11 research outputs found
In-orbit Performance of UVIT on ASTROSAT
We present the in-orbit performance and the first results from the
ultra-violet Imaging telescope (UVIT) on ASTROSAT. UVIT consists of two
identical 38cm coaligned telescopes, one for the FUV channel (130-180nm) and
the other for the NUV (200-300nm) and VIS (320-550nm) channels, with a field of
view of 28 . The FUV and the NUV detectors are operated in the high
gain photon counting mode whereas the VIS detector is operated in the low gain
integration mode. The FUV and NUV channels have filters and gratings, whereas
the VIS channel has filters. The ASTROSAT was launched on 28th September 2015.
The performance verification of UVIT was carried out after the opening of the
UVIT doors on 30th November 2015, till the end of March 2016 within the
allotted time of 50 days for calibration. All the on-board systems were found
to be working satisfactorily. During the PV phase, the UVIT observed several
calibration sources to characterise the instrument and a few objects to
demonstrate the capability of the UVIT. The resolution of the UVIT was found to
be about 1.4 - 1.7 in the FUV and NUV. The sensitivity in various
filters were calibrated using standard stars (white dwarfs), to estimate the
zero-point magnitudes as well as the flux conversion factor. The gratings were
also calibrated to estimate their resolution as well as effective area. The
sensitivity of the filters were found to be reduced up to 15\% with respect to
the ground calibrations. The sensitivity variation is monitored on a monthly
basis. UVIT is all set to roll out science results with its imaging capability
with good resolution and large field of view, capability to sample the UV
spectral region using different filters and capability to perform variability
studies in the UV.Comment: 10 pages, To appear in SPIE conference proceedings, SPIE conference
paper, 201
High-Performance Computing for SKA Transient Search: Use of FPGA based Accelerators -- a brief review
This paper presents the High-Performance computing efforts with FPGA for the
accelerated pulsar/transient search for the SKA. Case studies are presented
from within SKA and pathfinder telescopes highlighting future opportunities. It
reviews the scenario that has shifted from offline processing of the radio
telescope data to digitizing several hundreds/thousands of antenna outputs over
huge bandwidths, forming several 100s of beams, and processing the data in the
SKA real-time pulsar search pipelines. A brief account of the different
architectures of the accelerators, primarily the new generation Field
Programmable Gate Array-based accelerators, showing their critical roles to
achieve high-performance computing and in handling the enormous data volume
problems of the SKA is presented here. It also presents the power-performance
efficiency of this emerging technology and presents potential future scenarios.Comment: Accepted for JoAA, SKA Special issue on SKA (2022
Low-frequency observations of drifting, non-thermal continuum radio emission associated with the solar coronal mass ejections
Low-frequency (80 MHz) imaging and spectral (≈85-20 MHz) observations of moving type IV radio bursts associated with coronal mass ejections (CMEs) from the Sun on three different days are reported. The estimated drift speed of the bursts is in the range ≈150-500 km s–1. We find that all three bursts are most likely due to second harmonic plasma emission from the enhanced electron density in the associated white-light CMEs. The derived maximum magnetic field strength of the latter is B ≈ 4 G at a radial distance of r ≈ 1.6 R ☉
RRI-GBT MULTI-BAND RECEIVER: MOTIVATION, DESIGN, AND DEVELOPMENT
We report the design and development of a self-contained multi-band receiver (MBR) system, intended for use with a single large aperture to facilitate sensitive and high time-resolution observations simultaneously in 10 discrete frequency bands sampling a wide spectral span (100-1500 MHz) in a nearly log-periodic fashion. The development of this system was primarily motivated by need for tomographic studies of pulsar polar emission regions. Although the system design is optimized for the primary goal, it is also suited for several other interesting astronomical investigations. The system consists of a dual-polarization multi-band feed (with discrete responses corresponding to the 10 bands pre-selected as relatively radio frequency interference free), a common wide-band radio frequency front-end, and independent back-end receiver chains for the 10 individual sub-bands. The raw voltage time sequences corresponding to 16 MHz bandwidth each for the two linear polarization channels and the 10 bands are recorded at the Nyquist rate simultaneously. We present the preliminary results from the tests and pulsar observations carried out with the Robert C. Byrd Green Bank Telescope using this receiver. The system performance implied by these results and possible improvements are also briefly discussed