Airborne Tropical Tropopause Experiment

NOAA Water (NW) is an airborne, two-channel, closed-path tunable diode laser absorption spectrometer developed by NOAA. It measures water vapor and enhanced total water content in the upper troposphere and lower stratosphere. Originally designed for installation on NASA’s Global Hawk Uncrewed Aircraft System (UAS), it can also be deployed on other high-altitude aircraft. It uses second harmonic detection near the 2.7 μm wavelength to measure water vapor. Its typical sampling frequency is 1 Hz.

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 Hawkeye Combination Cloud Particle Probe is an in situ airborne probe developed by SPEC, Inc. It was initially designed to be flown on NASA’s Global Hawk Uncrewed Aerial Vehicle (UAV). Hawkeye includes four probes: the Fast Cloud Droplet Probe (FCDP), a 10-micron channel 2D-S Probe, a 50-micron channel 2D-S Probe, and a Cloud Particle Imager (CPI). Hawkeye captures images of cloud particles and measures particle size distribution and concentration. The FCDP has a size range of 1.5 to 50 μm with a resolution of 3 μm. The 10-micron channel 2D-S probe covers a size range of 10 to 1280 μm, while the 50-micron channel 2D-S covers 50 to 6400 μm. The CPI provides a resolution of 2.3 μm, a size range from 2.3 to 2300 μm, and a frame rate up to 400 frames per second.

The Fast Cloud Droplet Probe (FCDP) is an in situ airborne cloud probe manufactured by SPEC Inc. The FCDP measures the concentration and size of cloud droplets by detecting light scattered by particles. It detects particles with diameters ranging from 1.5 to 50 microns and typically records measurements at 1 Hz.

The Meteorological Measurement System (MMS) is an in situ airborne instrument used to measure atmospheric state parameters. MMS provides high-resolution, accurate measurements of atmospheric pressure, temperature, and wind direction and speed immediately around the plane. Additional parameters that can be derived include potential temperature, true airspeed, turbulence dissipation rate, and Reynolds number. Measurements of all parameters are typically collected at a rate of 20 Hz.

Differential Optical Absorption Spectroscopy (DOAS) is a passive spectrometer technique used to measure trace gas concentrations. It detects trace gases by measuring specific, narrow-band absorptions in the ultraviolet and visible light spectrum. DOAS is typically used to detect ozone (O3), nitrogen dioxide (NO2), formaldehyde (CH2O), and sulfur dioxide (SO2). It is suitable for both airborne and ground-based applications.

The Whole Air Sampler (WAS) is an airborne in-situ instrument that collects air samples for analyzing trace gases, such as nonmethane hydrocarbons (NMHCs), halocarbons, alkyl nitrates, and various sulfur compounds found in the troposphere. Air samples collected by the WAS are then analyzed using gas chromatography and mass spectrometry to identify the gases present. The WAS collects samples every minute, allowing scientists to get a clear picture of the environment's chemical composition as research aircraft pass through.

The Uncrewed Aircraft Systems (UAS) Chromatograph for Atmospheric Trace Species (UCATS) is an in situ airborne instrument suite that measures trace gases in the atmosphere. It includes three separate instruments: a three-channel gas chromatograph (GC), a dual-beam ozone photometer (OZ), and a tunable diode laser (TDL) spectrometer. The GC measures nitrous oxide (N2O) and sulfur hexafluoride (SF6) every 70 seconds and detects hydrogen (H2), methane (CH4), and carbon monoxide (CO) every 140 seconds. The OZ sensor operates at 254 nm and provides ozone measurements every 10 seconds. The TDL spectrometer operates at 1370 nm and offers water vapor measurements every 1 second. UCATS was designed for operation on UAS, but it has also been deployed on piloted aircraft.

The Microwave Temperature Profiler (MTP) is an airborne microwave radiometer developed by the Jet Propulsion Laboratory and later modified by NCAR. It measures brightness temperature from oxygen molecules at 56.363 GHz, 57.612 GHz, and 58.363 GHz. These measurements are converted into air temperature through a statistical retrieval process. It samples across 10 viewing angles and has a vertical resolution of 150 m near the aircraft. MTP provides profiles every 17 seconds with about 4 km of horizontal spacing.

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.

The Cloud Physics Lidar (CPL) is an airborne lidar system designed specifically to provide multi-wavelength measurements of cirrus clouds, sub-visual cirrus clouds, and aerosols. It measures lidar backscatter at three wavelengths: 355 nm, 532 nm, and 1064 nm. These measurements can be used to determine cloud optical depth, particle size distribution, extinction profiles, aerosol layers, and other properties. CPL has a vertical resolution of 30 m and a typical horizontal resolution of 200 m. It has a measurement sampling rate of 1 Hz.

The NOAA Dual-Beam UV-Absorption Ozone Photometer (NOAA-O3) is an in situ optical balloon-borne and airborne instrument that measures ozone concentrations in the troposphere and lower stratosphere. It operates at a wavelength of 254 nm, enabling it to calculate ozone number density due to the precise ozone absorption cross section at that wavelength. It has a sampling rate of 2 Hz and a horizontal resolution of 100 to 200 meters during typical research flights.

The Solar Spectral Flux Radiometer (SSFR) is an airborne radiometer developed by the Ames Atmospheric Radiation Group. It measures solar spectral irradiance in the troposphere. SSFR works within the 300-2150 nm wavelength range and offers a spectral resolution of 8-12 nm. It typically collects data at 1 Hz and has a radiometric accuracy of 3%.

The Uncrewed Aerial System (UAS) Laser Hygrometer (ULH) is an in situ airborne hygrometer developed at the Jet Propulsion Laboratory (JPL). It was designed to measure water vapor in the upper troposphere and lower stratosphere on UAS. It uses a continuous laser (1370 nm) beam and two mirrors to detect the water vapor concentration around the aircraft. ULH can provide data rates up to 20 Hz, allowing for a spatial resolution of 10 meters or less. It has a detection limit of less than 1 ppmv.