Snapshot Imaging with the Australia Telescope Compact Array

1995 ◽  
Vol 12 (2) ◽  
pp. 227-238 ◽  
Author(s):  
A. M. Burgess ◽  
R. W. Hunstead
Keyword(s):  
Dynamic Range ◽  
Angular Size ◽  
Integration Time ◽  
More Care ◽  
Snapshot Imaging ◽  
The One ◽  
5 Ghz ◽  
Total Integration ◽  
Deconvolution Techniques ◽  
Compact Array

AbstractRadio snapshot imaging is an efficient observing method which allows several sources to be observed in the one session. Snapshot observing with the Australia Telescope Compact Array (ATCA) involves special difficulties, as the small number of antennas combined with the short total integration time leads to high sidelobe levels in the raw images. The images can be improved markedly by standard deconvolution techniques, but more care is required in their use because of the difficulty in distinguishing real emission from artefacts. This study, based on a set of snapshot observations of strong sources at 5 GHz, gives guidance on both the planning of observations and the data reduction. We show that snapshot imaging with the 6 km ATCA can achieve a dynamic range of 100–200:1 provided certain conditions are met, namely a peak flux density > 100 mJy, an angular size ≤ 30″ and an hour-angle coverage spanning at least six well-separated 5-minute cuts. When observing weak sources it is essential for calibration sources to be selected carefully and observed frequently.

DYNAMIC RANGE EXTENSION OF CMOS IMAGE SENSORS USING MULTI-INTEGRATION TECHNIQUE WITH COMPACT READOUT

2013 ◽  
Vol 22 (06) ◽  
pp. 1350042 ◽  
Author(s):  
ZHIYUAN GAO ◽  
SUYING YAO ◽  
JIANGTAO XU ◽  
CHAO XU
Keyword(s):  
Dynamic Range ◽  
Image Sensors ◽  
Range Extension ◽  
Integration Time ◽  
Integration Technique ◽  
Cmos Image Sensors ◽  
Readout Time ◽  
Pixel Array ◽  
The One ◽  
The Time Domain

A multi-integration technology with compact readout method to extend CMOS image sensor's dynamic range is presented. Compared with the timing of rolling readout, compact readout extends the available pixel readout time by adjusting the time-domain offset between two adjacent rows and each integration time in one frame. Thus the column readout bus is working continuously rather than intermittently, which makes good use of the whole integration time and the available readout time can be extended. This dynamic range extension technology was implemented on a prototype chip with a 128 × 128 pixel array. The pixel readout time with compact readout method is almost as 3 times long as the one with rolling readout method while 39 dB dynamic range extension is achieved at 120 fps.

scholarly journals Small All-Range Lidar for Asteroid and Comet Core Missions

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 3081
Author(s):  
Xiaoli Sun ◽  
Daniel R. Cremons ◽  
Erwan Mazarico ◽  
Guangning Yang ◽  
James B. Abshire ◽  
...  
Keyword(s):  
Fiber Lasers ◽  
Dynamic Range ◽  
Photon Counting ◽  
Avalanche Photodiode ◽  
Integration Time ◽  
Sample Collection ◽  
Long Distance ◽  
Linear Mode ◽  
Internal Gain ◽  
Pseudo Noise

We report the development of a new type of space lidar specifically designed for missions to small planetary bodies for both topographic mapping and support of sample collection or landing. The instrument is designed to have a wide dynamic range with several operation modes for different mission phases. The laser transmitter consists of a fiber laser that is intensity modulated with a return-to-zero pseudo-noise (RZPN) code. The receiver detects the coded pulse-train by correlating the detected signal with the RZPN kernel. Unlike regular pseudo noise (PN) lidars, the RZPN kernel is set to zero outside laser firing windows, which removes most of the background noise over the receiver integration time. This technique enables the use of low peak-power but high pulse-rate lasers, such as fiber lasers, for long-distance ranging without aliasing. The laser power and the internal gain of the detector can both be adjusted to give a wide measurement dynamic range. The laser modulation code pattern can also be reconfigured in orbit to optimize measurements to different measurement environments. The receiver uses a multi-pixel linear mode photon-counting HgCdTe avalanche photodiode (APD) array with near quantum limited sensitivity at near to mid infrared wavelengths where many fiber lasers and diode lasers operate. The instrument is modular and versatile and can be built mostly with components developed by the optical communication industry.

Modelling of Io’s Atmosphere for the IVO Mission

2021 ◽  
Author(s):  
Peter Wurz ◽  
Audrey Vorburger ◽  
Alfred McEwen ◽  
Kathy Mandt ◽  
Ashley Davies ◽  
...  
Keyword(s):  
Mass Loss ◽  
Dynamic Range ◽  
Detection Threshold ◽  
Mass Range ◽  
Mission Design ◽  
Integration Time ◽  
Many Worlds ◽  
Initial State ◽  
Atmospheric Escape ◽  
Tidal Heating

<p>The Io Volcano Observer (IVO) is a proposed NASA Discovery-class mission (currently in Phase A), that would launch<span> in early 2029, arrive at </span> Jupiter in the early 2033, and perform ten flybys of Io while in Jupiter's orbit. IVO's mission motto is to 'follow the heat', shedding light onto tidal heating as a fundamental planetary process. Specifically, IVO will determine (i) how and where heat is generated in Io's interior, (ii) how heat is transported to the surface, and (iii) how Io has evolved with time. The answers to these questions will fill fundamental gaps in the current understanding of the evolution and habitability of many worlds across our Solar System and beyond where tidal heating plays a key role, and will give us insight into how early Earth, Moon, and Mars may have worked.</p><p>One of the five key science questions IVO will be addressing is determining Io's mass loss via atmospheric escape. Understanding Io's mass loss today will offer information on how the chemistry of Io has been altered from its initial state and would provide useful clues on how atmospheres on other bodies have evolved over time. IVO plans on measuring Io's mass loss in situ with the Ion and Neutral Mass Spectrometer (INMS), a successor to the instrument currently being built for the JUpiter Icy moons Explorer (JUICE). INMS will measure neutrals and ions in the mass range 1 – 300 u, with a mass resolution (M/ΔM) of 500, a dynamic range of > 10<sup>5</sup>, a detection threshold of 100 cm<sup>–3</sup> for an integration time of 5 s, and a cadence of 0.5 – 300 s per spectrum.</p><p>In preparation for IVO, we model atmospheric density profiles of species known and expected to be present on Io's surface from both measurements and previous modelling efforts. Based on the IVO mission design, we present three different measurement scenarios for INMS we expect to encounter at Io based on the planned flybys: (i) a purely sublimated atmosphere, (ii) the 'hot' atmosphere generated by lava fields, and (iii) the plume gases resulting from volcanic activity. We calculate the expected mass spectra to be recorded by INMS during these flybys for these atmospheric scenarios.</p>

The VSOP 5 GHz Active Galactic Nucleus Survey. IV. The Angular Size/Brightness Temperature Distribution

2004 ◽  
Vol 616 (1) ◽  
pp. 110-122 ◽  
Author(s):  
S. Horiuchi ◽  
E. B. Fomalont ◽  
W. K. Scott, A. R. Taylor ◽  
J. E. J. Lovell ◽  
G. A. Moellenbrock ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Brightness Temperature ◽  
Active Galactic Nucleus ◽  
Angular Size ◽  
5 Ghz

scholarly journals Filamentary Nebulosity Surrounding M87

1987 ◽  
Vol 117 ◽  
pp. 216-217
Author(s):  
S. van den Bergh ◽  
C. J. Pritchet
Keyword(s):  
Broad Band ◽  
Integration Time ◽  
The Difference ◽  
Total Integration

Recently we have obtained both Hα + [NII] and broad-band red exposures of a number of galaxies with an RCA 320 × 512 CCD at the prime-focus of the 3.6 m CFH Telescope. Figure 1 shows the difference between Hα and red exposures (each with a total integration time of 60 min) of M87 = NGC4486.

scholarly journals High Dynamic Range Imaging with TDC-Based CMOS SPAD Arrays

Instruments ◽  
2019 ◽  
Vol 3 (3) ◽  
pp. 38 ◽  
Author(s):  
Majid Zarghami ◽  
Leonardo Gasparini ◽  
Matteo Perenzoni ◽  
Lucio Pancheri
Keyword(s):  
Dynamic Range ◽  
Single Photon ◽  
Photon Counting ◽  
Complementary Metal Oxide Semiconductor ◽  
High Dynamic Range ◽  
Oxide Semiconductor ◽  
Photon Flux ◽  
Integration Time ◽  
Rate Dependent ◽  
High Dynamic

This paper investigates the use of image sensors based on complementary metal–oxide–semiconductor (CMOS) single-photon avalanche diodes (SPADs) in high dynamic range (HDR) imaging by combining photon counts and timestamps. The proposed method is validated experimentally with an SPAD detector based on a per-pixel time-to-digital converter (TDC) architecture. The detector, featuring 32 × 32 pixels with 44.64-µm pitch, 19.48% fill factor, and time-resolving capability of ~295-ps, was fabricated in a 150-nm CMOS standard technology. At high photon flux densities, the pixel output is saturated when operating in photon-counting mode, thus limiting the DR of this imager. This limitation can be overcome by exploiting the distribution of photon arrival times in each pixel, which shows an exponential behavior with a decay rate dependent on the photon flux level. By fitting the histogram curve with the exponential decay function, the extracted time constant is used to estimate the photon count. This approach achieves 138.7-dB dynamic range within 30-ms of integration time, and can be further extended by using a timestamping mechanism with a higher resolution.

scholarly journals Radio jet and lobe of 3C273

1986 ◽  
Vol 119 ◽  
pp. 211-214
Author(s):  
R.J. Davis
Keyword(s):  
Radio Emission ◽  
Opposite Direction ◽  
Dynamic Range ◽  
Bulk Flow ◽  
Radio Sources ◽  
Relativistic Motion ◽  
Ridge Line ◽  
The Core ◽  
Superluminal Motion ◽  
The One

The ‘superluminal’ motion observed in the cores of radio sources such as 3C273 is now accepted as evidence of relativistic motion within a few parsecs of the centre, but it is less clear whether such speeds persist out to kiloparsec scales. The one-sidedness of such sources is often cited as evidence of relativistic Doppler beaming, but could equally be intrinsic. New MERLIN maps of 3C273 at 151 MHz and 408 MHz have been made with dynamic range of 4.103:1 and 104:1 respectively. These show that (i) there is an extended region or lobe to the south of the main jet; (ii) the radio emission of the jet is continuous from the core to beyond the limit of the optical jet; (iii) no counter-component can be found in the opposite direction to the jet. The ridge-line of the jet shows a ‘wiggle’, the wavelength of which decreases by a factor of 6 along its length. This is interpreted as a deceleration of the bulk flow along the jet.

scholarly journals VLBI Cores in a Sample of Radio Galaxies

1988 ◽  
Vol 129 ◽  
pp. 75-76
Author(s):  
G. Comoretto ◽  
L. Feretti ◽  
G. Giovannini
Keyword(s):  
Statistical Study ◽  
Dynamic Range ◽  
Total Sample ◽  
Radio Galaxies ◽  
Log P ◽  
Complete Sample ◽  
Radio Structure ◽  
First Results ◽  
5 Ghz ◽  
Radio Power

We present the first results of a statistical study of the milliarcsec structure in a complete sample of radio galaxies. We have selected from the B2 and 3CR samples of galaxies the sources which present, at the VLA or WSRT angular resolution, an unresolved core with a flux density at 5 GHz Sc ≥ 100 mJy. The total sample consists of 30 radio galaxies, 17 from the B2 and 13 from the 3CR catalog. This complete sample covers a range of total radio power at 408 MHz log P = 23.5 – 26.5 W/Hz (low-intermediate luminosity). The radio structure of these sources on the arcsec-arcmin scale is well known, thanks to good dynamic range VLA and/or WSRT maps; a large variety of structures is present in the sample, from classical doubles to head-tail sources; flat, inverted and steep spectrum cores are also present.

Numerical Simulation of Heavy Particle Dispersion Time Step and Nonlinear Drag Considerations

1992 ◽  
Vol 114 (1) ◽  
pp. 100-106 ◽  
Author(s):  
Lian-Ping Wang ◽  
D. E. Stock
Keyword(s):  
Numerical Simulation ◽  
Numerical Experiments ◽  
Heavy Particle ◽  
Free Fall ◽  
Particle Dispersion ◽  
Integration Time ◽  
Fall Velocity ◽  
Time Step ◽  
Physical Experiments ◽  
Total Integration

Numerical experiments can be used to study heavy particle dispersion by tracking particles through a numerically generated instantaneous turbulent flow field. In this manner, data can be generated to supplement physical experiments. To perform the numerical experiments efficiently and accurately, the time step used when tracking the particles through the fluid must be chosen correctly. After finding a suitable time step for one particular simulation, the time step must be reduced as the total integration time increases and as the free-fall velocity of the particle increases. Based on the numerical calculations, we suggest that the nonlinear drag be included in a numerical simulation if the ratio of the particle’s Stokes free-fall velocity to the fluid rms velocity is greater than two.

Dynamic Range Enhancement of Photodiode Array Spectra

1987 ◽  
Vol 41 (8) ◽  
pp. 1383-1387 ◽  
Author(s):  
Douglas F. Wirsz ◽  
R. J. Browne ◽  
M. W. Blades
Keyword(s):  
Data Acquisition ◽  
Dynamic Range ◽  
Computer Control ◽  
Photomultiplier Tube ◽  
Integration Time ◽  
Single Spectrum ◽  
Noise Floor ◽  
Photodiode Array

The dynamic range of the photodiode array is typically 30 dB. In situations requiring a dynamic range greater than 30 dB, the photomultiplier tube is a popular alternative, but the advantage of multiwavelength simultaneous data acquisition—possible with a photodioide array—is lost. A method has been developed to enhance the dynamic range of spectra taken with the use of a photodiode array. A set of spectra is collected under computer control at varied integration times, and the optimum integration time is chosen individually for each detecting element. As a result, an improvement in the suppression of the noise floor is achieved, leading to a single spectrum with an enhanced dynamic range of 50 dB.

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