For the ASO-S/HXI payload, the accuracy of the flare reconstruction is reliant on important factors such as the alignment of the dual grating and the precise measurement of observation orientation. To guarantee optima...For the ASO-S/HXI payload, the accuracy of the flare reconstruction is reliant on important factors such as the alignment of the dual grating and the precise measurement of observation orientation. To guarantee optimal functionality of the instrument throughout its life cycle, the Solar Aspect System (SAS) is imperative to ensure that measurements are accurate and reliable. This is achieved by capturing the target motion and utilizing a physical model-based inversion algorithm. However, the SAS optical system’s inversion model is a typical ill-posed inverse problem due to its optical parameters, which results in small target sampling errors triggering unacceptable shifts in the solution. To enhance inversion accuracy and make it more robust against observation errors, we suggest dividing the inversion operation into two stages based on the SAS spot motion model. First, the as-rigid-aspossible (ARAP) transformation algorithm calculates the relative rotations and an intermediate variable between the substrates. Second, we solve an inversion linear equation for the relative translation of the substrates, the offset of the optical axes, and the observation orientation. To address the ill-posed challenge, the Tikhonov method grounded on the discrepancy criterion and the maximum a posteriori (MAP) method founded on the Bayesian framework are utilized. The simulation results exhibit that the ARAP method achieves a solution with a rotational error of roughly±3 5 (1/2-quantile);both regularization techniques are successful in enhancing the stability of the solution, the variance of error in the MAP method is even smaller—it achieves a translational error of approximately±18μm (1/2-quantile) in comparison to the Tikhonov method’s error of around±24μm (1/2-quantile). Furthermore, the SAS practical application data indicates the method’s usability in this study. Lastly, this paper discusses the intrinsic interconnections between the regularization 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
This paper presents an ultra-low noise L-band radio astronomical cryogenic receiver for the Fivehundred-meter Aperture Spherical radio Telescope(FAST) telescope. The development of key low noise microwave parts of cou...This paper presents an ultra-low noise L-band radio astronomical cryogenic receiver for the Fivehundred-meter Aperture Spherical radio Telescope(FAST) telescope. The development of key low noise microwave parts of coupling low noise amplifier(Coupling-LNA) and conical quad-ridge orthogonal mode transducers(OMT) and reasonable system integration achieve outstanding performance of receiver. It covers the frequency range of 1.2 GHz to 1.8 GHz. Novel cryogenic Coupling-LNAs with low noise, large return loss, high dynamic range and the function of coupling calibration signals are developed for the proposed receiver. Amplification and coupling function circuits are integrated as a single Coupling-LNA with full noise temperature of 4 K at the physical temperature of 15 K. Its return loss is more than 18 d B, and output1 d B compression power is +5 d Bm. A cryogenic dewar is fabricated to provide 55 K and 15 K cryogenic environment for OMT and Coupling-LNAs, respectively. The receiver's system noise temperature is below9 K referred to feed aperture plane. Benefiting from optimal design and precise mechanical treatment, good scattering performance of OMT and equalized radiation patterns of horn are achieved with an antenna efficiency above 75%.展开更多
This paper presents an ultra-wide bandwidth(UWB)low-frequency radio astronomical cryogenic receiver for the Five-hundred-meter Aperture Spherical radio Telescope(FAST).It covers 6.6:1 bandwidth from 0.5 to 3.3 GHz.The...This paper presents an ultra-wide bandwidth(UWB)low-frequency radio astronomical cryogenic receiver for the Five-hundred-meter Aperture Spherical radio Telescope(FAST).It covers 6.6:1 bandwidth from 0.5 to 3.3 GHz.The receiver consists of a Quad-Ridged Flared Horn(QRFH),a cryogenic microwave unit,an optical transceiver and a warm microwave and frequency mixing unit.A QRFH with a concentric-loaded dielectric spear is developed:the average return losses are larger than 20 d B;the average ports polarization isolation is 43.87 d B;the average dish efficiency is higher than 65%.Many UWB cryogenic low loss components are developed for the fabrication of a cryogenic microwave unit.The average noise temperature lower than 14.2 K and 22.5 K are achieved as referred to the input ports of cryogenic Dewar and the output of horn,respectively.Compared to other similar advanced UWB receivers,such as Parkes 0.7-4.2 GHz(6:1 bandwidth)receiver and FAST 0.27-1.62 GHz(6:1 bandwidth)receiver,wider relative bandwidth of the proposed receiver is achieved and it is a new attempt to expand the bandwidth of UWB low-frequency receiver.展开更多
基金the Strategic Priority Research Program on Space Science of the Chinese Academy of Sciences,the grant No.XDA15320104,with additional contributions from the Purple Mountain Observatory(PMO)of the Chinese Academy of Sciences and the National Space Science Center(NSSC).
文摘For the ASO-S/HXI payload, the accuracy of the flare reconstruction is reliant on important factors such as the alignment of the dual grating and the precise measurement of observation orientation. To guarantee optimal functionality of the instrument throughout its life cycle, the Solar Aspect System (SAS) is imperative to ensure that measurements are accurate and reliable. This is achieved by capturing the target motion and utilizing a physical model-based inversion algorithm. However, the SAS optical system’s inversion model is a typical ill-posed inverse problem due to its optical parameters, which results in small target sampling errors triggering unacceptable shifts in the solution. To enhance inversion accuracy and make it more robust against observation errors, we suggest dividing the inversion operation into two stages based on the SAS spot motion model. First, the as-rigid-aspossible (ARAP) transformation algorithm calculates the relative rotations and an intermediate variable between the substrates. Second, we solve an inversion linear equation for the relative translation of the substrates, the offset of the optical axes, and the observation orientation. To address the ill-posed challenge, the Tikhonov method grounded on the discrepancy criterion and the maximum a posteriori (MAP) method founded on the Bayesian framework are utilized. The simulation results exhibit that the ARAP method achieves a solution with a rotational error of roughly±3 5 (1/2-quantile);both regularization techniques are successful in enhancing the stability of the solution, the variance of error in the MAP method is even smaller—it achieves a translational error of approximately±18μm (1/2-quantile) in comparison to the Tikhonov method’s error of around±24μm (1/2-quantile). Furthermore, the SAS practical application data indicates the method’s usability in this study. Lastly, this paper discusses the intrinsic interconnections between the regularization 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supported by the National Key R&D Program of China(2018YFE0202900)the National Natural Science Foundation of China(U1831110)。
文摘This paper presents an ultra-low noise L-band radio astronomical cryogenic receiver for the Fivehundred-meter Aperture Spherical radio Telescope(FAST) telescope. The development of key low noise microwave parts of coupling low noise amplifier(Coupling-LNA) and conical quad-ridge orthogonal mode transducers(OMT) and reasonable system integration achieve outstanding performance of receiver. It covers the frequency range of 1.2 GHz to 1.8 GHz. Novel cryogenic Coupling-LNAs with low noise, large return loss, high dynamic range and the function of coupling calibration signals are developed for the proposed receiver. Amplification and coupling function circuits are integrated as a single Coupling-LNA with full noise temperature of 4 K at the physical temperature of 15 K. Its return loss is more than 18 d B, and output1 d B compression power is +5 d Bm. A cryogenic dewar is fabricated to provide 55 K and 15 K cryogenic environment for OMT and Coupling-LNAs, respectively. The receiver's system noise temperature is below9 K referred to feed aperture plane. Benefiting from optimal design and precise mechanical treatment, good scattering performance of OMT and equalized radiation patterns of horn are achieved with an antenna efficiency above 75%.
基金supported by the National Key R&D Program of China(2018YFE0202900)the National Natural Science Foundation of China(U1831110)。
文摘This paper presents an ultra-wide bandwidth(UWB)low-frequency radio astronomical cryogenic receiver for the Five-hundred-meter Aperture Spherical radio Telescope(FAST).It covers 6.6:1 bandwidth from 0.5 to 3.3 GHz.The receiver consists of a Quad-Ridged Flared Horn(QRFH),a cryogenic microwave unit,an optical transceiver and a warm microwave and frequency mixing unit.A QRFH with a concentric-loaded dielectric spear is developed:the average return losses are larger than 20 d B;the average ports polarization isolation is 43.87 d B;the average dish efficiency is higher than 65%.Many UWB cryogenic low loss components are developed for the fabrication of a cryogenic microwave unit.The average noise temperature lower than 14.2 K and 22.5 K are achieved as referred to the input ports of cryogenic Dewar and the output of horn,respectively.Compared to other similar advanced UWB receivers,such as Parkes 0.7-4.2 GHz(6:1 bandwidth)receiver and FAST 0.27-1.62 GHz(6:1 bandwidth)receiver,wider relative bandwidth of the proposed receiver is achieved and it is a new attempt to expand the bandwidth of UWB low-frequency receiver.
