# High-Precision Pointing and Tracking System Design for Near-Space Balloon-Based Optical Observation  
[PERSON]  
1 Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; [EMAIL_ADDRESS]. (4) Low launch and maintenance costs. Compared to space optical detection platforms, the launch and maintenance costs of floating optical detection platforms are low. High-altitude balloons have lower launch costs. They can also be recycled and the system using parachutes be reused alongside the use of other recycling technologies [5]. Typical near-space balloon-based optical detection experiments performed in recent years are shown in Table 1. The United States has the most outstanding development in the field of near-space balloon-based optical detection, with a strong capacity reaching up to several tons, a long duration exceeding one year, high azimuth accuracy, and stable attitude control [6; 7; 8]. In recent years, the United States has implemented many optical detection projects based on near-space spaceborne observation platforms. In these detection projects, the altitude range of balloon flight ranges from 30 km to 40 km, and the optical observation spectrum includes the ultraviolet spectrum, visible spectrum, and infrared spectrum [9; 10; 11; 12]. The typical representative of near-space optical observations is the balloon-borne large-aperture submillimeter series telescope (BLAST, Pittsburgh, NC, USA). BLAST adopts a coaxial Cassegrain optical system, including a primary mirror with a diameter of 1.9 m and a secondary mirror with a diameter of 0.4 m. BLAST has made two successful flights, departing from the Arctic in 2005 and Antarctica in 2006, achieving the first high-resolution and large-scale submillimeter imaging in near space [13; 14; 15; 16]. In 2010 and 2012, BLAST-Pol completed two near-space flight tests around Antarctica at the McMurdo Station to observe the situation of the Milky Way and extraterrestrial objects, with an average flight altitude of 40 km [17; 18]. In 2018-2019, the next-generation balloon-borne large-aperture submillimeter telescope (BLAST-TNG) of the United States also carried out a near-space submillimeter wave mapping experiment at the McMurdo Station in Antarctica [19; 20]. In 2005, Italy conducted a near-space flight observation experiment on a high-performance balloon-mounted pod (HiPeG). The optical detection payload used in this experiment was a high-resolution hard X-ray telescope. In order to meet the demand for the attitude angle in optical imaging, the high-performance balloon-mounted pod adopts one high-performance GPS and one highly dynamic star sensor to ensure the stability and accuracy of the observation attitude, with a pointing accuracy better than \(10^{\prime\prime}\)[21]. In 2009, the \"Sunrise\" program, implemented by Germany and the United States, aimed to conduct solar observations in near space as part of its long-endurance balloon project, flying at altitudes ranging from 35 km to 37 km. In addition to the telescope, the entire near-space observation platform also includes a high-precision pointing control system and an attitude stabilization system, which can achieve a tracking accuracy of \(7.5^{\prime\prime}\) to the sun [22]. In 2010, the United States successfully conducted a near-space observation experiment with the Stratospheric Terahertz Observatory (STO) telescope, with a flight altitude of approximately 35 km and a flight time of over 14 days. Combined with control mechanisms such as reaction wheels, the pointing accuracy and attitude stability accuracy of the entire system were better than \(1^{\prime\prime}\)[23]. In 2016, Sweden successfully conducted a near-space balloon-based POGO observation experiment. Flywheels and other attitude control systems were installed to provide stability of the first-level attitude. High-precision star sensors were used to provide the angle, and the accuracy was better than 0.01 degrees [24; 25].