Yudong Zhang

First light on the 127-element adaptive optical system for 1.8-m telescope

A 127-element adaptive optical system has been developed and integrated into a 1.8-m astronomical telescope in September 2009. In addition, the first light on a high-resolution imaging for stars has been achieved (September 23, 2009). In this letter, a 127-element adaptive optical system for 1.8-m telescope is described briefly. Moreover, star observation results in the first run are reported. Results show that the angular resolution of the system after adaptive optics correction can attain 0.1 arcsec, which approaches the diffraction limit of 1.8-m telescope at 700-900 nm band.

Progress on the 127-element adaptive optical system for 1.8m telescope

The 127-element adaptive optical system for the 1.8m astronomical telescope is being developed. In this system, the wavefront correction loop consists of a 127-element deformable mirror, a Hartmann-Shack (H-S) wavefront sensor, and a high-speed digital wavefront processor. The tracking system consists of a tip-tilt mirror, a tracking sensor and a tracking processor. The wavelength for the H-S wavefront sensor ranges from 400-700nm. The imaging observation wavelengths range from 700-1000nm and 1000-1700nm respectively. In this paper, the optical configuration of 1.8m telescope will be briefly introduced. The 127-element adaptive optical system is described in detailed. Furthermore, the preliminary performances and test results on the 127-element adaptive optical system is reported.

Performance on the 61-element upgraded adaptive optical system for 1.2-m telescope of the Yunnan Observatory

The 61-element upgraded adaptive optical system for the 1.2m telescope of Yannan Observatory for astronomical observation had been in operation since May 2004. In this paper, the 61-element upgraded adaptive optical system for 1.2m telescope of Yunnan Observatory will be briefly described. The performance on the 61-element upgraded adaptive optical system is analyzed. Furthermore, the observational results for the stars will be presented.

Adaptive optical system based on deformable secondary mirror on 1.8-meter telescope

In 2009, A 127-element adaptive system had been manufactured and installed at the Coude room of the 1.8-meter telescope at the Gaomeigu site of Yunnan Astronomical Observatory, Chinese Academy of Sciences. A set of new adaptive optical system based on a 73-element deformable secondary mirror is being developed and will be integrated into the 1.8-meter telescope. The 73-element deformable secondary mirror with convex reflecting surface is designed to be compatible with the Cassegrain focus of the 1.8-meter telescope. Comparing with the AO system of Coude focus, the AO system on the deformable secondary mirror adopts much less reflections and consequently restrains the thermal noise and increases the energy transmitting to the system. The design and simulation results of this system will be described in this paper. Furthermore, the preliminary test result of the deformable secondary mirror in the lab is also presented.

First observations on the 127-element adaptive optical system for 1.8m telescope

The 127-element adaptive optical system, which consists of a tracking loop with a tip-tilt mirror, a tracking system and a tracking processor, and a wavefront correction loop with a 127-element deformable mirror, a Hartmann-Shack wavefront sensor, and a wavefront processor, had been developed and integrated into the 1.8m astronomical telescope in September 2009. The First observations on the high resolution imaging for the stars had been done from September 23 2009 in the first light to March 2010. In this paper, the 127-element adaptive optical system for 1.8m telescope is described briefly and the star observation results in the first run are reported. The results show the angular resolution of the system can attain or approach the diffraction limit of 1.8m telescope at I band (700nm-1000nm) and J band (1000nm-1700nm).

Performance analysis of a Shack-Hartman wavefront sensor with variable subaperture pixels

The major error source of Shack-Hartmann wavefront sensor consists of the photon noise, the readout noise, and the sampling error. In this paper, the measurement error of Shack-Hartmann wavefront sensor with variable subaperture pixels is analyzed under the consideration of various threshold values and detecting dynamic ranges. A generalized expression, which is used for fitting the sampling error of Shack-Hartmann wavefront sensor with variable subaperture pixels, is presented. The computational results and the experimental results of the measurement error of Shack-Hartmann wavefront sensor with different pixels per subaperture are also given.

Piezoelectric deformable mirror technologies for astronomy at IOE, CAS

Institute of Optics & Electronics (IOE), Chinese Academy of Sciences (CAS) has more than 30 years’ experience on piezoelectric deformable mirror (DM) technologies research and developing since early 1980s. Several DMs of IOE have been used in many different application systems. A brief history of piezoelectric DMs development in IOE and several recently achievements, and the main characters, performance and test results of the DMs for astronomy will be presented in this paper. 1) High-order DM. DM prototype with 913-element for 4m telescope has been fabricated and tested in laboratory. 2) Adaptive Secondary Mirror (ASM). A 73-element ASM prototype with 12 microns stroke for 1.8m telescope has been fabricated. It will be installed onto the 1.8m telescope with a compact adaptive optics (AO) system. 3) Small spacing DM. A 6mm spacing 127-element DM based on the same construction with the High-order DM has been used in AO system of 1m New Vacuum Solar Telescope (NVST) in Yunnan Observatories. Higher density (3mm spacing) DM based on a novel construction has being developed. In 2012, the novel DM prototype with 100-element was fabricated and tested carefully in laboratory. Beside, a 6mm spacing 151-element DM based on the novel construction has being fabricated for the solar AO system.

Photon returns test of the pulsed sodium guide star laser on the 1.8 meter telescope

A microsecond pulsed sodium has been developed in TIPC laser physics research center, the power of this laser is around 20W and the length of the pulse is about 120 microseconds. In 2011, an experiment to project the TIPC prototype laser to the sky and measure the photon returns of the laser has been held on the 1.8 meter telescope in Yunnan observation site. During the sky test, an artificial sodium beacon has been successfully generated, and the brightness of the sodium beacon is around 8.7M in V Band. In the 2012 test campaign, the sodium column density facility has mounted on the telescope to test the local sodium density and structure and the sodium density test result is around 2.2x1013/m2.

LGS adaptive optics system with long-pulsed sodium laser on Lijiang 1.8 meter telescope 2014-2016 observation campaign

During 2014-2016, the Laser guide star (LGS) adaptive optics (AO) system observation campaign has been carried out on Lijiang 1.8 meter telescope. During the campaign, two generation LGS AO systems have been developed and installed. In 2014, a long-pulsed solid Sodium prototype laser with 20W@400Hz, a beam transfer optical (BTO) system, and a laser launch telescope (LLT) with 300mm diameter were mounted onto the telescope and moved with telescope azimuth journal. At the same time, a 37-elements compact LGS AO system had been mounted on the Bent-Cassegrain focus and got its first light on observing HIP43963 (mV= 8.18mv) and reached Sr=0.27 in J Band after LGS AO compensation. In 2016, the solid Sodium laser has been upgrade to stable 32W@800Hz while D2a plus D2b repumping is used to increase the photon return, and a totally new LGS AO system with 164-elements Deformable Mirror, Linux Real Time Controller, inner closed loop Tip/tilt mirror, Multiple-PMT tracking detector is established and installed on the telescope. And the throughput for the BTO/LLT is improved nearly 20%. The campaign process, the performance of the two LGS AO systems especially the latter one, the characteristics of the BTO/LLT system and the result are present in this paper.

Coupling Efficiency Measurements for Long-pulsed Solid Sodium Laser Based on Measured Sodium Profile Data

In 2013, a serial sky test has been held on 1.8 meter telescope in Yunnan observation site after 2011-2012 Laser guide star photon return test. In this test, the long-pulsed sodium laser and the launch telescope have been upgraded, a smaller and brighter beacon has been observed. During the test, a sodium column density lidar and atmospheric coherence length measurement equipment were working at the same time. The coupling efficiency test result with the sky test layout, data processing, sodium beacon spot size analysis, sodium profile data will be presented in this paper.