Gaofen (Chinese: 高分; pinyin: Gāofēn; lit. 'high resolution') is a series of Chinese high-resolutionEarth imaging satellites launched as part of the China High-resolution Earth Observation System (CHEOS) program.[1][2] CHEOS is a state-sponsored, civilian Earth-observation program used for agricultural, disaster, resource, and environmental monitoring. Proposed in 2006 and approved in 2010, the CHEOS program consists of the Gaofen series of space-based satellites, near-space and airborne systems such as airships and UAVs, ground systems that conduct data receipt, processing, calibration, and taskings, and a system of applications that fuse observation data with other sources to produce usable information and knowledge.[2][3]
Although the first seven Gaofen satellites and their payloads have been heavily detailed, little to no details on Gaofen 8 and later satellites have been revealed prompting suggestions that Gaofen satellites may be dual purpose supporting both civilian and military missions.[2][4][5][6][7]
The Advanced Hyperspectral Imagery (AHSI) sensor payload aboard Gaofen-5 claims to be the first space-based hyperspectral imaging sensor utilizing both convex grating spectrophotometry and a three concentric-mirror (Offner) configuration.[10] The AHSI uses spectrophotometry to measure the light spectra reflected, transmitted, or emitted by an imaged object to detect or identify objects on the ground.[10] In civilian applications, the AHSI allows analysts to conduct environmental monitoring and resource discovery while in a military application would allow analysts to detect and identify an adversary's equipment or spot non-multi-spectral camouflage.[10][11][12] AHSI has a 30 meter spatial resolution and 5 nanometer spectral resolution in the visible, near-infrared (NIR), and short-wave infrared (SWIR) wavelength ranges.[12]
Gaofen-5's Directional Polarimetric Camera (DPC) is China's first space-based multi-angle polarimetric camera.[9] Prior to GF-5's launch, in September 2016, China had experimented with polarimetric imaging in 2016 aboard the Tiangong-2 space laboratory and launched its Cloud and Aerosol Polarimetric Imager (CAPI) aboard TanSat in December of that year.[9][16] CAPI imaged clouds within 670 and 1640 nanometer channels but was restricted to fixed-angle imaging. The DPC aboard Gaofen-5 enables atmosphericspectroscopy in three polarized bands (90, 670, and 865 nm; polarized at 0°, 60°, and 120°) and five non-polarized bands (443, 565, 763, 765, and 910 nm), all wavelengths from green to near-infrared (NIR). A step motor rotates the 512 × 512 pixelcharge-coupled device (CCD) imager ±50° providing a 1,850 km swath of imagery at 3.3 km resolution.[9][17]
Satellites
Since the program's start in 2013, the People's Republic of China has launched 30 Gaofen-series satellites and has not yet experienced a launch failure. Jilin-1 satellites described as 'Gaofen' are not part of the government's Gaofen series, rather are described as having high resolution (Chinese: 高分; pinyin: Gāofēn).[18]
^Qi, Lu (27 December 2021). "呂琪：夜空中最亮的星—盤點中國系列衛星" [[Military Blog Review] Lv Qi: The Brightest Star in the Night Sky - Inventory of Chinese Satellites]. Lite News Hong Kong (in Chinese). Archived from the original on 4 September 2022. Retrieved 4 September 2022.
^ abcChen, Liangfu (13 October 2016). Mission Overview GaoFen-5(PDF). 12th Meeting of the CEOS Atmospheric Composition Virtual Constellation (PowerPoint presentation). Seoul, Korea. Archived(PDF) from the original on 23 October 2022. Retrieved 23 October 2022.
