In order to effectively suppress the effect of the skylight background on the detection performance of the optical telescope and make it have the advantages of the all-time operation and the high star-magnitude detection, a new detection method based on the shearing interference and the phase modulation is proposed in this paper. This method utilizes the discrepancy of the spatial coherence between the target (smaller size) and the skylight background (larger size). By adjusting the shearing amount reasonably, the target light can form the interference fringes, while the skylight background cannot. Then, the phase modulation technique is used to form the moving interference fringes over the detector. Afterward, the periodical electrical signal is formed by the photoelectrical conversion of the detector. Finally, the weak signal detection equipment can be used to extract the target signal from the skylight background noise. This paper introduces the scheme design and the theoretical analysis of the new detection method and also presents the detection performance simulation of this new method.

This paper proposes a reverse procedure detection method for space target streaks based on motion parameter estimation. According to the phase shift characteristics of the spectrum, the interframe phase difference is used to obtain the displacement vectors of the target streak and image background, and then the morphological parameters of the target streak are estimated. In addition, a streak window is designed on the basis of the parameters, utilizing the local grayscale correlation in two image frames to carry out target searching and positioning with the interval of the target displacement vector. Images from different scenes are used to evaluate the adaptability of our method, and the experimental results suggest that the expected targets can be detected successfully with subpixel precision in all telescope operating modes. The proposed frequency-domain reverse procedure detection method avoids the problem of fake target confirmation caused by blind detection in traditional methods and overcomes the interference produced when the target streak passes through a bright star. Moreover, first target tracking and then positioning, which cannot be performed with time-domain methods, can be achieved. Our proposed method is attractive for multiple applications, such as space target cataloging, early warning and orbit prediction.

To overcome the influence of the daytime skylight background on long-distance optical detection, a new type of shearing interference detection system was proposed to improve the detection performance of the traditional detection system for finding dark objects such as dim stars during the daytime. This article focuses on the basic principle and mathematical model as well as the simulation and experimental research of the new type of shearing interference detection system. The comparison of the detection performance between this new-type detection system and the traditional system is also carried out in this article. The experimental results show that the detection performance of the new type of shearing interference detection system is significantly better than that of the traditional system, and the image signal-to-noise ratio of this new-type system (about 13.2) is much higher than that of the best result of the traditional detection system (about 5.1).

为了获得成像质量较好且成像时间较少的新型傅里叶望远镜成像策略, 本文比较了三种降采样成像策略(压缩感知方法(CS)、低频全采样方法(LF)和变密度随机采样方法(VD))与传统傅里叶望远镜(FT)在图像质量和成像时间上的差异. 分析方法如下: 利用传统FT外场实验所获得的目标频谱数据作为基础, 三种降采样方法(LF, VD和CS)分别按照各自的采样模式和重构方法实现目标图像的重构; 通过直观观察和Strehl比两种方法比较三种降采样方法与传统FT在图像质量上的差异; 通过分析成像时间的组成要素, 初步比较三种降采样方法与传统FT在成像时间上的差异. 分析表明: 1) 压缩感知方法的图像质量优于其他两种降采样方法(LF和VD), 但略低于传统成像结果; 2) 压缩感知方法在成像质量上略低于传统FT, 但在成像时间上却明显小于传统FT; 3)分析中采用的外场数据均含噪声, 这说明上述三种降采样重构过程对噪声有较好的鲁棒性. 综合上述分析结果可以看出, 基于压缩感知的傅里叶望远镜(CS-FT)是在实际含噪情况下可大幅减少成像时间的优良成像策略.

In order to achieve the remote application of inverse synthetic aperture laser radar for high resolution spatial situational awareness, it is essential to analyze the main factors that restrict its remote application. This study combines the range equation of inverse synthetic aperture lidar with the stimulated Brillouin threshold power equation to investigate the variation of laser transmitting power with distance. Additionally, by utilizing the excited Brillouin threshold power equation, laser linewidth formula, and pulse width characteristics of pulse signal, we examine the variation law of laser coherence that meets corresponding power requirements at different distances. The results indicate that a detection distance of 22 km and below can be achieved using continuous fiber lasers without compensation. Coherence compensation is necessary for distances between 22 km and 57 km. For distances ranging from 57 km to 3000 km, pulsed solid-state lasers are used to analyze coherence and conclude that imaging non-cooperative targets within this range is feasible. It is observed that coherence compensation is required from 57 km to 2179 km, becoming more challenging after 2000 km. Furthermore, pulsed solid-state lasers can still be utilized for imaging cooperative targets within a range of 2179–3273 km; however, coherence compensation remains necessary and becomes increasingly difficult. Finally, several coherent length compensation schemes are proposed in order to extend the imaging range of inverse synthetic aperture LiDAR to approximately 3000 km.

The challenge of observing faint space objects during daytime has long hindered the full-time utilization of ground-based telescopes. Interference detection technology serves as a novel approach for suppressing skylight background noise, which can be employed either independently to mitigate skylight background or combined with conventional methods to achieve enhanced suppression capabilities. This study focuses on the observational performance of an interference detection system for actual faint space targets in daylight conditions. Through observations of three stellar targets (Arcturus, Vega, and Polaris) during sunset, we present, to our knowledge, the first demonstration of daytime stellar detection using an interference detection system. By comparing observational results between the shearing interference detection system and the conventional detection system for these stellar targets, this work reveals that the shearing interference method significantly outperforms traditional approaches—both in terms of visual image quality and target signal-to-noise ratio (SNR). Specifically, the shearing interference system achieved SNRs of 15.4 for Arcturus, 23.3 for Vega, and 23.3 for Polaris, whereas conventional methods attained maximum SNRs of only 5.0 (Arcturus), 10.7 (Vega), and 3.8 (Polaris).