Close Approach Analysis Between Space Object
An introduction to the analytical and numerical methods commonly applied to the space object approaching analysis is unfolded.
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Close Approach Analysis Between Space Object
The close approach analysis is to determine the time when two objects enter to the spherical or ellipsoidal range and the corresponding relative distance, the components of relative distance, the relative velocity and the conjunction angle, with the orbital data (orbital elements or high precision orbital ephemeris) of two objects are known and the close approach threshold (spherical or ellipsoidal threshold surface) and the time interval are predefined. The close approach analysis is not only significant in the conjunction assessment, but also used on different space mission analysis such as observing time determination of space-based space surveillance and reconstruction of spacecraft’s maneuver. The prefilter is needed to eliminate the objects that are impossible to conjunction the interesting spacecraft before further close approach analysis. The common prefilter methods include the apogee-perigee filter and altitude difference filter [1–3]. The close approach analysis methods can be categorized to the analytical method and the numerical method based on the orbital data and algorithm used. The analytical methods are based on the orbital elements and geometrical analysis of the orbital elements, obtain the close approach events’ information by the analytical algorithm like derivative. The numerical methods are based on the orbital ephemeris of objects at certain time steps during a certain interval, or the position and velocity information from orbital model. The relative position and close approach information are obtained by numerical processing methods such as difference, interpolation, fitting, polynomial root-finding to the orbital ephemerides or position and velocity information. The advantages of analytical methods are their computing speed and straightforward physical meanings, while the drawbacks are their sensitivity to the type of orbit and the type of orbital data and missing alarm risk due to the perturbations. The advantages of numerical methods are their relative low missing alarm risk and their robustness to the type of orbit, the type of orbital data, and the orbital models. The disadvantages are longer computing time. With the advent of ever increasing computer capacities numerical methods are more applicable in the future. © National Defense Industry Press, Beijing and Springer Nature Singapore Pte Ltd. 2017 L. Chen et al., Orbital Data Applications for Space Objects, DOI 10.1007/978-981-10-2963-9_4
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Analytical Methods to Determine Close Approach Hoots’s Method
Hoots proposed an analytical method to determine close approaches between satellites based on the geometrical filter in 1984 [3]. This method determines the close approaches by a series of altitude filter, orbital geometry filter and phase filter. This analytical filtering method is the early and mature algorithm, most of the other analytical methods are the improvement of Hoots’s method [1, 4]. This detection concept for proximity ev
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