We reported about an experiment aimed at verifying the statistical technique, which has been proposed first by Mikhail S. Belen'Kii to solve the tilt indetermination problem from the laser guide star(LGS) adaptive optics(AO) system. The tilt components of wave fronts were measured synchronously from a Rayleigh guide star by use of a 25-cm telescope as an auxiliary telescope and from a star by use of a telescope with a 1.2-m aperture at Yunnan Observatories. The result shown that the instability of the auxiliary telescope's tracking system is an important error source for the tilt measurement.
As a novel network coordinate measurement system based on multi-directional positioning, workspace Measurement and Positioning System (wMPS) has outstanding advantages of good parallelism, wide measurement range and high measurement accuracy, which makes it to be the research hotspots and important development direction in the field of large-scale measurement. Since station deployment has a significant impact on the measurement range and accuracy, and also restricts the use-cost, the optimization method of station deployment was researched in this paper. Firstly, positioning error model was established. Then focusing on the small network consisted of three stations, the typical deployments and error distribution characteristics were studied. Finally, through measuring the simulated fuselage using typical deployments at the industrial spot and comparing the results with Laser Tracker, some conclusions are obtained. The comparison results show that under existing prototype conditions, I_3 typical deployment of which three stations are distributed in a straight line has an average error of 0.30 mm and the maximum error is 0.50 mm in the range of 12 m. Meanwhile, C_3 typical deployment of which three stations are uniformly distributed in the half-circumference of an circle has an average error of 0.17 mm and the maximum error is 0.28 mm. Obviously, C_3 typical deployment has a higher control effect on precision than I_3 type. The research work provides effective theoretical support for global measurement network optimization in the future work.
As an astronomical image post-processing technique, deconvolution from wavefront sensing (DWFS) is a powerful and
low cost method for adaptive optics (AO) images reduction. It is based on deconvolution of short exposure images and
simultaneous measuring wavefront sensor data, both are provided by adaptive optics system to improve the quality of
images. However, for extended or dim sources observing, limited precision of the Wave Front Sensor (WFS) will lead to
inferior correction quality of AO images, also these can hardly enhanced by DWFS method. We show here a simple and
efficient solution, which combines the DWFS method with a shift-and-add (SAA) image reconstruction technique,
designed for reduction of astronomical data obtained with AO system, especially extended objects. This scheme has been
applied to the upgraded 61-actuator Shack-Hartmann based adaptive optics system, partially primary corrected extended
object images at Yunnan observatory 1.2m telescope for astronomical high resolution imaging. Experimental result of
Mars was presented.
Atmospheric turbulence affects the direction and shape of laser beam on long distance laser ranging, especially on the Lunar Laser Ranging (LLR). That will result in decreasing the returned photon numbers on ground station when it performs the LLR. It is need to compensate turbulence effects in real-time on the LLR, first for the effects of atmospheric tip-tilt. In this paper, we present the experiment results at Yunnan Observatory 1.2m telescope that use a small area near the retro-reflector array on the moon surface as an expanded source to detect and compute the atmospheric tip-tilt signal in real time.
A 61-actuator adaptive optical system has been upgraded at Yunnan
observatory 1.2m telescope since 2004, and is
only one visible wavelength AO system in China now. Considering its relative small diameter and angular resolution,
the main purpose of this AO system, besides the high resolution astronomical imaging, is for long distance laser
ranging. This paper describes these AO system performances and its observation results, and the possible application
on lunar laser ranging.
The UnISIS adaptive optics system is now completed and ready for science observations. We describe the experience we have gained in building and using the system, and we give a preview of one new science goal: the use of Gaussian aperture pupil masks for high-contrast imaging of companion objects near bright stars. A key aspect of the UnISIS design is the simultaneous use of two wavefront sensors, one for natural stars and the other for the laser guide star. We demonstrate the performance of this calibration system with results from on-the-bench tests. We describe several practical aspects of observing at Mt. Wilson including our ability to predict the nights of best seeing with weather data available on-line. We also show how the laser guide star return signal is enhanced by observing at large zenith angles and compare this to Rayleigh scattering models.
Science commissioning of the UnISIS adaptive optics system is underway. In addition to showing test images from this effort, two other topics are discussed. These include a progress report on our continuing effort to improve the UV throughput of the UnISIS laser guide star projection and detection system and our effort to migrate the closed-loop computation engine from OS/2 to real time Linux. The two new improvements to the UV throughput of the laser guide star system involve new high-throughput prisms for the Pockels cell switch and a plan to increase the projected laser energy using anamorphic magnification in the laser beam as it emerges from the Excimer laser.
The goal of this paper is to discuss the turbulent effects on the laser beam of the lunar laser ranging (LLR), and to use the real-time tilt compensation for the LLR. In this new technique, a small area near the retroreflector array on the moon surface will be used as an extended source to detect the wavefront tilt. Then the absolute difference algorithm will be used to calculate the wavefront tilt and to reconstruct it, and it will be used to drive a tip-tilt mirror in the laser transmit path to carry on the real-time tilt compensation for the laser beam on the LLR. After the compensation, the returned laser photons from the moon retroreflector to the ground telescope will be increased a factor of 6 to 40, depend on the turbulence.
Astrodynamical Space Test of Relativity using Optical Devices (ASTROD) is a newly proposed space mission with deep space laser ranging. Its scientific goals are to measure the relativistic parameters with 3-6 order better sensitivity. The Mini-ASTROD is a down-scaled version ofthe ASTROD. The laser ranging with a distance of 1 or 2 AU between the spacecraft and the ground station will be performed. So the turbulence effects for the laser beam propagation must be considered. A new idea of the real-time tilt correction of the laser beam on the ASTROD and the Mini-ASTROD is proposed. The technical plan for this purpose at the laser ranging system of Yunnan Observatory 1 .2m telescope is introduced in this paper.
A 50 watt excimer laser (lambda equals 351 nm) has been installed at the Mt. Wilson 2.5- meter telescope in California as part of the UnISIS adaptive optics system. This laser is used to produce Rayleigh guide stars 18 km above Mt. Wilson. In its initial configuration the projection optics are used to create a single laser guide star. The optical system is designed to allow an easy switch to accommodate three laser guide stars if (1) the laser return signal is sufficiently bright and (2) the laser guide star wavefront sensor has a read noise low enough to detect the split signal. The three guide stars are projected simultaneously in a triangular configuration above the telescope pupil. This three laser guide star system design is the first to confront directly the problem of focal anisoplanatism with an array of laser guide stars. The three guide star array provides a test for theoretical analyses of arrays of laser guide stars which will be an inevitable part of the adaptive optics systems of 8-meter and 10-meter class telescopes.