First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment

Generic Gamma-Ray Sensors (Gen-Gamma) are non-specific instruments mounted on a platform that measure gamma radiation. They are typically passive sensors that detect the energy of emitted gamma radiation. Gamma-ray measurements are used to identify radioactive isotopes for environmental monitoring and geological studies.

Radiosondes are balloon-borne instrument packages that collect profiles of pressure, temperature, humidity, and wind. These sensors are connected to a radio transmitter that sends the measurements to a ground receiver, typically operating in the 400-406 MHz range. They typically provide measurements every 1-6 seconds, depending on the radiosonde type and manufacturer. Radiosondes are used for weather forecasting, ground-truthing satellite data, atmospheric research, and as input for weather prediction models.

The Side-Looking Airborne Radar (SLAR) is an airborne imaging system that points perpendicular to the flight direction. SLAR emits a beam of energy toward the surface, perpendicular to the flight path, and detects the return signals to create radar images of the terrain. It typically operates in the X-band (8-12 GHz). SLAR can collect imagery regardless of weather or time of day and has been used to map geological features and cloud-covered regions because of its ability to penetrate clouds.

The Lyman-alpha Hygrometer is an in situ hygrometer designed for deployment on airborne or ground-based platforms. It measures water vapor absorption at the Lyman-alpha wavelength (121.6 nm) of atomic hydrogen to determine the total water content in the atmosphere. It has a detection limit of 0.1 ppmv and a typical data acquisition rate of 1 second. The Lyman-alpha hygrometer provides water vapor measurements with 6% accuracy and 5% precision.

Generic-Atmospheric State (Gen-AtmsState) refers to non-specific instruments on a platform that measure atmospheric state parameters. These are typically in situ sensors that measure temperature, pressure, humidity, and wind speed and direction. Types of atmospheric state instruments include thermometers, hygrometers, barometers, and anemometers.

Rosemount Pressure Probes are in situ airborne pressure sensors manufactured by Rosemount, Inc. They provide high-precision atmospheric pressure measurements and are typically used to collect flight-level meteorological observations. Rosemount Pressure Probes include various pressure transducers, gauges, and multivariable and coplanar transmitters.

Rosemount Temperature Probes are in situ airborne temperature sensors manufactured by Rosemount, Inc. They provide atmospheric temperature measurements and are typically used to collect flight-level meteorological observations. Rosemount Temperature Probes consist of temperature transmitters, thermocouple sensors, resistance temperature detectors, and other temperature sensors.

Accelerometers are in situ sensors that measure the acceleration experienced by an object. They use electromagnetic sensing to detect the object's vibration. The vibration exerts a force on the sensor, producing an electrical charge that indicates the magnitude of the force and can be used to determine the acceleration. Accelerometers are typically used on aircraft to collect flight navigation information. They have also been deployed on research vessels and other water-based platforms, such as buoys.

Generic-Atmospheric State (Gen-AtmsState) refers to non-specific instruments on a platform that measure atmospheric state parameters. These are typically in situ sensors that measure temperature, pressure, humidity, and wind speed and direction. Types of atmospheric state instruments include thermometers, hygrometers, barometers, and anemometers.

Rosemount Pressure Probes are in situ airborne pressure sensors manufactured by Rosemount, Inc. They provide high-precision atmospheric pressure measurements and are typically used to collect flight-level meteorological observations. Rosemount Pressure Probes include various pressure transducers, gauges, and multivariable and coplanar transmitters.

Accelerometers are in situ sensors that measure the acceleration experienced by an object. They use electromagnetic sensing to detect the object's vibration. The vibration exerts a force on the sensor, producing an electrical charge that indicates the magnitude of the force and can be used to determine the acceleration. Accelerometers are typically used on aircraft to collect flight navigation information. They have also been deployed on research vessels and other water-based platforms, such as buoys.

The Precision Radiation Thermometer (PRT-5) is an in situ infrared temperature sensor. It provides non-contact infrared (8-14 μm) temperature measurements from -50 to 150 degrees Celsius with an accuracy of 0.5 degrees Celsius. It has a typical field of view of 2 degrees and a response time of 0.3 Hz, 3 Hz, or 30 Hz. PRT-5 can be deployed on aircraft, vehicles, research vessels, and other ground-based platforms. It can be used to measure sea surface, ocean water, cloud, and air temperatures.

Rosemount Temperature Probes are in situ airborne temperature sensors manufactured by Rosemount, Inc. They provide atmospheric temperature measurements and are typically used to collect flight-level meteorological observations. Rosemount Temperature Probes consist of temperature transmitters, thermocouple sensors, resistance temperature detectors, and other temperature sensors.

Video cameras capture footage of various phenomena for research. They are used on aircraft to provide continuous views of weather and terrain below the flight path. Video cameras are also employed to verify the aircraft's flight track. Additionally, they are deployed at field sites to monitor changes in vegetation, land cover, clouds, air quality, glaciers, and other Earth science phenomena.

A pyranometer is a ground-based or airborne radiation sensor that measures solar irradiance over a hemispherical field of view. It detects the amount of solar energy reaching the surface, capturing both direct and diffuse sunlight. Pyranometers operate across a spectral range of 280-3000 nm. They are most commonly used for solar monitoring, climate research, weather forecasting, agriculture, and energy management.

LI-COR Gas Analyzers are in situ gas analyzers manufactured by LI-COR. They can be deployed on aircraft, research vessels, vehicles, balloons, and ground-based platforms. They provide measurements of trace gases such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and water vapor (H2O). Most models use Optical Feedback-Cavity Enhanced Absorption Spectroscopy (OF-CEAS) to collect measurements. LI-COR gas analyzers have a typical measurement rate of 1 Hz and an operating temperature range of -25 to 45 degrees Celsius.

The Side-Looking Airborne Radar (SLAR) is an airborne imaging system that points perpendicular to the flight direction. SLAR emits a beam of energy toward the surface, perpendicular to the flight path, and detects the return signals to create radar images of the terrain. It typically operates in the X-band (8-12 GHz). SLAR can collect imagery regardless of weather or time of day and has been used to map geological features and cloud-covered regions because of its ability to penetrate clouds.

Generic-Atmospheric State (Gen-AtmsState) refers to non-specific instruments on a platform that measure atmospheric state parameters. These are typically in situ sensors that measure temperature, pressure, humidity, and wind speed and direction. Types of atmospheric state instruments include thermometers, hygrometers, barometers, and anemometers.

Rosemount Pressure Probes are in situ airborne pressure sensors manufactured by Rosemount, Inc. They provide high-precision atmospheric pressure measurements and are typically used to collect flight-level meteorological observations. Rosemount Pressure Probes include various pressure transducers, gauges, and multivariable and coplanar transmitters.

The King Probe is an in situ airborne cloud instrument developed by Warren King (Commonwealth Scientific and Industrial Research Organisation) and manufactured by Particle Measuring Systems (PMS) and Droplet Measurement Technologies (DMT). It measures cloud liquid water content (LWC) by detecting the heat released during droplet vaporization. It operates at a constant temperature of approximately 100°C and outputs data at 1 to 10 Hz. The probe is commonly used in studies of cloud microphysics and aircraft icing.

The Active Scattering Aerosol Spectrometer Probe (ASASP) is an airborne in situ spectrometer manufactured by Particle Measurement Systems, Inc. It measures the intensity of light scattered by aerosol particles to determine particle size distribution and concentration. The wide-angle ASASP probes detect light scattered between 35 and 120 degrees from the laser-beam axis.

The Precision Radiation Thermometer (PRT-5) is an in situ infrared temperature sensor. It provides non-contact infrared (8-14 μm) temperature measurements from -50 to 150 degrees Celsius with an accuracy of 0.5 degrees Celsius. It has a typical field of view of 2 degrees and a response time of 0.3 Hz, 3 Hz, or 30 Hz. PRT-5 can be deployed on aircraft, vehicles, research vessels, and other ground-based platforms. It can be used to measure sea surface, ocean water, cloud, and air temperatures.

NOx/NOxy is an in situ chemiluminescence instrument that measures nitrogen oxides and ozone in the atmosphere. It provides spatial resolution better than 100 meters at typical DC-8 research flight speeds. NOx/NOxy can be deployed on ground-based, airborne, and shipborne platforms, supporting a range of atmospheric chemistry and air quality studies.

Rosemount Temperature Probes are in situ airborne temperature sensors manufactured by Rosemount, Inc. They provide atmospheric temperature measurements and are typically used to collect flight-level meteorological observations. Rosemount Temperature Probes consist of temperature transmitters, thermocouple sensors, resistance temperature detectors, and other temperature sensors.

Thermo Scientific Gas Analyzers are in situ gas analyzers manufactured by ThermoFisher Scientific. They provide precise measurements of trace gases, including ozone, carbon dioxide, carbon monoxide, and sulfur dioxide. Thermo Scientific Gas Analyzers can be deployed on aircraft, research vessels, and ground-based platforms.

The Lyman-alpha Hygrometer is an in situ hygrometer designed for deployment on airborne or ground-based platforms. It measures water vapor absorption at the Lyman-alpha wavelength (121.6 nm) of atomic hydrogen to determine the total water content in the atmosphere. It has a detection limit of 0.1 ppmv and a typical data acquisition rate of 1 second. The Lyman-alpha hygrometer provides water vapor measurements with 6% accuracy and 5% precision.

The Forward Scattering Spectrometer Probe (FSSP) is an in situ airborne optical particle counter developed by Particle Measuring Systems, Inc. It determines particle size distribution by measuring the light intensity scattered by individual particles within a cloud. The FSSP detects particles from 0.5 to 47 μm in diameter. It operates at a wavelength of 633 nm and typically samples at 1 Hz.

A pyrgeometer is a ground-based or airborne passive radiation sensor that measures downward and upward longwave radiation in the 4-50 μm spectral range. It uses a thermopile sensor to detect changes in resistance or voltage, which are then used to determine longwave radiation. These measurements can be used to calculate the infrared radiation flux. Pyrgeometers are typically used for climatological, meteorological, and agricultural applications.

Video cameras capture footage of various phenomena for research. They are used on aircraft to provide continuous views of weather and terrain below the flight path. Video cameras are also employed to verify the aircraft's flight track. Additionally, they are deployed at field sites to monitor changes in vegetation, land cover, clouds, air quality, glaciers, and other Earth science phenomena.

A pyranometer is a ground-based or airborne radiation sensor that measures solar irradiance over a hemispherical field of view. It detects the amount of solar energy reaching the surface, capturing both direct and diffuse sunlight. Pyranometers operate across a spectral range of 280-3000 nm. They are most commonly used for solar monitoring, climate research, weather forecasting, agriculture, and energy management.

The Johnson-Williams Cloud Water Meter (CWM) is an airborne hot-wire probe designed by Johnson-Williams, Inc. The CWM measures the liquid water content (LWC) of clouds by detecting resistivity changes caused by cloud droplets evaporating from an exposed heated wire. It measures LWC from 0 to 6 grams per cubic meter and operates at airspeeds between 50 and 150 meters per second. The device operates on a constant current and typically records data at 2 Hz.

The Rosemount Icing Detector (RICE) is an in-situ airborne probe developed by Rosemount Inc. It uses magnetostrictive oscillation to detect shifts in frequency caused by ice accumulating on the sensing cylinder. These frequency changes correlate with the rate of ice buildup, which helps determine liquid water content. RICE typically samples every second.

The Modular Multiband Radiometer (MMR) is an airborne multispectral radiometer manufactured by Barnes Engineering Company. The MMR measures radiance across 8 spectral bands spanning the infrared and visible wavelengths (0.4-12.5 μm), producing images of vegetation and other surface features. At an altitude of 300 meters, the MMR has an instantaneous field of view (IFOV) of about 79 meters and a 15-degree field of view (FOV). It is typically deployed on small aircraft, such as helicopters, but can also be used on ground-based platforms.

C-band scatterometers are active, non-imaging scatterometers that measure microwave backscatter. They are typically used to measure ocean surface winds but can also measure ice, vegetation, and soil surface properties. They operate in the C-band frequency range (4-8 GHz) and can provide measurements during both daytime and nighttime.

The Spectron Engineering-590 (SE-590) Spectroradiometer is a portable instrument manufactured by Spectron Engineering. It can be used on both airborne and ground-based platforms. The SE-590 uses a charge-coupled device (CCD) area array detector to measure reflectance. It operates across the visible to short-wave infrared spectral range (350-2500 nm). The SE-590 has a ground resolution of 4.5 meters when flown at an altitude of 300 meters.

Soil temperature sensors are in situ, ground-based sensors used to measure and monitor soil temperature. They use thermistors or thermocouples to detect changes in resistance and calculate temperature. Soil temperature sensors are used for agricultural purposes, environmental monitoring, and ecological research.

Sound Detection and Ranging (SODAR) is an active, ground-based acoustic sensor that measures atmospheric winds and turbulence. It emits acoustic energy into the atmosphere and detects the strength and frequency of the backscattered signal. The backscattered signal can be used to determine the horizontal wind field, assuming the scattered energy moves with the mean wind. SODARs are frequently used in boundary layer studies to measure turbulence and wind profiles.

Sunphotometers are passive optical sensors that measure the amount of sunlight. They are pointed directly at the sun to measure direct sunlight, not sunlight scattered by aerosols. These measurements can be used to determine aerosol optical depth by applying Beer’s Law. Sunphotometers have been deployed on aircraft, research vessels, and field sites for aerosol research and monitoring.

A pyrgeometer is a ground-based or airborne passive radiation sensor that measures downward and upward longwave radiation in the 4-50 μm spectral range. It uses a thermopile sensor to detect changes in resistance or voltage, which are then used to determine longwave radiation. These measurements can be used to calculate the infrared radiation flux. Pyrgeometers are typically used for climatological, meteorological, and agricultural applications.

A pyranometer is a ground-based or airborne radiation sensor that measures solar irradiance over a hemispherical field of view. It detects the amount of solar energy reaching the surface, capturing both direct and diffuse sunlight. Pyranometers operate across a spectral range of 280-3000 nm. They are most commonly used for solar monitoring, climate research, weather forecasting, agriculture, and energy management.

The Volume Imaging Lidar (VIL) is a ground-based lidar system operated by the University of Wisconsin. It is an elastic backscatter lidar operating at 1064 nm. It provides aerosol backscatter profiles with a range resolution of 7.5 m or 15 m. VIL has a maximum range of 18 km and a repetition rate of 30 Hz. The Naval Research Laboratory (NRL) also operates a VIL with similar specifications.

LI-COR Gas Analyzers are in situ gas analyzers manufactured by LI-COR. They can be deployed on aircraft, research vessels, vehicles, balloons, and ground-based platforms. They provide measurements of trace gases such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and water vapor (H2O). Most models use Optical Feedback-Cavity Enhanced Absorption Spectroscopy (OF-CEAS) to collect measurements. LI-COR gas analyzers have a typical measurement rate of 1 Hz and an operating temperature range of -25 to 45 degrees Celsius.

Generic-Atmospheric State (Gen-AtmsState) refers to non-specific instruments on a platform that measure atmospheric state parameters. These are typically in situ sensors that measure temperature, pressure, humidity, and wind speed and direction. Types of atmospheric state instruments include thermometers, hygrometers, barometers, and anemometers.

Generic-Chemistry Related Sensors (Gen-Chemistry) refers to non-specific instruments on a platform used for atmospheric chemistry measurements. These are typically in situ analyzers that measure chemical compounds such as trace gases, halocarbons, volatile organic compounds, nitrates, aerosols, and other chemical species. Measurements can include mixing ratios, composition, particle size, optical properties, and particle size distribution.

Eddy Covariance Flux Towers are in situ micrometeorological surface towers. They are equipped with gas sensors to continuously measure trace gas fluxes between the land surface and the atmosphere. Eddy Covariance Towers are typically used to measure fluxes of carbon dioxide (CO2), methane (CH4), and water vapor (H2O). These towers are also equipped with various meteorological sensors to measure air temperature, precipitation, wind, radiation, and soil temperature.

The LI-COR Plant Canopy Analyzer is an in situ instrument manufactured by LI-COR for leaf area index (LAI) measurements. It measures diffuse sky radiation passing through the canopy at five zenith angles to determine LAI and other canopy characteristics. It can be used under most sky conditions and across canopy types, including row crops, grasslands, isolated trees, and forests. The optical sensor within the Plant Canopy Analyzer has a wavelength range of 320-490 nm. It has a field of view of 148 degrees and an operating temperature range of -20 to 50 degrees Celsius.

Generic-Radiometers refer to non-specific radiometers on a platform. These are typically passive microwave radiometers that measure brightness temperature. Radiometers can be used to retrieve temperature and water vapor profiles, soil moisture content, ocean salinity, precipitation and cloud properties, and vegetation.

Digital cameras provide imagery for research applications. Cameras are mounted on aircraft to collect aerial imagery for mapping and surveying, environmental monitoring, cloud observations, agriculture, geological studies, and other Earth science applications. They are also deployed at field sites to capture visual observations that monitor changes in land cover, vegetation, clouds, air quality, glaciers, and other phenomena.

The LI-COR Quantum Sensor is a ground-based, in situ radiation sensor manufactured by LI-COR. It collects precise measurements of photosynthetically active radiation (PAR) beneath vegetation or under artificial light sources. The sensor detects radiation within the same light spectrum (400 - 700 nm) that plants use for photosynthesis. While primarily used for ground-based measurements, the LI-COR Quantum Sensor can also be mounted on aircraft. It is suitable for long-term deployments and remains durable in high temperatures and humidity.

The Spectron Engineering-590 (SE-590) Spectroradiometer is a portable instrument manufactured by Spectron Engineering. It can be used on both airborne and ground-based platforms. The SE-590 uses a charge-coupled device (CCD) area array detector to measure reflectance. It operates across the visible to short-wave infrared spectral range (350-2500 nm). The SE-590 has a ground resolution of 4.5 meters when flown at an altitude of 300 meters.

The Lyman-alpha Hygrometer is an in situ hygrometer designed for deployment on airborne or ground-based platforms. It measures water vapor absorption at the Lyman-alpha wavelength (121.6 nm) of atomic hydrogen to determine the total water content in the atmosphere. It has a detection limit of 0.1 ppmv and a typical data acquisition rate of 1 second. The Lyman-alpha hygrometer provides water vapor measurements with 6% accuracy and 5% precision.

Soil moisture probes are in situ, ground-based sensors that measure soil water content. The most common type of soil moisture probe used in scientific research employs dielectric permittivity techniques, such as capacitance or time-domain reflectometry. These probes measure the soil's charge-storage capacity to determine soil moisture content. They typically operate at frequencies around 50 MHz and above to reduce sensitivity to salinity. Soil moisture probes provide continuous measurements and are relatively easy to deploy.

Infrared Thermometers (IRTs) are ground-based pyrometers that measure the brightness temperature of a scene within their field of view. They determine brightness temperature by detecting electromagnetic radiation emitted by Earth’s surface. These measurements are used to determine either the surface skin temperature or the sea surface temperature, depending on whether the platform is on land or water. IRTs typically operate within the 8- to 14-μm wavelength range.

Rain gauges are ground-based instruments that directly measure the amount of liquid precipitation over a specified period. Different types of rain gauges, such as tipping buckets and weighing gauges, collect and record data in various ways. Because of their small size and easy setup, rain gauges can be placed in different locations and are often used alongside other precipitation instruments, such as disdrometers, to gather additional details, such as precipitation rate and size distribution.

The Modular Multiband Radiometer (MMR) is an airborne multispectral radiometer manufactured by Barnes Engineering Company. The MMR measures radiance across 8 spectral bands spanning the infrared and visible wavelengths (0.4-12.5 μm), producing images of vegetation and other surface features. At an altitude of 300 meters, the MMR has an instantaneous field of view (IFOV) of about 79 meters and a 15-degree field of view (FOV). It is typically deployed on small aircraft, such as helicopters, but can also be used on ground-based platforms.

Stream gauges are ground-based sensors that measure the water level, or stage, of rivers and streams at specific locations. The flow, or discharge, of a river can then be calculated from these stage measurements. These gauges provide continuous data, making them useful for monitoring flood risk and water supply. The United States Geological Survey (USGS) operates a network of over 10,000 stream gauges across the United States to support flood prediction and water resource management.

The NOAA/WPL Pulsed Coherent Doppler Lidar is a ground-based lidar system developed by the NOAA Wave Propagation Laboratory (WPL). It measures radial velocity as a function of range by using light-scattering particles in the air as tracers to derive wind profiles and momentum fluxes. It operates at a wavelength of 10.59 μm and has a pulse repetition rate of 1 to 20 Hz. It provides velocity azimuth display (VAD) scans, range height indication (RHI), and volume or roster scans with a range resolution of 150 meters.

The Portable Apparatus for Rapid Acquisition of Bidirectional Observations of the Land and Atmosphere (PARABOLA) is a passive, ground-based, spherical-scanning radiometer. It measures surface reflectance across eight spectral channels. The first four channels (444, 551, 650, and 860 nm) align with spectral bands from the Multi-angle Imaging SpectroRadiometer (MISR) on the Terra satellite for validation. The remaining four channels characterize water vapor (944 nm), aerosol optical depth at longer wavelengths (1028 and 1650 nm), and photosynthetically active radiation (400-700 nm). PARABOLA measurements can be used to derive the surface bidirectional reflectance factor and sky and surface radiances. A complete scan of both the sky and ground hemispheres takes approximately 3 minutes.

Soil temperature sensors are in situ, ground-based sensors used to measure and monitor soil temperature. They use thermistors or thermocouples to detect changes in resistance and calculate temperature. Soil temperature sensors are used for agricultural purposes, environmental monitoring, and ecological research.

Sound Detection and Ranging (SODAR) is an active, ground-based acoustic sensor that measures atmospheric winds and turbulence. It emits acoustic energy into the atmosphere and detects the strength and frequency of the backscattered signal. The backscattered signal can be used to determine the horizontal wind field, assuming the scattered energy moves with the mean wind. SODARs are frequently used in boundary layer studies to measure turbulence and wind profiles.

Sunphotometers are passive optical sensors that measure the amount of sunlight. They are pointed directly at the sun to measure direct sunlight, not sunlight scattered by aerosols. These measurements can be used to determine aerosol optical depth by applying Beer’s Law. Sunphotometers have been deployed on aircraft, research vessels, and field sites for aerosol research and monitoring.

A pyrgeometer is a ground-based or airborne passive radiation sensor that measures downward and upward longwave radiation in the 4-50 μm spectral range. It uses a thermopile sensor to detect changes in resistance or voltage, which are then used to determine longwave radiation. These measurements can be used to calculate the infrared radiation flux. Pyrgeometers are typically used for climatological, meteorological, and agricultural applications.

A pyranometer is a ground-based or airborne radiation sensor that measures solar irradiance over a hemispherical field of view. It detects the amount of solar energy reaching the surface, capturing both direct and diffuse sunlight. Pyranometers operate across a spectral range of 280-3000 nm. They are most commonly used for solar monitoring, climate research, weather forecasting, agriculture, and energy management.

The Volume Imaging Lidar (VIL) is a ground-based lidar system operated by the University of Wisconsin. It is an elastic backscatter lidar operating at 1064 nm. It provides aerosol backscatter profiles with a range resolution of 7.5 m or 15 m. VIL has a maximum range of 18 km and a repetition rate of 30 Hz. The Naval Research Laboratory (NRL) also operates a VIL with similar specifications.

LI-COR Gas Analyzers are in situ gas analyzers manufactured by LI-COR. They can be deployed on aircraft, research vessels, vehicles, balloons, and ground-based platforms. They provide measurements of trace gases such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and water vapor (H2O). Most models use Optical Feedback-Cavity Enhanced Absorption Spectroscopy (OF-CEAS) to collect measurements. LI-COR gas analyzers have a typical measurement rate of 1 Hz and an operating temperature range of -25 to 45 degrees Celsius.

Generic-Atmospheric State (Gen-AtmsState) refers to non-specific instruments on a platform that measure atmospheric state parameters. These are typically in situ sensors that measure temperature, pressure, humidity, and wind speed and direction. Types of atmospheric state instruments include thermometers, hygrometers, barometers, and anemometers.

Generic-Chemistry Related Sensors (Gen-Chemistry) refers to non-specific instruments on a platform used for atmospheric chemistry measurements. These are typically in situ analyzers that measure chemical compounds such as trace gases, halocarbons, volatile organic compounds, nitrates, aerosols, and other chemical species. Measurements can include mixing ratios, composition, particle size, optical properties, and particle size distribution.

Eddy Covariance Flux Towers are in situ micrometeorological surface towers. They are equipped with gas sensors to continuously measure trace gas fluxes between the land surface and the atmosphere. Eddy Covariance Towers are typically used to measure fluxes of carbon dioxide (CO2), methane (CH4), and water vapor (H2O). These towers are also equipped with various meteorological sensors to measure air temperature, precipitation, wind, radiation, and soil temperature.

The LI-COR Plant Canopy Analyzer is an in situ instrument manufactured by LI-COR for leaf area index (LAI) measurements. It measures diffuse sky radiation passing through the canopy at five zenith angles to determine LAI and other canopy characteristics. It can be used under most sky conditions and across canopy types, including row crops, grasslands, isolated trees, and forests. The optical sensor within the Plant Canopy Analyzer has a wavelength range of 320-490 nm. It has a field of view of 148 degrees and an operating temperature range of -20 to 50 degrees Celsius.

Generic-Radiometers refer to non-specific radiometers on a platform. These are typically passive microwave radiometers that measure brightness temperature. Radiometers can be used to retrieve temperature and water vapor profiles, soil moisture content, ocean salinity, precipitation and cloud properties, and vegetation.

Digital cameras provide imagery for research applications. Cameras are mounted on aircraft to collect aerial imagery for mapping and surveying, environmental monitoring, cloud observations, agriculture, geological studies, and other Earth science applications. They are also deployed at field sites to capture visual observations that monitor changes in land cover, vegetation, clouds, air quality, glaciers, and other phenomena.

The LI-COR Quantum Sensor is a ground-based, in situ radiation sensor manufactured by LI-COR. It collects precise measurements of photosynthetically active radiation (PAR) beneath vegetation or under artificial light sources. The sensor detects radiation within the same light spectrum (400 - 700 nm) that plants use for photosynthesis. While primarily used for ground-based measurements, the LI-COR Quantum Sensor can also be mounted on aircraft. It is suitable for long-term deployments and remains durable in high temperatures and humidity.

The Spectron Engineering-590 (SE-590) Spectroradiometer is a portable instrument manufactured by Spectron Engineering. It can be used on both airborne and ground-based platforms. The SE-590 uses a charge-coupled device (CCD) area array detector to measure reflectance. It operates across the visible to short-wave infrared spectral range (350-2500 nm). The SE-590 has a ground resolution of 4.5 meters when flown at an altitude of 300 meters.

The Lyman-alpha Hygrometer is an in situ hygrometer designed for deployment on airborne or ground-based platforms. It measures water vapor absorption at the Lyman-alpha wavelength (121.6 nm) of atomic hydrogen to determine the total water content in the atmosphere. It has a detection limit of 0.1 ppmv and a typical data acquisition rate of 1 second. The Lyman-alpha hygrometer provides water vapor measurements with 6% accuracy and 5% precision.

Soil moisture probes are in situ, ground-based sensors that measure soil water content. The most common type of soil moisture probe used in scientific research employs dielectric permittivity techniques, such as capacitance or time-domain reflectometry. These probes measure the soil's charge-storage capacity to determine soil moisture content. They typically operate at frequencies around 50 MHz and above to reduce sensitivity to salinity. Soil moisture probes provide continuous measurements and are relatively easy to deploy.

Infrared Thermometers (IRTs) are ground-based pyrometers that measure the brightness temperature of a scene within their field of view. They determine brightness temperature by detecting electromagnetic radiation emitted by Earth’s surface. These measurements are used to determine either the surface skin temperature or the sea surface temperature, depending on whether the platform is on land or water. IRTs typically operate within the 8- to 14-μm wavelength range.

Rain gauges are ground-based instruments that directly measure the amount of liquid precipitation over a specified period. Different types of rain gauges, such as tipping buckets and weighing gauges, collect and record data in various ways. Because of their small size and easy setup, rain gauges can be placed in different locations and are often used alongside other precipitation instruments, such as disdrometers, to gather additional details, such as precipitation rate and size distribution.

The Modular Multiband Radiometer (MMR) is an airborne multispectral radiometer manufactured by Barnes Engineering Company. The MMR measures radiance across 8 spectral bands spanning the infrared and visible wavelengths (0.4-12.5 μm), producing images of vegetation and other surface features. At an altitude of 300 meters, the MMR has an instantaneous field of view (IFOV) of about 79 meters and a 15-degree field of view (FOV). It is typically deployed on small aircraft, such as helicopters, but can also be used on ground-based platforms.

Stream gauges are ground-based sensors that measure the water level, or stage, of rivers and streams at specific locations. The flow, or discharge, of a river can then be calculated from these stage measurements. These gauges provide continuous data, making them useful for monitoring flood risk and water supply. The United States Geological Survey (USGS) operates a network of over 10,000 stream gauges across the United States to support flood prediction and water resource management.

The Portable Apparatus for Rapid Acquisition of Bidirectional Observations of the Land and Atmosphere (PARABOLA) is a passive, ground-based, spherical-scanning radiometer. It measures surface reflectance across eight spectral channels. The first four channels (444, 551, 650, and 860 nm) align with spectral bands from the Multi-angle Imaging SpectroRadiometer (MISR) on the Terra satellite for validation. The remaining four channels characterize water vapor (944 nm), aerosol optical depth at longer wavelengths (1028 and 1650 nm), and photosynthetically active radiation (400-700 nm). PARABOLA measurements can be used to derive the surface bidirectional reflectance factor and sky and surface radiances. A complete scan of both the sky and ground hemispheres takes approximately 3 minutes.

The Modular Multiband Radiometer (MMR) is an airborne multispectral radiometer manufactured by Barnes Engineering Company. The MMR measures radiance across 8 spectral bands spanning the infrared and visible wavelengths (0.4-12.5 μm), producing images of vegetation and other surface features. At an altitude of 300 meters, the MMR has an instantaneous field of view (IFOV) of about 79 meters and a 15-degree field of view (FOV). It is typically deployed on small aircraft, such as helicopters, but can also be used on ground-based platforms.

C-band scatterometers are active, non-imaging scatterometers that measure microwave backscatter. They are typically used to measure ocean surface winds but can also measure ice, vegetation, and soil surface properties. They operate in the C-band frequency range (4-8 GHz) and can provide measurements during both daytime and nighttime.

The Spectron Engineering-590 (SE-590) Spectroradiometer is a portable instrument manufactured by Spectron Engineering. It can be used on both airborne and ground-based platforms. The SE-590 uses a charge-coupled device (CCD) area array detector to measure reflectance. It operates across the visible to short-wave infrared spectral range (350-2500 nm). The SE-590 has a ground resolution of 4.5 meters when flown at an altitude of 300 meters.

Spectrometers are instruments that separate and analyze the spectral components of a substance. They typically measure electromagnetic radiation that has been reflected, absorbed, or transmitted by a sample. Spectrometers operate across the ultraviolet to infrared spectrum. The most common types include optical, nuclear magnetic resonance, and mass spectrometers. They can be deployed on aircraft, research vessels, vehicles, and other ground-based platforms.

Infrared Thermometers (IRTs) are ground-based pyrometers that measure the brightness temperature of a scene within their field of view. They determine brightness temperature by detecting electromagnetic radiation emitted by Earth’s surface. These measurements are used to determine either the surface skin temperature or the sea surface temperature, depending on whether the platform is on land or water. IRTs typically operate within the 8- to 14-μm wavelength range.