by 20.25 cm to provide time of flight (TOF) measurements. The trajectory system measures dust particle flux, mass distribution, velocity and trajectory. The instrument also includes the SPADUS Ancillary Diagnostic Sensor (ADS) subsystem, which measured energetic charged particles (electrons, protons, etc).The PVDF dust trajectory system detected a total of 368 dust impacts over the SPADUS live-time interval of 739 days, yielding an average particle flux of 0.50 impacts/day. Of these 368 impacts, 35 were D1-D2 type events—where particles impacted and penetrated a D1 sensor, then impacted a D2 rear array sensor—allowing for time-of-flight measurements. Of the 35 D1-D2 impacts on SPADUS, we identified 19 D1-D2 impacts yielding TOF values. Of these 19 events, 14 were ambiguous (either bound or interplanetary) and 5 were unambiguous interplanetary impacts. Examples of particle orbits for debris particles as well as D1-D2 impacts are detailed. We also describe transient particle streams detected by the SPADUS trajectory system, resulting from the passage of ARGOS through streams of debris particles in Earth orbit. One of the streams was shown to result from detection by SPADUS of the debris generated by the explosion of a Chinese booster rocket.The SPADUS flight data accumulated over the 30-month mission shows that PVDF-based dust instruments utilizing two planar arrays of PVDF dust sensors in a TOF arrangement—can provide useful measurements of particle velocity, mass distribution, flux, trajectory and particle orbital elements.     

A star-based method for precise wavelength calibration of the Chinese Space Station Telescope(CSST) slitless spectroscopic survey

The Chinese Space Station Telescope(CSST)spectroscopic survey aims to deliver high-quality low-resolution(R>200)slitless spectra for hundreds of millions of targets down to a limiting magnitude of about 21 mag,distributed within a large survey area(17500 deg2)and covering a wide wavelength range(255-1000 nm by three bands GU,GV,and GI).As slitless spectroscopy precludes the usage of wavelength calibration lamps,wavelength calibration is one of the most challenging issues in the reduction of slitless spectra,yet it plays a key role in measuring precise radial velocities of stars and redshifts of galaxies.In this work,we propose a star-based method that can monitor and correct for possible errors in the CSST wavelength calibration using normal scientific observations,taking advantage of the facts that(ⅰ)there are about ten million stars with reliable radial velocities now available thanks to spectroscopic surveys like LAMOST,(ⅱ)the large field of view of CSST enables efficient observations of such stars in a short period of time,and(ⅲ)radial velocities of such stars can be reliably measured using only a narrow segment of CSST spectra.We demonstrate that it is possible to achieve a wavelength calibration precision of a few km s^-1 for the GU band,and about 10 to 20 kms^-1 for the GV and GI bands,with only a few hundred velocity standard stars.Implementations of the method to other surveys are also discussed.     

Solar dynamics imaging system a back-end instrument for the proposed NLST

The Solar Dynamics Imaging System (SDIS) will be one of the focal plane instruments operated at the National Large Solar Telescope (NLST). The prime objective of the instrument is to obtain high spatial and temporal resolution images of the region of interest on the Sun in the wavelength range from 390 nm to 900 nm. The SDIS provides filtergrams using broad-band filters while preserving the Strehl ratio provided by the telescope. Furthermore, the SDIS is expected to provide observations that allow image reconstruction to extract wave front information and achieve a homogenous image quality over the entire FOV.     

Deep Hubble Space Telescope imaging surveys and the formation of spheroidal galaxies

We have extended our previous analysis of morphologically selected elliptical and S0 galaxies in the Hubble Deep Field (HDF) North to include Hubble Space Telescope ( HST ) data in the HDF South and the HDFS–NICMOS areas. Our final sample amounts to 69 E/S0 galaxies with K <20.15 over an area of 11 arcmin². Although a moderately small number over a modest sky area, this sample benefits from the best imaging and photometric data available on high-redshift galaxies. Multi-waveband photometry allows us to estimate with good accuracy the redshifts for the majority of these galaxies, which lack a spectroscopic measure. We confirm our previous findings that massive E/S0s tend to disappear from flux-limited samples at z >1.4. This adds to the evidence that the rest-frame colours and spectral energy distributions (SEDs) of the numerous objects found at 0.8< z <1.2 are inconsistent with a very high redshift of formation for the bulk of stars, while they are more consistent with protracted (either continuous or episodic) star formation down to z ≤1. These results based on high-quality imaging on a small field can be complemented with data from colour-selected extremely red objects (EROs) on much larger sky areas: our claimed demise of E/S0s going from z =1 to z =1.5 is paralleled by a similarly fast decrease in the areal density of EROs when the colour limit is changed from ( R − K )=5 to ( R − K )=6 (corresponding to z ≃1 and z ≃1.3 respectively). Altogether, the redshift interval from 1 to 2 seems to correspond to a very active phase for the assembly of massive E/S0 galaxies in the field, and also probably one where a substantial fraction of their stars are formed.     

The experiment with the fast X-ray monitor (BRM) instrument onboard the CORONAS-PHOTON satellite

The “Fast X-ray Monitor” (BRM) instrument operated in the complex of the scientific instruments onboard the CORONAS-PHOTON satellite from February 19, 2009, until December 1, 2009. The instrument is intended for the registration of the hard X-ray radiation of solar flares in the 20–600 keV energy range in six differential energy channels (20–30, 30–40, 40–50, 50–70, 70–130, and 130–600 keV) with temporal resolution to 1 ms. In the instrument, a detector based on the YAP: Ce scintillator is used; this detector is 70 mm in diameter and 10 mm thick (the decay time is about 28 ns). For the decrease of the back-ground charge of the detector, the collimator limiting the angle of view of the instrument of value 12° is mounted over the scintillator. The effective area of the detector amounts to 27.7 cm² (at the X-ray radiation energy 80 keV), and the dead time of the detector is 1 μs. Over the operation onboard the CORONAS-PHOTON satellite, the BRM instrument has registered gamma ray burst series and, perhaps, one solar flare of the class C1.3 on October 26, 2009.     

The importance of intermediate size space missions to maintain access for astronomers to the space windows (Science with the World Space Observatory)

General, technological and scientific premises of new UV-opticalobservatory (e.g. World Space Observatory) are briefly discussed. The 2-m class telescopewith high-resolution spectrograph and imaging camera seems to be a proper combination for the multipurpose observatory.     

A rocket instrument for imaging the aurora by means of high speed photometric scanning

A high resolution rocket-borne mechanical flying spot scanner has evolved from similar ground-based instruments. The spinning motion of the rocket together with that of a motor-driven prism are used to scan a narrow-angle photometer systematically and repetitively over the full 4π sr region around the rocket. Outputs from two wavelengths selected by narrow-band interference filters are available from the one instrument. The large quantity of data thus obtained are first reproduced in pictorial form making it relatively easy to identify auroral and airglow features which can then be studied quantitatively. Computer reduction of the data also makes it possible to determine the attitude of the vehicle carrying the scanner to an accuracy better than can be achieved with an aspect magnetometer. Results illustrating the capabilities of the instrument and data analysis system have been obtained from rocket AKD-VB-27 which was launched from the Churchill Research Range, 20 January 1971.     

Relics of the primordial origin of space and time in the low energy world

In the earliest stage of cosmological evolution due to high matter densities space and time most likely admitted a very complex geometrical and topological structure. After themalization, statistical averaging and cooling, flat Minkowski space developed but statistical fluctuations from this averaged out space-time may still exist in the low energy world. In the following, we explore the consequences of these fluctuations in the low energy world based on a microscopic uncertainty principle for time. Phenomena such as spin polarization precession, spectral shifts, spin flips, C.P. violating phenomena and neutron interferometry may all be influenced by these fluctuations and we discuss just how the conventional theory of these temporal phenomena could be affected by fluctuations away from Minkowski space-time. We also discuss the experimental limits on the discrete time interval setting the scale of these fluctuations along with possible temporal changes of the discrete time interval over cosmological time scales in the spirit of Dirac's Large number hypothesis.     

The size distribution of Jupiter's main ring from Galileo imaging and spectroscopy

Galileo's Solid State Imaging experiment (SSI) obtained 36 visible wavelength images of Jupiter's ring system during the nominal mission (Ockert-Bell et al., 1999, Icarus 138, 188-213) and another 21 during the extended mission. The Near Infrared Mapping Spectrometer (NIMS) recorded an observation of Jupiter's main ring during orbit C3 at wavelengths from 0.7 to 5.2 μm; a second observation was attempted during orbit E4. We analyze the high phase angle NIMS and SSI observations to constrain the size distribution of the main ring's micron-sized dust population. This portion of the population is best constrained at high phase angles, as the light scattering behavior of small dust grains dominates at these geometries and contributions from larger ring particles are negligible. High phase angle images of the main ring obtained by the Voyager spacecraft covered phase angles between 173.8° and 176.9° (Showalter et al., 1987, Icarus 69, 458-498). Galileo images extend this range up to 178.6°. We model the Galileo phase curve and the ring spectra from the C3 NIMS ring observation as the combination of two power law distributions. Our analysis of the main ring phase curve and the NIMS spectra suggests the size distribution of the smallest ring particles is a power law with an index of 2.0±0.3 below a size of ∼15 μm that transitions to a power law with an index of 5.0±1.5 at larger sizes. This combined power law distribution, or “broken power law” distribution, yields a better fit to the NIMS data than do the power law distributions that have previously been fit to the Voyager imaging data (Showalter et al., 1987, Icarus 69, 458-498). The broken power law distribution reconciles the results of Showalter et al. (1987, Icarus 69, 458-498) and McMuldroch et al. (2000, Icarus 146, 1-11), who also analyzed the NIMS data, and can be considered as an obvious extension of a simple power law. This more complex size distribution could indicate that ring particle production rates and/or lifetimes vary with size and may relate to the physical processes that control their evolution. The significant near arm/far arm asymmetry reported elsewhere (see Showalter et al., 1987, Icarus 69, 458-498; Ockert-Bell et al., 1999, Icarus 138, 188-213) persists in the data even after the main ring is isolated in the SSI images. However, the sense of the asymmetry seen in Galileo images differs from that seen in Voyager images. We interpret this asymmetry as a broad-scale, azimuthal brightness variation. No consistent association with the magnetic field of Jupiter has been observed. It is possible that these longitudinal variations may be similar to the random brightness fluctuations observed in Saturn's F ring by Voyager (Smith et al., 1982, Science 215, 504-537) and during the 1995 ring plane crossings (Nicholson et al., 1996, Science 272, 509-515; Bosh and Rivkin, 1996, Science 272, 518-521; Poulet et al., 2000, Icarus 144, 135-148). Stochastic events may thus play a significant role in the evolution of the jovian main ring.     

The origin of (90) Antiope from component-resolved near-infrared spectroscopy

The origin of the similarly-sized binary Asteroid (90) Antiope remains an unsolved puzzle. To constrain the origin of this unique double system, we recorded individual spectra of the components using SPIFFI, a near-infrared integral field spectrograph fed by SINFONI, an adaptive optics module available on VLT-UT4. Using our previously published orbital model, we requested telescope time when the separation of the components of (90) Antiope was larger than 0.087″, to minimize the contamination between components, during the February 2009 opposition. Several multi-spectral data-cubes in J band (SNR = 40) and H + K band (SNR = 100) were recorded in three epochs and revealed the two components of (90) Antiope. After developing a specific photometric extraction method and running an error analysis by Monte-Carlo simulations, we successfully extracted reliable spectra of both components from 1.1 to 2.4 μm taken on the night of February 21, 2009. These spectra do not display any significant absorption features due to mafic mineral, ices, or organics, and their slopes are in agreement with both components being C- or Cb-type asteroids. Their constant flux ratio indicates that both components’ surface reflectances are quite similar, with a 1-sigma variation of 7%. By comparison with 2MASS J, H, K color distribution of observed Themis family members, we conclude that both bodies were most likely formed at the same time and from the same material. The similarly-sized system could indeed be the result of the breakup of a rubble-pile proto-Antiope into two equal-sized bodies, but other scenarios of formation implying a common origin should also be considered.     

Detection of ferric iron in an exsolved lunar pyroxene using electron energy loss spectroscopy (EELS): Implications for space weathering and redox conditions on the Moon

To shed light on the mechanism of formation of nanophase iron particles (npFe) in space-weathered materials from airless bodies, we analyzed exsolved and unexsolved space-weathered lunar pyroxenes from Apollo 17 sample 71501. The exsolved pyroxene allowed for the observation of the effects of space weathering on similar mineral phases with variable composition. Using coordinated scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy (EELS), we determined that two coexisting pyroxenes in the exsolved grain showed systematic variations in response to space weathering, despite equivalent exposure conditions. The npFe in the space-weathered rim of augite lamellae were smaller and fewer than the npFe in the rim of pigeonite lamellae. EELS spectrum imaging revealed the presence and heterogeneous distribution of Fe⁰, Fe²⁺, and Fe³⁺ in the exsolved pyroxene. Metallic iron occurred in the npFe, a mixture of Fe²⁺ and Fe³⁺ occurred in the pigeonite lamellae, and the augite lamellae contained virtually all Fe³⁺. Approximately 50% of the total Fe measured in the exsolved pyroxene grain was ferric. Partitioning of Fe²⁺ and Fe³⁺ among the lamellae is invoked to explain the difference in npFe development in pigeonite and augite. The results of this study, the first to identify Fe³⁺ in a crystalline lunar ferromagnesian silicate, have implications for our understanding of how space weathering might proceed in oxidized phases. Furthermore, the discovery of an Fe³⁺-rich pyroxene also supports attribution of the 0.7 μm absorption feature observed in Galileo Solid State Imager data to oxidized Fe in clinopyroxenes.     

Infrared imaging and spectroscopy with arrays at the University of Montreal

The Montreal Infrared Camera (MONICA) consists of a LN₂ cryostat enclosing a NICMOS3 array, re-imaging optics and a filter wheel mechanism containing broad-band and circular variable filters. A polarimetry mode with a warm half wave plate and a cold polarizer/filter combination is also supported. At the CFHT 0.5 (FWHM) images are routinely obtained with limiting magnitudes of 22.8 at J and 21.7 at K (S/N=3 in 1hr).The Spectrometre Infrarouge de Montréal (SIMON) is a versatile grating spectrometer with spectral resolutions ranging from 300 to 5000. Presently under construction, this spectrometer will initially contain a 512×512 HgCdTe array. Use of reflective optics will allow a future upgrade to a similar format InSb array, extending the wavelength coverage to 5m. SIMON will also have an imaging mode to facilitate the centering of objects within interchangeable slits.