Influences of various space current systems on the geomagnetic field in near-Earth space

Ground and space-based observations of the geomagnetic field are usually a superposition of different sources from the Earth’s core,lithosphere,ocean,ionosphere,and magnetosphere,and also from field-aligned currents coupling the ionosphere and magnetosphere—the meridional currents that connect the two hemispheres and the induced currents due to the variations of fields over time.The fluctuation of magnetic fields generated by these highly dynamic space currents greatly limits the accuracy of the geomagnetic models.In order to better accomplish the scientific objectives of Macao Science Satellite-1(MSS-1),and to improve existing geomagnetic field models,we present here for the first time a self-consistent coupling of solar wind,magnetosphere,and ionosphere,which represents the most developed numerical simulation method for space physics research so far,making it possible to quantify the contribution of different current systems to the total observed magnetic field(B).The results show that numerical simulation can capture main magnetic disturbance characteristics with significant precision.Partial ring current is a major contributor to the latitudinal magnetic perturbation near the equator.Magnetopause and magnetotail currents affect the radial magnetic perturbation around the mid-latitudes.Field-aligned and Pedersen currents produce significant longitudinal and latitudinal magnetic perturbations at high latitudes.

Autonomous navigation method and technology implementation of high-precision solar spectral velocity measurement

The velocity information of spacecraft can be directly obtained by the autonomous navigation method based on astronomical spectral velocity measurement. It provides complete direct velocity measurement information for the traditional navigation methods represented by astronomical angle measurement and astronomical ranging, which is of great significance for spacecraft high precision autonomous navigation. This paper comprehensively introduces the principle and navigation method of astronomical spectral velocity measurement, as well as the technical realization of the solar atomic frequency discriminator for autonomous navigation(SAFDAN) based on atomic frequency discrimination velocity measurement. The new SAFDAN is the first instrument to measure the Doppler velocity of spacecraft relative to the Sun. Carried by the CHASE mission, the in-orbit experiment of the SAFDAN is realized, and the in-orbit velocity measurement accuracy reaches 1.93 m/s, which effectively verifies the feasibility of the astronomical spectral velocity measurement method and technology.

Levitated-body ultra-high pointing accuracy and stability satellite platform of the CHASE mission

The CHASE satellite is designed based on the novel ultra-high pointing accuracy and stability levitated-body satellite platform,which breaks the traditional idea of rigidly connecting the satellite platform and payload. When operating in orbit, the platform and payload are non-connected and spatially levitated. By separately arranging the “noisy” and “quiet” devices, the complicated influence of platform vibration on the payload pointing direction is effectively avoided. Using the novel master-slave collaborative control method, the pointing accuracy and stability of the payload are improved considerably. In this paper, the basic principles, overall scheme, control method, and engineering implementation of a levitated-body satellite platform are discussed.Combined with the CHASE mission in-orbit data, the actual attitude pointing precision and stability of a levitated-body satellite platform are analyzed and evaluated.