Mapping distortion of detectors in UVIT onboard AstroSat observatory

Ultraviolet Imaging Telescope (UVIT) is one of the payloads onboard AstroSat, India’s first multi-wavelength Astronomy mission. UVIT is primarily designed to make high resolution images in wide field, in three wavelength channels simultaneously: FUV (130–180 nm), NUV (200–300 nm) and VIS (320–550 nm). The intensified imagers used in UVIT suffer from distortions, and a correction is necessary for these to achieve good astrometry. In this article we describe the methodology and calculations used to estimate the distortions in ground calibrations.     

Charged Particle Monitor on the Astrosat Mission

Charged Particle Monitor (CPM) on-board the Astrosat satellite is an instrument designed to detect the flux of charged particles at the satellite location. A Cesium Iodide Thallium (CsI(Tl)) crystal is used with a Kapton window to detect protons with energies greater than 1 MeV. The ground calibration of CPM was done using gamma-rays from radioactive sources and protons from particle accelerators. Based on the ground calibration results, energy deposition above 1 MeV are accepted and particle counts are recorded. It is found that CPM counts are steady and the signal for the onset and exit of South Atlantic Anomaly (SAA) region are generated in a very reliable and stable manner.     

A general observatory control software framework design for existing small and mid-size telescopes

A general framework for observatory control software would help to improve the efficiency of observation and operation of telescopes, and would also be advantageous for remote and joint observations. We describe a general framework for observatory control software, which considers principles of flexibility and inheritance to meet the expectations from observers and technical personnel. This framework includes observation scheduling, device control and data storage. The design is based on a finite state machine that controls the whole process.     

The NHXM observatory

Exploration of the X-ray sky has established X-ray astronomy as a fundamental astrophysical discipline. While our knowledge of the sky below 10?keV has increased dramatically (??8 orders of magnitude) by use of grazing incidence optics, we still await a similar improvement above 10?keV, where to date only collimated instruments have been used. Also ripe for exploration is the field of X-ray polarimetry, an unused fundamental tool to understand the physics and morphology of X-ray sources. Here we present a novel mission, the New Hard X-ray Mission (NHXM) that brings together for the first time simultaneous high-sensitivity, hard-X-ray imaging, broadband spectroscopy and polarimetry. NHXM will perform groundbreaking science in key scientific areas, including: black hole cosmic evolution, census and accretion physics; acceleration mechanism and non-thermal emission; physics of matter under extreme conditions. NHXM is designed specifically to address these topics via: broad 0.5?C80 (120) keV band for imaging and spectroscopy; 20?arcsec (15 goal) Half Energy Width (HEW) angular resolution at 30?keV; sensitivity limits more than 3 orders of magnitude better than those available in present day instruments; broadband (2?C35?keV) imaging polarimetry. In addition, NHXM has the ability to locate and actively monitor sources in different states of activity and to repoint within 1 to 2?h. This mission has been proposed to ESA in response to the Cosmic Vision M3 call. Its satellite configuration and payload subsystems were studied as part of previous national efforts permitting us to design a mature configuration that is compatible with a VEGA launch already by 2020.     

Simulation of old open clusters for UVIT on ASTROSAT

The Ultra Violet Imaging Telescope(UVIT) is one of the payloads on the first Indian multiwavelength satellite ASTROSAT,which is expected to be launched by the Indian Space Research Organisation(ISRO) in the year 2015.We have performed simulations of UV studies of old open clusters for the UVIT.The colour magnitude diagrams(CMDs) and spatial appearances have been created using 10 filters associated with the FUV channel(130-180 nm) and NUV channel(200-300 nm)that are available for observations on the UVIT,for the three old open clusters M67,NGC 188 and NGC 6791.The CMDs are simulated for different filter combinations,and they are used to identify the loci of various evolutionary sequences,white dwarfs,blue stragglers,red giants,subgiants,turn off stars and the main sequence of the clusters.The present work helps in identifying a potential area of study in the case of these three old open clusters by considering the availability of filters and the detection limits of the instrument.We also recommend filter combinations,which can be used to detect and study the above mentioned evolutionary stages.The simulations and the results presented here are essential for the optimal use of the UVIT for studies of old open clusters.     

In-orbit Performance of UVIT and First Results

The performance of the ultraviolet telescope (UVIT) on-board AstroSat is reported. The performance in orbit is also compared with estimates made from the calibrations done on the ground. The sensitivity is found to be within \(\sim \)15% of the estimates, and the spatial resolution in the NUV is found to exceed significantly the design value of \(1.8^{\prime \prime }\) and it is marginally better in the FUV. Images obtained from UVIT are presented to illustrate the details revealed by the high spatial resolution. The potential of multi-band observations in the ultraviolet with high spatial resolution is illustrated by some results.     

The infrared space observatory camera

At the focal plane of the ISO 60 cm telescope, ISOCAM will take images of the sky in the wavelength range 2.5 to 17 m. It features two independent channels, containing each a 32×32 array detector. The long wavelength (4–17 m) detector, developed by LIR-LETI specifically for ISOCAM, is a Si:Ga array bonded with indium bumps to a DV readout circuit. The short wavelength (2.5–5.5 m) detector, developed by SAT, is an InSb array with a CID readout.Only one channel operates at a time. The channel selection is obtained with two field mirrors supported by a wheel. The field mirror in operation is in the focal plane of the telescope, covering the 3 arcmin field of view, and reflecting the light into one or into the other channel.In each channel, 10 or 12 discrete band pass filters and CVFs with resolution 45 are mounted on a wheel. A second wheel supports a set of lenses, which reimage the focal plane of the telescope on the array, with a pixel field of view of 1.5, 3, 6 or 12 arcsec.Two integrating spheres, illuminated through small holes by black body sources, are mounted on the selection wheel, for flat fielding and calibration purposes.The flight model of ISOCAM, fully tested and calibrated, has been, delivered to ESA and is ready to be integrated in the satellite, whose expected launch date is September 1995.     

Cosmic GRB 060428C detected in the field of view of the IBIS and SPI telescopes onboard the INTEGRAL observatory and its early afterglow

While analyzing the archival data of the INTEGRAL observatory, we detected and localized a cosmic gamma-ray burst recorded on April 28, 2006, by the IBIS/ISGRI and SPI telescopes in their fields of view. Since the burst was not revealed by the INTEGRAL burst alert system (IBAS), information about its coordinates was not distributed in time and no search for its afterglow was conducted. The burst was recorded by the KONUS/WIND and RHES SI satellites. Its 20–200-keV fluence was 2.3 × 10^?6 erg cm^?2, the peak flux was 3.6 × 10^?7 erg cm^?2 s^?1 (3.9 phot. cm^?2 s^?1). The burst had a complex multipeaked profile and stood out among typical bursts by an increase in its hardness with time. At the flux peak, the spectrum was characterized by a photon index α ? ?1.5 and a peak energy E _p ? 95 keV. The burst lasted for ～12 s, after which its afterglow decaying as a power law with an index γ ～ ?4.5 was observed at energies 15–45 keV. The spectral hardness decreased noticeably during the afterglow.     

High-resolution spectrographs on medium-diameter telescopes

The problem of high-resolution spectroscopic observations on telescopes with diameters of D = 0.5–1.5 m is considered. Examples of the optimum technical solutions and survivability of certain telescopes and methods of observation are given in retrospect. Improvements in the technique of spectroscopy allow one to also consider the potential of those instruments that were not originally intended for use in high-resolution spectroscopy. Arguments in favor of using medium-diameter telescopes in modern high-resolution spectroscopy are discussed. This review is connected to the 100th anniversary of the 122-cm telescope of the Crimean Astrophysical Observatory.     

Extragalactic integral field spectroscopy on the Gemini telescopes

We have been undertaking a programme on the Gemini 8‐m telescopes to demonstrate the power of integral field spectroscopy, using the optical GMOS spectrograph, and the new CIRPASS instrument in the near‐infrared. Here we present some preliminary results from 3D spectroscopy of extra‐galactic objects, mapping the emission lines in a 3CR radio galaxy and in a gravitationally lensed arc, exploring dark matter sub‐structure through observations of an Einstein Cross gravitational lens, and the star formation time‐scales of young massive clusters in the starburst galaxy NGC 1140. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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)     

The IPS work in Beijing astronomical observatory

This article describes the IPS work in the Beijing astronomical observatory including the hardware and software of the instrument and some theoretical research.The project is supported by the China National Nature Science Fundation under the program 49391400     

The Digicon system of Cima Ekar observatory

This paper describes the Digicon system in current operation for spectroscopic acquisition at the 182-cm telescope of Cima Ekar (Asiago). An example of observation of the emission-line galaxy VV 565 provides evidence of the quality of the system.     

The Coronal Diagnostic Spectrometer for the solar and heliospheric observatory

The Coronal Diagnostic Spectrometer is designed to probe the solar atmosphere through the detection of spectral emission lines in the extreme ultraviolet wavelength range 150 – 800 . By observing the intensities of selected lines and line profiles, we may derive temperature, density, flow and abundance information for the plasmas in the solar atmosphere. Spatial and temporal resolutions of down to a few arcseconds and seconds, respectively, allow such studies to be made within the fine-scale structure of the solar corona. Futhermore, coverage of large wavelength bands provides the capability for simultaneously observing the properties of plasmas across the wide temperature ranges of the solar atmosphere.     

A decade of cost-reduction in very large telescopes (The SST as prototype of special-purpose telescopes)

Many design and technical innovations over the past ten or fifteen years have reduced the costs of very large telescopes by nearly an order of magnitude over those of classical designs. Still a further order of magnitude reduction is possible if the telescope is specialized for on-axis spectroscopy, giving up especially the luxuries of wide field, multiple focal positions, and access to all the sky at will. The SST (Spectroscopic Survey Telescope) with use eighty-five 1 m circular mirrors mounted in a steel frame composed of hundreds of interlocking tetrahedrons, keeping a fixed elevation angle of 60° with rotation only in azimuth. Using an optical fiber it will feed as much light to spectrographs as can be done by a conventional 8 m telescope, yet has a target basic completion cost of only $6 million.Paper presented at the Symposium on the JNLT and Related Engineering Development, Tokyo, November 29–December 2, 1988.     

The Spin-X wide-field X-ray monitor of the Spectrum-X-Gamma astrophysical observatory

The Spin-X wide-field X-ray monitor of the Spectrum-X-Gamma astrophysical observatory, which is based on the principle of a coded-aperture telescope, is designed to detect and localize cosmic gammaray-burst (GRB) sources; to survey large areas of the sky in search of new transients; and to carry out long-term observations of bright Galactic sources, including X-ray bursters. The monitor consists of two noncoaxial identical modules, Spin-X1 and Spin-X2, which together cover 6.8% of the sky. The high-apogee, four-day orbit of the Spectrum-XG satellite allows the instrument to be in observing mode more than 50% of the time. Having simulated the rate of GRB detection by Spin-X, we show that extrapolating BATSE 50–300-keV average data on the number of GRBs, their duration, and their mean energy spectrum to the X-ray energy band leads to disagreement with the observed detection rate of GRBs in the X-ray band. The number of GRBs that can be detected and localized with an accuracy r≤3′ (3σ) (the error-circle radius) by Spin-X is estimated to be ten bursts per year. We present data on the Spin-X sensitivity achievable during long-term observations of persistent and transient sources and on its sensitivity to X-ray bursts from Galactic sources in the 2–30-keV energy band.