Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the world’s largest single dish radio telescope,which is located in Guizhou Province,in southwest China.The FAST feed cabin is supported and positioned by...Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the world’s largest single dish radio telescope,which is located in Guizhou Province,in southwest China.The FAST feed cabin is supported and positioned by six steel cables.The deviation of the feed position and orientation would lead to loss in the telescope efficiency.In this paper,a series of electromagnetic(EM)simulations of the FAST facility with varying feed positions and orientation offsets was performed.The maximum gain of FAST is about 82.3 dBi and the sibelobe is–32 dB with respect to the main beam at 3 GHz.The simulation results have demonstrated that the telescope efficiency loss is more sensitive to the lateral feed deviation compared with the axial deviation.The telescope efficiency would decrease by 8.2%due to the FAST feed position deviation of 10 mm rms when the observing frequency is 3 GHz.The FAST feed deviation basically has no effect on the sidelobes and cross polarization characteristic according to the simulations.展开更多
As the most sensitive single-dish radio telescope,the Five-hundred Aperture Spherical radio Telescope(FAST)is very susceptive to radio frequency interference(RFI)from active radio services.Moreover,due to the rapid de...As the most sensitive single-dish radio telescope,the Five-hundred Aperture Spherical radio Telescope(FAST)is very susceptive to radio frequency interference(RFI)from active radio services.Moreover,due to the rapid development of space applications and research,satellite interference has become one of the main RFI sources for FAST,particularly at the L band.Therefore,we have developed several measures to mitigate satellite RFI.On the one hand,an antenna with 4.5-meter diameter has been constructed and installed at the FAST site to detect the satellite interference in the frequency band between 1 to 5 GHz.Meanwhile,we have developed a satellite RFI database based on the FAST sky coverage,the observing frequency bands,and known satellite systems.By combining the satellite RFI monitoring antenna and the database,we have established a satellite RFI mitigation system.With this system,we can not only track satellites to collect their characteristics and update the database but also help the observer to program the observing plan by predicting satellite interference.During the practical observation of FAST at the L band,the feasibility of this system to mitigate satellite RFI has been proved.In particular,the system effectively avoids strong satellite interference from entering the main beam of the telescope and causing receiver saturation.展开更多
The Five-hundred-meter Aperture Spherical radio Telescope(FAST) is by far the largest telescope of any kind ever built. FAST produced its first light in September 2016 and it is now under commissioning, with normal op...The Five-hundred-meter Aperture Spherical radio Telescope(FAST) is by far the largest telescope of any kind ever built. FAST produced its first light in September 2016 and it is now under commissioning, with normal operation to commence in late 2019. During testing and early science operation, FAST has started making astronomical discoveries, particularly pulsars of various kinds, including millisecond pulsars, binaries, gamma-ray pulsars, etc. The papers in this mini-volume propose ambitious observational projects to advance our knowledge of astronomy, astrophysics and fundamental physics in many ways.Although it may take FAST many years to achieve all the goals explained in these papers, taken together they define a powerful strategic vision for the next decade.展开更多
Radio Frequency Interference(RFI)mitigation is essential for supporting the science output of Five-hundred-meter Aperture Spherical radio Telescope(FAST)due to its high sensitivity.In order to protect FAST from RFI,an...Radio Frequency Interference(RFI)mitigation is essential for supporting the science output of Five-hundred-meter Aperture Spherical radio Telescope(FAST)due to its high sensitivity.In order to protect FAST from RFI,an Electromagnetic Compatibility(EMC)study has been carried out and the operation of a Radio Quiet Zone(RQZ)is ongoing.RFI measurements of the telescope instruments and monitoring of the active radio services outside the site have revealed the radiation properties of the RFI sources.Based on the measurement results and theoretical analysis,various EMC methods have been implemented for the telescope to decrease the RFIs.Meanwhile,the main RFI sources in the FAST RQZ,such as mobile stations,broadcast stations and navigation instruments,have been identified,and the technical measures have been adopted to protect the quiet radio environment around the site.The early science outputs of FAST have demonstrated the efficiency of RFI mitigation methods.展开更多
This paper reports on the time and frequency standard system for the Five-hundred meter Aperture Spherical radio Telescope(FAST),including the system design,stability measurements and pulsar timing observations.The st...This paper reports on the time and frequency standard system for the Five-hundred meter Aperture Spherical radio Telescope(FAST),including the system design,stability measurements and pulsar timing observations.The stability and drift rate of the frequency standard are calculated using 1-year monitoring data.The UTC-NIM Disciplined Oscillator(NIMDO)system improves the system time accuracy and stability to the level of 5 ns.Pulsar timing observations were carried out for several months.The weighted RMS of timing residuals reaches the level of less than 3.0μs.展开更多
H Ⅱ regions made of gas ionized by radiations from young massive stars,are widely distributed in the Milky Way.They are tracers for star formation,and their distributions are correlated with the Galactic spiral struc...H Ⅱ regions made of gas ionized by radiations from young massive stars,are widely distributed in the Milky Way.They are tracers for star formation,and their distributions are correlated with the Galactic spiral structure.Radio recombination lines(RRLs) of hydrogen and other atoms allow for the most precise determination of physical parameters such as temperature and density.However,RRLs at around 1.4 GHz from HⅡ regions are weak and their detections are difficult.As a result,only a limited number of detections have been obtained yet.The 19-beam receiver on board of the Five-hundred-meter Aperture Spherical radio Telescope(FAST) can simultaneously cover 23 RRLs for Hnα,Henα,and Cnα(n=164-186),respectively.This,combined with its unparalleled collecting area,makes FAST the most powerful telescope to detect weak RRLs.In this pilot survey,we use FAST to observe nine HⅡ regions at L band.We allocate20 minutes pointing time for each source to achieve a sensitivity of around 9 mK in a velocity resolution of2.0 km s^(-1).In total,21 RRLs for Hnα and Cnα at 1.0-1.5 GHz have been simultaneously detected with strong emission signals.Overall,the detection rates for the H167α and C167α RRLs are 100%,while that for the He167α RRL is 33.3%.Using hydrogen and helium RRLs,we measure the electron density,electron temperature,and pressure for three HⅡ regions.This pilot survey demonstrates the capability of FAST in RRL measurements,and a statistically meaningful sample with RRL detection,through which knowledge about Galactic spiral structure and evolution can be obtained,is expected in the future.展开更多
The active reflector of FAST （ five-hundred-meter aperture spherical radio telescope） is suppor- ted by a ring beam and a cable-net structure, in which nodes are actively controlled to form series of real-time parab...The active reflector of FAST （ five-hundred-meter aperture spherical radio telescope） is suppor- ted by a ring beam and a cable-net structure, in which nodes are actively controlled to form series of real-time paraboloids. To ensure the security and stability of the supporting structure, tension must be monitored for some typical cables. Considering the stringent requirements in accuracy and long- term stability, magnetic flux sensor, vibrating wire strain gauge and fiber bragg grating strain gauge are screened for the cable tension monitoring of the supporting cable-net. Specifically, receivers of radio telescopes have strict restriction on electro magnetic interference （EMI） or radio frequency in- terference （RFI）. These three types of sensors are evaluated from the view of EMIfRFI. Firstly, these fundamentals are theoretically analyzed. Secondly, typical sensor signals are collected in the time and analyzed in the frequency domain, which shows the characteristic in the frequency domain. Finally, typical sensors are tested in an anechoic chamber to get the EMI levels. Theoretical analysis shows that Fiber Bragg Grating strain gauge itself will not lead to EMI/RFI. According to GJB151 A, frequency domain analysis and test results show that for the vibrating wire strain gauge and magnetic flux sensor themselves, testable EMIfRF1 levels are typically below the background noise of the ane- choic chamber. FAST finally choses these three sensors as the monitoring sensors of its cable ten- sion. The proposed study is also a reference to the monitoring equipment selection of other radio tele- scopes and large structures.展开更多
The Five-hundred-meter Aperture Spherical radio Telescope （FAST） adopts an active deformable main reflector which is composed of 4450 triangular panels. During an observation, the illuminated area of the reflector i...The Five-hundred-meter Aperture Spherical radio Telescope （FAST） adopts an active deformable main reflector which is composed of 4450 triangular panels. During an observation, the illuminated area of the reflector is deformed into a 300-m diameter paraboloid and directed toward a source. To achieve accurate control of the reflector shape, positions of 2226 nodes distributed around the entire reflector must be measured with sufficient precision within a limited time, which is a challenging task because of the large scale. Measurement of the FAST reflector makes use of stations and node targets. However, in this case the effect of the atmosphere on measurement accuracy is a significant issue. This paper investigates a differen- tial correction method for total stations measurement of the FAST reflector. A multi-benchmark differential correction method, including a scheme for benchmark selection and weight assignment, is proposed. On- site evaluation experiments show there is an improvement of 70%-80% in measurement accuracy compared with the uncorrected measurement, verifying the effectiveness of the proposed method.展开更多
The FAST radio telescope has significantly better sensitivity than any other current radio telescope.Consequently,FAST has discovered over a thousand new pulsars in sky regions already searched for 50 yr.The Galactic ...The FAST radio telescope has significantly better sensitivity than any other current radio telescope.Consequently,FAST has discovered over a thousand new pulsars in sky regions already searched for 50 yr.The Galactic Plane Pulsar Snapshot(GPPS)survey found three-quarters of these new pulsars.The article by Han et al.(2025)details the latest batch of 473 discoveries,bringing the total to 751.展开更多
基金funded by the National Natural Science Foundation of China(Grant No.11303062)
文摘Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the world’s largest single dish radio telescope,which is located in Guizhou Province,in southwest China.The FAST feed cabin is supported and positioned by six steel cables.The deviation of the feed position and orientation would lead to loss in the telescope efficiency.In this paper,a series of electromagnetic(EM)simulations of the FAST facility with varying feed positions and orientation offsets was performed.The maximum gain of FAST is about 82.3 dBi and the sibelobe is–32 dB with respect to the main beam at 3 GHz.The simulation results have demonstrated that the telescope efficiency loss is more sensitive to the lateral feed deviation compared with the axial deviation.The telescope efficiency would decrease by 8.2%due to the FAST feed position deviation of 10 mm rms when the observing frequency is 3 GHz.The FAST feed deviation basically has no effect on the sidelobes and cross polarization characteristic according to the simulations.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB23000000)the National Key Research and Development Program(No.2019YFB1312704)+2 种基金the National Natural Science Foundation of China(Program No.U1831128)the International Partnership Program of Chinese Academy of Sciences(Program No.114A11KYSB20160008)supported by the National Development and Reform Commission,the Key Laboratory of FAST of CAS。
文摘As the most sensitive single-dish radio telescope,the Five-hundred Aperture Spherical radio Telescope(FAST)is very susceptive to radio frequency interference(RFI)from active radio services.Moreover,due to the rapid development of space applications and research,satellite interference has become one of the main RFI sources for FAST,particularly at the L band.Therefore,we have developed several measures to mitigate satellite RFI.On the one hand,an antenna with 4.5-meter diameter has been constructed and installed at the FAST site to detect the satellite interference in the frequency band between 1 to 5 GHz.Meanwhile,we have developed a satellite RFI database based on the FAST sky coverage,the observing frequency bands,and known satellite systems.By combining the satellite RFI monitoring antenna and the database,we have established a satellite RFI mitigation system.With this system,we can not only track satellites to collect their characteristics and update the database but also help the observer to program the observing plan by predicting satellite interference.During the practical observation of FAST at the L band,the feasibility of this system to mitigate satellite RFI has been proved.In particular,the system effectively avoids strong satellite interference from entering the main beam of the telescope and causing receiver saturation.
基金the support from the National Key R&D Program of China (2017YFA0402600)the National Natural Science Foundation of China (11725313)
文摘The Five-hundred-meter Aperture Spherical radio Telescope(FAST) is by far the largest telescope of any kind ever built. FAST produced its first light in September 2016 and it is now under commissioning, with normal operation to commence in late 2019. During testing and early science operation, FAST has started making astronomical discoveries, particularly pulsars of various kinds, including millisecond pulsars, binaries, gamma-ray pulsars, etc. The papers in this mini-volume propose ambitious observational projects to advance our knowledge of astronomy, astrophysics and fundamental physics in many ways.Although it may take FAST many years to achieve all the goals explained in these papers, taken together they define a powerful strategic vision for the next decade.
基金supported by the National Development and Reform Commission,and the Key Laboratory of FAST of CAS
文摘Radio Frequency Interference(RFI)mitigation is essential for supporting the science output of Five-hundred-meter Aperture Spherical radio Telescope(FAST)due to its high sensitivity.In order to protect FAST from RFI,an Electromagnetic Compatibility(EMC)study has been carried out and the operation of a Radio Quiet Zone(RQZ)is ongoing.RFI measurements of the telescope instruments and monitoring of the active radio services outside the site have revealed the radiation properties of the RFI sources.Based on the measurement results and theoretical analysis,various EMC methods have been implemented for the telescope to decrease the RFIs.Meanwhile,the main RFI sources in the FAST RQZ,such as mobile stations,broadcast stations and navigation instruments,have been identified,and the technical measures have been adopted to protect the quiet radio environment around the site.The early science outputs of FAST have demonstrated the efficiency of RFI mitigation methods.
基金supported by the Joint Research Fund in Astronomy(Grant Nos.U1931129,U1631115 and U1831117)under cooperative agreement between NSFC and Chinese Academy of Sciences(CAS)NSFC-STINT Grant 11611130023(CH2015-6360)the National Natural Science Foundation of China(NSFC,Grant No.11403054)
文摘This paper reports on the time and frequency standard system for the Five-hundred meter Aperture Spherical radio Telescope(FAST),including the system design,stability measurements and pulsar timing observations.The stability and drift rate of the frequency standard are calculated using 1-year monitoring data.The UTC-NIM Disciplined Oscillator(NIMDO)system improves the system time accuracy and stability to the level of 5 ns.Pulsar timing observations were carried out for several months.The weighted RMS of timing residuals reaches the level of less than 3.0μs.
基金support from the National Key R&D Program of China (2018YFE0202900)support by the NAOC Nebula Talents Program+2 种基金the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CASthe support from the Youth Innovation Promotion Association of CASsupported by the National Natural Science Foundation of China (Grant Nos.11703040,W820301904,11988101,11933011 and 11833009)。
文摘H Ⅱ regions made of gas ionized by radiations from young massive stars,are widely distributed in the Milky Way.They are tracers for star formation,and their distributions are correlated with the Galactic spiral structure.Radio recombination lines(RRLs) of hydrogen and other atoms allow for the most precise determination of physical parameters such as temperature and density.However,RRLs at around 1.4 GHz from HⅡ regions are weak and their detections are difficult.As a result,only a limited number of detections have been obtained yet.The 19-beam receiver on board of the Five-hundred-meter Aperture Spherical radio Telescope(FAST) can simultaneously cover 23 RRLs for Hnα,Henα,and Cnα(n=164-186),respectively.This,combined with its unparalleled collecting area,makes FAST the most powerful telescope to detect weak RRLs.In this pilot survey,we use FAST to observe nine HⅡ regions at L band.We allocate20 minutes pointing time for each source to achieve a sensitivity of around 9 mK in a velocity resolution of2.0 km s^(-1).In total,21 RRLs for Hnα and Cnα at 1.0-1.5 GHz have been simultaneously detected with strong emission signals.Overall,the detection rates for the H167α and C167α RRLs are 100%,while that for the He167α RRL is 33.3%.Using hydrogen and helium RRLs,we measure the electron density,electron temperature,and pressure for three HⅡ regions.This pilot survey demonstrates the capability of FAST in RRL measurements,and a statistically meaningful sample with RRL detection,through which knowledge about Galactic spiral structure and evolution can be obtained,is expected in the future.
基金Supported by the National Natural Science Foundation of China(No.11173035,11273036,11303059)
文摘The active reflector of FAST （ five-hundred-meter aperture spherical radio telescope） is suppor- ted by a ring beam and a cable-net structure, in which nodes are actively controlled to form series of real-time paraboloids. To ensure the security and stability of the supporting structure, tension must be monitored for some typical cables. Considering the stringent requirements in accuracy and long- term stability, magnetic flux sensor, vibrating wire strain gauge and fiber bragg grating strain gauge are screened for the cable tension monitoring of the supporting cable-net. Specifically, receivers of radio telescopes have strict restriction on electro magnetic interference （EMI） or radio frequency in- terference （RFI）. These three types of sensors are evaluated from the view of EMIfRFI. Firstly, these fundamentals are theoretically analyzed. Secondly, typical sensor signals are collected in the time and analyzed in the frequency domain, which shows the characteristic in the frequency domain. Finally, typical sensors are tested in an anechoic chamber to get the EMI levels. Theoretical analysis shows that Fiber Bragg Grating strain gauge itself will not lead to EMI/RFI. According to GJB151 A, frequency domain analysis and test results show that for the vibrating wire strain gauge and magnetic flux sensor themselves, testable EMIfRF1 levels are typically below the background noise of the ane- choic chamber. FAST finally choses these three sensors as the monitoring sensors of its cable ten- sion. The proposed study is also a reference to the monitoring equipment selection of other radio tele- scopes and large structures.
基金supported by the Project Research of Adaptive Modeling and Control Strategy in the FAST Active Reflector of the National Natural Science Foundation of China(Grant No.11273001)the Key Laboratory of Radio Astronomy,Chinese Academy of Sciences
文摘The Five-hundred-meter Aperture Spherical radio Telescope （FAST） adopts an active deformable main reflector which is composed of 4450 triangular panels. During an observation, the illuminated area of the reflector is deformed into a 300-m diameter paraboloid and directed toward a source. To achieve accurate control of the reflector shape, positions of 2226 nodes distributed around the entire reflector must be measured with sufficient precision within a limited time, which is a challenging task because of the large scale. Measurement of the FAST reflector makes use of stations and node targets. However, in this case the effect of the atmosphere on measurement accuracy is a significant issue. This paper investigates a differen- tial correction method for total stations measurement of the FAST reflector. A multi-benchmark differential correction method, including a scheme for benchmark selection and weight assignment, is proposed. On- site evaluation experiments show there is an improvement of 70%-80% in measurement accuracy compared with the uncorrected measurement, verifying the effectiveness of the proposed method.
文摘The FAST radio telescope has significantly better sensitivity than any other current radio telescope.Consequently,FAST has discovered over a thousand new pulsars in sky regions already searched for 50 yr.The Galactic Plane Pulsar Snapshot(GPPS)survey found three-quarters of these new pulsars.The article by Han et al.(2025)details the latest batch of 473 discoveries,bringing the total to 751.
