反常折射引起的地面天文观测残差的周年变化

我国光学天文观测有相当长历史，观测精度也较高，但是与国际系统相比。无论是测时还是测纬，所有仪器残差都有类似的周年变化，本文作者认为部分原因是由于我国季节变化引起的大气等密度层倾斜，从而产生的反常折射所引起的，文中对反常折射的规律进行了研究，导出了由于气象参数变化而引起的反常折射公式，并与测时，测纬的残差周年项进行了对比，结果表明用反常折射可以部分地解释我国天文观测残差的周年变化。     

Properties of optical fibres at cryogenic temperatures

A perhaps surprising property of optical fibres is that they remain flexible at cryogenic temperatures. This implies that they may be used for multiple-object and integral field spectroscopy in the thermal infrared in cryogenic instrumentation. In this paper the results of performance tests of optical fibres (silica and zirconium fluoride) at cryogenic temperatures are presented. By mounting the fibres in glass tubes with the appropriate adhesive, it was found that only negligible focal ratio degradation occurs when the fibre is cooled to 77 K.     

Model of optical turbulence profile at Cerro Pachón

New measurements of optical turbulence profile at the Cerro Pachón observatory in Chile are analysed jointly with previously published data to model the variations of the intensity and thickness of the ground layer and free atmosphere under a variety of observing conditions. This work is motivated by the need to predict statistically the performance of ground-layer adaptice optics. We find that the ground-layer profile can be represented by a decaying exponent with a scale height of 20–40 m, increasing to 100 m under bad conditions. The zone from 6 to 500 m contributes typically about 61 per cent to the total integral, the latter causing a median seeing of 0.77 arcsec. Turbulence integrals in the ground layer and in free atmosphere vary independently of each other, in 50 per cent of cases they deviate by less than 1.8 times from their respective median values. The existence of periods with low turbulence in the free atmosphere and their importance for adaptive optics is stressed.     

双波长卫星激光测距

双波长卫星激光测距不必借助大气改正模型，利用双波长往返时间差就可以进行大气折射改正，采用皮秒级事件计时器等技术测量往返时间差，修正精度可以达到毫米量级，介绍了这一领域的研究进展、双波长大气改正的基本原理，分析了双波长激光测距的精度，最后对双波长卫星激光测距前景进行了展望。     

Phasing segmented mirrors using defocused images at visible wavelengths

Plans for future optical telescopes of diameter more than 10 m are based on segmented mirrors, made up of hundreds or even thousands of segments. A challenge for these telescopes is the alignment in piston (cophasing) where phase differences between individual segments have to be reduced to a small fraction of the observing wavelength in order to avoid degradation of image quality.
Based on the phase discontinuity sensing method used at the Keck telescopes to measure small piston errors using infrared wavelengths, we develop a new method that allows fast high-precision measurements of large piston errors even at visible wavelengths.     

数字滤波技术在射电天文测量中的应用

随着数字技术的发展，数字信号处理芯片的速度越来越快，这为高速数字滤波的实时实现提供了可能。简要阐述了数字滤波的原理，并对两种数字滤波的实现方法进行了分析；给出了数字滤波较模拟滤波的优势；介绍了数字滤波在射电天文测量中的各种应用。