## 1 Introduction  
Over the course of more than half a century, the field of Earth observation technology has witnessed remarkable advancements. Fueled by a series of Earth Observation pro-grams worldwide, artificial satellites equipped with sensors spanning the spectrum from visible and infrared to microwave bands have proliferated at various orbital altitudes. These sensors are employed on aircraft, ground-based platforms, and diverse Earth orbit satellites, contributing significantly to the study of Earth's atmosphere, oceans, and terrestrial surfaces. Earth observation technology has emerged as a robust tool, facilitating the collection of copious remote sensing data that underpins crucial areas such as resource surveying, environmental monitoring, and climate change studies. However, despite the considerable strides made in Earth observation, the growing need to deepen our understanding of the Earth system and its impact on the human habitat has compelled the development of fresh Earth observation platforms and technologies. Existing Earth observation satellites, while effective, possess limitations in their capacity to provide a comprehensive, systematic perspective on our planet, thus constraining scientific investigations in Earth system science [1; 2; 3]. Low Earth Orbit (LEO) satellites offer high spatial resolution and versatile viewing angles, yet they struggle to deliver global data with both temporal consistency and spatial continuity. Conversely, Geostationary Earth Orbit (GEO) satellites maintain continuous regional coverage but are limited in their ability to observe the Polar Regions. Recognizing that no single satellite platform can fully meet the diverse demands of Earth observation, it becomes imperative to explore the merits of distinct platforms and develop new Earth observation systems that integrate these various platforms [3; 4; 5; 6]. Lagrange points represent a class of gravitational equilibrium positions within a rotating two-body celestial system, such as the Earth-Moon system or the Sun-Earth system. Spacecraft stationed at Lagrange points within the Earth-Moon system offers the unique advantage of achieving full coverage of celestial bodies while maintaining a relatively stable geometric relationship with both the Earth and the Moon, leading to reduced propellant consumption. Moreover, there are low energy transfer orbits from the Earth to the Earth-Moon L1 point. This means that the cost of space transportation is much lower compared with other locations at the same altitude, which is conducive to the construction of high-orbit Earth observation platforms [7; 8]. In the past century, the application of Lagrange points within the Sun-Earth system predates that of the Earth-Moon system. Successful missions to Sun-Earth L-points date back to the launch of ISEE-3 in 1978, the first artificial satellite to orbit L1. These missions were primarily designed for space observation, such as solar observatories, while a few were dedicated to Earth observation. Notable examples include ISEE-3 and WIND at L1 within the Sun-Earth system, which served in part to monitor the Earth's magnetosphere. A joint mission in 2015, DSCOVR, contributed data on Earth's albedo, ozone, and aerosols [9; 10; 11; 12]. Aboard DSCOVR, the National Institute of Standards and Technology Advanced Radiometer (NISTAR) observed the entire dayside hemisphere of the Earth, providing a broadband spectral signature of the Earth to support planetary measurements and exoplanet studies [13]. Recent years have witnessed a resurgence of interest in lunar exploration, with a corresponding upsurge in attention directed toward the Lagrange points within the Earth-Moon system. Earth-lunar space exploration is of great significance in relay communications, autonomous navigation and positioning, space science and space exploration, manned space stations, earth remote sensing, and situational awareness.