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Eight months of vector magnetic field measurements from the Macau Scientific Satellite‐1 (MSS‐1), supplemented by higher latitude field intensity measurements from the Swarm satellites, are used to derive an MSS‐1 Initial Field Model (MIFM). Robust root‐mean‐square misfits between MIFM and the three components of the MSS‐1 vector field data are found to be below 3.3 nT. MIFM agrees well with the CHAOS‐7 field model and we find even better agreement with an identically parameterized model derived only from Swarm data. MSS‐1 and Swarm vector data can moreover be fit simultaneously with only a small increase in misfit (by less than 0.2 nT). We show that both lithospheric anomalies and core surface field changes can be studied using MSS‐1 data. With its fast coverage of local times MSS‐1 is a valuable addition to the global geomagnetic observing system. Plain Language Summary: Earth's magnetic field is an essential part of our planetary environment. The global state of the field and its time variations are today carefully monitored from space by satellites. However rather few satellites provide measurements with the accuracy needed for detailed scientific studies and for the construction of geomagnetic reference models used for navigation. We show that vector magnetic field measurements from the Macau Scientific Satellite 1 (MSS‐1), launched in May 2023, are suitable for building high quality reference models of Earth's magnetic field. We show that time changes of field at the core‐mantle boundary and field anomalies related to lithospheric magnetization can be mapped using an initial 8 months of MSS‐1 data. Thanks to its low inclination orbit, MSS‐1 covers all local times, for latitudes up to ± $\pm $41°, within 2 months. This complements the coverage of existing polar‐orbiting satellites and provides new opportunities to study rapid geomagnetic field changes. Key Points: Macau Scientific Satellite‐1 provides the first vector magnetic field measurements with absolute accuracy from a low inclination orbitGeomagnetic field models constructed using vector data only from MSS‐1 are suitable for scientific studies of core and lithospheric fieldsBy covering all local times within 2 months, MSS‐1 provides a new class of observational constraints on rapid geomagnetic field variations [ABSTRACT FROM AUTHOR]

The Macau Science Satellites (MSS‐1) mission, consisting of twin low earth orbit satellites (Satellite A and B), is the first low‐inclination and high‐precision geomagnetic surveying satellite project in China. Among the multiple scientific payloads equipped with the scientific satellites, MSS‐1 carries a GNSS radio occultation (RO) receiver on Satellite A, and aims to observe the Earth's ionosphere and monitor the space weather especially in the South Atlantic Anomaly (SAA) area. This paper focuses on the ionospheric data of MSS‐1 obtained during the first 3 months after its launch, and assesses the RO products as well as initial scintillation measurements. Results show that MSS‐1 RO data have very good agreement with contemporary COSMIC‐2 and ionosonde observations. The scintillation amplitude indices S4 are comparable with that of COSMIC‐2 and well reflect the occurrence rates and distributions of equatorial plasma bubble and sporadic E (Es) in June solstice season. Special attentions are paid to the SAA longitude sector and inspire explorations on the seasonal variations and local‐time dependences of ionospheric irregularities. Key Points: The MSS‐1 ionospheric radio occultation products are comparable with COSMIC‐2 and ionosondesScintillation characteristics in the June solstice season are well reflected based on MSS‐1 high‐rate measurements [ABSTRACT FROM AUTHOR]

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 Macau 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.

The Earth’s “lithosphere” is its outer shell, made up of the Earth’s crust and outermost mantle. The part of the Earth’s magnetic field that originates in the lithosphere consists of a superposition of magnetic anomalies with a broad spectrum of sizes and intensities, which arise from geological and tectonic features. The lithospheric magnetic field is known from surface observations, and on larger scales from above-surface measurements. The increase in recent decades of satellites dedicated to measuring the Earth’s magnetic field has improved significantly our models of the Earth’s magnetic environment. Based on these increasing observations, a number of comprehensive field models have been constructed, some of which focus solely on the lithosphere, such as the MF model series. We present a map of lithospheric magnetic anomalies at 400 km altitude, based on a vertically integrated magnetization model. This height was chosen because it is the expected orbital altitude of the Macau Science Satellite-1 (MSS-1) mission. The model presented herein indicates that the amplitude of the lithospheric anomalies at 400 km altitude is between −14.8 nT and 18.2 nT. This information is useful because it provides a reference for the lithospheric source of the Earth’s magnetic field that contributes to the magnetic measurements made from satellite instruments. The low inclination orbit of the MSS-1 mission will provide information that is sensitive to lateral variation within the lithosphere; these variations arise from plate tectonic features with longitudinal extent. In conclusion, the new MSS-1 mission will provide valuable information in detecting compositional variations in the lithosphere, and in delineating large-scale geological structures.