 Subjects -> ASTRONOMY (Total: 94 journals)
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- Performance Analysis Techniques for Real-Time Broadband RFI Filtering
System of uGMRT
Authors: K. D. Buch, R. Kale, K. D. Naik, R. Aragade, M. Muley, S. Kudale, B. Ajith Kumar
Abstract: Journal of Astronomical Instrumentation, Ahead of Print.
Electromagnetic radiation from human activities, known as man-made Radio Frequency Interference (RFI), adversely affects radio astronomy observations. In the vicinity of the Upgraded Giant Metrewave Radio Telescope (uGMRT) array, the sparking on power lines is the major cause of interference at observing frequencies less than 800[math]MHz. A real-time broadband RFI detection and filtering system is implemented as part of the uGMRT wideband signal processing backend to mitigate the effect of broadband RFI. Performance analysis techniques used for testing and commissioning the system for observations in the beamformer and correlator modes of the uGMRT are presented. The concept and implementation of recording simultaneous unfiltered and filtered data along with data analysis and interpretation is illustrated using an example. For the beamformer mode, spectrogram, single spectral channel, and its Fourier transform is used for performance analysis whereas, in the correlator mode, the cross-correlation function, closure phase, and visibilities from the simultaneously recorded unfiltered and filtered is carried out. These techniques are used for testing the performance of the broadband RFI filter and releasing it for uGMRT users.
Citation: Journal of Astronomical Instrumentation
PubDate: 2022-04-28T07:00:00Z
DOI: 10.1142/S2251171722500088
- Evaluation of Controllers and Development of a New In-House Controller for
the Teledyne HxRG Focal Plane Array for the IRSIS Satellite Payload
Authors: M. B. Naik, D. K. Ojha, S. K. Ghosh, P. Manoj, J. P. Ninan, S. Ghosh, S. L. A. D’Costa, S. S. Poojary, S. B. Bhagat, P. R. Sandimani, H. Shah, R. B. Jadhav, S. M. Gharat, G. S. Meshram, B. G. Bagade
Abstract: Journal of Astronomical Instrumentation, Ahead of Print.
The Infrared Astronomy Group (Department of Astronomy and Astrophysics) at Tata Institute of Fundamental Research (TIFR) is presently developing controllers for the Teledyne HxRG Focal Plane Arrays (FPAs) to be used on board the Infrared Spectroscopic Imaging Survey (IRSIS) satellite payload. In this paper, we discuss the results of our tests with different FPA controllers such as the Astronomical Research Cameras (ARC) controller, Teledyne’s SIDECAR ASIC as well as our new in-house designed Array controller. As part of the development phase of the IRSIS instrument, which is an optical fiber-based Integral Field Unit (IFU) Near-Infrared (NIR) Spectrometer, a laboratory model with limited NIR bandwidth was built which consisted of various subsystems like a Ritchey–Chretien (RC) 30[math]cm telescope, optical fiber IFU, spectrometer optics, and the Teledyne H2RG detector module. We discuss the various developments during the building and testing of the IRSIS laboratory model and the technical aspects of the prototype in-house H2RG controller.
Citation: Journal of Astronomical Instrumentation
PubDate: 2022-04-08T07:00:00Z
DOI: 10.1142/S225117172250009X
- SDR Pathfinder for Understanding Transient and Noise-Level Interference in
the Karoo (SPUTNIK)
Authors: Alec T. Josaitis, David R. DeBoer, Eloy de Lera Acedo
Abstract: Journal of Astronomical Instrumentation, Ahead of Print.
In this work, the SDR Pathfinder for Understanding Transient and Noise-level Interference in the Karoo (SPUTNIK) is presented. We describe how a low-cost radio frequency interference (RFI) monitoring system, using solely consumer-off-the-shelf (COTS) components, directly contributes to the analysis efforts of a precision 21[math]cm cosmology instrument. A SPUTNIK system overview is provided, as well as a generalized software-defined radio (SDR) internal calibration technique to achieve wideband, [math][math]dBm-level accuracy and a measured dynamic range of [math][math]dB.
Citation: Journal of Astronomical Instrumentation
PubDate: 2022-03-23T07:00:00Z
DOI: 10.1142/S2251171722500064
- Compact Scintillator Array Detector (ComSAD) for Sounding Rocket and
CubeSat Missions
Authors: Pu Kai Wang, Chih-Yun Chen, Hsiang-Chieh Hsu, Mu-Hsin Chang, Wei Tai Liu, Hui-Kuan Fang, Ting-Chou Wu, Wen-Hao Chen, Chin Cheng Tsai, Alfred Bing-Chih Chen, Yi Yang
Abstract: Journal of Astronomical Instrumentation, Ahead of Print.
The development of CubeSats and more frequent launch chances of sounding rockets are a total game changer to the space program, and it allows us to build space instruments that are technologically feasible and affordable. Therefore, it gives us a good opportunity to build a small cosmic-ray detector which has capabilities to measure the flux, direction, and even energy of cosmic rays at an altitude above the limitation of balloon experiments, and it may open a new door for building a constellation of detectors to study cosmic-ray physics. Compact Scintillator Array Detector (ComSAD) is a funded sounding rocket mission of Taiwan’s National Space Organization. In this paper, we present the concept, design, and performance of ComSAD which is also suitable for future CubeSat missions.
Citation: Journal of Astronomical Instrumentation
PubDate: 2022-03-23T07:00:00Z
DOI: 10.1142/S2251171722500076
- Life Cycle of Data Processing Center of RadioAstron Project
Authors: Marina V. Shatskaya, Nikolai A. Fedorov, Sergey F. Likhachev, Sergey I. Seliverstov, Dmitry A. Sychev
Abstract: Journal of Astronomical Instrumentation, Ahead of Print.
This paper is about the Data Processing Center (DPC) working within the RadioAstron project. Since the launch of the space radio telescope to orbit in July 2011, the DPC underwent significant quantitative and qualitative changes as the project developed. This paper describes the schemes, structure, stages of the processing center development, current upgrades and new technologies introduced in the DPC throughout the entire period of its operation. For technical reasons, the scheduled observations in the project were terminated in January 2019. However, still the work of the DPC continued. Today, the most valuable thing we have is information. There is now a unique archive of service and scientific data of the project in our possession, and a data bank of the RadioAstron project is underway, which will ensure a proper access to scientific and service information for all interested experts, as well as provide an opportunity for an additional data analysis.
Citation: Journal of Astronomical Instrumentation
PubDate: 2022-03-09T08:00:00Z
DOI: 10.1142/S2251171722500040
- Mersenne Beam-Compressor with Field-Flattener Optics as Main Telescope
Design for Extremely Large Telescopes and Telescope Arrays
Authors: Nishant Neeraj Gadey
Abstract: Journal of Astronomical Instrumentation, Ahead of Print.
The Mersenne beam-compressor is the fundamental arrangement for two mirror reflecting telescopes. The Mersenne beam-compressor consists of two confocal paraboloids. The design produces an aberration-free, collimated output beam, which makes it easy to relocate the beam to any distant location. This property of Mersenne beam compressors makes them near-ideal for telescopes with requirements for ultra-stable instruments and interferometric applications. The only problem against such application is the Petzval field curvature that is induced in the output beam. This becomes very pronounced at very high compression ratios, which are required for interferometry with large aperture telescopes. The high compression ratio is a problem because, such large aperture telescopes are also required to deliver good performance at Nasmyth and Coude locations, to be feasible. This is not possible at high compression ratios using conventional design of Mersenne beam-compressor, due to prohibitively strong field curvature. Here, we propose powered and un-powered field-flattener optics to address the problem of field curvature in Mersenne beam-compressor. After passing through this set of optics, the output beam is completely aberration free. This arrangement can produce very high compression ratios, which are useful for various special applications. We also illustrate the performance of such a system using example designs. The performance analysis shows that such a design can give considerably high performance at distant locations of foci as compared to existing relay systems.
Citation: Journal of Astronomical Instrumentation
PubDate: 2022-03-05T08:00:00Z
DOI: 10.1142/S2251171722500052
- Experimental Validation of a Novel Concept to Reduce Optical Surface Wave
Front Errors by Using Deformable Bushes at Opto-Mechanical Interfaces
Authors: S. Nagabhushana, B. Raghavendra Prasad, Suresh Nagesh, Suresh Venkata Nara, D. S. Sandeep, P. U. Kamath, Shalab Misra, Bhavana Hegde, D. Utkarsha, Mrityunjay Kumar Sinha, S. Kathiravan, V. Natarajan, S. Pawan Kumar, Amit Kumar
Abstract: Journal of Astronomical Instrumentation, Ahead of Print.
One of the major objectives of the optomechanics is to support large optics required for the purpose and also to maintain high dynamic stability in operation. This requirement calls for more number of supports, to support large optics. While addressing this issue, the mounting system tends to become non-kinematic and distorts the optical surface and leads to poor image quality. The distorted optical surfaces bring in increased RMS surface wavefront errors which will result in poor image quality. In this context, a new concept is proposed in our previous publication (Nagabhushana et al., 2021) which involves introduction of deformable bushes at the optomechanical interfaces. These are deformed by applied clamping forces and also enabling all degrees of freedom (DOF) to be arrested. This also ensures that the clamping force in axial DOF is limited to a minimal value. This technique enables to arrest of axial DOF without exerting the clamping force on the optomechanical assembly there by reduces optical aberrations and improves the mounting system’s dynamic stability. This is because deformable bushes absorb all the clamping forces and the strain has no impact on the mount and therefore does not lead deformation of the optical surface. The clamping forces are simulated by Finite Element (FE) methods. Further, in this paper, the concept is verified and validated by experiments. The simulation results are observed to be in close correlation with experiment results. Improved stability is also observed by additional constraints introduced to optomechanical mounts with no compromise in wavefront errors.
Citation: Journal of Astronomical Instrumentation
PubDate: 2022-03-02T08:00:00Z
DOI: 10.1142/S2251171722500039
- Radio Antenna Design for Sky-Averaged 21[math]cm Cosmology Experiments:
The REACH Case
Authors: J. Cumner, E. de Lera Acedo, D. I. L. de Villiers, D. Anstey, C. I. Kolitsidas, B. Gurdon, N. Fagnoni, P. Alexander, G. Bernardi, H. T. J. Bevins, S. Carey, J. Cavillot, R. Chiello, C. Craeye, W. Croukamp, J. A. Ely, A. Fialkov, T. Gessey-Jones, Q. Gueuning, W. Handley, R. Hills, A. T. Josaitis, G. Kulkarni, A. Magro, R. Maiolino, P. D. Meerburg, S. Mittal, J. R. Pritchard, E. Puchwein, N. Razavi-Ghods, I. L. V. Roque, A. Saxena, K. H. Scheutwinkel, E. Shen, P. H. Sims, O. Smirnov, M. Spinelli, K. Zarb-Adami
Abstract: Journal of Astronomical Instrumentation, Ahead of Print.
Following the reported detection of an absorption profile associated with the 21[math]cm sky-averaged signal from the Cosmic Dawn by the EDGES experiment in 2018, a number of experiments have been set up to verify this result. This paper discusses the design process used for global 21[math]cm experiments, focusing specifically on the Radio Experiment for the Analysis of Cosmic Hydrogen (REACH). This experiment will seek to understand and compensate for systematic errors present using detailed modeling and characterization of the instrumentation. Detailed quantitative figures of merit and numerical modeling are used to assist the design process of the REACH dipole antenna (one of the two antenna designs for REACH Phase I). This design process produced a 2.5:1 frequency bandwidth dipole. The aim of this design was to balance spectral smoothness and low impedance reflections with the ability to describe and understand the antenna response to the sky signal to inform the critically important calibration during observation and data analysis.
Citation: Journal of Astronomical Instrumentation
PubDate: 2022-02-09T08:00:00Z
DOI: 10.1142/S2251171722500015
- Characterization and Quantum Efficiency Determination of Monocrystalline
Silicon Solar Cells as Sensors for Precise Flux Calibration
Authors: Sasha Brownsberger, Lige Zhang, David Andrade, Christopher W. Stubbs
Abstract: Journal of Astronomical Instrumentation, Ahead of Print.
As the precision frontier of astrophysics advances toward the one millimagnitude level, flux calibration of photometric instrumentation remains an ongoing challenge. We present the results of a lab-bench assessment of the viability of monocrystalline silicon solar cells to serve as large-aperture (up to 125[math]mm diameter), high-precision photodetectors. We measure the electrical properties, spatial response uniformity, quantum efficiency (QE), and frequency response of third-generation C60 solar cells, manufactured by Sunpower. Our new results, combined with our previous study of these cells’ linearity, dark current, and noise characteristics, suggest that these devices hold considerable promise, with QE and linearity that rival those of traditional, small-aperture photodiodes. We argue that any photocalibration project that relies on precise knowledge of the intensity of a large-diameter optical beam should consider using solar cells as calibrating photodetectors.
Citation: Journal of Astronomical Instrumentation
PubDate: 2022-02-07T08:00:00Z
DOI: 10.1142/S2251171722500027
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