Gaofen () is a series of Chinese

high-resolution Image resolution is the detail an image holds. The term applies to digital images, film images, and other types of images. "Higher resolution" means more image detail. Image resolution can be measured in various ways. Resolution quantifies how cl ...

Earth imaging satellite An Earth observation satellite or Earth remote sensing satellite is a satellite used or designed for Earth observation (EO) from orbit, including spy satellites and similar ones intended for non-military uses such as environmental monitoring, me ...

s launched as part of the China High-resolution Earth Observation System (CHEOS) program. CHEOS is a state-sponsored, civilian Earth-observation program used for

agricultural Agriculture or farming is the practice of cultivating Plant, plants and livestock. Agriculture was the key development in the rise of Sedentism, sedentary human civilization, whereby farming of Domestication, domesticated species created food ...

disaster A disaster is a serious problem occurring over a short or long period of time that causes widespread human, material, economic or environmental loss which exceeds the ability of the affected community or society to cope using its own resources ...

resource Resource refers to all the materials available in our environment which are technologically accessible, economically feasible and culturally sustainable and help us to satisfy our needs and wants. Resources can broadly be classified upon their ...

, and

environmental monitoring Environmental monitoring describes the processes and activities that need to take place to characterize and monitor the quality of the environment. Environmental monitoring is used in the preparation of environmental impact assessments, as well a ...

. Proposed in 2006 and approved in 2010, the CHEOS program consists of the Gaofen series of space-based

satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...

s, near-space and airborne systems such as

airship An airship or dirigible balloon is a type of aerostat or lighter-than-air aircraft that can navigate through the air under its own power. Aerostats gain their lift from a lifting gas that is less dense than the surrounding air. In early ...

s and

UAVs An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without any human pilot, crew, or passengers on board. UAVs are a component of an unmanned aircraft system (UAS), which includes adding a ground-based controlle ...

, 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. 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. In 2003, the

China National Space Administration China National Space Administration (CNSA; ) is the government agency of the People's Republic of China that is responsible for civil space administration and international space cooperation, including organizing or leading foreign exchanges ...

(CNSA) agreed with

Roscosmos The State Space Corporation "Roscosmos" (russian: Государственная корпорация по космической деятельности «Роскосмос»), commonly known simply as Roscosmos (russian: Роскосмос) ...

to share Gaofen data for data from Russia's Earth observation satellites of similar capability. This agreement was expanded in August 2021 when leaders from

BRICS BRICS is an acronym for five leading emerging economies: Brazil, Russia, India, China, and South Africa. The first four were initially grouped as "BRIC" (or "the BRICs") in 2001 by Goldman Sachs economist Jim O'Neill, who coined the ter ...

space agencies This is a list of government agencies engaged in activities related to outer space and space exploration. As of 2022, 77 different government space agencies are in existence, 16 of which have launch capabilities. Six government space agencies ...

agreed to share space-based remote sensing data.

Notable satellites

Gaofen-5

Gaofen-5 has been lauded as the "flagship of the environment and atmosphere observation satellite in the CHEOS program". Launched on 8 May 2018 from

Taiyuan Satellite Launch Center The Taiyuan Satellite Launch Center (TSLC) also known as ''Base 25'' (), is a People's Republic of China space and defense launch facility (spaceport). It is situated in Kelan County, Xinzhou, Shanxi Province and is the second of four launch ...

(TSLC) into

sun-synchronous orbit A Sun-synchronous orbit (SSO), also called a heliosynchronous orbit, is a nearly polar orbit around a planet, in which the satellite passes over any given point of the planet's surface at the same local mean solar time. More technically, it is ...

, Gaofen-5 carries six

payloads Payload is the object or the entity which is being carried by an aircraft or launch vehicle. Sometimes payload also refers to the carrying capacity of an aircraft or launch vehicle, usually measured in terms of weight. Depending on the nature of ...

: an Advanced Hyperspectral Imagery sensor (AHSI), Atmospheric

Infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

Ultraspectral Sensor (AIUS), Directional Polarization Camera (DPC), Environment Monitoring Instrument (EMI), Greenhouse-gases Monitoring Instrument (GMI), and Visual and Infrared

Multispectral Multispectral imaging captures image data within specific wavelength ranges across the electromagnetic spectrum. The wavelengths may be separated by filters or detected with the use of instruments that are sensitive to particular wavelengths, ...

Sensor (VIMS). 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. 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. In civilian applications, the AHSI allows analysts to conduct

and

discovery while in a military application would allow analysts to detect and identify an adversary's equipment or spot non-

multi-spectral camouflage Multi-spectral camouflage is the use of counter-surveillance techniques to conceal objects from detection across several parts of the electromagnetic spectrum at the same time. While traditional military camouflage attempts to hide an object in t ...

. AHSI has a 30 meter

spatial resolution In physics and geosciences, the term spatial resolution refers to distance between independent measurements, or the physical dimension that represents a pixel of the image. While in some instruments, like cameras and telescopes, spatial resolutio ...

and 5 nanometer

spectral resolution The spectral resolution of a spectrograph, or, more generally, of a frequency spectrum, is a measure of its ability to resolve features in the electromagnetic spectrum. It is usually denoted by \Delta\lambda, and is closely related to the resolvi ...

in the visible, near-infrared (NIR), and short-wave infrared (SWIR)

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...

ranges. The Atmospheric Infrared Ultraspectral Sensor (AIUS) payload aboard Gaofen-5 is China's first

hyperspectral Hyperspectral imaging collects and processes information from across the electromagnetic spectrum. The goal of hyperspectral imaging is to obtain the spectrum for each pixel in the image of a scene, with the purpose of finding objects, identifyi ...

occultation An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks ...

spectrometer A spectrometer () is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where the ...

meaning it measures the spectra of imaged atmospheric particles between the sensor and the Sun. AIUS allows scientists to monitor

atmospheric circulation Atmospheric circulation is the large-scale movement of air and together with ocean circulation is the means by which thermal energy is redistributed on the surface of the Earth. The Earth's atmospheric circulation varies from year to year, but t ...

by tracing (

water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous pha ...

), temperature, pressure, and various carbon and halogen-containing gas pollutants such as chloroflourocarbons (CFCs),

dinitrogen pentoxide Dinitrogen pentoxide is the chemical compound with the formula , also known as nitrogen pentoxide or nitric anhydride. It is one of the binary nitrogen oxides, a family of compounds that only contain nitrogen and oxygen. It exists as colourless ...

, and

chlorine nitrate Chlorine nitrate, with chemical formula ClNO3 is an important atmospheric gas present in the stratosphere. It is an important sink of chlorine that contributes to the depletion of ozone. It explosively reacts with metals, metal chlorides, alcohol ...

. A

Michelson interferometer The Michelson interferometer is a common configuration for optical interferometry and was invented by the 19/20th-century American physicist Albert Abraham Michelson. Using a beam splitter, a light source is split into two arms. Each of those li ...

, AIUS images wavelengths between 2.4 and 13.3

micrometers The micrometre (American and British English spelling differences#-re, -er, international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American and British English spelling differences# ...

(near to mid-wave

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

) at a 0.3

centimeter 330px, Different lengths as in respect to the Electromagnetic spectrum, measured by the Metre and its deriveds scales. The Microwave are in-between 1 meter to 1 millimeter. A centimetre (international spelling) or centimeter (American spellin ...

resolution and a ±10°

field of view The field of view (FoV) is the extent of the observable world that is seen at any given moment. In the case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation. Humans a ...

. Gaofen-5's Directional Polarimetric Camera (DPC) is China's first space-based multi-angle polarimetric camera. Prior to GF-5's launch, in September 2016, China had experimented with polarimetric imaging in 2016 aboard the

Tiangong-2 Tiangong-2 () was a Chinese space laboratory and part of the Project 921-2 space station program. Tiangong-2 was launched on 15 September 2016. It was deorbited as planned on 19 July 2019. Tiangong-2 was neither designed nor planned to be a p ...

space laboratory and launched its Cloud and Aerosol Polarimetric Imager (CAPI) aboard

TanSat TanSat, also known as CarbonSat, is a Chinese Earth observation satellite dedicated to monitoring carbon dioxide in Earth's atmosphere. It is generally classified as a minisatellite, and is the first dedicated carbon mission of the Chinese spac ...

in December of that year. CAPI imaged clouds within 670 and 1640

nanometer 330px, Different lengths as in respect to the molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American and British English spelling differences#-re ...

channels but was restricted to fixed-angle imaging. The DPC aboard Gaofen-5 enables

atmospheric An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...

spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...

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 Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 Nanometre, nm. In subtractive color systems, used in painting and color printing, it is created by ...

near-infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...

(NIR). A step motor rotates the 512 × 512

pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the smal ...

charge-coupled device A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...

(CCD) imager ±50° providing a 1,850 km swath of

imagery Imagery is visual symbolism, or figurative language that evokes a mental image or other kinds of sense impressions, especially in a literary work, but also in other activities such as psychotherapy. Forms There are five major types of sensory ima ...

at 3.3 km resolution.

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 ().

References

{{CNSA space program, state=collapsed Earth observation satellites of China Satellite series Spacecraft launched by Long March rockets

Notable satellites

Gaofen-5

Satellites

See also

References