## 1 Introduction  
Since the launch of the first satellite on 4 October 1957, approximately 15,302 artificial spacecraft have been deployed through 6346 launch missions worldwide by the end of 2022 (as shown in Figures 1 and 2) [1]. The fragments generated from those rocket launches and disabled spacecraft have resulted in millions of pieces of space debris, posing a significant threat to operational satellites in space [2, 3]. In 1983, the space shuttle Challenger experienced the first ever significant collision with space debris in human history. This incident resulted in damage to Challenger's window and the premature termination of the mission. Subsequently, several severe instances of space debris colliding with operational satellites in orbit have been observed. In each case, the impact caused substantial damage or even the complete disintegration of the affected spacecraft [4]. With the space environment becoming increasingly crowded, it is crucial to ensure the safety of space assets in orbit and prevent potential damage from space debris collisions. This urgency highlights the need for timely and continuous sensing and measurement of the operational orbits of objects in space. Recognizing the imperative of protecting on-orbit spacecraft from collisions with space debris, major spacefaring nations worldwide have universally developed their own space situational awareness systems. In the mid-20 th century, the United States and the Soviet Union pioneered the development of ground-based space situational awareness systems. As we entered the 21 st century, other spacefaring nations, including Europe, Japan, India, and China, significantly enhanced their capabilities in space situational awareness, aiming to address the challenges posed by the increasingly congested space environment and ensure the security of their respective space assets. In recent years, significant attention has been directed towards space-based optical systems for space situational awareness. Unlike ground-based systems, those dependent on space-based optical platforms provide unique advantages, such as a wide observational field, extended daily monitoring time, and immunity to atmospheric or cloud cover. These features facilitate the timely and continuous surveillance of both space regions and targets. Furthermore, through orbital networking or orbital maneuvers, space-based optical space situational awareness systems can attain persistent monitoring and conduct close-range reconnaissance of space targets. In the technical framework of space situational awareness utilizing optical monitoring systems in space, the determination of the orbits of space targets constitutes its core and foundation. After acquiring detection data, space-based situational awareness platforms employ orbit determination methods to convert sensor data into precise parameters defining the orbital state of the targets. This process serves as the essential bridge for transforming sensor detection information into assessments of the orbits of space targets and alert information. This foundational procedure is integral for estimating the on-orbit operational status of space targets, cataloging space objects, and conducting analyses related to space contact and collisions. In this paper, a comprehensive overview of the development history of space situational awareness systems and the present state of research on orbit determination methods  
Figure 1: The number of launch missions worldwide from 1957 to 2022. Figure 2: The number of spacecraft launched worldwide from 1957 to 2022.  
employing space-based optical platforms is provided. First, it delineates the status of space situational awareness policies and equipment in major spacefaring nations, analyzing the practical engineering demands in this domain. Subsequently, the existing state of relevant theoretical research in the three stages of orbit determination--short-arc association, initial orbit determination, and precise orbit determination--is introduced.