Five hundred meter aperture spherical radio telescope (FAST) will be the largest radio telescope in the world. The innovative engineering concept and design pave a new road to realizing a huge single dish in the most ...Five hundred meter aperture spherical radio telescope (FAST) will be the largest radio telescope in the world. The innovative engineering concept and design pave a new road to realizing a huge single dish in the most effective way. Three outstanding features of the telescope are the unique karst depressions as the sites, the active main reflector which corrects spherical aberration on the ground to achieve full polarization and a wide band without involving a complex feed system, and the light focus cabin driven by cables and servomechanism plus a parallel robot as secondary adjustable system to carry the most precise parts of the receivers. Being the most sensitive radio telescope, FAST will enable astronomers to jumpstart many of the science goals, for example, the neutral hydrogen line surveying in distant galaxies out to very large redshifts, looking for the first shining star, detecting thousands of new pulsars, etc. Extremely interesting and exotic objects may yet await discovery by FAST. As a multi-science platform, the telescope will provide treasures to astronomers, as well as bring prosperity to other research, e.g. space weather study, deep space exploration and national security. The construction of FAST itself is expected to promote the development in high technology of relevant fields.展开更多
The Chinese Area Positioning System （CAPS） is a positioning system based on satellite communication that is fundamentally different from the 3＂G＂ （GPS, GLONASS and GALILEO） systems. The latter use special-purpos...The Chinese Area Positioning System （CAPS） is a positioning system based on satellite communication that is fundamentally different from the 3＂G＂ （GPS, GLONASS and GALILEO） systems. The latter use special-purpose navigation satellites to broadcast navigation information generated on-board to users, while the CAPS transfers ground-generated navigation information to users via the communication satellite. In order to achieve accurate Positioning, Velocity and Time （PVT）, the CAPS employs the following strategies to over- come the three main obstacles caused by using the communication satellite： （a） by real-time following-up frequency stabilization to achieve stable frequency; （b） by using a single carrier in the transponder with 36 MHz band-width to gain sufficient power; （c） by incorporating Decommissioned Geostationary Orbit communication satellite （DGEO）, barometric pressure and Inclined Geostationary Orbit communication satellite （IGSO） to achieve the 3-D posi- tioning. Furthermore, the abundant transponders available on DGEO can be used to realize the large capacity of communication as well as the integrated navigation and communication. With the communication functions incorporated, five new functions appear in the CAPS： （1） combination of navigation and communication; （2） combination of navigation and high accu- racy orbit measurement; （3） combination of navigation message and wide/local area differen- tial processing; （4） combination of the switching of satellites, frequencies and codes; and （5） combination of the navigation message and the barometric altimetry. The CAPS is thereby labelled a PVT5C system of high accuracy. In order to validate the working principle and the performance of the CAPS, a trial system was established in the course of two years at a cost of about 20 million dollars. The trial constellation consists of two GEO satellites located at E87.5° and E110.5°, two DGEOs located at E130° and E142°, as well as barometric altimetr展开更多
Gamma ray source detection above 30 TeV is an encouraging approach for finding galactic cosmic ray sources. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulati...Gamma ray source detection above 30 TeV is an encouraging approach for finding galactic cosmic ray sources. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulation for various types of sources above 100 GeV. In order to target those goals, a large air shower particle detector array of 1 km^2 （the LHAASO project） at 4300 m a.s.l, is proposed, By adding two MagicⅡ- type telescopes in the array as proposed, LHAASO will be enhanced in source morphologic investigation power. The proposed array will be utilized also for energy spectrum measurement for individual cosmic ray species above 30 TeV. By re-configuring the wide field of view telescopes into fluorescence light detector array, the aperture of the detector array can be enlarged to cover an energy region above 100 PeV where the second knee is located. Cosmic ray spectrum and composition will be measured in order to transfer an energy scale to ultra high energy cosmic ray experiments.展开更多
It is a long dream to realize the communication and navigation functionality in a satellite system in the world. This paper introduces how to establish the system, a positioning system based on communication satellite...It is a long dream to realize the communication and navigation functionality in a satellite system in the world. This paper introduces how to establish the system, a positioning system based on communication satellites called Chinese Area Positioning System (CAPS). Instead of the typical navigation satellites, the communication satellites are configured firstly to transfer navigation signals from ground stations, and can be used to obtain service of the positioning, velocity and time, and to achieve the function of navigation and positioning. Some key technique issues should be first solved; they include the accuracy position determination and orbit prediction of the communication satellites, the measur- ing and calculation of transfer time of the signals, the carrier frequency drift in communication satellite signal transfer, how to improve the geometrical configuration of the constellation in the system, and the integration of navigation & communication. Several innovative methods are developed to make the new system have full functions of navigation and communication. Based on the development of crucial techniques and methods, the CAPS demonstration system has been designed and developed. Four communication satellites in the geosynchronous orbit (GEO) located at 87.5°E, 110.5°E, 134°E, 142°E and barometric altimetry are used in the CAPS system. The GEO satellites located at 134°E and 142°E are decommissioned GEO (DGEO) satellites. C-band is used as the navigation band. Dual frequency at C1=4143.15 MHz and C2=3826.02 MHz as well as dual codes with standard code (CA code and precision code (P code)) are adopted. The ground segment consists of five ground stations; the master station is in Lintong, Xi’an. The ground stations take a lot of responsibilities, including monitor and management of the operation of all system components, determination of the satellite position and prediction of the satellite orbit, accomplishment of the virtual atomic clock measurement, transmission and receiving navigation sign展开更多
This study presents a general outline of the Qitai radio telescope(QTT)project.Qitai,the site of the telescope,is a county of Xinjiang Uygur Autonomous Region of China,located in the east Tianshan Mountains at an elev...This study presents a general outline of the Qitai radio telescope(QTT)project.Qitai,the site of the telescope,is a county of Xinjiang Uygur Autonomous Region of China,located in the east Tianshan Mountains at an elevation of about 1800 m.The QTT is a fully steerable,Gregorian-type telescope with a standard parabolic main reflector of 110 m diameter.The QTT has adopted an umbrella support,homology-symmetric lightweight design.The main reflector is active so that the deformation caused by gravity can be corrected.The structural design aims to ultimately allow high-sensitivity observations from 150 MHz up to115 GHz.To satisfy the requirements for early scientific goals,the QTTwill be equipped with ultra-wideband receivers and large field-of-view multi-beam receivers.A multi-function signal-processing system based on RFSo C and GPU processor chips will be developed.These will enable the QTT to operate in pulsar,spectral line,continuum and Very Long Baseline Interferometer(VLBI)observing modes.Electromagnetic compatibility(EMC)and radio frequency interference(RFI)control techniques are adopted throughout the system design.The QTT will form a world-class observational platform for the detection of lowfrequency(nano Hertz)gravitational waves through pulsar timing array(PTA)techniques,pulsar surveys,the discovery of binary black-hole systems,and exploring dark matter and the origin of life in the universe.The QTT will also play an important role in improving the Chinese and international VLBI networks,allowing high-sensitivity and high-resolution observations of the nuclei of distant galaxies and gravitational lensing systems.Deep astrometric observations will also contribute to improving the accuracy of the celestial reference frame.Potentially,the QTT will be able to support future space activities such as planetary exploration in the solar system and to contribute to the search for extraterrestrial intelligence.展开更多
To improve our understanding of the formation and evolution of the Moon, one of the payloads onboard the Chang＇e-3 （CE-3） rover is Lunar Penetrating Radar （LPR）. This investigation is the first attempt to explore...To improve our understanding of the formation and evolution of the Moon, one of the payloads onboard the Chang＇e-3 （CE-3） rover is Lunar Penetrating Radar （LPR）. This investigation is the first attempt to explore the lunar subsurface structure by using ground penetrating radar with high resolution. We have probed the subsur- face to a depth of several hundred meters using LPR. In-orbit testing, data processing and the preliminary results are presented. These observations have revealed the con- figuration of regolith where the thickness of regolith varies from about 4 m to 6 m. In addition, one layer of lunar rock, which is about 330 m deep and might have been accumulated during the depositional hiatus of mare basalts, was detected.展开更多
Introduction The Large High Altitude Air Shower Observatory plans to build a hybrid extensive air shower array with an area of about 1 km^(2) at an altitude of 4,410 m a.s.l.in Sichuan province,China,to explore the or...Introduction The Large High Altitude Air Shower Observatory plans to build a hybrid extensive air shower array with an area of about 1 km^(2) at an altitude of 4,410 m a.s.l.in Sichuan province,China,to explore the origin of high-energy cosmic rays.KM2A LHAASO-KM2A will detect gamma ray sources with a sensitivity of about 1%Crab Unit at 100 TeV.It covers an area of 1 km^(2) with a total of 5195 scintillation detectors.Its angular resolution reaches about 0.3 degrees,and the energy resolution is better than 25%.With the help of 1171 muon detectors,cosmic nuclei background will be rejected to a level of 10-4 at 50 TeV.The design and performances of the scintillation detectors and muon detectors are described in detail.WCDA LHAASO-WCDA focuses on surveying the northern sky for steady and transient sources from 100 GeV to 20 TeV,with a very high background rejection power and a good angular resolution.The WCDA consists of three water ponds with a total area of 78,000 m^(2),and the effective water depth is 4 m.Each water pond is divided into 5m×5m cells partitioned by black plastic curtains to prevent penetration of the light from neighboring cells.An 8-inch PMT sits at the bottom center of each cell,looking upward to collect Cherenkov light generated by shower secondary particles in water.WFCTA LHAASO-WFCTA is composed of 12 wide-field-of-view Cherenkov/fluorescence telescopes.Each telescope consists of a spherical light collector of about 4.7 m^(2) and focal plane camera of 32×32 pixels with a pixel size of 0.5 degree.LHAASO prototype arrays A prototype array about 1%of LHAASO has been constructed at Yangbajing Cosmic Ray Observatory and has been in operation for more than 2 years.Its performance fully meets the design requirements.Conclusion The LHAASO detectors are designed to fulfill the physical goals in gamma ray astronomy and cosmic ray physics.One-fourth of LHAASO will be constructed and put into operation to produce physical data by the end of 2018.The whole array will be finished in the beginning of 2021.展开更多
More and more proposals, or potential projects have been proposed in recent two years. We try to briefly outline these new proposals, although most of them are in fact only in their conception studies. The progress of...More and more proposals, or potential projects have been proposed in recent two years. We try to briefly outline these new proposals, although most of them are in fact only in their conception studies. The progress of previously mentioned projects, like Space Solar Telescope (SST), the Hard X-ray Modulation Telescope (HXMT), as well as newly initiated LUnar Resource Explorer (LUREX), will be introduced elsewhere.展开更多
基金the Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant No. 10433020).
文摘Five hundred meter aperture spherical radio telescope (FAST) will be the largest radio telescope in the world. The innovative engineering concept and design pave a new road to realizing a huge single dish in the most effective way. Three outstanding features of the telescope are the unique karst depressions as the sites, the active main reflector which corrects spherical aberration on the ground to achieve full polarization and a wide band without involving a complex feed system, and the light focus cabin driven by cables and servomechanism plus a parallel robot as secondary adjustable system to carry the most precise parts of the receivers. Being the most sensitive radio telescope, FAST will enable astronomers to jumpstart many of the science goals, for example, the neutral hydrogen line surveying in distant galaxies out to very large redshifts, looking for the first shining star, detecting thousands of new pulsars, etc. Extremely interesting and exotic objects may yet await discovery by FAST. As a multi-science platform, the telescope will provide treasures to astronomers, as well as bring prosperity to other research, e.g. space weather study, deep space exploration and national security. The construction of FAST itself is expected to promote the development in high technology of relevant fields.
基金supported by Ministry of science and Technology of China (Nos.2007CB815500, 2004AA105030and 2007AA12Z3423)Chinese Academy of science (No.KGCXI-21)the National Natural Science Foundation of China (No.10453001).
文摘The Chinese Area Positioning System （CAPS） is a positioning system based on satellite communication that is fundamentally different from the 3＂G＂ （GPS, GLONASS and GALILEO） systems. The latter use special-purpose navigation satellites to broadcast navigation information generated on-board to users, while the CAPS transfers ground-generated navigation information to users via the communication satellite. In order to achieve accurate Positioning, Velocity and Time （PVT）, the CAPS employs the following strategies to over- come the three main obstacles caused by using the communication satellite： （a） by real-time following-up frequency stabilization to achieve stable frequency; （b） by using a single carrier in the transponder with 36 MHz band-width to gain sufficient power; （c） by incorporating Decommissioned Geostationary Orbit communication satellite （DGEO）, barometric pressure and Inclined Geostationary Orbit communication satellite （IGSO） to achieve the 3-D posi- tioning. Furthermore, the abundant transponders available on DGEO can be used to realize the large capacity of communication as well as the integrated navigation and communication. With the communication functions incorporated, five new functions appear in the CAPS： （1） combination of navigation and communication; （2） combination of navigation and high accu- racy orbit measurement; （3） combination of navigation message and wide/local area differen- tial processing; （4） combination of the switching of satellites, frequencies and codes; and （5） combination of the navigation message and the barometric altimetry. The CAPS is thereby labelled a PVT5C system of high accuracy. In order to validate the working principle and the performance of the CAPS, a trial system was established in the course of two years at a cost of about 20 million dollars. The trial constellation consists of two GEO satellites located at E87.5° and E110.5°, two DGEOs located at E130° and E142°, as well as barometric altimetr
基金Supported by Knowledge Innovation Fund (U-526) of IHEP,China
文摘Gamma ray source detection above 30 TeV is an encouraging approach for finding galactic cosmic ray sources. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulation for various types of sources above 100 GeV. In order to target those goals, a large air shower particle detector array of 1 km^2 （the LHAASO project） at 4300 m a.s.l, is proposed, By adding two MagicⅡ- type telescopes in the array as proposed, LHAASO will be enhanced in source morphologic investigation power. The proposed array will be utilized also for energy spectrum measurement for individual cosmic ray species above 30 TeV. By re-configuring the wide field of view telescopes into fluorescence light detector array, the aperture of the detector array can be enlarged to cover an energy region above 100 PeV where the second knee is located. Cosmic ray spectrum and composition will be measured in order to transfer an energy scale to ultra high energy cosmic ray experiments.
基金Supported by the National Natural Science Foundation of China (Grant No. 10453001)the National Basic Research Program of China (Grant No. 2007CB815500)+1 种基金the National High Technology Research and Development Program of China (Grant No. 2004AA105030)the Funds of the Chinese Academy of Sciences for Key Topics in Innovation Engineering (Grant No. KGCXI-21)
文摘It is a long dream to realize the communication and navigation functionality in a satellite system in the world. This paper introduces how to establish the system, a positioning system based on communication satellites called Chinese Area Positioning System (CAPS). Instead of the typical navigation satellites, the communication satellites are configured firstly to transfer navigation signals from ground stations, and can be used to obtain service of the positioning, velocity and time, and to achieve the function of navigation and positioning. Some key technique issues should be first solved; they include the accuracy position determination and orbit prediction of the communication satellites, the measur- ing and calculation of transfer time of the signals, the carrier frequency drift in communication satellite signal transfer, how to improve the geometrical configuration of the constellation in the system, and the integration of navigation & communication. Several innovative methods are developed to make the new system have full functions of navigation and communication. Based on the development of crucial techniques and methods, the CAPS demonstration system has been designed and developed. Four communication satellites in the geosynchronous orbit (GEO) located at 87.5°E, 110.5°E, 134°E, 142°E and barometric altimetry are used in the CAPS system. The GEO satellites located at 134°E and 142°E are decommissioned GEO (DGEO) satellites. C-band is used as the navigation band. Dual frequency at C1=4143.15 MHz and C2=3826.02 MHz as well as dual codes with standard code (CA code and precision code (P code)) are adopted. The ground segment consists of five ground stations; the master station is in Lintong, Xi’an. The ground stations take a lot of responsibilities, including monitor and management of the operation of all system components, determination of the satellite position and prediction of the satellite orbit, accomplishment of the virtual atomic clock measurement, transmission and receiving navigation sign
基金supported by the National Key Research and Development Program of China(Grant Nos.2021YFC2203501,2021YFC2203502,2021YFC2203503,and 2021YFC2203600)the National Natural Science Foundation of China(Grant Nos.12173077,11873082,11803080,and 12003062)+3 种基金the Scientific Instrument Developing Project of the Chinese Academy of Sciences(Grant No.PTYQ2022YZZD01)the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instrumentsbudgeted from the Ministry of Finance of China and Administrated by the Chinese Academy of Sciencesthe Chinese Academy of Sciences“Light of West China”Program(Grant No.2021-XBQNXZ-030)。
文摘This study presents a general outline of the Qitai radio telescope(QTT)project.Qitai,the site of the telescope,is a county of Xinjiang Uygur Autonomous Region of China,located in the east Tianshan Mountains at an elevation of about 1800 m.The QTT is a fully steerable,Gregorian-type telescope with a standard parabolic main reflector of 110 m diameter.The QTT has adopted an umbrella support,homology-symmetric lightweight design.The main reflector is active so that the deformation caused by gravity can be corrected.The structural design aims to ultimately allow high-sensitivity observations from 150 MHz up to115 GHz.To satisfy the requirements for early scientific goals,the QTTwill be equipped with ultra-wideband receivers and large field-of-view multi-beam receivers.A multi-function signal-processing system based on RFSo C and GPU processor chips will be developed.These will enable the QTT to operate in pulsar,spectral line,continuum and Very Long Baseline Interferometer(VLBI)observing modes.Electromagnetic compatibility(EMC)and radio frequency interference(RFI)control techniques are adopted throughout the system design.The QTT will form a world-class observational platform for the detection of lowfrequency(nano Hertz)gravitational waves through pulsar timing array(PTA)techniques,pulsar surveys,the discovery of binary black-hole systems,and exploring dark matter and the origin of life in the universe.The QTT will also play an important role in improving the Chinese and international VLBI networks,allowing high-sensitivity and high-resolution observations of the nuclei of distant galaxies and gravitational lensing systems.Deep astrometric observations will also contribute to improving the accuracy of the celestial reference frame.Potentially,the QTT will be able to support future space activities such as planetary exploration in the solar system and to contribute to the search for extraterrestrial intelligence.
基金Supported by the National Natural Science Foundation of China
文摘To improve our understanding of the formation and evolution of the Moon, one of the payloads onboard the Chang＇e-3 （CE-3） rover is Lunar Penetrating Radar （LPR）. This investigation is the first attempt to explore the lunar subsurface structure by using ground penetrating radar with high resolution. We have probed the subsur- face to a depth of several hundred meters using LPR. In-orbit testing, data processing and the preliminary results are presented. These observations have revealed the con- figuration of regolith where the thickness of regolith varies from about 4 m to 6 m. In addition, one layer of lunar rock, which is about 330 m deep and might have been accumulated during the depositional hiatus of mare basalts, was detected.
基金This work is supported in China by NSFC(Nos.11205165,11375210,11375224,11405181,11475190 and 11635011)the Chinese Academy of Sciences,Institute of High Energy Physics,the Key Laboratory of Particle Astrophysics,CAS.
文摘Introduction The Large High Altitude Air Shower Observatory plans to build a hybrid extensive air shower array with an area of about 1 km^(2) at an altitude of 4,410 m a.s.l.in Sichuan province,China,to explore the origin of high-energy cosmic rays.KM2A LHAASO-KM2A will detect gamma ray sources with a sensitivity of about 1%Crab Unit at 100 TeV.It covers an area of 1 km^(2) with a total of 5195 scintillation detectors.Its angular resolution reaches about 0.3 degrees,and the energy resolution is better than 25%.With the help of 1171 muon detectors,cosmic nuclei background will be rejected to a level of 10-4 at 50 TeV.The design and performances of the scintillation detectors and muon detectors are described in detail.WCDA LHAASO-WCDA focuses on surveying the northern sky for steady and transient sources from 100 GeV to 20 TeV,with a very high background rejection power and a good angular resolution.The WCDA consists of three water ponds with a total area of 78,000 m^(2),and the effective water depth is 4 m.Each water pond is divided into 5m×5m cells partitioned by black plastic curtains to prevent penetration of the light from neighboring cells.An 8-inch PMT sits at the bottom center of each cell,looking upward to collect Cherenkov light generated by shower secondary particles in water.WFCTA LHAASO-WFCTA is composed of 12 wide-field-of-view Cherenkov/fluorescence telescopes.Each telescope consists of a spherical light collector of about 4.7 m^(2) and focal plane camera of 32×32 pixels with a pixel size of 0.5 degree.LHAASO prototype arrays A prototype array about 1%of LHAASO has been constructed at Yangbajing Cosmic Ray Observatory and has been in operation for more than 2 years.Its performance fully meets the design requirements.Conclusion The LHAASO detectors are designed to fulfill the physical goals in gamma ray astronomy and cosmic ray physics.One-fourth of LHAASO will be constructed and put into operation to produce physical data by the end of 2018.The whole array will be finished in the beginning of 2021.
文摘More and more proposals, or potential projects have been proposed in recent two years. We try to briefly outline these new proposals, although most of them are in fact only in their conception studies. The progress of previously mentioned projects, like Space Solar Telescope (SST), the Hard X-ray Modulation Telescope (HXMT), as well as newly initiated LUnar Resource Explorer (LUREX), will be introduced elsewhere.
