# High-Precision Pointing and Tracking System Design for Near-Space Balloon-Based Optical Observation
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Time** & **Country** & **Name** & **Index** \\ \hline
2005 & The United States & BLAST & 40 km \\
2005 & Italy & HiPeG & \(10^{\prime\prime}\) \\
2009 & Germany and the United States & Sunrise & 35 km to 37 km, \(7.5^{\prime\prime}\) \\
2010 & The United States & STO & \(35\) km, \(1^{\prime\prime}\) \\
2016 & Sweden & POGO & \(0.01^{\circ}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Near-space balloon-based optical detection experiments. In 2018, the Chinese Academy of Sciences launched the \"Near Space Science Experiment System\" project, also known as the \"Honghu Project\", which aims to establish a middle- and high-level scientific exploration platform in near space, providing a new way for balloon-based optical observation in near space. Relying on the superior optical observation conditions in near space and the advantages of high-altitude balloons, the \"Honghu Project\" can improve China's understanding and prediction level of the space environment [26]. Typical optical detections include multi-band airglow imagers, spherical coronagraphs, solar FUV/UV spectrometers, and enhanced ultraviolet spectrometers [27; 28; 29; 30]. These imaging systems need to ensure the stability of the optical axis and the absence of pixel aliasing during the imaging process. However, they also need to continuously track the observed target. The multi-band airglow imager is used for the imaging and observation of narrowband airglow radiation in four bands within the visible light near-infrared range. Airglow radiation is an atmospheric luminescence phenomenon with extremely weak intensity, a narrow wavelength band, and a wide distribution range. Therefore, when observing in near space, it is necessary to ensure stable pointing of the designated area to ensure that the image does not blur under the long-term exposure of minutes. In 2020 and 2021, two experiments were conducted to observe near-space airborne glow. There was no stable pointing system in 2020, but a stable pointing system was added in 2021. The spherical coronal observation experiment was conducted only once in 2022, and this experiment included a stable pointing and tracking system. A solar FUV/UV spectrometer conducted three near-space flight tests in 2019, 2020, and 2021. Among them, there was no stable pointing and tracking system in the 2019 experiment, but a stable pointing and tracking system for the sun was included in 2020 and 2021. The enhanced ultraviolet spectrometer conducted three near-space flight experiments in 2020, 2021, and 2022. Among them, there was no stable pointing and tracking system in the 2020 and 2021 tests, and 2022 included a stable pointing and tracking system for the sun. In these optical detection experiments, in order to ensure the stability of the optical axis of the optical detection load and the stable tracking of the target, a stable pointing and tracking system was designed, which can compensate for changes in the pitch angle, roll angle, and azimuth angle of the platform during the near-space flight. This article takes the near-space spherical coronagraph stable pointing and tracking system as an example to introduce how to provide a more suitable observation environment for optical observation loads on a near-space spherical platform. The second part introduces the system design for the observation experiment of the spherical coronagraph, mainly including the design of the optical observation platform, the design of the first-level stable pointing, and the design of the second-level stable pointing and tracking system. The third part of this article introduces the situation of near-space spherical coronal observation experiments, mainly including ground observation experiments and near-space spherical coronal observation experiments.