The development of the GAMMA-400 γ-ray telescope continues. The GAMMA-400 is designed to measure fluxes of γ-rays and the electron-positron cosmic-ray component possibly associated with annihilation or decay of dark matter particles; and to search for and study in detail discrete γ-ray sources, to measure the energy spectra of Galactic and extragalactic diffuse γ-rays, and to study γ-ray bursts and γ-rays from the active Sun. The energy range for measuring γ-rays and electrons (positrons) is from 100 MeV to 3000 GeV. For 100-GeV γ-rays, the γ-ray telescope has an angular resolution of ∼0.01°, an energy resolution of ∼1%, and a proton rejection factor of ∼5 × 105. The GAMMA-400 will be installed onboard the Russian Space Observatory.

The present design of the new space observatory GAMMA-400 is presented in this paper. The instrument has been designed for the optimal detection of gamma rays in a broad energy range (from ~100 MeV up to 3 TeV), with excellent angular and energy resolution. The observatory will also allow precise and high statistic studies of the electron component in the cosmic rays up to the multi TeV region, as well as protons and nuclei spectra up to the knee region. The GAMMA-400 observatory will allow to address a broad range of science topics, like search for signatures of dark matter, studies of Galactic and extragalactic gamma-ray sources, Galactic and extragalactic diffuse emission, gamma-ray bursts and charged cosmic rays acceleration and diffusion mechanism up to the knee.

GAMMA-400 is a new space mission which will be installed on board the Russian space platform Navigator. It is scheduled to be launched at the beginning of the next decade. GAMMA-400 is designed to study simultaneously gamma rays (up to 3 TeV) and cosmic rays (electrons and positrons from 1 GeV to 20 TeV, nuclei up to 10^15-10^16 eV). Being a dual-purpose mission, GAMMA-400 will be able to address some of the most impelling science topics, such as search for signatures of dark matter, cosmic-rays origin and propagation, and the nature of transients. GAMMA-400 will try to solve the unanswered questions on these topics by high-precision measurements of the Galactic and extragalactic gamma-ray sources, Galactic and extragalactic diffuse emission and the spectra of cosmic-ray electrons + positrons and nuclei, thanks to excellent energy and angular resolutions.

The experiment Sileye-3/Alteino was placed on board the International Space Station on 27 April 2002. The instrument is constituted by a cosmic ray silicon detector and an electroencephalograph. The main scientific aims include the investigation of the Light Flash phenomenon, the study of astronaut brain activity in space when subject to cosmic rays, the measurement of the radiation environment and the nuclear abundances inside the ISS. The instrument cosmic ray detector was active for 130 hours. In addition 6 astronaut Light Flash observation sessions were held, resulting in the observation of this phenomenon on the ISS.

An algorithm for reconstructing the characteristics (charge, mass, and energy) of cosmic-radiation nuclei with 20- to 200-MeV/nucleon energies is described. The detector is a telescope of three two-coordinate planes with two 1-mm-thick iron filters inserted between them. Each plane is composed of two strip silicon detectors with 3.6-mm-wide orthogonally oriented strips, an effective area of 6 × 6 cm 2 , and a thickness of 380 μm. The algorithm for reconstructing the nuclei characteristics is based on the analysis of how the specific ionization losses change as the nuclei pass through the filter material. The results of the Monte Carlo simulation are presented for the energy dependence of the telescope acceptance and the energy deposited in the detectors by different nuclei in view of the detector calibration on the nuclear beams of the accelerator. The mass resolution of the telescope is ∼30, 12, and 5% for He, N, and Al nuclei, respectively. The energy resolution, which is ∼20%, is much the same for all nuclei.

The SilEye experiment aims to study the cause and processes related to the anomalous Light Flashes (LF) perceived by astronausts in orbit and their relation with Cosmic Rays. These observations will be also useful in the study of the long duration manned space flight environment. Two PC-driven silicon detector telescopes have been built and placed aboard Space Station MIR. SilEye-1 was launched in 1995 and provided particles track and LF information; the data gathered indicate a linear dependence of FLF(Hz) (4 2) 103 5.3 1.7 104 Fpart(Hz) if South Atlantic Anomaly fluxes are not included. Even though higher statistic is required, this is an indication that heavy ion interactions with the eye are the main LF cause. To improve quality and quantity of measurements, a second apparatus, SilEye-2, was placed on MIR in 1997, and started work from August 1998. This instrument provides energetic information, which allows nuclear identification in selected energy ranges; we present preliminary measurements of the radiation field inside MIR performed with SilEye-2 detector in June 1998.

We propose a silicon telescope to be placed in a satellite for the search of gamma-ray sources in the energy range between 25 MeV and 100 GeV. The proposed experiment will have an area of 2500 cm(2), an energy resolution ranging from 7% to 8% and an angular resolution from 0.2 and 0.1 degrees between 1 GeV and 10 GeV. The telescope is based on the use of silicon strip detectors. Together with the energy measurement, a calorimeter of this type allows the determination of. the particle type and its al rival direction, through the analysis of the spatial and energetic distribution of the electromagnetic shower produced. Detectors based on silicon technology have many advantages for space applications: no gas refilling: system or high voltages, no need of photomultipliers (low consumption), short dead time, possibility of self-triggering. The GILDA project has been designed having in mind the weight limitation of 400 kg required by the Resource-01 satellite and it is carried out in the framework of the RIM (Russian Italian Mission) program. The launch is foreseen for the beginning of the next century.

In this paper new techniques for the realization of a high energy gamma-ray telescope are presented, based on the adoption of silicon strip detectors and lead scintillating fibers. The simulated performances of this instrument show that the silicon strip technology adopted by GILDA (Gamma-ray Imaging Large Detector for Astrophysics) could improve the performance of EGRET, which is so far the most successful experiment of a high energy gamma-ray telescope, though having less volume and weight.

High energy gamma-ray astrophysics has greatly developed in the last few years because of the results of EGRET[1], on the Compton Gamma Ray Observatory. The satellite observations have shown the importance of continuing the investigation of high energy gamma radiation but the emerging of new astrophysical and cosmological problems require for future experiments the realization of telescopes with parameters significatively improved with respect to the previous missions. In a traditional point of view, this is achieved with the increase of the lenght L of the device and, consequently, the mass of the telescope and satellite (growing as L(3)). Such kinds of experiments are becoming rather expensive and are approaching the maximum value in cost, satellite mass and consuming resources. The telescope project GILDA presented in this paper is based on the use of silicon strip detectors. The silicon technique consents to obtain a much wider solid angle aperture; in this way we can have more sensitivity without a growing in the size of the instrument. Here we show that also the calorimeter part alone of GILDA can be used for the detection of high gamma rays.

The telescope ‘Gamma-1’ is designed to investigate cosmic gamma rays in the energy range from 50 MeV to 5000 MeV. The geometrical sensitive area of the telescope amounts to 1500 cm2, the angular resolution in each direction is equal to 1.2° at the energy 300 MeV and is about 20′ when including a coded mask in the telescope, the energy resolution changes from 70% at 100 MeV to 35% at 550 MeV. The characteristics of the telescope and its systems have been determined by the Monte-Carlo method as well as by accelerator calibrations. Discrete sources at the intensity level of 10−7 quanta cm−2 s−1 may be recorded in a year of observations with the gamma-ray telescope ‘Gamma-1’ with a source location accuracy of ≈ 10 arc min.