Gulfstream V - NSF

The Three-View Cloud Particle Imager (3V-CPI) measures the size, shape and concentration of water drops and ice particles in clouds. The probe is a combination of three imaging instruments. Two of them comprise a 2D-S (Two- Dimensional Stereo hydrometeor spectrometer), in which two high-resolution (about 9 mm resolution) 2D probes image particles as they pass through laser beams that are orthogonal to each other. If particles also lie in the intersection of the sensitive areas of the two beams, they are seen by both 2D probes. In that case, the third instrument, a Cloud Particle Imager (CPI), is triggered to take a high-resolution picture, via a briefly illuminated high-resolution imaging array. This image has a pixel size of about 2.3 µm and so provides very high resolution for determining shapes and habits of ice crystals. The probe is particularly suited to imaging such crystals, but also provides good detection of other hydrometeors including large cloud droplets, drizzle and small rain drops, and other precipitation particles.

The 2DC probe records images of hydrometeors that pass through its sample volume, and so provides measurements of ice or water drop concentration, their size distribution, and their shapes. It obtains these images by recording the status (illuminated or shadowed) of a 64-element photodiode array as the shadow of the hydrometeor passes over the array. Probes with 25 µm and 10 µm resolution are available; at 25 µm, the 64-element array provides a sample of about 8 L per 100 m of flight. Images of individual particles are recorded, usually with no loss except at very high concentrations. Special records containing these images in digital form are recorded as needed, so they will be interspersed with the standard periodically sampled records. The 2DC probe was originally manufactured by Particle Measuring Systems, Inc., but the electronics have been replaced with high-speed circuitry matched to the flight speed of the G-V, data transmission has been changed to USB-2, the photodiode array was replaced with one having twice as many elements and supporting faster response, and other changes were made to the optics and electronics of the G-V 2DCs.

Because the depth of field reduces to less than the distance between the arms that define the sample aperture for particle sizes less than about 125 µm, and because diffraction makes the sizes of such small particles hard to determine, the probe has limited ability to measure concentrations at sizes less than about 100 µm, even though it has resolution smaller than this. The array size and optics limit the largest size that can be imaged fully to 1600 µm for the 25-µm-resolution probe. The probe also has been shown to measure falsely high concentrations as a result of shattering (Korolev et al., 2011), so new tips have been installed that reduce but do not eliminate the effects of shattering.

The Picarro CO2/CH4 Flight Analyzer is a real time, trace gas monitor capable of measuring these gases with parts-per-billion (ppbv) sensitivity onboard aircraft with varying cabin pressure and environmental conditions. The analyzer is based on Wavelength-Scanned Cavity Ring Down Spectroscopy (WS-CRDS), a time-based measurement utilizing a near-infrared laser to measure a spectral signature of the molecule. Gas is circulated in an optical measurement cavity with an effective path length of up to 20 kilometers. A patented, high-precision wavelength monitor makes certain that only the spectral feature of interest is being monitored, greatly reducing the analyzer’s sensitivity to interfering gas species, and enabling ultra-trace gas concentration measurements even if there are other gases present. As a result, the analyzer maintains high linearity, precision, and accuracy over changing environmental conditions with minimal calibration required.

The Picarro CO2/CH4 Flight Analyzer is a real time, trace gas monitor capable of measuring these gases with parts-per-billion (ppbv) sensitivity onboard aircraft with varying cabin pressure and environmental conditions. The analyzer is based on Wavelength-Scanned Cavity Ring Down Spectroscopy (WS-CRDS), a time-based measurement utilizing a near-infrared laser to measure a spectral signature of the molecule. Gas is circulated in an optical measurement cavity with an effective path length of up to 20 kilometers. A patented, high-precision wavelength monitor makes certain that only the spectral feature of interest is being monitored, greatly reducing the analyzer’s sensitivity to interfering gas species, and enabling ultra-trace gas concentration measurements even if there are other gases present. As a result, the analyzer maintains high linearity, precision, and accuracy over changing environmental conditions with minimal calibration required.

TOGA measures volatile organic compounds (VOCs). TOGA was deployed with an Agilent quadrupole mass spectrometer from 2006 through 2018. Since 2019, the TOGA has been equipped with a TOFWERK high-resolution time-of-flight (HR-TOF) mass spectrometer detector (TOGA-TOF). Specific data will be obtained for radical precursors, tracers of anthropogenic and biogenic activities, tracers of urban and biomass combustion emissions, tracers of ocean emissions, products of oxidative processing, precursors to aerosol formation, and compounds important for aerosol modification and transformation. TOGA measures a wide range of VOCs with high sensitivity (low to sub-ppt), frequency (2 minutes or better), accuracy (20% or better), and precision (<3%). Over 100 species are routinely measured throughout the troposphere and lower stratosphere from the surface to 16 km or higher. See table for list of VOCs that have been quantified using TOGA and TOGA-TOF. The TOGA-TOF is contained in a dual extended HIAPER rack, weighs approximately 225 kg and consumes ~1 kW of power. The major components of the instrument are the inlet, cryogenic preconcentrator, gas chromatograph, time-of-flight mass spectrometer detector, zero air/calibration system, and the control/data acquisition system. All processes and data acquisition are computer controlled.

The UHSAS is an optical-scattering, laser-based aerosol particle spectrometer for sizing particles in the 0.06 – 1 μm range. The instrument counts particles in up to 100 user-specified sizing bins, with a resolution as fine as 1 nm/bin. This high sensitivity makes the UHSAS ideal for aerosol research and filter testing.

A laser illuminates particles, which scatter light that is then collected by two pairs of Mangin optics. One pair of optics images onto a highly sensitive avalanche photodiode (APD) for detecting the smallest particles. The other pair images onto a low-gain PIN photodiode for detecting particles in the larger size range of the instrument. Each detector is amplified in a current-to-voltage stage that feeds into the analog electronics system. The amplification allows the system to detect particles as small as 60 nm.

The Unmanned Aircraft Systems (UAS) Chromatograph for Atmospheric Trace Species (UCATS) was designed and built for autonomous operation on remotely piloted aircraft, but has also been used on manned aircraft. It uses chromatography to separate atmospheric trace gases along narrow heated columns, followed by precise and accurate detection with electron capture detectors. There are currently three chromatography channels on UCATS, which measure nitrous oxide (N2O) and sulfur hexafluoride (SF6); CFC-11, CFC-12, CFC-113, and halon 1211; and chloroform (CHCl3) and carbon tetrachloride. On an earlier version of UCATS, with only two channels, we also measured methane, hydrogen, and carbon monoxide, along with N2O and SF6. In addition, there is a small ozone instrument and a tunable diode laser instrument for water vapor. Gas is pumped into the instruments from an inlet outside the aircraft, measured, and vented. UCATS has flown on the Altair UAS, the GV during HIPPO, the NASA Global Hawk UAS during the Global Hawk Pacific (GloPac) and ATTREX missions, where a record was set for the longest duration research flight (more than 28 hours), the DC-8 for ATom, and the ER-2 for DCOTSS. UCATS is relatively lightweight and compact, making it ideal for smaller platforms, but it is easily adaptable to a mid-size platform like the GV or Global Hawk. The data are used to measure sources and sinks of trace gases involved in climate and air quality, as well as transport through the atmosphere.

UCATS is three different instruments in one enclosure:

1. 3-channel (formerly 2-channel, up until 2020) gas chromatograph (GC)
2. Dual-beam ozone photometer (OZ)
3. Tunable diode laser (TDL) spectrometer for water vapor (WV)

Ozone (O3) in the lower stratosphere (LS) is responsible for absorbing much of the biologically damaging ultraviolet (UV) radiation from the sunlight, and thus plays a critical role in protecting Earth's environment. By absorbing UV light, O3 heats the surrounding air, leading to the vertical stratification and dynamic stability that define the stratosphere. Manmade halogen compounds, such as CFCs, cause significant damage to the O3 layer in the LS and lead to the formation of the Antarctic ozone hole. Accurate measurement of O3 in the LS is the first step toward understanding and protecting stratospheric O3. The Ozone Photometer was designed specifically for autonomous, precise, and accurate O3 measurements in the upper troposphere and lower stratosphere (UT/LS). Flown for thousands of hours onboard the NASA ER-2, NASA WB-57, and NSF GV high-altitude aircraft, this instrument has played a key role in improving our understanding of O3 photochemistry in the UT/LS. Furthermore, its accurate data has been used, and continues to be highly sought after, for satellite validation, and studies of radiation balance, stratosphere-troposphere exchange, and air parcel mixing. Contacts: Ru-Shan Gao, David Fahey, Troy Thornberry, Laurel Watts, Steve Ciciora