The sudden disappearance of a dark filament observed on October 26, 1989

We present H monochromatic and spectroscopic observations of the sudden disappearance of a dark filament located near the center of the solar disk on October 26, 1989. The event was not associated with the flare activity. The dark filament first disintegrated into two loop-like components, and then each component successively showed ascending motion with a velocity greater than 30 km s^–1. Comparison of the H pictures taken before and after the start of this event suggests that the dark filament was originally composed of two magnetic flux loops.     

基于ROACH的微波全息法相关机设计

基于ROACH开发平台设计了一套适用于微波全息法测量的高性能实时数字相关机,采用了带通采样技术,无需在相关机之前进行基带转换,使全息测量硬件系统更加简洁;采样速率为10 Mbps~1 000 Mbps可调,采用数字混频、数字滤波,信号带宽和频率分辨率都易于调整,具有很大的灵活性和可扩展性。测试结果表明该相关机测量精度高、稳定性好、准确可靠。     

A survey of possible impact structures on 25143 Itokawa

We determined the morphologies and dimensions of possible impact craters on the surface of Asteroid 25143 Itokawa from images taken by the Hayabusa spacecraft. Circular depressions, circular features with flat floors or convex floors, and circular features with smooth surfaces were identified as possible craters. The survey identified 38 candidates with widely varying morphologies including rough, smooth and saddle-shaped floors, a lack of raised rims and fresh material exposures. The average depth/diameter ratio was 0.08±0.03: these craters are very shallow relative to craters observed on other asteroids. These shallow craters are a result of (1) target curvature influencing the cratering process, (2) raised rim not being generated by this process, and (3) fines infilling the craters. As many of the crater candidates have an unusual appearance, we used a classification scheme that reflects the likelihood of an observed candidate's formation by a hypervelocity impact. We considered a variety of alternative interpretations while developing this scheme, including inherited features from a proto-Itokawa, spall scars created by the disruption of the proto-Itokawa, spall scars following the formation of a large crater on Itokawa itself, and apparent depressions due to random arrangements of boulders. The size-frequency distribution of the crater candidates was close to the empirical saturation line at the largest diameter, and then decline with decreasing diameter.     

马卡良335的微光变观测

介绍了马卡良 335分别发生于 1998年和 1999年的两次短时标光变。其中的一次是微光变 ,发生于 1999年 11月 2 0日 ,微光变区域的大小约 0 .80 7光时。还对微光变的可能机制进行了讨论     

云南天文台大气视宁度观测和初步探讨

介绍了为云南丽江高美古选址点作对比的云南天文台点的大气视宁度观测统计和结果，对观测过程中的有关问题作了初步探讨。对高美古和云南天文台的１９９５年５月和１９９５年１２月２０日观测资料作了对比，结果表明：高美古选址点的视宁度明显优于云南天文台。     

Multi-cloud model (MCM) method and its applications to the study on asymmetric spectral profiles

A method of multi-cloud model (MCM) is proposed in this paper in order to research asymmetric profiles of spectral line formed by solar discrete active objects aligned along the line-of-sight difection. Based on the MCM method, under the conditions of certain assumptions and approximations, the line-of-sight velocityV and three other physical parameter approximation values, (i.e. Doppler width _D , source functionS and optical depth at line center ₀) within different clouds may be derived simultaneously by fitting both profiles theoretical and observational. An application example of the method withm=3 shows that MCM method is suitable to measure the velocity fields of multi-object at the same time from their non-Gaussian profiles of complex. TheV and _D derived from the method are reliable,S and ₀ are approximation. An influence of the variations of initial values in the parameter on the solution is given as well.