# Telescopic Network of Zhulong for Orbit Determination and Prediction of Space Objects
###### Abstract
When the reflected light or radiation from a space object enters the telescope's field of view, it can be detected by the sensor, allowing for the extraction of the object's position information from the captured image. In precision OD and OP, it is usually necessary to extract this positional information and convert it to the desired coordinate system, such as the right ascension/declination or elevation/azimuth coordinate system. Angle data are an important type of measurement data for precise OD and OP of space objects [13]. The accuracy of angle data is related to image resolution and other factors, typically measured in arcseconds. For instance, at a distance of 1000 km from the telescope, an arcsecond corresponds to approximately 5 m. For example, the angular data obtained by the optical telescope at Mount Stromlo in Australia have an error of less than 1.5 arcseconds [14]. There are also some similar small optical telescopes, such as Changchun LEO EA [15], Changchun GEO EA [16], Falcon [17], OWL-Net [18], FocusGEO [19], SSON [20], AGO70 [21], and APOSOS [22]. Observation using telescopes requires that the space object be illuminated by the sun. The observation is limited by various factors, including weather conditions, the relative position of the space object and the observation platform, the size of the object, and the performance of the telescope. Most angular data for LEO are sparse, with sparsity manifested in two aspects: firstly, the duration of angular data is less than 1% of the orbital period, and the duration of angular data is related to the field of view (FoV) of the telescope, its working mode (tracking, scanning), and space object altitude; secondly, the time interval between two angular arcs is usually large. For example, a study of the angular arc data of 3388 space objects from a telescope in Changchun over a month showed that the average time interval between two angular arc data for the same object was approximately 3 days [23]. Due to limited angular arc data, the process of determining the orbit of a space object often cannot accurately estimate empirical acceleration and struggles to estimate ballistic coefficients. As a result, it absorbs atmospheric mass density model errors. This results in errors of several kilometers when predicting the orbit of the LEO objects for several days with limited angular arc data [15; 24; 25]. The Zhulong telescopic observation network provides a cost-effective and efficient method for acquiring orbital measurement data of space objects, enabling space scientists globally to share and utilize these data. The network's angular data enable more accurate prediction of the orbits of space objects, which is crucial for avoiding space collisions, assessing the impact of space debris, and studying astrophysics [26]. The following texts introduce the fundamental information about the Zhulong observation network. Then, the accuracy of angular arc data is assessed using CPF (Consolidated Prediction Format) orbital data. Finally, accurate OD and OP measurements are conducted using angular measurement data. The conclusion is at the end of the article.