# BDS Orbit Maneuver Detection Based on Epoch-Updated Orbits Estimated by SRIF
## 1 Introduction  
Satellites are influenced by the non-spherical gravity of the earth as well as other perturbations, such as solar radiation pressure (SRP) and the gravitational effects of celestial bodies such as the Sun, Moon, and other objects in space [1]. Over time, satellite orbits may deviate from their intended values, necessitating the implementation of orbit maneuvers by propulsion devices to maintain an optimal satellite orbit constellation. This procedure is commonly referred to as orbit maneuvers [2; 3]. The frequency of orbit maneuvers is primarily determined by the characteristics of the orbits, particularly their rotation periods [4]. GEO and IGSO satellites have a greater frequency of orbit maneuvers in comparison to MEO satellites due to the resonance effect induced by the earth's rotation [5]. The BeiDou Satellite Navigation System (BDS) is comprised of GEO, IGSO, and MEO satellites, resulting in a much higher frequency of orbit maneuvers in comparison to other satellite navigation systems [3; 6; 7]. Orbit maneuvers can cause the orbit of a maneuvering satellite to be insufficiently described by a single orbit arc, leading to the loss of real-time and post-processing precise products from the product providers, such as the Analysis Centers of International GNSS Service (IGS) and International GNSS Monitoring & Assessment System (iGMAS). Due to the loss of precise GNSS service products, the continuity, reliability, and integrity of GNSSservices can be decreased. This is particularly serious in complex environments such as canyons and urban areas, where adding one more satellite observation can greatly enhance the positioning performance of precise point positioning (PPP). The accurate detection of orbit maneuvers in time is critical in adjusting precise orbit determination strategies. Without it, the GNSS observations may be falsely excluded as outliers due to the system errors of maneuvering satellites, which could potentially crush the whole estimator. Due to the orbit maneuver information being undisclosed by BDS officials, research on satellite orbit maneuver detection is necessary. In the past, great efforts were made towards the orbit maneuver detection of GNSS satellites. Orbit maneuvers can be detected and analyzed by using the orbital elements from broadcast ephemeris [3; 7; 8]. [PERSON] and [PERSON] et al., used the OMC (observation minus computation) and SPP (single point positioning) results according to broadcast ephemeris and pseudo-range observation data to detect orbit maneuver time [9; 10; 11]. [PERSON] and [PERSON] et al. detected the start and end times of orbit maneuvers based on triple-differenced observations [5; 12]. [PERSON] and [PERSON] detected the orbital maneuvers of the BeiDou Navigation Satellite System (BDS) using carrier phase observations and broadcast ephemeris data [13]. [PERSON] et al. utilized orbital monitoring data obtained from the China Area Positioning System (CAPS) to detect the orbital maneuvers of GEO satellites [14]. [PERSON] et al. detected the orbit maneuvers of BeiDou satellites using the orbit difference of post-processed precise orbit products, before and after the maneuvering [15]. The above efforts can be summarized into two types: based on the orbital elements and the observation residuals. The first type utilizes the precise orbit or orbit parameter data before and after the maneuver to accurately determine the orbit maneuvering satellite, but it cannot accurately detect the orbit maneuver time because the broadcast ephemeris is only updated once every 1-2 h and becomes invalid for 6-8 h after the orbit maneuver. The second method is based on the pseudo-range or carrier phase observations, but it has certain limitations due to the lack of an accurate orbit of the maneuvering satellite and the influence of observation outliers. The current research mainly focuses on using GNSS phase and pseudo-range observations to detect satellite orbit maneuvers.