Deriving Information on Surface Conditions from COlumn and VERtically Resolved Observations Relevant to Air Quality

The High Spectral Resolution Lidar 2 (HSRL-2) is an airborne lidar developed by NASA's Langley Research Center. HSRL-2 measures aerosol backscatter at 355, 532, and 1064 nm wavelengths and aerosol extinction at 355 and 532 nm wavelengths. It has a horizontal resolution of 1-2 km and a vertical resolution of 15 m, with measurements taken approximately every 0.5 seconds. It replaced the original High Spectral Resolution Lidar (HSRL).

The Airborne Compact Atmospheric Mapper (ACAM) is a remote-sensing airborne spectrometer developed at NASA's Goddard Space Flight Center (GSFC). It uses two thermally stabilized spectrometers to measure nitrogen dioxide, sulfur dioxide, ozone, formaldehyde, and aerosols across the ultraviolet, visible, and near-infrared spectra (310-900 nm). ACAM typically functions at a spatial resolution of 30 meters and a temporal resolution of 2 Hz. Data from ACAM can be employed for calibration and validation of observations from the Aura satellite.

The NASA Micro-Pulse Lidar Network (MPLNET) is a worldwide ground-based network of Micro-Pulse Lidar (MPL) systems that has been operational since 1999. MPLNET offers continuous observations of aerosol and cloud vertical structures as well as boundary layer height from the surface up to 30 km. The MPL systems operate at a wavelength range of 523-532 nm and have a vertically-resolved spatial resolution of 30 to 75 meters, depending on the station. Many MPLNET sites are co-located with locations in the NASA Aerosol Robotic Network (AERONET) to help minimize retrieval errors.

The Pandora Spectrometer System is a ground-based UV-VIS spectrometer designed to measure column amounts of trace gases in the atmosphere. It employs total optical absorption spectroscopy for retrievals of ozone, nitrogen dioxide, formaldehyde, and other trace gases. Pandora operates within the 280-525 nm spectral range at a resolution of 0.6 nm. It can perform both direct sun and all-sky radiance measurements, with an overall measurement time of 80 seconds. Pandora is part of a network of identical instruments called the Pandonia Global Network.

The AErosol RObotic NETwork (AERONET) is a federated network of ground-based remote sensing aerosol sensors established by NASA and the PHOtométrie pour le Traitement Opérationnel de Normalisation Satellitaire (PHOTONS) in 1993. Each AERONET site includes a CIMEL Electronique sunphotometer that measures sun irradiance and sky radiances. These measurements are used to determine aerosol properties such as aerosol optical depth and extinction. The sunphotometers operate at nine wavelengths (340, 380, 440, 500, 675, 870, 937, 1020, and 1640 nm) and provide aerosol data approximately every 15 minutes. AERONET sites are distributed worldwide, enabling mapping of about 90% of the Earth’s surface.

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 various chemical compounds such as trace gases, halocarbons, volatile organic compounds, nitrates, aerosols, and other chemical species. Measurements can include mixing ratio, composition, particle size, optical properties, and particle size distribution.

Ceilometers are ground-based remote sensing sensors that measure cloud ceilings and vertical visibility. They utilize a laser or another light source to detect backscatter from clouds, precipitation, and aerosols. Ceilometers provide detailed and precise measurements under all weather conditions and are cost-effective to operate. They are commonly used in boundary layer and cloud research.

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

The Nittany Atmospheric Trailer & Integrated Validation Experiment (NATIVE) is a mobile research facility used for satellite validation, air quality monitoring, and pollution transport and deposition. The NATIVE payload includes in situ trace instruments, passive and active remote sensing instruments, and several meteorological probes. It is owned and operated by Pennsylvania State University.

Ozonesondes are in situ balloon-borne instruments used to measure ozone concentration profiles. An ozonesonde consists of an electrochemical ozone sensor connected with a meteorological radiosonde to collect ozone, temperature, pressure, and humidity measurements as it ascends through the atmosphere. It provides ozone profile measurements at a resolution of 100 to 150 m. Ozonesondes have a typical measurement rate of 0.1 Hz and can collect profiles up to around 35 km.

The Atmospheric Vertical Observations of CO2 in the Earth’s Troposphere (AVOCET) is an airborne in situ spectrometer built by NASA’s Langley Research Center (LaRC). AVOCET uses a differential, non-dispersive infrared spectrometer to provide high-resolution measurements of carbon dioxide (CO2). It operates at the 4.26 μm CO2 absorption band and has a measurement frequency of 5 Hz. Since the early 1990s, AVOCET has been used in multiple field studies and has taken part in over 450 science flights.

Condensation Particle Counters (CPCs) are in situ sensors that measure aerosol particle concentrations. CPCs determine aerosol levels by condensing fluid onto particles, causing them to grow to sizes detectable by optical scattering. Typically, CPCs can detect particles ranging from 7 nm to 3 μm, measure concentrations up to 100,000 particles per cubic centimeter, and provide readings every second. CPCs are manufactured by TSI Incorporated and can be used on airborne, shipborne, and ground-based platforms.

The Laser Aerosol Spectrometer (LAS) is an in situ airborne spectrometer manufactured by TSI, Inc. LAS measures particle size by analyzing how particles scatter light. It operates at a 633 nm wavelength and detects particles ranging from 0.09 to 7.5 μm. LAS can deliver complete particle size distributions at a rate of 10 Hz. It is commonly used as part of aerosol instrument suites, such as NASA’s Langley Aerosol Research Group Experiment (LARGE) and NOAA’s Aerosol Microphysical Properties (AMP).

The Particle Into Liquid Sampler (PILS) is an in situ aerosol sampler manufactured by Brechtel Manufacturing Inc. PILS can be used by both ground-based and airborne platforms to gather continuous data on ambient aerosol bulk composition. The particles collected by PILS are mixed with saturated water vapor to form droplets that are analyzed by either an ion chromatograph (IC) or a total organic carbon detector (TOC). PILS can detect aerosol particles ranging from 70 nm to 2.5 μm in size and offers a time resolution of 3 minutes for airborne measurements and 15 minutes for ground-based measurements.

The Particle Soot Absorption Photometer (PSAP) is an in situ airborne photometer manufactured by Radiance Research. It applies Beer's Law to measure the change in light transmission of aerosol particles. These measurements help determine aerosol absorption and extinction. PSAP operates across three wavelengths (467, 530, and 660 nm) and has a 1-second time resolution. It is usually deployed on aircraft, but it can also be used on ships and vehicles.

The Proton Transfer Mass Spectrometer (PTR-MS) is an in situ spectrometer used both on aircraft and ground, developed by the University of Innsbruck in Austria. It detects volatile organic compounds (VOCs) without the need for sample preparation at very low concentrations. PTR-MS employs chemical ionization mass spectrometry, enabling quick and highly sensitive VOC detection. It has a signal integration time ranging from 0.5 to 1 second.

The Thermal-Dissociation Laser Induced Fluorescence (TD-LIF) is an in situ airborne sensor developed at UC Berkeley. It combines the TD and LIF techniques to measure nitrogen dioxide (NO2), peroxynitrates, nitric acid (HNO3), and other stable organic nitrates in the atmosphere. TD-LIF operates at a wavelength of 585 nm and typically measures at a frequency of 1 Hz.

LI-COR Gas Analyzer is an in situ gas analyzer manufactured by LI-COR. They can be deployed on aircraft, research vessels, vehicles, balloons, and ground-based platforms. They provide measurements of various 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 Scanning Mobility Particle Sizer (SMPS) is an in situ aerosol sensor that can be operated on airborne or ground-based platforms, manufactured by TSI Incorporated. SMPS uses a differential mobility analyzer (DMA) to measure the electrical mobility diameter of aerosol particles, which helps determine the size distribution. It also counts the number of aerosol particles using a condensation particle counter (CPC). It detects particles in the size range of 10-1000 nm and typically takes about 10 seconds to complete each scan.

The Optical Particle Counter is an instrument based on the principle of light scattering from particles. It is a real time instrument that is typically used to measure particles above 0.05 μm in diameter.

The Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) is an in situ spectrometer developed by Droplet Measurement Technologies. It can be used on both airborne and ground-based platforms to measure aerosol size distribution and concentration. UHSAS determines particle size by detecting the peak light signals from aerosol particles illuminated by a 1054 nm laser. It can sample particles in the 60–1000 nm size range and operates at a sampling frequency of 10 Hz.

The Single Particle Soot Photometer (SP2) is an in situ laser-induced photometer developed by Droplet Measurement Technologies. SP2 measures the black carbon (BC) mass in individual aerosol particles, along with their optical and physical properties that contain BC. The device detects aerosol particles with diameters of 200-400 nm and can analyze up to 25,000 particles per second. It operates at a sampling rate of 1 Hz and uses a wavelength of 1.06 μm. It can be used on airborne or ground-based platforms and paired with a Humidified-Dual SP2 (HD-SP2).

The Difference Frequency Generation Absorption Spectrometer (DFGAS) is an in situ airborne spectrometer developed by the National Center for Atmospheric Research (NCAR). It employs difference-frequency generation (DFG) at 3.5 μm by combining two infrared laser sources operating at 1562 and 1083 nm to measure formaldehyde in the atmosphere. DFGAS gathers measurements in 1-second intervals for approximately 60 to 120 seconds, depending on measurement requirements. DFGAS has since been replaced by the Compact Atmospheric Multispecies Spectrometer (CAMS).

The Aerodynamic Particle Sizer (APS) is an in situ spectrometer manufactured by TSI Instruments. APS measures aerodynamic particles in the 0.5-20 μm size range. It also measures the light-scattering intensity of the particles in the 0.37-20 μm optical size range. APS provides particle size distributions for 52 channels at a typical sampling time of 1 second. It uses a laser diode operating at 655 nm and has a size resolution of 0.02 μm at 1 μm. APS can be deployed on aircraft, ships, or ground-based platforms.

The Diode Laser Hygrometer (DLH) is an in situ airborne hygrometer developed by NASA’s Langley Research Center (LaRC). It uses tunable diode laser absorption to detect water vapor in the atmosphere. DLH operates in the near-infrared range at about 1.4 μm and has a measurement frequency of 100 Hz. It can deliver precise measurements of water vapor even when flying through clouds.

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

Nephelometers are in situ optical sensors that can be airborne or ground-based. They measure the total scattering and backscattering of aerosol particles in the atmosphere. Nephelometers operate at three wavelengths: 450 nm, 550 nm, and 700 nm, with a typical time resolution of 1 Hz.

The Differential Absorption Carbon monOxide Measurements (DACOM) is an airborne in situ spectrometer system. It uses the differential absorption technique and an infrared tunable diode laser (TDL) to collect measurements of nitrous oxide (N2O), carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4) in the atmosphere. DACOM operates across the 4.7, 4.5, and 3.3 μm wavelengths to access the absorption lines for CO, N2O, and CH4. It has a measurement frequency of 5 Hz and a precision of about 1 ppbv.

The Langley Aerosol Research Group Experiment (LARGE) is an in situ airborne instrument suite that measures aerosol and cloud microphysical and optical properties, such as size distribution, number concentration, and scattering and absorption coefficients. LARGE includes several instruments, such as the Ultra-High Sensitivity Aerosol Spectrometer (UHSAS), Particle-Into-Liquid Sampler (PILS), Particle Soot Absorption Photometer (PSAP), Cloud and Aerosol Spectrometer (CAS), Cloud Imaging Probe (CIP), and additional cloud and aerosol sensors. The LARGE instruments operate over the 450-700 nm wavelength range, detect particles ranging from 0.003 to 20 μm, and measure at a frequency of 1 Hz. It is primarily used for airborne measurements but can also be deployed on ground-based platforms like vehicles.

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 various chemical compounds such as trace gases, halocarbons, volatile organic compounds, nitrates, aerosols, and other chemical species. Measurements can include mixing ratio, composition, particle size, optical properties, and particle size distribution.

The Micropulse Lidar (MPL) is a ground-based lidar system used for cloud detection. It measures lidar backscatter at 532 nm to retrieve cloud properties such as cloud top and base height. It can also be used for the detection of aerosols. MPL has a vertical resolution of 15 m and a maximum range of 18 km. MPL can operate autonomously and typically provides 10-second averaged data.

The Nittany Atmospheric Trailer & Integrated Validation Experiment (NATIVE) is a mobile research facility used for satellite validation, air quality monitoring, and pollution transport and deposition. The NATIVE payload includes in situ trace instruments, passive and active remote sensing instruments, and several meteorological probes. It is owned and operated by Pennsylvania State University.

The Tunable Optical Profiler for Aerosol and oZone (TOPAZ) is a lidar system designed by the NOAA Chemical Sciences Laboratory. It was originally designed for airborne operations, but it has been reconfigured for deployment in a trailer for ground-based operations. It uses differential absorption lidar (DIAL) technique to measure ozone concentrations and aerosol backscatter profiles up to 6 to 8 km above ground level (AGL). It operates in the 285 to 310 nm wavelength range and has an ozone profile vertical resolution of 5 m near the surface and 1000 m at 8 km AGL. TOPAZ is part of the NASA Tropospheric Ozone Lidar Network (TOLNet).

The NASA Micro-Pulse Lidar Network (MPLNET) is a worldwide ground-based network of Micro-Pulse Lidar (MPL) systems that has been operational since 1999. MPLNET offers continuous observations of aerosol and cloud vertical structures as well as boundary layer height from the surface up to 30 km. The MPL systems operate at a wavelength range of 523-532 nm and have a vertically-resolved spatial resolution of 30 to 75 meters, depending on the station. Many MPLNET sites are co-located with locations in the NASA Aerosol Robotic Network (AERONET) to help minimize retrieval errors.

The Pandora Spectrometer System is a ground-based UV-VIS spectrometer designed to measure column amounts of trace gases in the atmosphere. It employs total optical absorption spectroscopy for retrievals of ozone, nitrogen dioxide, formaldehyde, and other trace gases. Pandora operates within the 280-525 nm spectral range at a resolution of 0.6 nm. It can perform both direct sun and all-sky radiance measurements, with an overall measurement time of 80 seconds. Pandora is part of a network of identical instruments called the Pandonia Global Network.

The AErosol RObotic NETwork (AERONET) is a federated network of ground-based remote sensing aerosol sensors established by NASA and the PHOtométrie pour le Traitement Opérationnel de Normalisation Satellitaire (PHOTONS) in 1993. Each AERONET site includes a CIMEL Electronique sunphotometer that measures sun irradiance and sky radiances. These measurements are used to determine aerosol properties such as aerosol optical depth and extinction. The sunphotometers operate at nine wavelengths (340, 380, 440, 500, 675, 870, 937, 1020, and 1640 nm) and provide aerosol data approximately every 15 minutes. AERONET sites are distributed worldwide, enabling mapping of about 90% of the Earth’s surface.

Generic-Atmospheric State (Gen-AtmsState) refers to non-specific instruments on a platform used for measurements of atmospheric state parameters. These are typically in situ sensors that measure temperature, pressure, humidity, and wind speed/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 various chemical compounds such as trace gases, halocarbons, volatile organic compounds, nitrates, aerosols, and other chemical species. Measurements can include mixing ratio, composition, particle size, optical properties, and particle size distribution.

The Atmospheric Vertical Observations of CO2 in the Earth’s Troposphere (AVOCET) is an airborne in situ spectrometer built by NASA’s Langley Research Center (LaRC). AVOCET uses a differential, non-dispersive infrared spectrometer to provide high-resolution measurements of carbon dioxide (CO2). It operates at the 4.26 μm CO2 absorption band and has a measurement frequency of 5 Hz. Since the early 1990s, AVOCET has been used in multiple field studies and has taken part in over 450 science flights.

Condensation Particle Counters (CPCs) are in situ sensors that measure aerosol particle concentrations. CPCs determine aerosol levels by condensing fluid onto particles, causing them to grow to sizes detectable by optical scattering. Typically, CPCs can detect particles ranging from 7 nm to 3 μm, measure concentrations up to 100,000 particles per cubic centimeter, and provide readings every second. CPCs are manufactured by TSI Incorporated and can be used on airborne, shipborne, and ground-based platforms.

The Particle Into Liquid Sampler (PILS) is an in situ aerosol sampler manufactured by Brechtel Manufacturing Inc. PILS can be used by both ground-based and airborne platforms to gather continuous data on ambient aerosol bulk composition. The particles collected by PILS are mixed with saturated water vapor to form droplets that are analyzed by either an ion chromatograph (IC) or a total organic carbon detector (TOC). PILS can detect aerosol particles ranging from 70 nm to 2.5 μm in size and offers a time resolution of 3 minutes for airborne measurements and 15 minutes for ground-based measurements.

The Particle Soot Absorption Photometer (PSAP) is an in situ airborne photometer manufactured by Radiance Research. It applies Beer's Law to measure the change in light transmission of aerosol particles. These measurements help determine aerosol absorption and extinction. PSAP operates across three wavelengths (467, 530, and 660 nm) and has a 1-second time resolution. It is usually deployed on aircraft, but it can also be used on ships and vehicles.

The Proton Transfer Mass Spectrometer (PTR-MS) is an in situ spectrometer used both on aircraft and ground, developed by the University of Innsbruck in Austria. It detects volatile organic compounds (VOCs) without the need for sample preparation at very low concentrations. PTR-MS employs chemical ionization mass spectrometry, enabling quick and highly sensitive VOC detection. It has a signal integration time ranging from 0.5 to 1 second.

The Thermal-Dissociation Laser Induced Fluorescence (TD-LIF) is an in situ airborne sensor developed at UC Berkeley. It combines the TD and LIF techniques to measure nitrogen dioxide (NO2), peroxynitrates, nitric acid (HNO3), and other stable organic nitrates in the atmosphere. TD-LIF operates at a wavelength of 585 nm and typically measures at a frequency of 1 Hz.

LI-COR Gas Analyzer is an in situ gas analyzer manufactured by LI-COR. They can be deployed on aircraft, research vessels, vehicles, balloons, and ground-based platforms. They provide measurements of various 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 Scanning Mobility Particle Sizer (SMPS) is an in situ aerosol sensor that can be operated on airborne or ground-based platforms, manufactured by TSI Incorporated. SMPS uses a differential mobility analyzer (DMA) to measure the electrical mobility diameter of aerosol particles, which helps determine the size distribution. It also counts the number of aerosol particles using a condensation particle counter (CPC). It detects particles in the size range of 10-1000 nm and typically takes about 10 seconds to complete each scan.

The Optical Particle Counter is an instrument based on the principle of light scattering from particles. It is a real time instrument that is typically used to measure particles above 0.05 μm in diameter.

The Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) is an in situ spectrometer developed by Droplet Measurement Technologies. It can be used on both airborne and ground-based platforms to measure aerosol size distribution and concentration. UHSAS determines particle size by detecting the peak light signals from aerosol particles illuminated by a 1054 nm laser. It can sample particles in the 60–1000 nm size range and operates at a sampling frequency of 10 Hz.

The Single Particle Soot Photometer (SP2) is an in situ laser-induced photometer developed by Droplet Measurement Technologies. SP2 measures the black carbon (BC) mass in individual aerosol particles, along with their optical and physical properties that contain BC. The device detects aerosol particles with diameters of 200-400 nm and can analyze up to 25,000 particles per second. It operates at a sampling rate of 1 Hz and uses a wavelength of 1.06 μm. It can be used on airborne or ground-based platforms and paired with a Humidified-Dual SP2 (HD-SP2).

The Difference Frequency Generation Absorption Spectrometer (DFGAS) is an in situ airborne spectrometer developed by the National Center for Atmospheric Research (NCAR). It employs difference-frequency generation (DFG) at 3.5 μm by combining two infrared laser sources operating at 1562 and 1083 nm to measure formaldehyde in the atmosphere. DFGAS gathers measurements in 1-second intervals for approximately 60 to 120 seconds, depending on measurement requirements. DFGAS has since been replaced by the Compact Atmospheric Multispecies Spectrometer (CAMS).

The Aerodynamic Particle Sizer (APS) is an in situ spectrometer manufactured by TSI Instruments. APS measures aerodynamic particles in the 0.5-20 μm size range. It also measures the light-scattering intensity of the particles in the 0.37-20 μm optical size range. APS provides particle size distributions for 52 channels at a typical sampling time of 1 second. It uses a laser diode operating at 655 nm and has a size resolution of 0.02 μm at 1 μm. APS can be deployed on aircraft, ships, or ground-based platforms.

The Condensation Nuclei Counter (CNC) is optical method for counting atmospheric aerosol particles.

The Diode Laser Hygrometer (DLH) is an in situ airborne hygrometer developed by NASA’s Langley Research Center (LaRC). It uses tunable diode laser absorption to detect water vapor in the atmosphere. DLH operates in the near-infrared range at about 1.4 μm and has a measurement frequency of 100 Hz. It can deliver precise measurements of water vapor even when flying through clouds.

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

Nephelometers are in situ optical sensors that can be airborne or ground-based. They measure the total scattering and backscattering of aerosol particles in the atmosphere. Nephelometers operate at three wavelengths: 450 nm, 550 nm, and 700 nm, with a typical time resolution of 1 Hz.

The Differential Absorption Carbon monOxide Measurements (DACOM) is an airborne in situ spectrometer system. It uses the differential absorption technique and an infrared tunable diode laser (TDL) to collect measurements of nitrous oxide (N2O), carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4) in the atmosphere. DACOM operates across the 4.7, 4.5, and 3.3 μm wavelengths to access the absorption lines for CO, N2O, and CH4. It has a measurement frequency of 5 Hz and a precision of about 1 ppbv.

The Langley Aerosol Research Group Experiment (LARGE) is an in situ airborne instrument suite that measures aerosol and cloud microphysical and optical properties, such as size distribution, number concentration, and scattering and absorption coefficients. LARGE includes several instruments, such as the Ultra-High Sensitivity Aerosol Spectrometer (UHSAS), Particle-Into-Liquid Sampler (PILS), Particle Soot Absorption Photometer (PSAP), Cloud and Aerosol Spectrometer (CAS), Cloud Imaging Probe (CIP), and additional cloud and aerosol sensors. The LARGE instruments operate over the 450-700 nm wavelength range, detect particles ranging from 0.003 to 20 μm, and measure at a frequency of 1 Hz. It is primarily used for airborne measurements but can also be deployed on ground-based platforms like vehicles.

The High Spectral Resolution Lidar 2 (HSRL-2) is an airborne lidar developed by NASA's Langley Research Center. HSRL-2 measures aerosol backscatter at 355, 532, and 1064 nm wavelengths and aerosol extinction at 355 and 532 nm wavelengths. It has a horizontal resolution of 1-2 km and a vertical resolution of 15 m, with measurements taken approximately every 0.5 seconds. It replaced the original High Spectral Resolution Lidar (HSRL).

The Airborne Compact Atmospheric Mapper (ACAM) is a remote-sensing airborne spectrometer developed at NASA's Goddard Space Flight Center (GSFC). It uses two thermally stabilized spectrometers to measure nitrogen dioxide, sulfur dioxide, ozone, formaldehyde, and aerosols across the ultraviolet, visible, and near-infrared spectra (310-900 nm). ACAM typically functions at a spatial resolution of 30 meters and a temporal resolution of 2 Hz. Data from ACAM can be employed for calibration and validation of observations from the Aura satellite.

GEOstationary Coastal and Air Pollution Events (GEO-CAPE) Airborne Simulator (GCAS) is an airborne push-broom instrument with two spectrometers. It was developed by the Radiometric Calibration and Flight Development Laboratory at Goddard Space Flight Center (GSFC) as a simulator for the GEO-CAPE mission. The first spectrometer in GCAS operates in the ultraviolet to visible (300-490 nm) range for air quality observations of nitrogen dioxide (NO2), ozone (O3), formaldehyde (HCHO), and other trace gases. The second spectrometer operates in the visible to near-infrared (480-900 nm) range to provide measurements of ocean color. GCAS has a typical spatial resolution of 250m across track and 500m along track at an altitude of 9 km, with a frame rate of 12 Hz.

The Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) is an airborne pushbroom spectrometer built by Ball Aerospace with support from NASA’s Earth Science Technology Office. GeoTASO measures nadir backscattered solar radiation in the ultraviolet (290-400 nm) and visible (415-695 nm) wavelengths. These measurements can be used to determine aerosols and trace gases in the atmosphere, such as ozone, formaldehyde, and nitrogen dioxide. GeoTASO has a spatial resolution of approximately 250 m by 250 m and an integration time of 0.25 seconds.

The Atmospheric Vertical Observations of CO2 in the Earth’s Troposphere (AVOCET) is an airborne in situ spectrometer built by NASA’s Langley Research Center (LaRC). AVOCET uses a differential, non-dispersive infrared spectrometer to provide high-resolution measurements of carbon dioxide (CO2). It operates at the 4.26 μm CO2 absorption band and has a measurement frequency of 5 Hz. Since the early 1990s, AVOCET has been used in multiple field studies and has taken part in over 450 science flights.

The Polarized Imaging Nephelometer (PI-Neph) is an in situ airborne nephelometer developed at the Laboratory of Aerosols, Clouds, and Optics (LACO) at the University of Maryland Baltimore County (UMBC). PI-Neph measures the ambient scattering coefficient and phase matrix of aerosols to validate satellite aerosol observations. It simultaneously measures at 473 nm, 532 nm, and 671 nm wavelengths, with a scattering angle range of 2 to 178 degrees. PI-Neph typically records measurements every 12 or 36 seconds.

Condensation Particle Counters (CPCs) are in situ sensors that measure aerosol particle concentrations. CPCs determine aerosol levels by condensing fluid onto particles, causing them to grow to sizes detectable by optical scattering. Typically, CPCs can detect particles ranging from 7 nm to 3 μm, measure concentrations up to 100,000 particles per cubic centimeter, and provide readings every second. CPCs are manufactured by TSI Incorporated and can be used on airborne, shipborne, and ground-based platforms.

The Laser Aerosol Spectrometer (LAS) is an in situ airborne spectrometer manufactured by TSI, Inc. LAS measures particle size by analyzing how particles scatter light. It operates at a 633 nm wavelength and detects particles ranging from 0.09 to 7.5 μm. LAS can deliver complete particle size distributions at a rate of 10 Hz. It is commonly used as part of aerosol instrument suites, such as NASA’s Langley Aerosol Research Group Experiment (LARGE) and NOAA’s Aerosol Microphysical Properties (AMP).

The Particle Into Liquid Sampler (PILS) is an in situ aerosol sampler manufactured by Brechtel Manufacturing Inc. PILS can be used by both ground-based and airborne platforms to gather continuous data on ambient aerosol bulk composition. The particles collected by PILS are mixed with saturated water vapor to form droplets that are analyzed by either an ion chromatograph (IC) or a total organic carbon detector (TOC). PILS can detect aerosol particles ranging from 70 nm to 2.5 μm in size and offers a time resolution of 3 minutes for airborne measurements and 15 minutes for ground-based measurements.

The Particle Soot Absorption Photometer (PSAP) is an in situ airborne photometer manufactured by Radiance Research. It applies Beer's Law to measure the change in light transmission of aerosol particles. These measurements help determine aerosol absorption and extinction. PSAP operates across three wavelengths (467, 530, and 660 nm) and has a 1-second time resolution. It is usually deployed on aircraft, but it can also be used on ships and vehicles.

The Proton Transfer Mass Spectrometer (PTR-MS) is an in situ spectrometer used both on aircraft and ground, developed by the University of Innsbruck in Austria. It detects volatile organic compounds (VOCs) without the need for sample preparation at very low concentrations. PTR-MS employs chemical ionization mass spectrometry, enabling quick and highly sensitive VOC detection. It has a signal integration time ranging from 0.5 to 1 second.

The Thermal-Dissociation Laser Induced Fluorescence (TD-LIF) is an in situ airborne sensor developed at UC Berkeley. It combines the TD and LIF techniques to measure nitrogen dioxide (NO2), peroxynitrates, nitric acid (HNO3), and other stable organic nitrates in the atmosphere. TD-LIF operates at a wavelength of 585 nm and typically measures at a frequency of 1 Hz.

LI-COR Gas Analyzer is an in situ gas analyzer manufactured by LI-COR. They can be deployed on aircraft, research vessels, vehicles, balloons, and ground-based platforms. They provide measurements of various 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 Scanning Mobility Particle Sizer (SMPS) is an in situ aerosol sensor that can be operated on airborne or ground-based platforms, manufactured by TSI Incorporated. SMPS uses a differential mobility analyzer (DMA) to measure the electrical mobility diameter of aerosol particles, which helps determine the size distribution. It also counts the number of aerosol particles using a condensation particle counter (CPC). It detects particles in the size range of 10-1000 nm and typically takes about 10 seconds to complete each scan.

The Optical Particle Counter is an instrument based on the principle of light scattering from particles. It is a real time instrument that is typically used to measure particles above 0.05 μm in diameter.

The Picarro gas concentration analyzer is an in situ airborne or ground-based sensor manufactured by Picarro, Inc. It uses Wavelength-Scanned Cavity Ring Spectroscopy (WS-CRDS) to measure trace gases such as carbon dioxide, carbon monoxide, methane, and water vapor. For carbon dioxide measurements, the laser within Picarro operates at 1603 nm wavelength, while 1651 nm wavelength is used for methane and water vapor measurements. Picarro has a typical sampling time of 2.5 seconds. Depending on the model, Picarro can also provide measurements of carbon isotopes for gas concentrations.

The Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) is an in situ spectrometer developed by Droplet Measurement Technologies. It can be used on both airborne and ground-based platforms to measure aerosol size distribution and concentration. UHSAS determines particle size by detecting the peak light signals from aerosol particles illuminated by a 1054 nm laser. It can sample particles in the 60–1000 nm size range and operates at a sampling frequency of 10 Hz.

The Single Particle Soot Photometer (SP2) is an in situ laser-induced photometer developed by Droplet Measurement Technologies. SP2 measures the black carbon (BC) mass in individual aerosol particles, along with their optical and physical properties that contain BC. The device detects aerosol particles with diameters of 200-400 nm and can analyze up to 25,000 particles per second. It operates at a sampling rate of 1 Hz and uses a wavelength of 1.06 μm. It can be used on airborne or ground-based platforms and paired with a Humidified-Dual SP2 (HD-SP2).

The Difference Frequency Generation Absorption Spectrometer (DFGAS) is an in situ airborne spectrometer developed by the National Center for Atmospheric Research (NCAR). It employs difference-frequency generation (DFG) at 3.5 μm by combining two infrared laser sources operating at 1562 and 1083 nm to measure formaldehyde in the atmosphere. DFGAS gathers measurements in 1-second intervals for approximately 60 to 120 seconds, depending on measurement requirements. DFGAS has since been replaced by the Compact Atmospheric Multispecies Spectrometer (CAMS).

The Aerodynamic Particle Sizer (APS) is an in situ spectrometer manufactured by TSI Instruments. APS measures aerodynamic particles in the 0.5-20 μm size range. It also measures the light-scattering intensity of the particles in the 0.37-20 μm optical size range. APS provides particle size distributions for 52 channels at a typical sampling time of 1 second. It uses a laser diode operating at 655 nm and has a size resolution of 0.02 μm at 1 μm. APS can be deployed on aircraft, ships, or ground-based platforms.

The Condensation Nuclei Counter (CNC) is optical method for counting atmospheric aerosol particles.

The Diode Laser Hygrometer (DLH) is an in situ airborne hygrometer developed by NASA’s Langley Research Center (LaRC). It uses tunable diode laser absorption to detect water vapor in the atmosphere. DLH operates in the near-infrared range at about 1.4 μm and has a measurement frequency of 100 Hz. It can deliver precise measurements of water vapor even when flying through clouds.

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

Nephelometers are in situ optical sensors that can be airborne or ground-based. They measure the total scattering and backscattering of aerosol particles in the atmosphere. Nephelometers operate at three wavelengths: 450 nm, 550 nm, and 700 nm, with a typical time resolution of 1 Hz.

The Differential Absorption Carbon monOxide Measurements (DACOM) is an airborne in situ spectrometer system. It uses the differential absorption technique and an infrared tunable diode laser (TDL) to collect measurements of nitrous oxide (N2O), carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4) in the atmosphere. DACOM operates across the 4.7, 4.5, and 3.3 μm wavelengths to access the absorption lines for CO, N2O, and CH4. It has a measurement frequency of 5 Hz and a precision of about 1 ppbv.

The Langley Aerosol Research Group Experiment (LARGE) is an in situ airborne instrument suite that measures aerosol and cloud microphysical and optical properties, such as size distribution, number concentration, and scattering and absorption coefficients. LARGE includes several instruments, such as the Ultra-High Sensitivity Aerosol Spectrometer (UHSAS), Particle-Into-Liquid Sampler (PILS), Particle Soot Absorption Photometer (PSAP), Cloud and Aerosol Spectrometer (CAS), Cloud Imaging Probe (CIP), and additional cloud and aerosol sensors. The LARGE instruments operate over the 450-700 nm wavelength range, detect particles ranging from 0.003 to 20 μm, and measure at a frequency of 1 Hz. It is primarily used for airborne measurements but can also be deployed on ground-based platforms like vehicles.

The High Spectral Resolution Lidar 2 (HSRL-2) is an airborne lidar developed by NASA's Langley Research Center. HSRL-2 measures aerosol backscatter at 355, 532, and 1064 nm wavelengths and aerosol extinction at 355 and 532 nm wavelengths. It has a horizontal resolution of 1-2 km and a vertical resolution of 15 m, with measurements taken approximately every 0.5 seconds. It replaced the original High Spectral Resolution Lidar (HSRL).

The Airborne Compact Atmospheric Mapper (ACAM) is a remote-sensing airborne spectrometer developed at NASA's Goddard Space Flight Center (GSFC). It uses two thermally stabilized spectrometers to measure nitrogen dioxide, sulfur dioxide, ozone, formaldehyde, and aerosols across the ultraviolet, visible, and near-infrared spectra (310-900 nm). ACAM typically functions at a spatial resolution of 30 meters and a temporal resolution of 2 Hz. Data from ACAM can be employed for calibration and validation of observations from the Aura satellite.

The Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) is an airborne pushbroom spectrometer built by Ball Aerospace with support from NASA’s Earth Science Technology Office. GeoTASO measures nadir backscattered solar radiation in the ultraviolet (290-400 nm) and visible (415-695 nm) wavelengths. These measurements can be used to determine aerosols and trace gases in the atmosphere, such as ozone, formaldehyde, and nitrogen dioxide. GeoTASO has a spatial resolution of approximately 250 m by 250 m and an integration time of 0.25 seconds.

GEOstationary Coastal and Air Pollution Events (GEO-CAPE) Airborne Simulator (GCAS) is an airborne push-broom instrument with two spectrometers. It was developed by the Radiometric Calibration and Flight Development Laboratory at Goddard Space Flight Center (GSFC) as a simulator for the GEO-CAPE mission. The first spectrometer in GCAS operates in the ultraviolet to visible (300-490 nm) range for air quality observations of nitrogen dioxide (NO2), ozone (O3), formaldehyde (HCHO), and other trace gases. The second spectrometer operates in the visible to near-infrared (480-900 nm) range to provide measurements of ocean color. GCAS has a typical spatial resolution of 250m across track and 500m along track at an altitude of 9 km, with a frame rate of 12 Hz.

The Nittany Atmospheric Trailer & Integrated Validation Experiment (NATIVE) is a mobile research facility used for satellite validation, air quality monitoring, and pollution transport and deposition. The NATIVE payload includes in situ trace instruments, passive and active remote sensing instruments, and several meteorological probes. It is owned and operated by Pennsylvania State University.

The Tropospheric Ozone Lidar Network (TOLNet) is an interagency initiative involving NASA, NOAA, and USEPA that began in 2012. TOLNet provides highly time-resolved measurements of tropospheric ozone profiles to support air quality research and satellite validation. It includes several lidar systems across North America: JPL Table Mountain Facility (TMF) tropospheric ozone lidar, NOAA Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar, University of Alabama in Huntsville Rocket City Ozone Quality Evaluation in the Troposphere (RO3QET), Environment and Climate Change Canada’s Autonomous Mobile Ozone LIDAR Instrument for Tropospheric Experiments (AMOLITE), City College of New York Tropospheric Ozone Lidar System (NYTOLS), GSFC TROPospheric OZone (TROPOZ) DIAL, Langley Mobile Ozone Lidar (LMOL), and Hampton University Lidar Laboratory. The mobile systems within TOLNet can be deployed in the field to provide collocated measurements of ozone alongside balloon and airborne sensors.

The NASA Goddard Tropospheric Ozone Lidar (TROPOZ) is a mobile, ground-based lidar that is part of the Tropospheric Ozone Lidar Network (TOLNet). It employs the differential absorption lidar (DIAL) technique to measure ozone at wavelengths of 289 nm and 299 nm. TROPOZ has a range resolution of 15 meters, a repetition rate of 50 Hz, and can produce ozone profiles from 0.35 to 16 km above ground level.

The Langley Mobile Ozone Lidar (LMOL) is a mobile, ground-based lidar developed at NASA Langley Research Center (LaRC). It is a differential absorption lidar used to measure ozone, aerosols, and clouds. It operates at 287 nm and 292 nm for ozone retrievals and at 527 nm for aerosol detection. It has a pulse width of 70 ns and a range resolution of 7.5 m. LMOL is part of the Tropospheric Ozone Lidar Network (TOLNet), which is operated by NASA.

The NASA Micro-Pulse Lidar Network (MPLNET) is a worldwide ground-based network of Micro-Pulse Lidar (MPL) systems that has been operational since 1999. MPLNET offers continuous observations of aerosol and cloud vertical structures as well as boundary layer height from the surface up to 30 km. The MPL systems operate at a wavelength range of 523-532 nm and have a vertically-resolved spatial resolution of 30 to 75 meters, depending on the station. Many MPLNET sites are co-located with locations in the NASA Aerosol Robotic Network (AERONET) to help minimize retrieval errors.

The Pandora Spectrometer System is a ground-based UV-VIS spectrometer designed to measure column amounts of trace gases in the atmosphere. It employs total optical absorption spectroscopy for retrievals of ozone, nitrogen dioxide, formaldehyde, and other trace gases. Pandora operates within the 280-525 nm spectral range at a resolution of 0.6 nm. It can perform both direct sun and all-sky radiance measurements, with an overall measurement time of 80 seconds. Pandora is part of a network of identical instruments called the Pandonia Global Network.

The AErosol RObotic NETwork (AERONET) is a federated network of ground-based remote sensing aerosol sensors established by NASA and the PHOtométrie pour le Traitement Opérationnel de Normalisation Satellitaire (PHOTONS) in 1993. Each AERONET site includes a CIMEL Electronique sunphotometer that measures sun irradiance and sky radiances. These measurements are used to determine aerosol properties such as aerosol optical depth and extinction. The sunphotometers operate at nine wavelengths (340, 380, 440, 500, 675, 870, 937, 1020, and 1640 nm) and provide aerosol data approximately every 15 minutes. AERONET sites are distributed worldwide, enabling mapping of about 90% of the Earth’s surface.

Ceilometers are ground-based remote sensing sensors that measure cloud ceilings and vertical visibility. They utilize a laser or another light source to detect backscatter from clouds, precipitation, and aerosols. Ceilometers provide detailed and precise measurements under all weather conditions and are cost-effective to operate. They are commonly used in boundary layer and cloud research.

Generic-Atmospheric State (Gen-AtmsState) refers to non-specific instruments on a platform used for measurements of atmospheric state parameters. These are typically in situ sensors that measure temperature, pressure, humidity, and wind speed/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 various chemical compounds such as trace gases, halocarbons, volatile organic compounds, nitrates, aerosols, and other chemical species. Measurements can include mixing ratio, composition, particle size, optical properties, and particle size distribution.

The NASA Goddard Tropospheric Ozone Lidar (TROPOZ) is a mobile, ground-based lidar that is part of the Tropospheric Ozone Lidar Network (TOLNet). It employs the differential absorption lidar (DIAL) technique to measure ozone at wavelengths of 289 nm and 299 nm. TROPOZ has a range resolution of 15 meters, a repetition rate of 50 Hz, and can produce ozone profiles from 0.35 to 16 km above ground level.

The Tunable Optical Profiler for Aerosol and oZone (TOPAZ) is a lidar system designed by the NOAA Chemical Sciences Laboratory. It was originally designed for airborne operations, but it has been reconfigured for deployment in a trailer for ground-based operations. It uses differential absorption lidar (DIAL) technique to measure ozone concentrations and aerosol backscatter profiles up to 6 to 8 km above ground level (AGL). It operates in the 285 to 310 nm wavelength range and has an ozone profile vertical resolution of 5 m near the surface and 1000 m at 8 km AGL. TOPAZ is part of the NASA Tropospheric Ozone Lidar Network (TOLNet).

This data will be added in future versions

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

The Condensation Nuclei Counter (CNC) is optical method for counting atmospheric aerosol particles.

The Cloud Aerosol and Precipitation Spectrometer (CAPS) is an in situ airborne spectrometer manufactured by Droplet Measurement Technologies. It combines the Cloud Imaging Probe (CIP), the Cloud and Aerosol Spectrometer (CAS), and the Hotwire Liquid Water Content (LWC) Sensor into a single instrument. CAPS measures the size distribution of aerosol, cloud, and liquid droplets for particles between 50-1600 μm in size, with a time resolution of 1 Hz. It can also capture images of cloud particles and provide measurements of temperature, pressure, and LWC.

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 various chemical compounds such as trace gases, halocarbons, volatile organic compounds, nitrates, aerosols, and other chemical species. Measurements can include mixing ratio, composition, particle size, optical properties, and particle size distribution.

Nephelometers are in situ optical sensors that can be airborne or ground-based. They measure the total scattering and backscattering of aerosol particles in the atmosphere. Nephelometers operate at three wavelengths: 450 nm, 550 nm, and 700 nm, with a typical time resolution of 1 Hz.

The Langley Aerosol Research Group Experiment (LARGE) is an in situ airborne instrument suite that measures aerosol and cloud microphysical and optical properties, such as size distribution, number concentration, and scattering and absorption coefficients. LARGE includes several instruments, such as the Ultra-High Sensitivity Aerosol Spectrometer (UHSAS), Particle-Into-Liquid Sampler (PILS), Particle Soot Absorption Photometer (PSAP), Cloud and Aerosol Spectrometer (CAS), Cloud Imaging Probe (CIP), and additional cloud and aerosol sensors. The LARGE instruments operate over the 450-700 nm wavelength range, detect particles ranging from 0.003 to 20 μm, and measure at a frequency of 1 Hz. It is primarily used for airborne measurements but can also be deployed on ground-based platforms like vehicles.

The Scanning Mobility Particle Sizer (SMPS) is an in situ aerosol sensor that can be operated on airborne or ground-based platforms, manufactured by TSI Incorporated. SMPS uses a differential mobility analyzer (DMA) to measure the electrical mobility diameter of aerosol particles, which helps determine the size distribution. It also counts the number of aerosol particles using a condensation particle counter (CPC). It detects particles in the size range of 10-1000 nm and typically takes about 10 seconds to complete each scan.

The Atmospheric Vertical Observations of CO2 in the Earth’s Troposphere (AVOCET) is an airborne in situ spectrometer built by NASA’s Langley Research Center (LaRC). AVOCET uses a differential, non-dispersive infrared spectrometer to provide high-resolution measurements of carbon dioxide (CO2). It operates at the 4.26 μm CO2 absorption band and has a measurement frequency of 5 Hz. Since the early 1990s, AVOCET has been used in multiple field studies and has taken part in over 450 science flights.

This data will be added in future versions

Condensation Particle Counters (CPCs) are in situ sensors that measure aerosol particle concentrations. CPCs determine aerosol levels by condensing fluid onto particles, causing them to grow to sizes detectable by optical scattering. Typically, CPCs can detect particles ranging from 7 nm to 3 μm, measure concentrations up to 100,000 particles per cubic centimeter, and provide readings every second. CPCs are manufactured by TSI Incorporated and can be used on airborne, shipborne, and ground-based platforms.

The Laser Aerosol Spectrometer (LAS) is an in situ airborne spectrometer manufactured by TSI, Inc. LAS measures particle size by analyzing how particles scatter light. It operates at a 633 nm wavelength and detects particles ranging from 0.09 to 7.5 μm. LAS can deliver complete particle size distributions at a rate of 10 Hz. It is commonly used as part of aerosol instrument suites, such as NASA’s Langley Aerosol Research Group Experiment (LARGE) and NOAA’s Aerosol Microphysical Properties (AMP).

The Particle Into Liquid Sampler (PILS) is an in situ aerosol sampler manufactured by Brechtel Manufacturing Inc. PILS can be used by both ground-based and airborne platforms to gather continuous data on ambient aerosol bulk composition. The particles collected by PILS are mixed with saturated water vapor to form droplets that are analyzed by either an ion chromatograph (IC) or a total organic carbon detector (TOC). PILS can detect aerosol particles ranging from 70 nm to 2.5 μm in size and offers a time resolution of 3 minutes for airborne measurements and 15 minutes for ground-based measurements.

The Particle Soot Absorption Photometer (PSAP) is an in situ airborne photometer manufactured by Radiance Research. It applies Beer's Law to measure the change in light transmission of aerosol particles. These measurements help determine aerosol absorption and extinction. PSAP operates across three wavelengths (467, 530, and 660 nm) and has a 1-second time resolution. It is usually deployed on aircraft, but it can also be used on ships and vehicles.

The Proton Transfer Mass Spectrometer (PTR-MS) is an in situ spectrometer used both on aircraft and ground, developed by the University of Innsbruck in Austria. It detects volatile organic compounds (VOCs) without the need for sample preparation at very low concentrations. PTR-MS employs chemical ionization mass spectrometry, enabling quick and highly sensitive VOC detection. It has a signal integration time ranging from 0.5 to 1 second.

The Thermal-Dissociation Laser Induced Fluorescence (TD-LIF) is an in situ airborne sensor developed at UC Berkeley. It combines the TD and LIF techniques to measure nitrogen dioxide (NO2), peroxynitrates, nitric acid (HNO3), and other stable organic nitrates in the atmosphere. TD-LIF operates at a wavelength of 585 nm and typically measures at a frequency of 1 Hz.

LI-COR Gas Analyzer is an in situ gas analyzer manufactured by LI-COR. They can be deployed on aircraft, research vessels, vehicles, balloons, and ground-based platforms. They provide measurements of various 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 Scanning Mobility Particle Sizer (SMPS) is an in situ aerosol sensor that can be operated on airborne or ground-based platforms, manufactured by TSI Incorporated. SMPS uses a differential mobility analyzer (DMA) to measure the electrical mobility diameter of aerosol particles, which helps determine the size distribution. It also counts the number of aerosol particles using a condensation particle counter (CPC). It detects particles in the size range of 10-1000 nm and typically takes about 10 seconds to complete each scan.

The Optical Particle Counter is an instrument based on the principle of light scattering from particles. It is a real time instrument that is typically used to measure particles above 0.05 μm in diameter.

The Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) is an in situ spectrometer developed by Droplet Measurement Technologies. It can be used on both airborne and ground-based platforms to measure aerosol size distribution and concentration. UHSAS determines particle size by detecting the peak light signals from aerosol particles illuminated by a 1054 nm laser. It can sample particles in the 60–1000 nm size range and operates at a sampling frequency of 10 Hz.

The Cloud Absorption Radiometer (CAR) is an airborne multichannel scanning radiometer developed by the Goddard Space Flight Center (GSFC). CAR provides measurements of scattered radiance and bidirectional surface reflectance across 14 spectral bands in the visible and near-infrared wavelengths (0.34-2.30 µm). It also captures imagery of cloud and surface features on Earth. CAR has a scan rate of 1.67 Hz (100 rpm) and a spatial resolution of 4 meters at nadir, at an altitude of 200 meters above ground.

The Single Particle Soot Photometer (SP2) is an in situ laser-induced photometer developed by Droplet Measurement Technologies. SP2 measures the black carbon (BC) mass in individual aerosol particles, along with their optical and physical properties that contain BC. The device detects aerosol particles with diameters of 200-400 nm and can analyze up to 25,000 particles per second. It operates at a sampling rate of 1 Hz and uses a wavelength of 1.06 μm. It can be used on airborne or ground-based platforms and paired with a Humidified-Dual SP2 (HD-SP2).

The Difference Frequency Generation Absorption Spectrometer (DFGAS) is an in situ airborne spectrometer developed by the National Center for Atmospheric Research (NCAR). It employs difference-frequency generation (DFG) at 3.5 μm by combining two infrared laser sources operating at 1562 and 1083 nm to measure formaldehyde in the atmosphere. DFGAS gathers measurements in 1-second intervals for approximately 60 to 120 seconds, depending on measurement requirements. DFGAS has since been replaced by the Compact Atmospheric Multispecies Spectrometer (CAMS).

The Aerodynamic Particle Sizer (APS) is an in situ spectrometer manufactured by TSI Instruments. APS measures aerodynamic particles in the 0.5-20 μm size range. It also measures the light-scattering intensity of the particles in the 0.37-20 μm optical size range. APS provides particle size distributions for 52 channels at a typical sampling time of 1 second. It uses a laser diode operating at 655 nm and has a size resolution of 0.02 μm at 1 μm. APS can be deployed on aircraft, ships, or ground-based platforms.

The Condensation Nuclei Counter (CNC) is optical method for counting atmospheric aerosol particles.

The Diode Laser Hygrometer (DLH) is an in situ airborne hygrometer developed by NASA’s Langley Research Center (LaRC). It uses tunable diode laser absorption to detect water vapor in the atmosphere. DLH operates in the near-infrared range at about 1.4 μm and has a measurement frequency of 100 Hz. It can deliver precise measurements of water vapor even when flying through clouds.

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

The Cloud Imaging Probe (CIP) is an in situ airborne optical array probe manufactured by Droplet Measurement Technologies. It captures cloud particle images by recording shadows as particles pass through a laser. Additionally, it provides data on particle size distribution and cloud liquid water content. CIP typically has a resolution of 25 μm and can measure particles ranging from 12.5 μm to 1.55 mm.

Nephelometers are in situ optical sensors that can be airborne or ground-based. They measure the total scattering and backscattering of aerosol particles in the atmosphere. Nephelometers operate at three wavelengths: 450 nm, 550 nm, and 700 nm, with a typical time resolution of 1 Hz.

The Cloud and Aerosol Spectrometer (CAS) is an in situ airborne spectrometer manufactured by Droplet Measurement Technologies. It measures light scattering at 658 nm to determine aerosol and cloud particle size distributions from 0.51 to 50 μm. It also provides measurements of the refractive index and particle shape. CAS has a typical time resolution of 1 Hz and can measure concentrations greater than 1,000 particles per cubic meter.

The Differential Absorption Carbon monOxide Measurements (DACOM) is an airborne in situ spectrometer system. It uses the differential absorption technique and an infrared tunable diode laser (TDL) to collect measurements of nitrous oxide (N2O), carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4) in the atmosphere. DACOM operates across the 4.7, 4.5, and 3.3 μm wavelengths to access the absorption lines for CO, N2O, and CH4. It has a measurement frequency of 5 Hz and a precision of about 1 ppbv.

The Langley Aerosol Research Group Experiment (LARGE) is an in situ airborne instrument suite that measures aerosol and cloud microphysical and optical properties, such as size distribution, number concentration, and scattering and absorption coefficients. LARGE includes several instruments, such as the Ultra-High Sensitivity Aerosol Spectrometer (UHSAS), Particle-Into-Liquid Sampler (PILS), Particle Soot Absorption Photometer (PSAP), Cloud and Aerosol Spectrometer (CAS), Cloud Imaging Probe (CIP), and additional cloud and aerosol sensors. The LARGE instruments operate over the 450-700 nm wavelength range, detect particles ranging from 0.003 to 20 μm, and measure at a frequency of 1 Hz. It is primarily used for airborne measurements but can also be deployed on ground-based platforms like vehicles.

Radiosondes are a balloon-borne instrument package used to collect profile measurements of pressure, temperature, humidity, and winds. 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 at 1-6 seconds, depending on the type and manufacturer of the radiosonde. Radiosondes are used for weather forecasting, ground truth satellite data, atmospheric research, and input for weather prediction models.

Ozonesondes are in situ balloon-borne instruments used to measure ozone concentration profiles. An ozonesonde consists of an electrochemical ozone sensor connected with a meteorological radiosonde to collect ozone, temperature, pressure, and humidity measurements as it ascends through the atmosphere. It provides ozone profile measurements at a resolution of 100 to 150 m. Ozonesondes have a typical measurement rate of 0.1 Hz and can collect profiles up to around 35 km.