The Development of the FAST Project in China

The collecting area of a radio telescope is a figure of merit of that instruments's capability. A Five hundred meter Aperture Spherical Telescope (FAST) is proposed to be built in the unique karst area of southwest China, and will act, in a sense, as a prototype for the Square Kilometer Array (SKA). It will be over twice as large as Arecibo coupled with much wider sky coverage. Some results from site surveys for such a SKA concept are briefly reported. Technically, FAST is not simply a copy of the existing Arecibo telescope but has rather a number of innovations. Firstly, the proposed main spherical reflector, by conforming to a paraboloid of revolution in real time through actuated active control, enables the realization of both wide bandwidth and full polarization capability while using standard feed design. Secondly, a feed support system which integrates optical, mechanical and electronic technologies will effectively reduce the cost of the support structure and control system. With an overall diameter of 500 m and radius of its spherical surface of 300 m, FAST will be the world's largest single dish.

Five-hundred-meter Aperture Spherical Radio Telescope (FAST) is a Chinese mega-science project to build the largest and most sensitive single dish radio telescope in the world. To achieve precise positioning of FAST feed cabin, we need all-weather, large-span and high-precision real-time dynamic measurements. The coarse-adjusting measurement of the FAST feed support, uses RTK (Real Time Kinematic) with the fusion of BDS/GPS/GLONASS. This paper introduces the RTK measurement program of FAST feed support coarse-adjusting system. Combined with the measured data, it indicates the importance of BDS/GPS/GLONASS data fusion. We also use total station to evaluate the accuracy of RTK measurement. The results show that the accuracy of RTK with fusion of BDS/GPS/GLONASS meets the technical requirements, which can guarantee the normal observation and safe operation of FAST.

In order to guarantee the usage of active reflector and achieve the highest working frequency requirement, 5GHz, in FAST, fitting accuracy of the active reflector is supposed to be analyzed. In this chapter, a novel 3 DOFs parallel mechanism, 3-PSS with constraint leg, is proposed. This mechanism can fulfill the required movement to fit a paraboloid of revolution for the active reflector. The kinematics of 3-PSS+C mechanism is studied. Based on that, the one and two-dimensional fitting accuracy are calculated and the side length

Common signal-processing approximations produce artefacts when timing pulsars in relativistic binary systems, especially edge-on systems with tight orbits, such as the Double Pulsar. In this paper, we use extensive simulations to explore various patterns that arise from the inaccuracies of approximations made when correcting dispersion and Shapiro delay. In a relativistic binary, the velocity of the pulsar projected onto the line of sight varies significantly on short timescales, causing rapid changes in the apparent pulsar spin frequency, which is used to convert dispersive delays to pulsar rotational phase shifts. A well-known example of the consequences of this effect is the artificial variation of dispersion measure (DM) with binary phase, first observed in the Double Pulsar 20 years ago. We show that ignoring the Doppler shift of the spin frequency when computing the dispersive phase shift exactly reproduces the shape and magnitude of the reported DM variations. We also simulate and study two additional effects of much smaller magnitude, which are caused by the assumption that the spin frequency used to correct dispersion is constant over the duration of the sub-integration and over the observed bandwidth. We show that failure to account for these two effects leads to orbital phase-dependent dispersive smearing that leads to apparent orbital DM variations. The functional form of the variation depends on the orbital eccentricity. In addition, we find that a polynomial approximation of the timing model is unable to accurately describe the Shapiro delay of edge-on systems with orbits of less than four hours, which poses problems for the measurements of timing parameters, most notably the Shapiro delay. This will be a potential issue for sensitive facilities such as the Five-hundred-meter Aperture Spherical Telescope (FAST) and the forthcoming Square Kilometre Array (SKA); therefore, a more accurate phase predictor is indispensable.

A new kind of position control system for basic elements of sphere is introduced in the paper. Based on mechanical principle, structure analysis is made for the control system, which proved that it meets special need of the position control system of FAST (Five-hundred-meter Aperture Spherical Telescope). In addition, kinematics analysis is made for the compensation fit of the system and compensating size is calculated. Lastly, some results of experiment are given.

In recent years, superfluid dark matter (SfDM) has become a competitive model\nof emergent modified Newtonian dynamics (MOND) scenario: MOND phenomenons\nnaturally emerge as a derived concept due to an extra force mediated between\nbaryons by phonons as a result of axionlike particles condensed as superfluid\nat galactic scales; Beyond galactic scales, these axionlike particles behave as\nnormal fluid without phonon-mediated MOND-like force between baryons, therefore\nSfDM also maintains the usual success of $\\Lambda$CDM at cosmological scales.\nIn this paper, we use gravitational waves (GWs) to probe the relevant parameter\nspace of SfDM. GWs through Bose-Einstein condensate (BEC) could propagate with\na speed slightly deviation from the speed-of-light due to the change in the\neffective refractive index, which depends on the SfDM parameters and GW-source\nproperties. We find that Five hundred meter Aperture Spherical Telescope\n(FAST), Square Kilometre Array (SKA) and International Pulsar Timing Array\n(IPTA) are the most promising means as GW probe of relevant parameter space of\nSfDM. Future space-based GW detectors are also capable of probing SfDM if a\nmultimessenger approach is adopted.\n

A unique wide band receiver for radio astronomy has been designed and constructed. Receivers used for radio astronomy consist of two parts, the front end cold electronics and the back end warm electronics. While the cold electronics provides for a low noise amplifier and receiver calibrations, the warm electronics provides analog signal processing that shapes and filters the signals before digitizing. The following describes the unique features of the warm electronics receiver built by Caltech for installation on China's Five hundred meter Aperture Spherical Telescope (FAST).

The Five-hundred-meter Aperture Spherical Radio Telescope (FAST)—a large-aperture radio telescope constructed in a karst depression—is completing its commissioning. Several studies have been performed using FAST, including the discovery of over 100 pulsars. Nevertheless, the ability of a single telescope is still limited. The construction of other radio telescopes and telescope arrays around FAST will promote its use for new types of observations and help to achieve additional scientific goals. Based on the analyses of the basic properties of the karst depressions in the Guizhou Province—e.g., their morphologies, aperture diameters, and depths—some conceptual designs have been proposed for large-scale radio telescopes and telescopic arrays. They include a drift-scan survey array, a quasi-steerable radio telescope, a tilted radio telescope, and a fixed-reflector, low-frequency spherical radio telescope. The sky coverage and sensitivity have been calculated for each design, and possible science goals have been discussed, including searches for pulsars and fast radio bursts, as well as studies of variable radio sources. By coordinating their observations with FAST, these telescopes will greatly expand the observational capabilities of FAST and yield substantially more science results, especially in the area of time-domain astronomy.

First feed support system, which is one of the key technologies of Five hundred meter Aperture Spherical Telescope (FAST) was discussed in this paper. A 1:30 scaled model (20 m × 20 m × 6 m) has been built to make systemic research on the feasibility of the system. The root mean square of pointing error of moving cable car was measured and the displacements of cable car within the wind speed of 8 m/s, which is the maximal wind speed of the place where the FAST will be located, were evaluated. Then the total maximal pointing error of cable car was computed. Experimental results demonstrate that the total pointing error of the cable car is less than 50 cm, the required pointing accuracy error of the system.

Stray radiation is a considerable challenge for radio telescopes, requiring careful assessment due to its effects. This is crucial when the strong background flux from side lobes significantly affects the total flux, especially for extended sources. In this study, we introduced the beam pattern of the L-band receiver on the Five-hundred-meter Aperture Spherical Telescope (FAST), covering various frequencies based on recent observations. We discovered that the main beam efficiency of all beams exceeds 90% throughout the L band frequencies, with efficiency decreasing slowly as frequency increases. Subsequently, we developed a module to mitigate stray radiation effects, incorporating it into FAST’s standard HI data reduction process, referred to as HiFAST. Our analysis shows that side lobe flux’s influence, particularly for extended sources with significant surface density gradients, necessitates detailed evaluation. Corrections for the extended M33 galaxy can reach up to 20%. Moreover, the pattern data presented here is vital for studying HI intensity maps at high redshift. The module, along with HiFAST and beam pattern data across 15 frequency bins, can be accessed at https://hifast.readthedocs.io

Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese mega-science project to build the largest single dish radio telescope in the world. Being the most sensitive single dish radio telescope. It was completed and put into use in September 2016. Its innovative engineering concept and design pave a new road to realize a huge single dish in the most effective way. The idea of sitting a large spherical dish in a karst depression is rooted in Arecibo telescope. FAST is an Arecibo-type antenna with three outstanding aspects: the karst depression used as the site, which is large to host the 500-meter telescope and deep to allow a zenith angle of 40 degrees; the active main reflector correcting for spherical aberration on the ground to achieve a full polarization and a wide band without involving complex feed systems; and the light-weight feed cabin driven by cables and servomechanism plus a parallel robot as a secondary adjustable system to move with high precision. The common feature of the latter two innovations is the transformation of large scale rigid structures into large scale flexible structures. To realize precise real-time control, the challenge of measurement and control technology is very challenging. This review intends to introduce the implementation methods, the recent progress, results, problems and future development of FAST measurement and control.

We discuss the possibility of performing a substantial spectroscopic galaxy redshift survey selected via the 21-cm emission from neutral hydrogen using the Five-hundred metre Aperture Spherical Telescope (FAST) to be built in China. We consider issues related to the estimation of the source counts and optimizations of the survey, and discuss the constraints on cosmological models that such a survey could provide. We find that a survey taking around two years could detect similar to 10(7) galaxies with an average redshift of similar to 0.15 making the survey complementary to those already carried out at optical wavelengths. These conservative estimates have used the z = 0 H I mass function and have ignored the possibility of evolution. The results could be used to constrain Gamma=Omega(m)h to 5 per cent and the spectral index, n(s), to 7 per cent independent of cosmic microwave background data. If we also use simulated power spectra from the Planck satellite, we can constrain w to be within 5 per cent of -1.

We present Arecibo 327 MHz confirmation and follow-up studies of seven new pulsars discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). These pulsars are discovered in a pilot program of the Commensal Radio Astronomy FAST Survey (CRAFTS) with the ultra-wide-bandwidth commissioning receiver. Five of them are normal pulsars and two are extreme nulling slow pulsars. PSR J2111+2132’s dispersion measure(DM: 78.5 pc cm−3) is above the upper limits of the two Galactic free electron density models, NE2001 and YMW16, and PSR J2057+2133’s position is out of the Scutum-Crux Arm, making them uniquely useful for improving the Galactic free electron density model in their directions. We present a detailed single pulse analysis for the slow nulling pulsars. We show evidence that PSR J2323+1214’s main pulse component follows a non-Poisson distribution and marginal evidence for a sub-pulse-drift or recurrent period of 32.3±0.4 rotations from PSR J0539+0013. We discuss the implication of our finding to the pulsar radiation mechanism.

The anticipated discovery of a pulsar in orbit with a black hole is expected to provide a unique laboratory for black hole physics and gravity. In this context, the next generation of radio telescopes, like the Five-hundred-meter Aperture Spherical radio Telescope (FAST) and the Square Kilometre Array (SKA), with their unprecedented sensitivity, will play a key role. In this paper, we investigate the capability of future radio telescopes to probe the space–time of a black hole and test gravity theories by timing a pulsar orbiting a stellar-mass black hole (SBH). Based on mock data simulations, we show that a few years of timing observations of a sufficiently compact pulsar–SBH (PSR–SBH) system with future radio telescopes would allow precise measurements of the black hole mass and spin. A measurement precision of 1 per cent can be expected for the spin. Measuring the quadrupole moment of the black hole, needed to test general relativity's (GR's) no-hair theorem, requires extreme system configurations with compact orbits and a large SBH mass. Additionally, we show that a PSR–SBH system can lead to greatly improved constraints on alternative gravity theories even if they predict black holes (practically) identical to GR's. This is demonstrated for a specific class of scalar–tensor theories. Finally, we investigate the requirements for searching for PSR–SBH systems. It is shown that the high sensitivity of the next generation of radio telescopes is key for discovering compact PSR–SBH systems, as it will allow for sufficiently short survey integration times.

The Phased Array Feed (PAF) is considered as one of the next generation receivers for radio telescopes, which can significantly enlarge the instantaneous Field-of-View of large aperture single dish radio telescopes and enable more flexible observing configurations. Study efforts on PAF development for radio telescopes have been made for more than two decades and have become more and more applicable. We report the development of an ambient-temperature 19 element L-band PAF system and the experimental results including its far field beam pattern and system temperature measurement, which achieve the expectations. Implementing the aperture array beam-forming method, we demonstrate a wide-field Galactic H i observations in the radio camera mode. The results indicate that this system might be applicable for strong Galactic transient detections. This system could be directly equipped to large telescopes like the Five-hundred-meter Aperture Spherical radio Telescope (FAST) and FAST array in the future.