Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userParticle Effects on the ISGRI Instrument On-Board the INTEGRAL Satellite
60
0
0.0
(
0
)
Authors
Arnaud Claret
Ask ChatGPT about the research
No Arabic abstract
The INTEGRAL satellite was launched on October 17, 2002. All on-board instruments are operating successfully. In this paper, we focus on radiation effects on the Cadmium Telluride camera ISGRI. The spectral response of the camera is affected by cosmic particles depositing huge amount of energy, greater than the high threshold of the electronics. Our study raises the contribution of cosmic ray protons. Solutions are proposed to limit the degradation of spectral response of large pixel gamma cameras operating in space.
rate research
Read More
Data on board the future PLANCK Low Frequency Instrument (LFI), to measure the Cosmic Microwave Background (CMB) anisotropies, consist of $N$ differential temperature measurements, expanding a range of values we shall call $R$. Preliminary studies and telemetry allocation indicate the need of compressing these data by a ratio of $c_r simgt 10$. Here we present a study of entropy for (correlated multi-Gaussian discrete) noise, showing how the optimal compression $c_{r,opt}$, for a linearly discretized data set with $N_{bits}=log_2{N_{max}}$ bits is given by: $c_r simeq {N_{bits}/log_2(sqrt{2pi e} ~sigma_e/Delta)}$, where $sigma_eequiv (det C)^{1/2N}$ is some effective noise rms given by the covariance matrix $C$ and $Delta equiv R / N_{max}$ is the digital resolution. This $Delta$ only needs to be as small as the instrumental white noise RMS: $Delta simeq sigma_T simeq 2 mK$ (the nominal $mu K$ pixel sensitivity will only be achieved after averaging). Within the currently proposed $N_{bits}=16$ representation, a linear analogue to digital converter (ADC) will allow the digital storage of a large dynamic range of differential temperature $R= N_{max} Delta $ accounting for possible instrument drifts and instabilities (which could be reduced by proper on-board calibration). A well calibrated signal will be dominated by thermal (white) noise in the instrument: $sigma_e simeq sigma_T$, which could yield large compression rates $c_{r,opt} simeq 8$. This is the maximum lossless compression possible. In practice, point sources and $1/f$ noise will produce $sigma_e > sigma_T$ and $c_{r,opt} < 8$. This strategy seems safer than non-linear ADC or data reduction schemes (which could also be used at some stage).
The Gamma-ray Large Area Space Telescope (GLAST) is an observatory designed to perform gamma-ray astronomy in the energy range 20 MeV to 300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 25 MeV. GLAST will be launched at the end of 2007, opening a new and important window on a wide variety of high energy astrophysical phenomena . The main instrument of GLAST is the Large Area Telescope (LAT), which provides break-through high-energy measurements using techniques typically used in particle detectors for collider experiments. The LAT consists of 16 identical towers in a four-by-four grid, each one containing a pair conversion tracker and a hodoscopic crystal calorimeter, all covered by a segmented plastic scintillator anti-coincidence shield. The scientific return of the instrument depends very much on how accurately we know its performance, and how well we can monitor it and correct potential problems promptly. We report on a novel technique that we are developing to help in the characterization and monitoring of LAT by using the power of classification trees to pinpoint in a short time potential problems in the recorded data. The same technique could also be used to evaluate the effect on the overall LAT performance produced by potential instrumental problems.
The X and Gamma Imaging Spectrometer instrument on-board the THESEUS mission (selected by ESA in the framework of the Cosmic Vision M5 launch opportunity, currently in phase A) is based on a detection plane composed of several thousands of single active elements. Each element comprises a 4.5x4.5x30 mm 3 CsI(Tl) scintillator bar, optically coupled at both ends to Silicon Drift Detectors (SDDs). The SDDs acts both as photodetectors for the scintillation light and as direct X-ray sensors. In this paper the design of the XGIS detection plane is reviewed, outlining the strategic choices in terms of modularity and redundancy of the system. Results on detector-electronics prototypes are also described. Moreover, the design and development of the low-noise front-end electronics is presented, emphasizing the innovative architectural design based on custom-designed Application-Specific Integrated Circuits (ASICs).
The Scientific objectives of the LOFT mission, e.g., the study of the Neutron Star equation of state and of the Strong Gravity, require accurate energy, time and flux calibration for the 500k channels of the SDD detectors, as well as the knowledge of the detector dead-time and of the detector response with respect to the incident angle of the photons. We report here the evaluations made to asses the calibration issues for the LAD instrument. The strategies for both ground and on-board calibrations, including astrophysical observations, show that the goals are achievable within the current technologies.
We present the Micro-channel X-ray Telescope (MXT), a new narrow-field (about 1{deg}) telescope that will be flying on the Sino-French SVOM mission dedicated to Gamma-Ray Burst science, scheduled for launch in 2021. MXT is based on square micro pore optics (MPOs), coupled with a low noise CCD. The optics are based on a Lobster Eye design, while the CCD is a focal plane detector similar to the type developed for the seven eROSITA telescopes. MXT is a compact and light (<35 kg) telescope with a 1 m focal length, and it will provide an effective area of about 45 cmsq on axis at 1 keV. The MXT PSF is expected to be better than 4.2 arc min (FWHM) ensuring a localization accuracy of the afterglows of the SVOM GRBs to better than 1 arc min (90% c.l. with no systematics) provided MXT data are collected within 5 minutes after the trigger. The MXT sensitivity will be adequate to detect the afterglows for almost all the SVOM GRBs as well as to perform observations of non-GRB astrophysical objects. These performances are fully adapted to the SVOM science goals, and prove that small and light telescopes can be used for future small X-ray missions.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
