Pub Date : 2019-03-01DOI: 10.1142/S2251171719400117
T. Gunaratne, B. Carlson, G. Comoretto
The Square Kilometre Array (SKA) Phase 1 Mid Correlator Beamformer (Mid.CBF) adopts two novel methods to mitigate radio frequency interference (RFI) at the various stages of its signal chains. First, the pioneering Sample Clock Frequency Offset (SCFO) sampling suppresses interference which leaks into individual ‘Frequency-Slice’ (FS) (sub-bands) in the cross-correlations. Second, the ‘Shift-Resample-Shift-Back’ method minimizes the addition of noise due to strong clustered RFI. Empirical studies conducted with simulation of the systems confirm that the proposed methods significantly reduce the impact of RFI on the output of the radio telescope.
{"title":"Novel RFI Mitigation Methods in the Square Kilometre Array 1 Mid Correlator Beamformer","authors":"T. Gunaratne, B. Carlson, G. Comoretto","doi":"10.1142/S2251171719400117","DOIUrl":"https://doi.org/10.1142/S2251171719400117","url":null,"abstract":"The Square Kilometre Array (SKA) Phase 1 Mid Correlator Beamformer (Mid.CBF) adopts two novel methods to mitigate radio frequency interference (RFI) at the various stages of its signal chains. First, the pioneering Sample Clock Frequency Offset (SCFO) sampling suppresses interference which leaks into individual ‘Frequency-Slice’ (FS) (sub-bands) in the cross-correlations. Second, the ‘Shift-Resample-Shift-Back’ method minimizes the addition of noise due to strong clustered RFI. Empirical studies conducted with simulation of the systems confirm that the proposed methods significantly reduce the impact of RFI on the output of the radio telescope.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171719400117","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46862762","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 : 2019-03-01DOI: 10.1142/S2251171719400087
G. Nita, A. Keimpema, Z. Paragi
We investigate the performance of the generalized Spectral Kurtosis (SK) estimator in detecting and discriminating natural and artificial, very short duration transients in the 2-bit sampling time domain Very-Long-Baseline Interferometry (VLBI) data. We demonstrate that, while both types of transients may be efficiently detected, their natural or artificial nature cannot be distinguished if only a time domain SK analysis is performed. However, these two types of transients become distinguishable from each other in the spectral domain, after a 32-bit FFT operation is performed on the 2-bit time domain voltages. We discuss the implication of these findings on the ability of the Spectral Kurtosis estimator to automatically detect bright astronomical transient signals of interests, such as pulsar or fast radio bursts (FRB), in VLBI data streams that have been severely contaminated by unwanted radio frequency interference.
{"title":"Statistical Discrimination of RFI and Astronomical Transients in 2-bit Digitized Time Domain Signals","authors":"G. Nita, A. Keimpema, Z. Paragi","doi":"10.1142/S2251171719400087","DOIUrl":"https://doi.org/10.1142/S2251171719400087","url":null,"abstract":"We investigate the performance of the generalized Spectral Kurtosis (SK) estimator in detecting and discriminating natural and artificial, very short duration transients in the 2-bit sampling time domain Very-Long-Baseline Interferometry (VLBI) data. We demonstrate that, while both types of transients may be efficiently detected, their natural or artificial nature cannot be distinguished if only a time domain SK analysis is performed. However, these two types of transients become distinguishable from each other in the spectral domain, after a 32-bit FFT operation is performed on the 2-bit time domain voltages. We discuss the implication of these findings on the ability of the Spectral Kurtosis estimator to automatically detect bright astronomical transient signals of interests, such as pulsar or fast radio bursts (FRB), in VLBI data streams that have been severely contaminated by unwanted radio frequency interference.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171719400087","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45261012","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 : 2019-03-01DOI: 10.1142/S2251171719400130
Jan-Willem W. Steeb, D. Davidson, S. Wijnholds
In a recent paper, we presented a non-narrowband spatial radio frequency interference (RFI) mitigation algorithm for radio astronomy arrays. The algorithm constructs a 2nd-order filter by combining a 1st-order subspace subtraction method with a non-narrowband signal model. The model is based on the assumption that the frequency response is approximately flat and that the array is calibrated. In this paper, we consider the effects of array imperfections such as unknown complex gains and mutual coupling, incorporate these into the non-narrowband signal model and extend the RFI mitigation algorithm to include a calibration step. With a calibration step and no mutual coupling, the proposed algorithm was able to process twice the bandwidth per channel when compared to conventional narrowband techniques. This performance declines to 1.6 times greater bandwidth when the effect of mutual coupling is included. The evaluation of the algorithm was done using the layout of a Low Frequency Array (LOFAR) High Band Antenna (HBA) station and a digital audio broadcast recorded with a software defined radio.
{"title":"Mitigation of Non-Narrowband Radio Frequency Interference Incorporating Array Imperfections","authors":"Jan-Willem W. Steeb, D. Davidson, S. Wijnholds","doi":"10.1142/S2251171719400130","DOIUrl":"https://doi.org/10.1142/S2251171719400130","url":null,"abstract":"In a recent paper, we presented a non-narrowband spatial radio frequency interference (RFI) mitigation algorithm for radio astronomy arrays. The algorithm constructs a 2nd-order filter by combining a 1st-order subspace subtraction method with a non-narrowband signal model. The model is based on the assumption that the frequency response is approximately flat and that the array is calibrated. In this paper, we consider the effects of array imperfections such as unknown complex gains and mutual coupling, incorporate these into the non-narrowband signal model and extend the RFI mitigation algorithm to include a calibration step. With a calibration step and no mutual coupling, the proposed algorithm was able to process twice the bandwidth per channel when compared to conventional narrowband techniques. This performance declines to 1.6 times greater bandwidth when the effect of mutual coupling is included. The evaluation of the algorithm was done using the layout of a Low Frequency Array (LOFAR) High Band Antenna (HBA) station and a digital audio broadcast recorded with a software defined radio.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171719400130","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48858730","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 : 2019-03-01DOI: 10.1142/S2251171719400129
Shuimei Zhang, Yujie Gu, Yimin D. Zhang
Radio astronomical observations are increasingly contaminated by radio frequency interference (RFI), rendering the development of effective RFI suppression techniques a pressing task. In practice, the existence of model mismatch makes the observing environment more challenging. In this paper, we develop a robust astronomical imaging method in the presence of RFI and model mismatch. The key contribution of the proposed method is the accurate estimation of the actual signal steering vector by maximizing the beamformer output power subject to a constraint that prevents the estimated steering vector from converging to the interference steering vectors. The proposed method is formulated as a quadratically constrained quadratic programming problem that can be solved using efficient numerical approaches. Simulation results demonstrate the effectiveness of the proposed method.
{"title":"Robust Astronomical Imaging in the Presence of Radio Frequency Interference","authors":"Shuimei Zhang, Yujie Gu, Yimin D. Zhang","doi":"10.1142/S2251171719400129","DOIUrl":"https://doi.org/10.1142/S2251171719400129","url":null,"abstract":"Radio astronomical observations are increasingly contaminated by radio frequency interference (RFI), rendering the development of effective RFI suppression techniques a pressing task. In practice, the existence of model mismatch makes the observing environment more challenging. In this paper, we develop a robust astronomical imaging method in the presence of RFI and model mismatch. The key contribution of the proposed method is the accurate estimation of the actual signal steering vector by maximizing the beamformer output power subject to a constraint that prevents the estimated steering vector from converging to the interference steering vectors. The proposed method is formulated as a quadratically constrained quadratic programming problem that can be solved using efficient numerical approaches. Simulation results demonstrate the effectiveness of the proposed method.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171719400129","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45371045","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 : 2018-12-11DOI: 10.1142/S2251171719400026
B. Winkel, A. Jessner
Modern radio astronomical facilities are able to detect extremely weak electromagnetic signals not only from the universe but also from man-made radio frequency interference of various origins. These range from wanted signals to unwanted out-of-band emission of radio services and applications to electromagnetic interference produced by all kinds of electronic and electric devices. Energy harvesting wind turbines are not only equipped with electric power conversion hardware but also copious amounts of electronics to control and monitor the turbines. A wind turbine in the vicinity of a radio telescope could therefore lead to harmful interference, corrupting the measured astronomical data. Many observatories seek to coordinate placement of new wind farms with wind turbine manufacturers and operators, as well as with the local planning authorities, to avoid such a situation. In our study, we provide examples as well as guidelines for the determination of the separation distances between wind turbines and radio observatories, to enable a benign co-existence for both. The proposed calculations entail three basic steps. At first, the anticipated maximum emitted power level based on the European EN 550011 ( CISPR, 2015 ) standard, which applies to industrial devices, is determined. Then secondly, the propagation loss along the path to the radio receiver is computed via a model provided by the international telecommunication union. Finally, the received power is compared to the permitted power limit that pertains in the protected radio astronomical observing band under consideration. This procedure may be carried out for each location around a telescope site, in order to obtain a map of potentially problematic wind turbine positions.
{"title":"Compatibility Between Wind Turbines and the Radio Astronomy Service","authors":"B. Winkel, A. Jessner","doi":"10.1142/S2251171719400026","DOIUrl":"https://doi.org/10.1142/S2251171719400026","url":null,"abstract":"Modern radio astronomical facilities are able to detect extremely weak electromagnetic signals not only from the universe but also from man-made radio frequency interference of various origins. These range from wanted signals to unwanted out-of-band emission of radio services and applications to electromagnetic interference produced by all kinds of electronic and electric devices. Energy harvesting wind turbines are not only equipped with electric power conversion hardware but also copious amounts of electronics to control and monitor the turbines. A wind turbine in the vicinity of a radio telescope could therefore lead to harmful interference, corrupting the measured astronomical data. Many observatories seek to coordinate placement of new wind farms with wind turbine manufacturers and operators, as well as with the local planning authorities, to avoid such a situation. In our study, we provide examples as well as guidelines for the determination of the separation distances between wind turbines and radio observatories, to enable a benign co-existence for both. The proposed calculations entail three basic steps. At first, the anticipated maximum emitted power level based on the European EN 550011 ( CISPR, 2015 ) standard, which applies to industrial devices, is determined. Then secondly, the propagation loss along the path to the radio receiver is computed via a model provided by the international telecommunication union. Finally, the received power is compared to the permitted power limit that pertains in the protected radio astronomical observing band under consideration. This procedure may be carried out for each location around a telescope site, in order to obtain a map of potentially problematic wind turbine positions.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2018-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171719400026","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48969021","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 : 2018-12-01DOI: 10.1142/S2251171718400123
K. Ennico, E. Becklin, Jeanette H. Le, N. Rangwala, W. Reach, Alan Rhodes, T. Roellig, George L. Sarver, P. Temi, H. Yorke, E. Zavala
The Stratospheric Observatory for Infrared Astronomy (SOFIA), a joint project between NASA and the German Aerospace Center DLR, provides access to observations of the infrared and sub-millimeter universe. As its development timeline is unique compared to all other NASA astrophysics missions, a milestone called the Full Operation Capability (FOC) was defined to identify the start of science operations. SOFIA reached this in February 2014. With a wide range of imagers, spectrometers and a new polarimeter, SOFIA provides unique scientific results that cannot be obtained with a ground-based facility and any spacecraft expected in the next decade. The airborne platform has continued to mature its mission systems as part of a planned spiral development approach, particularly with upgradable instrumentation that opens up new science directions for the Observatory. A third generation instrument is planned for commissioning in 2019. This paper summarizes the current state of the Observatory with emphasis on the science and instrumentation updates since FOC.
{"title":"An Overview of the Stratospheric Observatory for Infrared Astronomy Since Full Operation Capability","authors":"K. Ennico, E. Becklin, Jeanette H. Le, N. Rangwala, W. Reach, Alan Rhodes, T. Roellig, George L. Sarver, P. Temi, H. Yorke, E. Zavala","doi":"10.1142/S2251171718400123","DOIUrl":"https://doi.org/10.1142/S2251171718400123","url":null,"abstract":"The Stratospheric Observatory for Infrared Astronomy (SOFIA), a joint project between NASA and the German Aerospace Center DLR, provides access to observations of the infrared and sub-millimeter universe. As its development timeline is unique compared to all other NASA astrophysics missions, a milestone called the Full Operation Capability (FOC) was defined to identify the start of science operations. SOFIA reached this in February 2014. With a wide range of imagers, spectrometers and a new polarimeter, SOFIA provides unique scientific results that cannot be obtained with a ground-based facility and any spacecraft expected in the next decade. The airborne platform has continued to mature its mission systems as part of a planned spiral development approach, particularly with upgradable instrumentation that opens up new science directions for the Observatory. A third generation instrument is planned for commissioning in 2019. This paper summarizes the current state of the Observatory with emphasis on the science and instrumentation updates since FOC.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171718400123","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42927462","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 : 2018-12-01DOI: 10.1142/S225117171840010X
K. Leppik, K. Bower, C. Kaminski, C. Trinh, T. Civeit, T. Kilsdonk
The Stratospheric Observatory for Infrared Astronomy (SOFIA) is NASA’s airborne observatory. Observing with SOFIA has different challenges than observing from a ground based, or even space-based observatory. Although pointing SOFIA is similar to pointing an alt/az telescope, positioning the telescope requires not only the telescope assembly but also the aircraft. SOFIA’s telescope assembly can move in altitude nominally between 20∘ and 60∘. Since the telescope is pointed out the left side of a modified Boeing 747, the azimuth is determined by the aircraft heading. As a result, observing plans become the basis for a flight plan, and the science observation and aircraft operations are intrinsically linked. This paper will discuss flight planning and execution on this unique observatory.
{"title":"SOFIA Flight Planning and Execution","authors":"K. Leppik, K. Bower, C. Kaminski, C. Trinh, T. Civeit, T. Kilsdonk","doi":"10.1142/S225117171840010X","DOIUrl":"https://doi.org/10.1142/S225117171840010X","url":null,"abstract":"The Stratospheric Observatory for Infrared Astronomy (SOFIA) is NASA’s airborne observatory. Observing with SOFIA has different challenges than observing from a ground based, or even space-based observatory. Although pointing SOFIA is similar to pointing an alt/az telescope, positioning the telescope requires not only the telescope assembly but also the aircraft. SOFIA’s telescope assembly can move in altitude nominally between 20∘ and 60∘. Since the telescope is pointed out the left side of a modified Boeing 747, the azimuth is determined by the aircraft heading. As a result, observing plans become the basis for a flight plan, and the science observation and aircraft operations are intrinsically linked. This paper will discuss flight planning and execution on this unique observatory.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S225117171840010X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44569556","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 : 2018-12-01DOI: 10.1142/S2251171718400093
Friederike Graf, Andreas Reinacher, H. Jakob, S. Fasoulas
The SOFIA telescope is a worldwide unique observatory that enables infrared astronomy aboard a Boeing 747SP at altitudes of up to 45[Formula: see text]kft. Contrary to any ground-based telescope, SOFIA is exposed not only to aerodynamic forces but also aircraft motion and excitation. Nevertheless, the ambitious scientific goals require a stable platform and very precise pointing. As of now, the telescope can be considered diffraction-limited in the far-infrared wavelengths beyond 50[Formula: see text][Formula: see text]m. A careful study of the different sources of blur revealed that image jitter is among the most influential. During the course of a flight, the telescope is exposed to various excitation levels, leading to deformation of its flexible structure and vibrations in a wide range of frequencies. Since SOFIA entered its operational phase, continuous efforts have been made to develop and implement upgrades in the pointing and control system. The original design was a robust and conservative structure aimed to ensure safe operations with several different science instruments and many unknown parameters. In recent years, more and more agile system components have followed to tackle the residual image motion. This paper introduces the telescope control system followed by a summary of recently installed upgrades and ends with an outlook on future developments on our way to diffraction-limited imaging beyond 25[Formula: see text][Formula: see text]m.
{"title":"Image Size and Control System Developments of the Airborne Telescope SOFIA","authors":"Friederike Graf, Andreas Reinacher, H. Jakob, S. Fasoulas","doi":"10.1142/S2251171718400093","DOIUrl":"https://doi.org/10.1142/S2251171718400093","url":null,"abstract":"The SOFIA telescope is a worldwide unique observatory that enables infrared astronomy aboard a Boeing 747SP at altitudes of up to 45[Formula: see text]kft. Contrary to any ground-based telescope, SOFIA is exposed not only to aerodynamic forces but also aircraft motion and excitation. Nevertheless, the ambitious scientific goals require a stable platform and very precise pointing. As of now, the telescope can be considered diffraction-limited in the far-infrared wavelengths beyond 50[Formula: see text][Formula: see text]m. A careful study of the different sources of blur revealed that image jitter is among the most influential. During the course of a flight, the telescope is exposed to various excitation levels, leading to deformation of its flexible structure and vibrations in a wide range of frequencies. Since SOFIA entered its operational phase, continuous efforts have been made to develop and implement upgrades in the pointing and control system. The original design was a robust and conservative structure aimed to ensure safe operations with several different science instruments and many unknown parameters. In recent years, more and more agile system components have followed to tackle the residual image motion. This paper introduces the telescope control system followed by a summary of recently installed upgrades and ends with an outlook on future developments on our way to diffraction-limited imaging beyond 25[Formula: see text][Formula: see text]m.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171718400093","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41403617","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 : 2018-12-01DOI: 10.1142/S225117171840007X
Andreas Reinacher, Friederike Graf, Benjamin Greiner, H. Jakob, Y. Lammen, Sarah Peter, M. Wiedemann, Oliver Zeile, H. Kaercher
The SOFIA telescope is a 2.5[Formula: see text]m class Cassegrain telescope with Nasmyth focus. It is the largest telescope ever integrated into an aircraft. The telescope is exposed to the stratospheric environment during the observations and the fact that the telescope’s foundation, which is a Boeing 747 SP, is vibrating and moving in all degrees of freedom (DoF) requires a highly specialized and sophisticated design. Based on the telescope of its predecessor, the Kuiper Airborne Observatory (KAO), the SOFIA telescope design had to evolve to accommodate a telescope 2.5 times the size of KAO. In several hundred successful observation flights, the telescope proved that it performs not only as specified, but is also extremely reliable. Nevertheless, the telescope’s software and hardware are continuously upgraded to optimize its performance without interfering with the observation schedules to reach even more ambitious image size and pointing jitter goals to enable additional science cases. In addition, manufacturing of the line-replaceable units is in process to ensure that the SOFIA telescope can perform without any major interruptions for the envisioned 20 year lifetime. Some of the main features of the SOFIA telescope are its suspension assembly (SUA), which decouples the telescope from SOFIA’s fuselage with air springs and a spherical oil bearing, the extremely stiff Nasmyth tube (NT), which connects cavity and cabin mounted components of the dumbbell design, and the Secondary Mirror Assembly (SMA), which is used for chopping and fast pointing corrections. This paper aims to give an overview of these and all other major telescope subsystems in operation today. In addition, some of the upgrades, either implemented recently or slated for implementation shortly, are introduced.
{"title":"The SOFIA Telescope in Full Operation","authors":"Andreas Reinacher, Friederike Graf, Benjamin Greiner, H. Jakob, Y. Lammen, Sarah Peter, M. Wiedemann, Oliver Zeile, H. Kaercher","doi":"10.1142/S225117171840007X","DOIUrl":"https://doi.org/10.1142/S225117171840007X","url":null,"abstract":"The SOFIA telescope is a 2.5[Formula: see text]m class Cassegrain telescope with Nasmyth focus. It is the largest telescope ever integrated into an aircraft. The telescope is exposed to the stratospheric environment during the observations and the fact that the telescope’s foundation, which is a Boeing 747 SP, is vibrating and moving in all degrees of freedom (DoF) requires a highly specialized and sophisticated design. Based on the telescope of its predecessor, the Kuiper Airborne Observatory (KAO), the SOFIA telescope design had to evolve to accommodate a telescope 2.5 times the size of KAO. In several hundred successful observation flights, the telescope proved that it performs not only as specified, but is also extremely reliable. Nevertheless, the telescope’s software and hardware are continuously upgraded to optimize its performance without interfering with the observation schedules to reach even more ambitious image size and pointing jitter goals to enable additional science cases. In addition, manufacturing of the line-replaceable units is in process to ensure that the SOFIA telescope can perform without any major interruptions for the envisioned 20 year lifetime. Some of the main features of the SOFIA telescope are its suspension assembly (SUA), which decouples the telescope from SOFIA’s fuselage with air springs and a spherical oil bearing, the extremely stiff Nasmyth tube (NT), which connects cavity and cabin mounted components of the dumbbell design, and the Secondary Mirror Assembly (SMA), which is used for chopping and fast pointing corrections. This paper aims to give an overview of these and all other major telescope subsystems in operation today. In addition, some of the upgrades, either implemented recently or slated for implementation shortly, are introduced.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S225117171840007X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46911160","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 : 2018-12-01DOI: 10.1142/S2251171718400111
P. Temi, D. Hoffman, K. Ennico, Jeanette H. Le
The Stratospheric Observatory for Infrared Astronomy (SOFIA), the largest airborne observatory in the world, is in full operation capability since February 2014 and is currently completing its Observing Cycle 6 Program. The first four years of operation have provided the opportunity to assess the high-level observatory’s technical performance and to identify additional observatory upgrades. Since the start of routine operations, performance and productivity in several areas of the observatory, including science, operations and engineering, have been tracked by metrics and statistics. In this paper we present the general observatory technical performance as the observatory has reached its maturity and has served the science community with over 2900[Formula: see text]h of scientific observations.
{"title":"SOFIA at Full Operation Capability: Technical Performance","authors":"P. Temi, D. Hoffman, K. Ennico, Jeanette H. Le","doi":"10.1142/S2251171718400111","DOIUrl":"https://doi.org/10.1142/S2251171718400111","url":null,"abstract":"The Stratospheric Observatory for Infrared Astronomy (SOFIA), the largest airborne observatory in the world, is in full operation capability since February 2014 and is currently completing its Observing Cycle 6 Program. The first four years of operation have provided the opportunity to assess the high-level observatory’s technical performance and to identify additional observatory upgrades. Since the start of routine operations, performance and productivity in several areas of the observatory, including science, operations and engineering, have been tracked by metrics and statistics. In this paper we present the general observatory technical performance as the observatory has reached its maturity and has served the science community with over 2900[Formula: see text]h of scientific observations.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171718400111","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47350267","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：