# Research on the Efficient Space Debris Observation Method Based on Optical Satellite Constellations
## 1 Introduction  
Space debris refers to the non-functional man-made objects in orbit. Human space activities have a history of more than 60 years, and it is estimated that there are over 30,000 pieces of debris larger than 1 cm, approx. one million pieces of debris larger than 1 cm, and hundreds of millions of millimeter-level space debris. Space debris and spacecraft move around the Earth at a high speed of more than 7.9 km/s, and the relative speed of space debris can reach more than 10 km/s when a collision occurs. The impact of a 1 cm-sized aluminum ball in space will produce a destructive force equivalent to the impact of a car on the highway. The consequences of the impacts of space debris above 1 cm are often devastating, and large-sized space debris above 10 cm will directly lead to spacecraft failure [1; 2; 3]. Space collisions have become more frequent in recent years. In 2019, there were more than 300 dangerous impacts between Chinese spacecraft in orbit and space debris. In 2013, the Ecuadorian CubeSats collided with Soviet rocket debris, causing the satellite to fail. On 12 June 2011, the solar cells of the IGSO-2 satellite of China's Beidou navigation constellation lost two circuits, and the conclusion confirmed that the satellite was hit by small debris. On 11 February 2009, the US commercial communications satellite Iridium-33 collided with Russia's abandoned Cosmos-2251 satellite, with a relative speed of 11.6 km per second, generating more than 2000 pieces of space debris, which caused strong repercussions from the international community [4]. With the development of human space activities, the number of space objects is increasing. At the same time, the development of large satellite constellations and the competition for space interests of various countries have made the space situation increasinglycomplex [5]. This poses a major threat to the security of space activities and space assets. It is necessary to obtain the orbit information of space objects in real time to meet the demand for accurately detecting space events [6]. Monitoring space objects using monitoring equipment and optimizing the scheduling of the monitoring system is an effective way to obtain the space object's status information [7]. By adopting efficient observation scheduling methods, the number of space objects and arcs observed by observation equipment in a certain period can be increased, and the observation efficiency can be improved [8]. Compared to traditional ground-based optical telescopes, space-based optical satellites have unique advantages because they run in orbit and their detection of space objects are not affected by the weather. In addition, the detector is closer to the space object, and an optical telescope with a smaller aperture can be used to observe the low-orbit space target at a shorter distance. Most space-based satellite constellations are deployed in low Earth orbit where space debris is mainly distributed. Therefore, satellite constellations can fully observe the low Earth orbit airspace where space objects are densely distributed, improve the detection quantity and frequency of space objects, make full use of space detection equipment, obtain a large amount of observation data in real time, realize the dynamic catalogue of space debris, provide early warning of dangerous collisions, and maintain the order of space traffic and the safety of space assets [9]. Reasonable monitoring task scheduling is the key for the effective operation of a space-based monitoring network. Especially due to the development of various space-based monitoring equipment and the improvement of the automation of observation equipment, new requirements have been put forward to optimize observation task scheduling. Space object observation scheduling optimization is bound to be closely related to the specific situation of equipment operation and the movement of the space object itself. Special research needs to be conducted on the specific application observation mode and the equipment operation state.