Pub Date : 2022-03-02DOI: 10.1142/s2251171722500039
S. Nagabhushana, B. R. Prasad, S. Nagesh, Suresh Venkata Nara, D. Sandeep, P. Kamath, Shalab Misra, Bhavana S. Hegde, D. Utkarsha, M. K. Sinha, S. Kathiravan, V. Natarajan, S. P. Kumar, Amit Kumar
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.
{"title":"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. R. Prasad, S. Nagesh, Suresh Venkata Nara, D. Sandeep, P. Kamath, Shalab Misra, Bhavana S. Hegde, D. Utkarsha, M. K. Sinha, S. Kathiravan, V. Natarajan, S. P. Kumar, Amit Kumar","doi":"10.1142/s2251171722500039","DOIUrl":"https://doi.org/10.1142/s2251171722500039","url":null,"abstract":"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.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47520903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-01DOI: 10.1142/s225117172250009x
M. B. Naik, D. Ojha, S. Ghosh, P. Manoj, J. Ninan, S. Ghosh, S. D’costa, S. Poojary, S. Bhagat, P. Sandimani, H. Shah, R. Jadhav, S. Gharat, G. Meshram, B. G. Bagade
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 manuscript we discuss the results of our tests with different FPA controllers like 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 fibre 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 cm telescope, optical fibre 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.
{"title":"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. Ojha, S. Ghosh, P. Manoj, J. Ninan, S. Ghosh, S. D’costa, S. Poojary, S. Bhagat, P. Sandimani, H. Shah, R. Jadhav, S. Gharat, G. Meshram, B. G. Bagade","doi":"10.1142/s225117172250009x","DOIUrl":"https://doi.org/10.1142/s225117172250009x","url":null,"abstract":"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 manuscript we discuss the results of our tests with different FPA controllers like 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 fibre 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 cm telescope, optical fibre 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.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45505182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-01DOI: 10.1142/S2251171722500088
K. Buch, R. Kale, K. Naik, Rahul Aragade, M. Muley, S. Kudale, Ajith Kumar
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 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.
{"title":"Performance Analysis Techniques for Real-time Broadband RFI Filtering System of uGMRT","authors":"K. Buch, R. Kale, K. Naik, Rahul Aragade, M. Muley, S. Kudale, Ajith Kumar","doi":"10.1142/S2251171722500088","DOIUrl":"https://doi.org/10.1142/S2251171722500088","url":null,"abstract":"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 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.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48310753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-31DOI: 10.1142/s2251171722500064
A. Josaitis, D. DeBoer, E. de Lera Acedo
{"title":"SDR Pathfinder for Understanding Transient and Noise-level Interference in the Karoo (SPUTNIK)","authors":"A. Josaitis, D. DeBoer, E. de Lera Acedo","doi":"10.1142/s2251171722500064","DOIUrl":"https://doi.org/10.1142/s2251171722500064","url":null,"abstract":"","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49231850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-31DOI: 10.1142/s2251171722500052
Nishant Neeraj Gadey
{"title":"Mersenne Beam-compressor with Field-flattener optics as Main Telescope design for Extremely Large Telescopes and Telescope Arrays","authors":"Nishant Neeraj Gadey","doi":"10.1142/s2251171722500052","DOIUrl":"https://doi.org/10.1142/s2251171722500052","url":null,"abstract":"","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42291947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-27DOI: 10.1142/S2251171722500167
Kalyani B. Bhopi, W. Tyndall, P. Sanghavi, K. Bandura, L. Newburgh, Jason Gallichio
Foreground mitigation is critical to all next-generation radio interferometers that target cosmology using the redshifted neutral hydrogen 21 cm emission line. Attempts to remove this foreground emission have led to new analysis techniques as well as new developments in hardware specifically dedicated to instrument beam and gain calibration, including stabilized signal injection into the interferometric array and drone-based platforms for beam mapping. The radio calibration sources currently used in the literature are broad-band incoherent sources that can only be detected as excess power and with no direct sensitivity to phase information. In this paper, we describe a digital radio source which uses Global Positioning Satellite (GPS) derived time stamps to form a deterministic signal that can be broadcast from an aerial platform. A copy of this source can be deployed locally at the instrument correlator such that the received signal from the aerial platform can be correlated with the local copy, and the resulting correlation can be measured in both amplitude and phase for each interferometric element. We define the requirements for such a source, describe an initial implementation and verification of this source using commercial Software Defined Radio boards, and present beam map slices from antenna range measurements using the commercial boards. We found that the commercial board did not meet all requirements, so we also suggest future directions using a more sophisticated chipset.
{"title":"A Digital Calibration Source for 21cm Cosmology Telescopes","authors":"Kalyani B. Bhopi, W. Tyndall, P. Sanghavi, K. Bandura, L. Newburgh, Jason Gallichio","doi":"10.1142/S2251171722500167","DOIUrl":"https://doi.org/10.1142/S2251171722500167","url":null,"abstract":"Foreground mitigation is critical to all next-generation radio interferometers that target cosmology using the redshifted neutral hydrogen 21 cm emission line. Attempts to remove this foreground emission have led to new analysis techniques as well as new developments in hardware specifically dedicated to instrument beam and gain calibration, including stabilized signal injection into the interferometric array and drone-based platforms for beam mapping. The radio calibration sources currently used in the literature are broad-band incoherent sources that can only be detected as excess power and with no direct sensitivity to phase information. In this paper, we describe a digital radio source which uses Global Positioning Satellite (GPS) derived time stamps to form a deterministic signal that can be broadcast from an aerial platform. A copy of this source can be deployed locally at the instrument correlator such that the received signal from the aerial platform can be correlated with the local copy, and the resulting correlation can be measured in both amplitude and phase for each interferometric element. We define the requirements for such a source, describe an initial implementation and verification of this source using commercial Software Defined Radio boards, and present beam map slices from antenna range measurements using the commercial boards. We found that the commercial board did not meet all requirements, so we also suggest future directions using a more sophisticated chipset.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49382485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-01DOI: 10.1142/s2251171721990014
{"title":"Cumulative Author Index Volume 10 (2021)","authors":"","doi":"10.1142/s2251171721990014","DOIUrl":"https://doi.org/10.1142/s2251171721990014","url":null,"abstract":"","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45719581","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-26DOI: 10.1142/S225117172150015X
C. Dilullo, J. Dowell, G. Taylor
We present recent improvements to the search for the global Cosmic Dawn signature using the Long Wavelength Array station located on the Sevilleta National Wildlife Refuge in New Mexico, USA (LWA–SV). These improvements are both in the methodology of the experiment and the hardware of the station. An improved observing strategy along with more sophisticated temperature calibration and foreground modelling schemes have led to improved residual RMS limits. A large improvement over previous work using LWA–SV is the use of a novel achromatic beamforming technique which has been developed for LWA–SV. We present results from an observing campaign which contains 29 days of observations between March 10, 2021 and April 1
{"title":"Improvements to the Search for Cosmic Dawn Using the Long Wavelength Array","authors":"C. Dilullo, J. Dowell, G. Taylor","doi":"10.1142/S225117172150015X","DOIUrl":"https://doi.org/10.1142/S225117172150015X","url":null,"abstract":"We present recent improvements to the search for the global Cosmic Dawn signature using the Long Wavelength Array station located on the Sevilleta National Wildlife Refuge in New Mexico, USA (LWA–SV). These improvements are both in the methodology of the experiment and the hardware of the station. An improved observing strategy along with more sophisticated temperature calibration and foreground modelling schemes have led to improved residual RMS limits. A large improvement over previous work using LWA–SV is the use of a novel achromatic beamforming technique which has been developed for LWA–SV. We present results from an observing campaign which contains 29 days of observations between March 10, 2021 and April 1","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2021-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45341931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-24DOI: 10.1142/S2251171722500076
Pusen Wang, Chih-Yun Chen, Hsiang-Chieh Hsu, Mu-Hsin Chang, W. Liu, H. Fang, Ting-Chou Wu, Wen-hao Chen, Chin Cheng Tsai, A. Chen, Yi Yang
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 a ff ordable. 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.
{"title":"Compact Scintillator Array Detector (ComSAD) for sounding rocket and CubeSat missions","authors":"Pusen Wang, Chih-Yun Chen, Hsiang-Chieh Hsu, Mu-Hsin Chang, W. Liu, H. Fang, Ting-Chou Wu, Wen-hao Chen, Chin Cheng Tsai, A. Chen, Yi Yang","doi":"10.1142/S2251171722500076","DOIUrl":"https://doi.org/10.1142/S2251171722500076","url":null,"abstract":"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 a ff ordable. 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.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2021-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42630136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-09DOI: 10.1142/s2251171721500148
J. Bunton, G. Comoretto, I. Morrison, D. C. Shaff, A. Deller, W. van Straten, A. Jameson
{"title":"Performance of Oversampled Polyphase Filterbank Inversion Via Fourier Transform: Continuous Signals","authors":"J. Bunton, G. Comoretto, I. Morrison, D. C. Shaff, A. Deller, W. van Straten, A. Jameson","doi":"10.1142/s2251171721500148","DOIUrl":"https://doi.org/10.1142/s2251171721500148","url":null,"abstract":"","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2021-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47873657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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