Chinsese Research Paper on High Altitude Balloon Observation Platform
Published in 2020 for the Aerospace Information Research Institute of the Chinese Academy of Sciences, this paper goes into experiments and observation techniques performed with High Altitude Balloons.
Here is an excerpt on the advantages a High Altitude Balloon has compared to aircraft and satellites:
>The traditional aircraft can hardly fly up to the near-space, and the satellites in space are not easy to detect down the near-space [3]. Therefore, near space is a new research hotspot that worth more observation and detection. A high-altitude balloon is one of the near-space exploration vehicles, and it has many advantages [4]. First of all, a high-altitude balloon can achieve low-cost sustained flight for months or even years. Compared with other air vehicles, the high-altitude balloon has long endurance time, which can achieve sustained and wider coverage for regional observation and detection [5,6,7]. Secondly, compared with satellite, a high-altitude balloon can take more and heavier loads, and increase the observation accuracy and range, for example, the spatial resolution and the signal strength of the optical observation load in near space can be increased greatly [8]. Thirdly, the payloads in the near space with high altitude balloons can be recycled with low cost and low risk, which is difficult to achieve by satellites.
The size of the balloon they were using in these experiments is about three busses in size, just as the spy balloon was.
>The high-altitude balloon used in the experiment was a zero-pressure balloon with a volume of 20,000 m3, the overall capacity was 325 Kg, and the payload capacity was 205 Kg.
Could be an early prototype of what we saw flying over CONUS
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7180688/