Time-varying Baseline Characteristics Analysis for Active and Passive Glacier Deep Exploration with Multi-satellites Formation Flying

In response to the global change background, the material balance and instability of ice sheets, as well as their impact on sea level changes, the spatiotemporal distribution, and changes of environmental factors such as sea ice, snow cover, and permafrost cryosphere, as well as the scientific issues and major applications in polar navigation development, require observation capabilities. Currently, there are still shortcomings in the observation capabilities of the internal state of ice sheets, the distribution and changes of sea ice, snow cover, and permafrost. The existing remote sensing methods mainly focus on surface and total material observation, and it is not yet possible to obtain high-resolution observation information on the internal temperature, density profile, layered structure, and snow water equivalent of the ice sheet. A new method for active and passive microwave detection has been proposed.A mother satellite carrying an active-passive microwave 3D glacier imager include ultra-wideband transmitting and receiving antenna, and a multi-frequency two-dimensional synthesize aperture radiometer. Six daughter satellites carry the active-passive microwave 3D glacier imager only include receiving antenna. The detection frequency is from 300 MHz to 2 GHz. 100 m high resolution of the underwater three-dimensional layered imaging and km level radiative brightness temperature imaging can be achieved. Mother satellite will transmit the signal, and all the daughter satellites will receive the signal. The ground resolution along the track and cross the track is about 100 m. And the penetration depth is about 4 km, and the vertical resolution is 5 m.The satellites fly in a circular orbit with 90° inclination and 500 km altitude. The formation configuration is a tilted linear formation, and the maximum distance between satellites is 5 km. In this paper, the mission requirements and technical specifications are analyzed. The distributed active microwave detection of the multi-satellite formation forms a synthetic aperture through the cross-track formation to improve the resolution, which can meet the requirements of the indicators. The synthetic aperture in the along-track direction can be realized by the combination of two-dimensional interference and push-broom. Pulse compression is used in the vertical direction to achieve three-dimensional layered imaging under the ice. Due to the limitation of the number of satellites, the sampling is sparse. Then, we will accumulate the data of multiple revisits for data processing. Three points located at latitude 70°, 80°, 90° are simulated as the examples in the paper. The observation duration and revisit time of the satellite formation are calculated. Then, the time-varying characteristics of the detection baselines formed by satellites and the corresponding point spread function are analyzed. The simulation results show that the theoretical spatial resolution can be achieved by multiple revisits data processing.