The NATALYA-2M spectrometer of high-energy radiations for the CORONAS-PHOTON space project

The NATALYA-2M high-energy radiation spectrometer is an element of the complex of scientific equipment of the CORONAS-PHOTON satellite. The instrument intended for registering gamma radiation of solar flares in the broad energy range of 0.2–1600 MeV as well as neutrons of solar origin with energies of 20–300 MeV represents itself as a scintillation spectrometer based on CsI(Tl) crystals with a total area of 32 × 38 cm² and the thickness of 18 cm. The spectra and time profiles of the gamma quanta count rates are measured in four subranges: R (0.2–2 MeV), L (1–18 MeV), M (7–250 MeV), and H (50–1600 MeV). Depending on the gamma radiation energy, the effective area of the instrument varies within the range from 750 to 900 cm², and the energy resolution at the Cs-137 line (662 keV) is 10%, it being about 30% at energies higher than 50 MeV. A system of stabilization based on the signal from the generator of reference light pulses is used to provide stability and automated adjustment of the parameters of spectrometric modules. The measuring channels of the instrument are calibrated during the flight using a source of “tagged” gamma quanta on the Co-60 radioactive isotope. Polystyrene scintillation counters are used to provide protection from the background of charged particles. The “CORONAS-PHOTON” spacecraft (SC) was launched from the Plesetsk spaceport on January 30, 2009, to a low circular near-Earth orbit (the altitude is 550 km, the inclination is 82.5°). On February 27, the first scientific data were obtained from the NATALYA-2M instrument. The results of the flight calibration of the instrument detectors in different energy channels demonstrated good agreement with the ground measurements. The paper describes the instrument and observational potentials of the NATALYA-2M spectrometer, gives the results of the adjustment and calibration, and exemplifies the registration of gamma-ray bursts (GRBs)on the orbit.     

CCD cameras and Spacewire interfaces for HERSCHEL/SCORE suborbital mission

The HERSCHEL/SCORE is a suborbital mission which will observe the solar corona in UV and in visible light for measurements of solar corona. The coronagraph for such observation is an Italian instrument and, in particular, the CCD camera detectors are developed at the XUVLab of the Department of Astronomy and Space Science of Florence University. Such detectors communicate with the onboard computer by means the IEEE1355 Spacewire standard interface (developed in our laboratories) and implement a lot of smart and custom procedures for imaging. The main innovation of SCORE coronagraph is the first use in space of a variable retarder plate based on liquid crystals and the optical design capable of simultaneous observation in UV and Visible light.     

Development of an Absolute Accelerometer for Extra-Solar Planet Detection

The method of stellar radial velocity variations has recently shown its capability by the first discovery of several extra-solar planets. Accuracies achieved today are in the range 3-10 m/s. The AAA (absolute astronomical accelerometer) is an instrument which aims to reach the photon noise limit for the measurement of velocity changes, with systematic errors of about 1 m/s, long term. The principle is to use a servo-controlled CCD spectrograph as a null detector, and to register always the lines of the star on the same CCD pixels. Thus, systematic errors linked to the Earth-induced large variations are cancelled. A tunable Fabry-Perot channelled spectrum is also following the star spectrum, while the FP thickness is measured by heterodyne detection of the beats between a tunable laser diode and a stabilized laser diode. A complete prototype of the instrument is operating with laboratory sources and the first results are presented. It is planned to use this system with a new spectrograph, to be coupled to the 152 cm telescope at Observatoire de Haute Provence.     

Fragmentation cross sections and search for nuclear fragments with fractional charge in relativistic heavy ion collisions

We present measurements of fragmentation cross sections of relativistic nuclei and upper limits for the production probability of nuclear fragments with fractional charge using CR39 nuclear track detectors and an automated scanning system. The measurements of the total and partial charge changing fragmentation cross sections concern 16 GeV/nucleon oxygen ions, 14.5 GeV/nucleon silicon ions and 200 GeV/nucleon sulphur ions interacting in copper and CR39 targets. No evidence for fractionally charged fragments was found requiring a minimum track length of 7 mm in CR39 detectors placed after a 14 mm copper target. The combined upper limit for the production probability of fractionally charged fragments relative to ordinary ones is at the level of 1.2–2.3 × 10^–4 (90% C.L.). The charge resolution of the CR39 detectors for an average of 10 measurements of the same track is σ = 0.05e at Z = 6.     

Solar-Blind Diamond Detectors for Lyra, the Solar VUV Radiometer on Board Proba II

Fabrication, packaging and experimental results on the calibration of metal-semiconductor-metal (MSM) photodetectors made on diamond are reported. LYRA (Lyman- RAdiometer onboard PROBA-2) will use diamond detectors for the first time in space for a solar physics instrument. A set of measurement campaigns was designed to obtain the XUV-to-VIS responsivity of the devices and other characterizations. The measurements of responsivity in EUV and VUV spectral ranges (40–240 nm) have been carried out by the Physkalisch-Technische Bundesanstalt (PTB) in Germany at the electron storage ring BESSY II. The longer wavelength range from 210 to 1127 nm was measured with monochromatic light by using a Xe-lamp at IMO-IMOMEC. The diamond detectors exhibit a photoresponse which lie in the 35–65 mA/W range at 200 nm (corresponding to an external quantum efficiency of 20–40%) and indicate a visible rejection ratio (200–500 nm) higher than four orders of magnitude.     

An imaging spectrometric observatory for spacelab

The capability to measure nearly simultaneously the entire spectrum of atmospheric emission from the extreme ultraviolet to the near infrared, with relatively high spectral resolution and high sensitivity, while also obtaining global and altitude coverage, would provide a database from which significant advances could be made in our current understanding of the atmosphere and its processes. The large payload capacity of the shuttle orbiter offers the first opportunity to put such instrumentation into space. The Imaging Spectrometric Observatory (ISO) comprises an array of five spectrometers designed to make full use of the shuttle as an observing platform for remote sensing of the atmosphere. ISO covers the wavelength range 300–12000 Å at 2–7 Å resolution. Use of area array detectors (intensified-CCD's) permits simultaneous measurements of ～1000 Å at a time. The instrument is capable of scanning the entire wavelength range in less than 20 s, or dwelling on weaker features for longer periods of time. The detectors are two dimensional and permit spectral imaging in one direction and spatial imaging in the other. The spatial imaging and spatial scanning features permit measurement of altitude profiles, or mapping of strongly spatially varying features such as aurorae. The instrument is designed to allow versatility. The various functions are programmable and software controlled. The key subsystems are modular for convenient replacement or upgrading. It is anticipated that the instrument will have applications not only in the area of atmospheric science, but also in studies of the ionosphere and magnetosphere, and in support of active experiments to be performed in space.     

The effective technique of the charged particles background discrimination in the atmospheric Cherenkov light detectors

It is shown that parameters of flashes, detected by multichannel image cameras of Cherenkov detectors with closed lids are close to those of Cherenkov flashes initiated by VHE gamma-quanta in the Earth atmosphere. Even after application of criteria for gamma-like events selection a considerable part of those flashes may be misclassified and accepted as gammas. Since the flashes of this kind are detected also during normal measurements with the opened lids of image cameras it just increases the background and, as a consequence, decreases the detector sensitivity even when one uses an anticoincidence scintillator shield around the camera (its efficiency is about 75 %). The use of detectors consisting of two (or more) sections no less than 20–30 m apart permits us to avoid the detection of both muon and local charged particles flashes in the course of observations.     

Monte-Carlo Simulations of Cosmic-ray and Internal Radiation Effects on ISOCAM on Board ISO

One of the main limitations to the sensitivity of the infrared camera ISOCAM on-board the Infrared Space Observatory (ISO) comes from responsivity variations and glitches caused by the impacts of charged particles in photo-detectors. Glitch rate measurements, glitch properties and removal methods have already been addressed during the first ISO detector workshop(Madrid, 1998) and published in a special issue of Experimental Astronomy. It appeared that glitch rate and most of glitch properties could be reproduced by Monte-Carlo simulations. This is very interesting in order to predict before launch the effect of charged particles in photo-detectors operated in space. This paper presents results of Monte-Carlo simulations of radiation effects on ISOCAM detectors. Glitch rates, spatial and energetic properties of glitches have been computed and are compared with measured values. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cosmic gamma-ray bursts detected in the RELEC experiment onboard the Vernov satellite

The RELEC scientific instrumentation onboard the Vernov spacecraft launched on July 8, 2014, included the DRGE gamma-ray and electron spectrometer. This instrument incorporates a set of scintillation phoswich detectors, including four identical X-ray and gamma-ray detectors in the energy range from 10 keV to 3 MeV with a total area of ~500 cm² directed toward the nadir, and an electron spectrometer containing three mutually orthogonal detector units with a geometry factor of ~2 cm² sr, which is also sensitive to X-rays and gamma-rays. The goal of the space experiment with the DRGE instrument was to investigate phenomena with fast temporal variability, in particular, terrestrial gammaray flashes (TGFs) and magnetospheric electron precipitations. However, the detectors of the DRGE instrument could record cosmic gamma-ray bursts (GRBs) and allowed one not only to perform a detailed analysis of the gamma-ray variability but also to compare the time profiles with the measurements made by other instruments of the RELEC scientific instrumentation (the detectors of optical and ultraviolet flashes, the radio-frequency and low-frequency analyzers of electromagnetic field parameters). We present the results of our observations of cosmicGRB 141011A and GRB 141104A, compare the parameters obtained in the GBM/Fermi and KONUS–Wind experiments, and estimate the redshifts and E _iso for the sources of these GRBs. The detectability of GRBs and good agreement between the independent estimates of their parameters obtained in various experiments are important factors of the successful operation of similar detectors onboard the Lomonosov spacecraft.     

Absolute photometric calibration of large aperture optical systems

A method of absolute calibration for the air shower fluorescence detectors of the Pierre Auger Observatory is presented, along with preliminary results from prototype equipment. A 2.5 m diameter light source uniformly illuminated by ultra-violet light emitting diodes is calibrated and mounted at the detector aperture. The resulting end-to-end measurement provides a 7% absolute photon calibration at a wavelength of 375 nm.     

Apodized Lyot coronagraph for SPHERE/VLT: II. Laboratory tests and performance

SPHERE (which stands for Spectro-Polarimetric High-contrast Exoplanet REsearch) is a second-generation Very Large Telescope (VLT) instrument dedicated to high-contrast direct imaging of exoplanets whose first-light is scheduled for 2011. Within this complex instrument one of the central components is the apodized Lyot coronagraph (ALC). The principal aim of this paper is to report the first laboratory experiment of the ALC designed for the SPHERE instrument. The performance and sensitivity of the optical configuration was first numerically studied with an end-to-end approach (see the results in paper I subtitled ??Detailed numerical study??). Made confident by the results, we then tested a prototype on an infrared coronagraphic bench. We measured the transmission profiles of the apodizer prototype and the coronagraphic performance of the apodized Lyot coronagraph in Y, J, and H bands. The coronagraph sensitivity to lateral and longitudinal misalignments of its three main components (apodizer, coronagraphic mask and Lyot stop) was finally studied in H band. We can conclude that the prototype meets the SPHERE technical requirements for coronagraphy.     

Cipher, A Polarimeter Telescope Concept for Hard X-Ray Astronomy

The polarisation of astrophysical source emission in the energy range from a few tens of keV up to the MeV region is an almost unexplored field of high-energy astrophysics. Till date, polarimetry in astrophysics–in the energy domain from hard X-rays up to soft γ-rays–has not been pursued due to the difficulties involved in obtaining sufficient sensitivity. Indeed for those few instruments that are capable of performing this type of measurement (e.g. the COMPTEL instrument on the Compton Gamma-ray Observatory and the IBIS instrument on INTEGRAL), polarimetry itself plays a secondary role in the mission objectives, as the efficiencies (0.5% and 10% maximum, respectively) and polarimetric Q factors (0.1 and 0.3, respectively) are relatively limited. In order to perform efficient polarimetric measurements for hard X-ray and soft gamma-ray sources, with an instrument of relatively robust and simple design, a CdTe based telescope (CIPHER: Coded Imager and Polarimeter for High Energy Radiation) is under study. This instrument is based on a thick (10 mm) CdTe position-sensitive spectrometer comprising four modules of 32 × 32 individual pixels, each with a surface area of 2 × 2 mm² (about 160 cm² total detection area). The polarimetric performance and design optimisation of the CIPHER detection surface have been studied by use of a Monte Carlo code. This detector, due to its intrinsic geometry, can allow efficient polarimetric measurements to be made between 100 keV and 1 MeV. In order to predict the polarimetric performance and to optimise the design and concept of the CIPHER detection plane, a Monte Carlo code based on GEANT4 library modules was developed to simulate the detector behaviour under a polarised photon flux. The Compton double event efficiency, as well bi-dimensional double event distribution maps and the corresponding polarimetric modulation factor will be presented and discussed. Modulation Q factors better than 0.50 and double event total efficiencies greater than 10% were calculated in the energy range between 100 keV and 1 MeV. Herein we will present and discuss the general problems that affect polarimetric measurements in space, such as the inclination of the source with respect to the telescope optical axis and background radiation. Q factor calculations for several beam inclinations as well as for background together with simulated astronomical sources will be presented and discussed.     

Effects of capillary reflection in the performance of the collimator of the Large Area Detector on board LOFT

The Large Observatory For X-ray Timing (LOFT) is one of the candidate missions selected by the European Space Agency for an initial assessment phase in the Cosmic Vision programme. It is proposed for the M3 launch slot and has broad scientific goals related to fast timing of astrophysical X-ray sources. LOFT will carry the Large Area Detector (LAD), as one of the two core science instruments, necessary to achieve the challenging objectives of the project. LAD is a collimated detector working in the energy range 2-50 keV with an effective area of approximately 10 m ²at 8 keV. The instrument comprises an array of modules located on deployable panels. Lead-glass microchannel plate (MCP) collimators are located in front of the large-area Silicon Drift Detectors (SDD) to reduce the background contamination from off-axis resolved point sources and from the diffuse X-ray background. The inner walls of the microchannel plate pores reflect grazing incidence X-ray photons with a probability that depends on energy. In this paper, we present a study performed with an ad-hoc simulator of the effects of this capillary reflectivity on the overall instrument performance. The reflectivity is derived from a limited set of laboratory measurements, used to constrain the model. The measurements were taken using a prototype collimator whose thickness is similar to that adopted in the current baseline design proposed for the LAD. We find that the experimentally measured level of reflectivity of the pore inner walls enhances the off-axis transmission at low energies, producing an almost flat-top response. The resulting background increase due to the diffuse cosmic X-ray emission and sources within the field of view does not degrade the instrument sensitivity.     

POLAR 5—an electron accelerator experiment within an aurora. 3. Evidence for significant spacecraft charging by an electron accelerator at ionospheric altitudes

The POLAR 5 rocket experiment carried an electron accelerator on a “daughter” payload which injected a 0,1 A beam of 10 keV electrons in a pulsed mode every 410ms. With spin and precession, injections were made over a wide range of pitch angles. Measurements from a double probe electric field instrument and from particle detectors on the “mother” payload and from a crude R.P.A. on the “daughter” payload are interpreted to indicate that the “daughter” charges to a potential between several hundred volts and 1 kV. The neutralizing return current to the “daughter” is shown to be assymetrically distributed with the majority being collected from the direction of the beam. The additional electrons necessary to neutralize the daughter are thought to be produced and heated through beam-plasma interactions postulated by Maehlum et al. (1980b) and Grandal et al. (1980) to explain the particle and optical measurements. Significant electric fields emanating from the charged “daughter” and the beam are seen at distances exceeding 100 m at the “mother” payload.     

The Durham/ESO SLODAR optical turbulence profiler

An instrument for monitoring of the vertical profile of atmospheric optical turbulence strength, employing the Slope Detection and Ranging (SLODAR) double star technique applied to a small telescope, has been developed by Durham University and the European South Observatory. The system has been deployed at the Cerro Paranal observatory in Chile for statistical characterization of the site. The instrument is configured to sample the turbulence at altitudes below 1.5 km with a vertical resolution of approximately 170 m. The system also functions as a general-purpose seeing monitor, measuring the integrated optical turbulence strength for the whole atmosphere, and hence the seeing width. We give technical details of the prototype and present data to characterize its performance. Comparisons with contemporaneous measurements from a differential image motion monitor (DIMM) and a multi-aperture scintillation sensor (MASS) are discussed. Statistical results for the optical turbulence profile at the Paranal site are presented. We find that, in the median case, 49 per cent of the total optical turbulence strength is associated with the surface layer (below 100 m), 35 per cent with the 'free atmosphere' (above 1500 m) and 16 per cent with the intermediate altitudes (100–1500 m).     

The SWAP EUV Imaging Telescope. Part II: In-flight Performance and Calibration

The Sun Watcher with Active Pixel System detector and Image Processing (SWAP) telescope was launched on 2 November 2009 onboard the ESA PROBA2 technological mission and has acquired images of the solar corona every one to two minutes for more than two years. The most important technological developments included in SWAP are a radiation-resistant CMOS-APS detector and a novel onboard data-prioritization scheme. Although such detectors have been used previously in space, they have never been used for long-term scientific observations on orbit. Thus SWAP requires a careful calibration to guarantee the science return of the instrument. Since launch we have regularly monitored the evolution of SWAP’s detector response in-flight to characterize both its performance and degradation over the course of the mission. These measurements are also used to reduce detector noise in calibrated images (by subtracting dark-current). Because accurate measurements of detector dark-current require large telescope off-points, we also monitored straylight levels in the instrument to ensure that these calibration measurements are not contaminated by residual signal from the Sun. Here we present the results of these tests and examine the variation of instrumental response and noise as a function of both time and temperature throughout the mission.     

CCD astronomical applications for X-ray temporal studies

Charge coupled devices (CCDs) are under active investigation as imaging detectors in future X-ray astronomy satellites. The exploitation of such detectors holds great promise because of their capability to perform simultaneous imaging and spectroscopy. Unfortunately, standard readout techniques give a temporal resolution insufficient to study X-ray sources showing variability on timescales less than few seconds. In this paper alternative, non-imaging readout modes are investigated, in order to achieve millisecond temporal resolution for point-like sources. Simulation results are presented for the EPIC camera, the focal plane instrument for ESA's mission XMM, showing that the required temporal capabilities can be reached without loss of energy resolution.Work performed in part at the IFC/CNR, Milan, supported by a special EPIC grant from LABEN S.p.A.