The first large format Si:Sb BIB arrays

The first 128×128 Si:Sb blocked impurity band (BIB) detectors, manufactured by Rockwell International, are sensitive detectors from 10 to at least 40 m. While further work is required to make these arrays suitable for the low backgrounds of space infrared telescopes, they can be used now for observations from the ground and aircraft.     

The UVIT telescopes on the Astrosat observatory

The UVIT telescopes are a payload package on the ISRO Astrosat observatory. They are co-aligned with three X-ray telescopes, and will operate simultaneously with them. The overall observatory is summarized, and details are given of the design, performance, and operation of the UVIT telescopes. These will offer close to arcsecond resolution over half-degree fields, simultaneously in FUV, NUV, and blue-visible bands. All bands have several filters and the UV bands have low-dispersion objective gratings.     

AGN Detection Ranges of MACE and TACTIC Imaging Gamma-Ray Telescopes

Two high-sensitivity imaging gamma-ray telescopes, MACE and TACTIC, are being set up at Mt. Abu, India, for making detailed spectral and temporal investigations of galactic and extragalactic gamma-ray sources in the photon energy bands. E 20–200 GeV and 0.5–5TeV respectively. Here, we estimate the effective red-shift ranges of these telescopes for detecting gamma-ray signals from the EGRET-detected AGN's and identify the most likely candidate-sources for detection by the MACE and the TACTIC, under the assumption that the EGRET-inferred power-law spectra for these AGN's extend into the GeV-TeV range without any change in shape. Extremum bounds of the relevant intergalactic background radiation fields, suggested by various observational and theoretical considerations, have been used to estimate the attenuation of VHE gamma-ray fluxes due to photon-photon pair-production process, leading to the desired z-ranges for these instruments.     

The new site testing survey in the Canary Islands' Observatories

The future establishment of large telescopes at the Observatorio del Roque de los Muchachos (ORM) has raised the necessity of designing a site-testing campaign, aimed specifically at selecting their emplacements, as well as characterizing correctly the local seeing behaviour and the fluctuations of the turbulent field in the area covered by the observatory.This paper describes the site evaluation programme to be carried out at the ORM during the next four years. The data obtained in this program will improve earlier tests in the critical areas of sub-are sec seeing, the size of the isoplanatic patch, the efecto Caldera and suitability for infrared astronomy, among others.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

A sky-noise measurement and its implication for ground-based infrared astronomy in the 10μm atmospheric window

A spectral analysis of the fluctuations of the infrared sky radiance at 10m was made at the ESO-site of La Silla in Northern Chile. The data are compared to literature. The consequences of the results on infrared observing for future large telescopes are discussed: our data suggest that in order to achieve background noise limited performance in the 10m atmospheric window chopping with frequencies of 8 Hz and amplitudes of 10 arcsec is mandatory.based on observations obtained at the European Southern Observatory, La Silla, Chile     

Robotic telescopes and networks: New tools for education and science

Nowadays many telescopes around the world are automated and some networks of robotic telescopes are active or planned. Such equipment could be used for thetraining of students and for science in the Universities of DCs and of newastronomical countries, by sending them observational data via Internetor through remotely controlled telescope. It seems that it is thetime to open up for discussion with UN and ESA organizations and also withIAU, how to implement links between robotic telescopes and suchUniversities applying for collaborations. Many scientific fields couldthus be accessible to them, for example on stellar variability, near-earthobject follow-up, -ray burst counterpart tracking, and so on.     

Multifrequency behayiour of the dwarf nova SS Cygni

Several years of coordinated multifrequency observations of the dwarf nova SS Cygni have been performed in order to study the accretion behaviour of this system in particular, and in general to clarify this crucial problem for the cataclysmic variables.From IUE measurements, together with those from optical and IR ground based telescopes, we have found orbital modulations in the continuum and in the equivalent widths of the emission lines. During quiescent phases the behaviour of SS Cygni are dependent on the type of the preceding outburst (long-type or short-type).In this paper we will discuss the physical implications one can derive from these results.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.Based on the observations performed with IUE (VILSPA) satellite, and with the telescopes of the Loiano and Roque de los Muchachos Observatories.     

Soft proton flux on <Emphasis Type="Italic">ATHENA</Emphasis> focal plane and its impact on the magnetic diverter design

The experience gained with the current generation of X-ray telescopes like Chandra and XMM-Newton has shown that low energy “soft” protons can pose a severe threat to the possibility to exploit scientific data, reducing the available exposure times by up to 50% and introducing a poorly reproducible background component. These soft protons are present in orbits outside the radiation belts and enter the mirrors, being concentrated towards the focal plane instruments, losing energy along their path and finally depositing their remaining energy in the detectors. Their contribution to the residual background will be even higher for ATHENA with respect to previous missions, given the much higher collecting area of the mirrors, even if the instruments will likely suffer no significant radiation damage from this particles flux. As a consequence this soft proton flux shall be damped with the use of a magnetic diverter to avoid excess background loading on the WFI or X-IFU instruments. We present here a first complete evaluation of this background component for the two focal plane instruments of the ATHENA mission in absence of a magnetic diverter, and derive the requirements for such device to reduce the soft protons induced background below the level required to enable the mission science. We estimate the soft proton flux expected in L2 for the interplanetary component and for the component generated locally by acceleration processes in the magnetotail. We produce a proton response matrix for each of the two instruments of ATHENA focal plane, exploiting two independent Monte Carlo simulations to estimate the optics concentration efficiency, and Geant4 simulations to evaluate the energy loss inside the radiation filters and deposited in the detector. With this modular approach we derive the expected fluxes and spectra for the soft protons component of the background. Finally, we calculate the specifics of a magnetic diverter able to reduce such flux below the required level for both X-IFU and WFI.     

TAUVEX - Tel Aviv University UV Explorer

TAUVEX - Tel Aviv University UV Explorer is a space telescope that is currently being built in Israel, to be flown on board the Russian international sattelite SRG - Spectrum Roentgen Gamma, in late 1995 or early 1996. TAUVEX is an imager in the near UV spectral window. Its major goal is to make a survey of about 10% of the UV sky, in the range = 1350 - 3500Å. A successful operation of TAUVEX will partially fill an important gap in our recognition of the sky, namely the distribution and the nature of the celestial UV sources, which are still mostly unknown. TAUVEX will also operate as a fast multicolor photometer in its UV range of operation. TAUVEX is aligned in parallel to the common optical axix of all the other instruments on board SRG, most of which are telescopes and monitors for high energy radiation. SRG will be thus able to perform for the first time in history simultaneous astronomical observations in one and the same celestial body, that cover together 7 order of magnitude of the recorded radiation. The observations of TAUVEX can be greatly enhanced by ground base observations.     

The short history of infrared space telescopes

While astronomical telescopes developed rather slowly over the last four centuries, infrared telescopes made a fast career in only four decades from high mountains to aircraft, balloons and satellites. They cover the huge wavelength region from 1 to 350 μ m and have uncovered the cold and dust hidden universe. While until today all infrared space telescopes had diameters of <1 m, cooled infrared observatories with 3.5 to 6.5m mirrors will be sent into heliocentric orbits at L2 within the next few years (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X-Ray Interferometry

For the astronomer, X-ray interferometry is the theory and practice of building dilute aperture telescopes for studying celestial X-ray sources. The short wavelengths and high surface brightness of X-ray sources will make the eventual scientific payoff very high, with direct imaging of the event horizons of black holes as the centerpiece. In this article, we review the history of X-ray interferometry and discuss the recent technical developments toward astronomical applications. We present several mission concepts and show they are achievable with todays technology.     

Importance of Small Telescopes in the Understanding of ActiveHot Stars Physics

Active hot stars (Be stars) have been observed and studied for more thantwo decades. They exhibit hydrogen emission lines in the visibledomain and often some emission lines of singly ionized metals.These emissions originate in a circumstellar envelope produced bya strong radiative stellar wind. Since the discovery of the prototype star of this class ( Cas) by Father A. Secchi in 1866, the basic physical properties of these objects are still poorly known. These stars are also very bright (most of them can be found in the Bright Star Catalogue) which make them good targetsfor small telescopes studies. In the following I will focus on some studies that can be done using a 40 cm telescope class. Then I willexplain how small telescopes can be combined in an interferometric network in order to reach one milliarcsecond (mas) angular resolutioneven if each telescope's aperture can be smaller thanten centimeters. With this technics it becomes possible to measurevery small and faint structures on the stellar surface of starsother than our sun.     

The Edinburgh-Cape blue object survey

The Edinburgh-Cape Blue Object Survey is a major survey to discover blue stellar objects brighter than B 18 in the southern sky. It is covering an area of sky of 10,000 square degrees with |b| > 30° and < 0°. The blue stellar objects are selected by automatic techniques from U and B pairs of UK Schmidt Telescope plates scanned with the COSMOS measuring machine. Follow-up photometry and spectroscopy are being obtained with the SAAO telescopes to classify objects brighter than B = 16.5. This paper describes the survey, the techniques used to extract the blue stellar objects, the photometric accuracy, the spectroscopic classification, and the completeness of the survey.     

Ground-based interferometry

This paper summarizes the limits of ground-based interferometry for differential astrometry as well as ground-based interferometry for direct detection of exo-planets and exo-zodi dust levels. For direct detection, ground-based interferometry at near IR wavelengths using large telescopes with adaptive optics offers a significant advantage over single telescopes with adaptive optics. Ground-based differential astrometry for exo-planet detection is extremely accurate with sufficient accuracy to detect Neptune mass planets around 400–600 nearby stars. Ground-based interferometry using large (>6m) telescopes is also capable of detecting the 10 m emission of the zodiacal light around nearby stars with zodi levels similar to our solar system     

The DARWIN project

Angel and co-workers have proposed to detect exoplanets around nearby stars in the infrared (6–17 m) and to analyze their spectra, searching for H₂O, CO₂, CH₄, NH₃, and O₃ spectral features. The presence or absence of CO₂ would indicate either a strong similarity or difference with Solar telluric planet atmospheres. Water would indicate a habitable planet, and O₃ would reveal significant photosynthesis activity, due to the presence of carbon chemistry based life. Like these authors, we suggest an infrared nulling interferometer pointing to the star and working as a coronograph. Our main contribution is to propose an observatory made of four to five 1-meter class telescopes observing from about 4 to 5 AU to avoid the Solar Zodiacal Light (ZL) background at 10m instead of four 8-meter ones observing from the Earth vicinity. This allows the mission to be feasible in thenear future. The concept, named DARWIN, is under consideration by the European Space Agency for its Horizon 2000 Plus program.     

Serendipitous UV source catalogues for 10 years of XMM and 5 years of Swift

Two UV serendipitous source catalogues are presented which were compiled based on the observations with two similar UV telescopes, one being on-board the ESA’s XMM Newton observatory and another—on-board the NASA’s Swift satellite. Both telescopes have similar optical and registration systems providing photometry in three ultraviolet and three visible bands. After processing a 10 years long series of observations from XMM and 5 years from Swift, we have compiled two source catalogues containing more than 4 million sources for XMM and 6 million sources for Swift. We describe the processing algorithms and present catalogue characteristics in comparison with each other.     

The solar-flare infrared continuum

We consider potential sources of infrared (1 to 1 mm) continuum in solar flares. Several mechanisms should produce detectable fluxes: in the 350 window for ground-based observations, impulsive emission will arise in synchrotron radiation from 1–10 MeV electrons, and possibly thermal (free-free) continuum from the source of the white-light flare; the hot flare plasma responsible for soft X-ray emission will also emit detectable fluxes of free-free continuum in the largest flares. At shorter wavelengths the dominant infrared emission will come from the H flare itself. Observations in the infrared wavelengths will help to complete our picture of flare structure in both the impulsive and gradual phases.     

New 8–13 μm Si:Ga/DRO hybrid arrays for very large telescopes

Since 1984, the CEA-LETI-LIR (Infrared Laboratory) has been involved in development of Si:Ga/DRO hybrid detector arrays dedicated to imaging of astronomical sources in the 8–13 m range. Successively, 32×32 element arrays were successfully manufactured for the ISOCAM camera and 64×64 arrays were fabricated for ground-based imaging. The latter detectors have been integrated in 3 cameras (C10, CAMIRAS and TIMMI for ESO) and have led to excellent astrophysical results since 1990.To equip instruments to be mounted on very large telescopes such as the European VLT at ESO, manufacture of new arrays has been undertaken and is currently under way at CEA-LETI-LIR. These new arrays will have a 128×192 format and will present the outstanding essential feature that their storage capacity will be able to be changed according to observation conditions (2 capacities will be implemented in the pixel).The main characteristics of these new detectors will be presented in this paper.     

The University of Durham Southern Hemisphere VHE gamma ray telescope

The design of very high energy (VHE) gamma ray telescopes is discussed and it is shown that a triple-mirror telescope operating in threefold fast coincidence provides an effective instrument. The design, construction and operation of a large VHE gamma ray telescope with an energy threshold of 300 GeV (at the zenith) and incorporating several novel features is described. The use of a coincidence guard ring technique is shown to result in the rejection of about 50% of the off-source (proton) events which form a high background and limit the sensitivity of such telescopes.