12,999 research outputs found
Low-level processing for real-time image analysis
A system that detects object outlines in television images in real time is described. A high-speed pipeline processor transforms the raw image into an edge map and a microprocessor, which is integrated into the system, clusters the edges, and represents them as chain codes. Image statistics, useful for higher level tasks such as pattern recognition, are computed by the microprocessor. Peak intensity and peak gradient values are extracted within a programmable window and are used for iris and focus control. The algorithms implemented in hardware and the pipeline processor architecture are described. The strategy for partitioning functions in the pipeline was chosen to make the implementation modular. The microprocessor interface allows flexible and adaptive control of the feature extraction process. The software algorithms for clustering edge segments, creating chain codes, and computing image statistics are also discussed. A strategy for real time image analysis that uses this system is given
Prompt emission polarimetry of Gamma Ray Bursts with ASTROSAT CZT-Imager
X-ray and Gamma-ray polarization measurements of the prompt emission of
Gamma-ray bursts (GRBs) are believed to be extremely important for testing
various models of GRBs. So far, the available measurements of hard X-ray
polarization of GRB prompt emission have not significantly constrained the GRB
models, particularly because of the difficulty of measuring polarization in
these bands. The CZT Imager (CZTI) onboard {\em AstroSat} is primarily an X-ray
spectroscopic instrument that also works as a wide angle GRB monitor due to the
transparency of its support structure above 100 keV. It also has experimentally
verified polarization measurement capability in the 100 300 keV energy
range and thus provides a unique opportunity to attempt spectro-polarimetric
studies of GRBs. Here we present the polarization data for the brightest 11
GRBs detected by CZTI during its first year of operation. Among these, 5 GRBs
show polarization signatures with 3, and 1 GRB shows
2 detection significance. We place upper limits for the remaining 5
GRBs. We provide details of the various tests performed to validate our
polarization measurements. While it is difficult yet to discriminate between
various emission models with the current sample alone, the large number of
polarization measurements CZTI expects to gather in its minimum lifetime of
five years should help to significantly improve our understanding of the prompt
emission.Comment: Accepted for Publication in ApJ ; a figure has been update
INTEGRAL: science highlights and future prospects
ESA's hard X-ray and soft gamma-ray observatory INTEGRAL is covering the 3
keV to 10 MeV energy band, with excellent sensitivity during long and
uninterrupted observations of a large field of view (~100 square degrees), with
ms time resolution and keV energy resolution. It links the energy band of
pointed soft X-ray missions such as XMM-Newton with that of high-energy
gamma-ray space missions such as Fermi and ground based TeV observatories. Key
results obtained so far include the first sky map in the light of the 511 keV
annihilation emission, the discovery of a new class of high mass X-ray binaries
and detection of polarization in cosmic high energy radiation. For the
foreseeable future, INTEGRAL will remain the only observatory allowing the
study of nucleosynthesis in our Galaxy, including the long overdue next nearby
supernova, through high-resolution gamma-ray line spectroscopy. Science results
to date and expected for the coming mission years span a wide range of
high-energy astrophysics, including studies of the distribution of positrons in
the Galaxy; reflection of gamma-rays off clouds in the interstellar medium near
the Galactic Centre; studies of black holes and neutron stars particularly in
high- mass systems; gamma-ray polarization measurements for X-ray binaries and
gamma-ray bursts, and sensitive detection capabilities for obscured active
galaxies with more than 1000 expected to be found until 2014. This paper
summarizes scientific highlights obtained since INTEGRAL's launch in 2002, and
outlines prospects for the INTEGRAL mission.Comment: 39 pages, accepted, 24 October 2011, Space Science Review
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