Hanik Kim

AMMAP on CAS500-3, launched in November 2025 into a ∼600 km Sun-synchronous orbit, combines a Langmuir probe (LP), biased with respect to the spacecraft body, and an impedance probe (IP), which derives the density from the upper-hybrid resonance regardless of the spacecraft potential. We report the operation from December 2025 to June 2026 and initial observations on two reference days in February and June. Before the orbital noon, the sun-pointing attitude turns the solar arrays toward the direction of flight and the spacecraft charges negatively beyond the LP sweep range, so that the LP collects only ions in 50–70% of the dayside sweeps. The IP is lost mainly in the low-density winter hemisphere, where its resonance is too weak. Where both are valid, the densities agree within a factor of ∼1.7 in the median, the IP typically 20–40% lower; both lie above the IRI model, the IP by a factor of 1.4–2.1 and the LP by 2.1–3.2. Even in the ion-only sweeps, the slope of the ion current increases with the density and, calibrated against the IP for each day, gives the density with a scatter of 20–35%. Taking the IP as the reference and filling its gaps with the calibrated LP data yields a continuous profile over more than 90% of the two orbits examined.

Spacecraft relative pose estimation for an uncooperative spacecraft is challenging because the target spacecraft neither provides sensor information to a chaser spacecraft nor contains markers that assist vision-based navigation. Moreover, the chaser does not have prior pose estimates when initiating the pose estimation. This paper proposes a new monocular pose estimation algorithm that addresses these issues in pose initialization situations for a known but uncooperative target spacecraft. The proposed algorithm finds convexity defect features from a target image and uses them as cues for matching feature points on the image to the points on the known target model. Based on this novel method for model matching, it estimates a pose by solving the PnP problem. Pose estimation simulations are carried out in three test scenarios, and each assesses the estimation accuracy and initialization performance by varying relative attitudes and distances. The simulation results show that the algorithm can estimate the poses of spacecraft models when a solar panel length and the number of solar panels are changed. Furthermore, a scenario considering the surface property of the spacecraft emphasizes that robust feature detection is essential for accurate pose estimation. This algorithm can be used for proximity operations with a known but uncooperative target spacecraft. Specifically, one of the main applications is relative navigation for on-orbit servicing.