98 research outputs found
Slewing Mirror Telescope and the Data-Acquisition System for the UFFO-Pathfinder
The Ultra-Fast Flash Observatory (UFFO) aims to detect the earliest moment of Gamma-Ray
Bursts (GRBs) which is not well known, resulting into the enhancement of GRB mechanism
understanding. The pathfinder mission was proposed to be a scaled-down version of UFFO,
and only contains the UFFO Burst Alert & Trigger Telescope (UBAT) measuring the
X-ray/gamma-ray with the wide-field of view and the Slewing Mirror Telescope (SMT) with a
rapid-response for the UV/optical photons. Once the UBAT detects a GRB candidate with the
position accuracy of 10 arcmin, the SMT steers the UV/optical photons from the candidate
to the telescope by the fast rotatable mirror and provides the early UV/optical photons
measurements with 4 arcsec accuracy. The SMT has a modified Ritchey-Chrètien telescope
with the aperture size of 10 cm diameter including the rotatable mirror and the image
readout by the intensified charge-coupled device. There is a key board called the UFFO
Data Acquisition system (UDAQ) that manages the communication of each telescope and also
of the satellite and the UFFO overall operation. This pathfinder is designed and built
within the limited size and weight of ~20 kg and the low power consumption up to
~30 W. We will discuss the design and performance of the UFFO-pathfinder, and its
integration to the Lomonosov satellite
Development of Motorized Slewing Mirror Stage for the UFFO Project
The Ultra-Fast Flash Observatory (UFFO) is a space observatory for optical follow-ups of
gamma ray bursts (GRBs), aiming to explore the first 60 seconds of GRBs optical emission.
UFFO is utilized to catch early optical emissions from GRBs within few sec after trigger
using a Gimbal mirror which redirects the optical path rather than slewing entire
spacecraft. We have developed a 15 cm two-axis Gimbal mirror stage for the UFFO-Pathfinder
which is going to be on board the Lomonosov satellite which is to be launched in 2013. The
stage is designed for fast and accurate motion with given budgets of 3 kg of mass and 3
Watt of power. By employing stepping motors, the slewing mirror can rotate faster than 15
deg/sec so that objects in the UFFO coverage (60 deg × 60 deg) can be targeted in
~1 sec. The obtained targeting resolution is better 2 arcmin using a close-loop
control with high precision rotary encoder. In this presentation, we will discuss details
of design, manufacturing, space qualification tests, as well as performance tests
Calibration and Simulation of the GRB trigger detector of the Ultra Fast Flash Observatory
The UFFO (Ultra-Fast Flash Observatory) is a GRB detector on board the Lomonosov
satellite, to be launched in 2013. The GRB trigger is provided by an X-ray detector,
called UBAT (UFFO Burst Alarm & Trigger Telescope), which detects X-rays from the GRB
and then triggers to determine the direction of the GRB and then alerts the Slewing Mirror
Telescope (SMT) to turn in the direction of the GRB and record the optical photon fluxes.
This report details the calibration of the two components: the MAPMTs and the YSO crystals
and simulations of the UBAT. The results shows that this design can observe a GRB within a
field of view of ±35° and can trigger in a time scale as short as 0.2 – 1.0 s
after the appearance of a GRB X-ray spike
Design and implementation of electronics and data acquisition system for Ultra-Fast Flash Observatory
The Ultra-Fast Flash Observatory (UFFO) Pathfinder for Gamma-Ray Bursts (GRBs) consists
of two telescopes. The UFFO Burst Alert & Trigger Telescope (UBAT) handles the
detection and localization of GRBs, and the Slewing Mirror Telescope (SMT) conducts the
measurement of the UV/optical afterglow. UBAT is equipped with an X-ray detector, analog
and digital signal readout electronics that detects X-rays from GRBs and determines the
location. SMT is equipped with a stepping motor and the associated electronics to rotate
the slewing mirror targeting the GRBs identified by UBAT. First the slewing mirror points
to a GRB, then SMT obtains the optical image of the GRB using the intensified CCD and its
readout electronics. The UFFO Data Acquisition system (UDAQ) is responsible for the
overall function and operation of the observatory and the communication with the satellite
main processor. In this paper we present the design and implementation of the electronics
of UBAT and SMT as well as the architecture and implementation of UDAQ
In-Flight Calibrations of UFFO-Pathfinder
The Ultra-Fast Flash Observatory (UFFO), which will be launched onboard the
Lomonosov spacecraft, contains two crucial instruments: UFFO Burst
Alert & Trigger Telescope (UBAT) for detection and localization of Gamma-Ray Bursts
(GRBs) and the fast-response Slewing Mirror Telescope (SMT) designed for the observation
of the prompt optical/UV counterparts. Here we discuss the in-space calibrations of the
UBAT detector and SMT telescope. After the launch, the observations of the standard X-ray
sources such as pulsar in Crab nebula will provide data for necessary calibrations of
UBAT. Several standard stars will be used for the photometric calibration of SMT. The
celestial X-ray sources, e.g. X-ray binaries with bright optical sources
in their close angular vicinity will serve for the cross-calibration of UBAT and SMT
Ultra-Fast Flash Observatory: Fast Response Space Missions for Early Time Phase of Gamma Ray Bursts
One of the unexplored domains in the study of gamma-ray bursts (GRBs) is the early time
phase of the optical light curve. We have proposed Ultra-Fast Flash Observatory (UFFO) to
address this question through extraordinary opportunities presented by a series of small
space missions. The UFFO is equipped with a fast-response Slewing Mirror Telescope that
uses a rapidly moving mirror or mirror array to redirect the optical beam rather than
slewing the entire spacecraft or telescope to aim the optical instrument at the GRB
position. The UFFO will probe the early optical rise of GRBs with sub-second response, for
the first time, opening a completely new frontier in GRB and transient studies. Its fast
response measurements of the optical emission of dozens of GRB each year will provide
unique probes of the burst mechanism and test the prospect of GRB as a new standard
candle, potentially opening up the z > 10 universe. We describe the current limit in
early photon measurements, the aspects of early photon physics, our soon-to-be-launched
UFFO-pathfinder mission, and our next planned mission, the UFFO-100
Slewing Mirror Telescope optics for the early observation of UV/optical photons from Gamma-Ray Bursts
We report on design, manufacture, and testing of a Slewing Mirror Telescope (SMT), the first of its kind and a part of Ultra-Fast Flash Observatory-pathfinder (UFFO-p) for space-based prompt measurement of early UV/optical light curves from Gamma-Ray Bursts (GRBs). Using a fast slewing mirror of 150 mm diameter mounted on a 2 axis gimbal stage, SMT can deliver the images of GRB optical counterparts to the intensified CCD detector within 1.5∼1.8 s over ± 35 degrees in the slewing field of view. Its Ritchey-Chrétien telescope of 100 mm diameter provides a 17 × 17 arcmin2 instantaneous field of view. Technical details of design, construction, the laboratory performance tests in space environments for this unique SMT are described in conjunction with the plan for in-orbit operation onboard the Lomonosov satellite in 2013. © 2013 Optical Society of America.This research was supported by the Korean Creative Research Initiatives (RCMST) of MEST/NRF, the Basic Science Research program of MEST/NRF (2010-0025056), the World Class University program of MEST/NRF (R32-2009-000-10130-0), the Spanish MINECO project AYA-2009-14027-C05-01, AYA-2011-29936-C05-01, AYA-2012-39727-C03-01, and AYA 2009-14000-C03-01/ESP, Taiwan's National Science Council Vanguard Program (100-2119-M-002-025) LeCosPA of National Taiwan University, Program of development of Lomonosov Moscow State University and Korean programs NRF 2012-0006632, 20100029390 and Yonsei-KASI joint research for the Frontiers of Astronomy and Space Science Program 2012Peer Reviewe
Kondo effect in coupled quantum dots: a Non-crossing approximation study
The out-of-equilibrium transport properties of a double quantum dot system in
the Kondo regime are studied theoretically by means of a two-impurity Anderson
Hamiltonian with inter-impurity hopping. The Hamiltonian, formulated in
slave-boson language, is solved by means of a generalization of the
non-crossing approximation (NCA) to the present problem. We provide benchmark
calculations of the predictions of the NCA for the linear and nonlinear
transport properties of coupled quantum dots in the Kondo regime. We give a
series of predictions that can be observed experimentally in linear and
nonlinear transport measurements through coupled quantum dots. Importantly, it
is demonstrated that measurements of the differential conductance , for the appropriate values of voltages and inter-dot tunneling
couplings, can give a direct observation of the coherent superposition between
the many-body Kondo states of each dot. This coherence can be also detected in
the linear transport through the system: the curve linear conductance vs
temperature is non-monotonic, with a maximum at a temperature
characterizing quantum coherence between both Kondo states.Comment: 20 pages, 17 figure
Readout of the UFFO Slewing Mirror Telescope to detect UV/optical photons from Gamma-Ray Bursts
Cosmic ray effect on the X-ray Trigger Telescope of UFFO/Lomonosov using YSO scintillation crystal array in space
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