Ground-based γ-ray astronomy has considerably developed during the last five years, which have attracted the attention of the wider scientific community.A brief review of ground-based γ-ray detectors is given. The basic observational techniques and constraints are discussed. The needs for future, the advantages of broadening the energy range are described.

Very high energy gamma-ray astronomy is now bringing an invaluable contributionto the understanding of violent phenomena in the Universe, as well as the searchfor exotic physics such as indirect detection of dark matter or a test ofLorentz invariance violation. The current Imaging Arrays of Cherenkov Telescopes(IACT) show that this technique is mature. In Europe, the community is gatheringaround the Cherenkov Telescope Array consortium, to design and build the next generationground-based array. It should reach an order of magnitude in sensitivity in awide energy band, ranging from 10 GeV to more than 100 TeV. This goal can beachieved with an array of 50–100 telescopes of various sizes at variousspacings. With about 2000 channels per camera, a specific effort has to be madeto design front-end electronics with a lower cost and better performances.A gain in cost and performances can be obtained by maximising the integration of thefront-end electronics in an ASIC. The amplifiers, analogue memories,digitization and first level buffering can be embedded in the same component.We present here the NECTAr project aiming at building a demonstrator element ofa generic camera built around this component.

We report on the status of the R&D for a digital Time Projection Chamber based on Micromegas detectors using the CMOS chip TimePix as a direct readout anode protected by highly resistive a-Si:H layer. A small chamber was built as a demonstrator of the 2-D and 3-D imaging capabilities of this technique. We illustrate the new capabilities of this detector for x-ray observation with data taken from radioactive sources. This small TPC is a very useful tool both for studying gas properties thanks to its good efficiency for single electrons, and for reconstructing photoelectron direction for use as a soft x-ray polarimeter.

This paper gives the main fields of interest for UV space borne observations. It gives also some examples of space missions dedicated to UV observations.

The detection is a real challenge for most of the UV-space missions. First, the classical detectors quantum efficiency is very low between 100 and 300 nm. The second point is that the useful flux is very low, and the photon counting is sometimes required. The stray light flux (visible light) is often strong so that additional filters are needed. In addition to the fact that these filters reduce the effective quantum efficiency, it is well known that the filter quality is a big constraint for the UV applications. For these reasons, dedicated detectors with high performances are required. Fortunately, strong improvement in detectors has been done for years and promising detectors are merging. After having reminded the different UV-space mission needs, this paper will present the available UV detectors. In the last part, the CNES Roadmap will be shortly discussed.

The next ESA spatial mission planned to study the Sun, Solar Orbiter (SO), necessitates very innovative EUV detectors. The commonly used silicon detectors suffer important limitations mainly in terms of UV robustness and dark current level. An alternative comes from diamond or III-nitride materials. In these materials, the radiation hardness, solar blindness and dark current are improved due to their wide bandgap. This paper presents the new developments on wide bandgap materials at the Royal Observatory of Belgium (ROB). We present also the LYRA instrument, the BOLD project, and the EUI instrument suite.

The fast development of nitrides has given the opportunity to investigate AlGaN as a material for ultraviolet detection. A camera based on such a material presents an extremely low dark current at room temperature. It can compete with technologies based on photocathodes, MCP intensifiers, back thinned CCD or hybrid CMOS focal plane arrays for low flux measurements. First, we will present results on focal plane array of 320 × 256 pixels with a pitch of 30 μm. The peak responsivity is tuned from 260 nm to 360 nm in different cameras. All these results are obtained in a standard SWIR supply chaine and with AlGaN Schottky diodes grown on sapphire. We will present here the first attempts to transfer the standard design Schottky photodiodes on from sapphire to silicon substrates. We will show the capability to remove the silicon substrate, to etch the window layer in order to extend the band width to lower wavelength and to maintain the AlGaN membrane integrity.

The World Space Observatory UltraViolet (WSO-UV) project is aninternational space observatory designed for observations in theultraviolet domain. The observatory includes a single 170 cmaperture telescope capable of high-resolution spectroscopy, longslit low-resolution spectroscopy and deep UV and optical imaging.

The objective of this paper is to briefly present the future spaceborne missions embarking visible and infrared instruments. We will do this through the ESA Cosmic Vision program which addresses the main questions that are high on the agenda of research across Europe (and, indeed worldwide) concerning the Universe and our place in it. This paper doesn't take into account planetary exploration missions.

We review recent and future ground based astronomical instruments in the visible and near IR domains associated with important detector development programs.

Modern Charge Coupled Devices (CCDs) offer very high performance for astronomical imaging both on the ground and in space. Here we present an overview of some key performance levels together with technologies that allow refinements to performance for these specialised applications.

Charge Transfer Inefficiency (CTI) is a well known effect of charge-coupled devices (CCD). The charge transfer from one pixel to the next is not perfect and is quantified by the fraction of charge successfully moved (clocked) between adjacent pixels. The amplitude of this effect depends on the signal level inside the pixel. In the context of high-precision radial velocity measurements using cross-dispersed echelle spectrograph, this CTI effect on a CCD recording spectral orders may introduce associated spectral lines shifts. Indeed if the signal level recorded on the spectra is changing, the CTI amplitude will change affecting the associated centroid of all spectral lines. Such effect may introduced radial velocity shifts of several  m s-1. We describe here CTI effect which is affecting the SOPHIE spectrograph installed on the 1.93-m telescope of Observatoire de Haute Provence (OHP). We calibrated the effect thanks to the Thorium-Argon lines and we applied a software correction on the spectra in order to assess the charge lost during the readout process on all pixels.

We present recent advances on ultra low noise visible detectors at Laboratoire d'Astrophysique de Marseille, photon counting and EMCCD developments in collaboration with Observatoire de haute provence, Laboratoire d'astrophysique de l'observatoire de Grenoble and Laboratoire d'Astrophysique Experimentale (Montreal). After a review of the progress with third generation Image Photon Counting Systems (IPCS), we present the OCAM camera, based on the E2V CCD220 EMCCD, part of the Opticon JRA2 programme, and the CCCP controller, a new controller for the 3DNTT instrument that reduces the clock induced charge of an EMCCD by a factor 10, making it competitive with IPCS detectors for very faint fluxes. We will finally present the RAPID project and the concept of photon counting avalanche photodiode CMOS device (in collaboration with CEA-LETI) which is foreseen to be the ultimate detector for the visible-IR range providing no readout noise, high QE and extremely fast readout.

Images in visible interferometry are characterised by their low coherence time, and except for brightest stars, the flux on the detector is much less than one photon per pixel per image. Algol and Comptage de Photons Nouvelle Génération (CPNG) are new photon counting cameras developed for high angular resolution in the visible. They are intensified CCDs built to benefit from improvements in photonic commercial components, and personal computer processing power. We present how we achieve optimal performances (sensitivity and spatiotemporal resolution) by the combination of proper optical and electronics design, and real-time elaborated data processing. The number of pixels is 532 × 516 and 768 × 640 read at a frame rate of 262 Hz and 50 Hz for CPNG and Algol respectively. The dark current is very low: 5 × 10-4 electron.pixel-1.s-1. Quantum efficiencies reach up to 36% in the visible with the GaAsP photocathodes and and 26% in the red with the GaAs ones, thanks to the sensitivity of the photocathodes and to the photon centroiding algorithm; they are likely the highest values reported for ICCDs.

True photon-counting devices in the optical may open a new observationnal window in astrophysics: photon statistics and quamtum properties of light. We rapidly develop below the scientific context and the mathematical basis to understand photon statistics. We discuss the relevance of microquasars in our galaxy as a strong scientific case for a possible photon-counting instrument.

The aim of this paper is to give an overview of CMOS imaging detectors (principles and technologies) and an overview of CNES activities in this domain.

CCD technology is preferred for devices used for scientific applications, as CMOS devices were plagued by high dark current, high read noise, etc. Developments in the last 15 years have help circumventing these limitations and CMOS devices could now compete with some of their CCD counterpart.

Since 2004, at the Laboratoire d'Astrophysique de Toulouse Tarbes (LATT), we work with CMOS APSdetectors, firstly to develop a large-field,high-resolution camerafor the observation of the solar supergranulation, secondlyto develop a fast camera for an adaptive optics test bench.In these two projects, we use detectors from FillFactory, now continued byCypress Semiconductor Corporation: IBIS4-14000, IBIS-16000, LUPA-4000,14 Mpixels, 16 Mpixels, 4 Mpixels respectively. The last one just readsin a 240 × 240 pixels window to obtain readout rate of 1000 Image/s.For these purposes we developed dedicated controllers to followthe high pixel rate and multi-output readout of this type of detectors.We also studied the characterization methods and measuredthe main parameters of these CMOS detectors to know their behaviour. Usingthese kinds of APS detectors in these two particular projects provesthat we can already find niches to use CMOS detectors in astronomy takingadvantage of their present specificities. Recent improvements likeback illumination, noise reduction, should rapidly open news possibilities.

This paper summarizes the possibilities of photoelectric and CCD photometry inSlovak observatories.

Up-conversion, or hybrid, detectors have been investigated in quantum communication experiments to replace Indium-Gallium-Arsenide avalanche photodiodes (InGaAs-APD) for the detection of infrared and telecom single photons. Those detectors are based on the supposedly noise-free process of frequency up-conversion, also called sum-frequency generation (SFG), using a second order (χ2) non-linear crystal. Powered by an intense pump laser, this process permits transposing with a certain probability the single photons at telecom wavelengths to the visible range where silicon APDs (Si-APD) operate with a much better performance than InGaAs detectors. To date, the literature reports up-conversion detectors having efficiency and noise figures comparable to that of the best commercially available IngaAs-APDs. However, in all of these previous realizations, a pump-induced noise is always observed which was initially expected to be as low as the dark count level of the Si-APDs. Although this additional noise represents a problem for the detection, up-conversion detectors have advantageously replaced InGaAs-APDs in various long-distance quantum cryptography schemes since they offer a continuous regime operation mode instead of a gated mode necessary for InGaAs-APDs, and the possibility of much higher counting rates. Despite attempted explanations, no detailed nor conclusive study of this noise has been reported.

The aim of this paper is to offer a definitive explanation for this noise.We first give a review of the state of the art by describing already demonstrated up-conversion detectors. We discuss these realizations especially regarding the choices made for the material, in bulk or guided configurations, the single photon wavelengths, and the pump scheme. Then we describe an original device made of waveguides integrated on periodically poled lithium niobate (PPLN)or on single-domain lithium niobate aimed at investigating the origin of the additional pump-induced noise. The poled waveguides are designed to up-convert single photons at 1550 nm to 600 nm when a 980 nm diode laser is used as pump. We obtain an overall efficiency of about 0.6% for a noise level of about 8 × 103 counts/s. This overall efficiency includes both insertion and propagation losses, and internal up-conversion and quantum detection (Si-APD) efficiencies. Despite a low efficiency value compared to what has been obtained so far by other groups, the efficiency/noise ratio is still comparable which still allows us investigating the noise issue.

From the spectrum obtained in both poled and non-poled waveguides we conclude that the noise comes from an alternative phase-matching scheme which permits creating paired photons at 1550 and 2700 nm wavelength by down-conversion of the 980 nm pump laser. Knowing that 1550 nm corresponds to the input signal wavelength, up-conversion of actual signal or pump-induced photons at this particular wavelength cannot be discriminated, therefore contributing to the noise at the final wavelength of 600 nm. We believe that this process of down-conversion of the pump laser to the signal wavelength (plus complementary wavelength) is responsible for the unexpected noise level reported in all the up-conversion detector realizations.