NASA - National Aeronautics and Space Administration

MOPITT (Measurements Of Pollution In The Troposphere) is a carbon monoxide and methane remote sounder launched in 1999 with the Terra spacecraft. An aircraft replica (MOPITT-A) was developed at the University of Toronto to perform validation of MOPITT radiances as well as small-scale pollution studies. MOPITT-A is based on the engineering model of MOPITT, modified for flight in NASA's ER-2 research aircraft. The instrument was first tested over California from the NASA Dryden Flight Research Center in July 2000.

The Large Area Collectors are flown on the ER-2 in support of the NASA-Johnson Space Flight Center Cosmic Dust Program. The LACs are used to collect comparatively unaltered cosmic dust from the stratosphere at ER-2 flight altitudes of 65,000 feet and above. Sufficient quantities of extraterrestrial materials are collected to allow chemical and mineralogical compositions of individual particles to be determined. Study of these materials whose sources may be comets, asteroid collisions, planetary impacts, and meteorite ablation provide valuable information about the origin and the history of the solar system.

The Configurable Scanning Submillimeter-wave Instrument/Radiometer (CoSSIR) is an airborne, 16-channel total power imaging radiometer that was primarily developed for the measurement of ice clouds. CoSSIR was first flown in CRYSTAL-FACE (Cirrus Regional Study of Tropical Anvils and Cirrus Layers – Florida Area Cirrus Experiment) in 2002, followed by CR-AVE (Costa Rica Aura Validation Experiment) in 2006, and TC4 (Tropical Composition, Cloud and Climate Coupling Experiment) in 2007. For CRYSTAL-FACE and CR-AVE, CoSSIR had 15 channels centered at 183±1, 183±3, 183±6.6, 220, 380±.8, 380±1.8, 380±3.3, 380±6.2, 487.25±0.8, 487.25±1.2, 487.25±3.3, and 640 GHz, where the three 487 GHz channels were dual-polarized (vertical and horizontal). For TC4, the 487 GHz channels were removed, 640 GHz was made dual-polarized, and an 874 GHz channel was added.

In 2022, CoSSIR was completely updated with new receivers under funds through the Airborne Instrument Technology Transition (AITT) to improve measurement accuracy and enable CoSSIR to be a stand-alone sensor that no longer shared a scan pedestal with its millimeter-wave sibling, CoSMIR. Frequencies were selected for CoSSIR to optimize snow and cloud ice profiling, and dual-polarization capability was added for all frequencies to provide information on particle size and shape. New channels are centered at 170.5, 177.3, 180.3, 182.3, 325±11.3, 325±3.55, 325±0.9, and 684 GHz. The updated CoSSIR flew for the first time in the 2023 deployment of IMPACTS (Investigation of Microphysics and Precipitation for Atlantic Coast Threatening Snowstorms) and operated nominally for the entire campaign, collecting a wide variety of observations over different types of clouds and precipitation.

All the receivers and radiometer electronics are housed in a small cylindrical scan head (21.5 cm in diameter and 28 cm in length) that is rotated by a two-axis gimbaled mechanism capable of generating a wide variety of scan profiles. Two calibration targets, one maintained at ambient (cold) temperature and another heated to a hot temperature of about 323 K, are closely coupled to the scan head and rotate with it about the azimuth axis. Radiometric signals from each channel are sampled at 10 ms intervals. These signals and housekeeping data are fed to the main computer in an external electronics box.

CoSMIR is an airborne, 9-channel total power imaging radiometer that was originally developed for the calibration/validation of the Special Sensor Microwave Imager/Sounder (SSMIS). When first completed in 2003, the system had four receivers that measured horizontally polarized radiation at 50.3, 52.8, 53.6, 150, 183.3±1, 183.3±3, and 183.3±6.6 GHz, and dual-polarized (vertical and horizontal) radiation at 91.665 GHz. Following the SSMIS calibration/validation efforts, CoSMIR served as the airborne high-frequency simulator for the Global Precipitation Measurement (GPM) Microwave Imager (GMI) in four GPM field campaigns from 2011 to 2015. The channels were modified slightly to match the GMI channels more closely: 53.6 was removed, 91.655 changed to 89.0, 150 changed to 165.5 and made dual-polarized, and 183.3±6.6 changed to 183.3±7. In 2020 and 2022, CoSMIR flew on the NASA ER-2 in IMPACTS (Investigation of Microphysics and Precipitation for Atlantic Coast Threatening Snowstorms). CoSMIR’s submillimeter-wave sibling (CoSSIR) flew in the third deployment of IMPACTS in 2023.

CoSMIR is currently undergoing modifications through Decadal Survey Incubation (DSI) funds to become CoSMIR-Hyperspectral (CoSMIR-H). CoSMIR-H will retain the current 89 and 165 GHz dual-polarized channels and switch out the 50 and 183 GHz receivers for hyperspectral receivers spanning 50-58 GHz and 175-191 GHz, providing thousands of channels at these frequencies instead of the current two 50-GHz and three 183-GHz channels. Test flights of CoSMIR-H are tentatively scheduled for Summer 2024.

All the CoSMIR receivers and radiometer electronics are housed in a small cylindrical scan head (21.5 cm in diameter and 28 cm in length) that is rotated by a two-axis gimbaled mechanism capable of generating a wide variety of scan profiles. Two calibration targets, one maintained at ambient (cold) temperature and another heated to a hot temperature of about 323 K, are closely coupled to the scan head and rotate with it about the azimuth axis. Radiometric signals from each channel are sampled at 10 ms intervals. These signals and housekeeping data are fed to the main computer in an external electronics box.

Clouds are a key element in the global hydrological cycle, and they have a significant role in the Earth’s energy budget through its influence on radiation budgets. Climate model simulations have demonstrated the importance of clouds in moderating and forcing the global energy budget. Despite the crucial role of clouds in climate and the breadth of our current knowledge, there are still many unanswered details. An improved understanding of the radiative impact of clouds on the climate system requires a comprehensive view of clouds that includes their physical dimensions, vertical and horizontal spatial distribution, detailed microphysical properties, and the dynamical processes producing them. However, the lack of fine-scale cloud data is apparent in current climate model simulations.

The Cloud Radar System (CRS) is a fully coherent, polarimeteric Doppler radar that is capable of detecting clouds and precipitation from the surface up to the aircraft altitude in the lower stratosphere. The radar is especially well suited for cirrus cloud studies because of its high sensitivity and fine spatial resolution.

The Cloud Physics Lidar, or CPL, is a backscatter lidar designed to operate simultaneously at 3 wavelengths: 1064, 532, and 355 nm. The purpose of the CPL is to provide multi-wavelength measurements of cirrus, subvisual cirrus, and aerosols with high temporal and spatial resolution. Figure 1 shows the entire CPL package in flight configuration. The CPL utilizes state-of-the-art technology with a high repetition rate, low pulse energy laser and photon-counting detection. Vertical resolution of the CPL measurements is fixed at 30 m; horizontal resolution can vary but is typically about 200 m. The CPL fundamentally measures range-resolved profiles of volume 180-degree backscatter coefficients. From the fundamental measurement, various data products are derived, including: time-height crosssection images; cloud and aerosol layer boundaries; optical depth for clouds, aerosol layers, and planetary boundary layer (PBL); and extinction profiles. The CPL was designed to fly on the NASA ER-2 aircraft but is adaptable to other platforms. Because the ER-2 typically flies at about 65,000 feet (20 km), onboard instruments are above 94% of the earth’s atmosphere, allowing ER-2 instruments to function as spaceborne instrument simulators. The ER-2 provides a unique platform for atmospheric profiling, particularly for active remote sensing instruments such as lidar, because the spatial coverage attainable by the ER-2 permits studies of aerosol properties across wide regions. Lidar profiling from the ER-2 platform is especially valuable because the cloud height structure, up to the limit of signal attenuation, is unambiguously measured.

DCS is a 16-megapixel color infrared digital camera system, providing high resolution imagery for mission tracking purposes Geo-referenced image products may be generated, when used in conjunction with a POS-AV system.

EDOP is an X-band (9.6 GHz) Doppler radar nose-mounted in the ER-2. The instrument has two antennas: one nadir-pointing with pitch stabilization, and the other forward pointing. The general objectives of EDOP are the measurement of the vertical structure of precipitation and air motions in mesoscale precipitation systems and the development of spaceborne radar algorithms for precipitation estimation.

EDOP measures high-resolution time-height sections of reflectivity and vertical hydrometeor velocity (and vertical air motion when the hydrometeor fall speed and aircraft motions are removed). An additional capability on the forward beam permits measurement of the linear depolarization ratio (LDR) which provides useful information on orientation of the hydrometeors (i.e., the canting angle), hydrometeor phase, size, etc. The dual beam geometry has advantages over a single beam. For example, along-track horizontal air motions can be calculated by using the displacement of the ER-2 to provide dual Doppler velocities (i.e., forward and nadir beams) at a particular altitude.

EDOP is designed as a turn-key system with real-time processing on-board the aircraft. The RF system consists of a coherent frequency synthesizer which generates the transmitted and local oscillator frequencies used in the system, a pulse modulated (0.5 to 2.0 micro-second pulse) high gain 20 kW Traveling Wave Tube Amplifier which is coupled through the duplexer to the antenna, and the receiver which is comprised of a low-noise (~1dB) GaAs preamplifier followed by a mixer for each of the receive channels. The composite system generates a nadir oriented beam with a co-polarized receiver and a 350 forward directed beam with co- and cross- polarized receivers. The antenna design consists of two separate offset-fed parabolic antennas, with high polarization isolation feed horns, mounted in the nose radome of the ER-2. The antennas are 0.76 m diameter resulting in a 30 beamwidth and a spot size of about 1.2 km at the surface (assuming a 20 km aircraft altitude). The two beams operate simultaneously from a single transmitter.

The FCAS II sizes particles in the approximate diameter range from 0.07 mm to 1 mm. Particles are sampled from the free stream with a near isokinetic sampler and are transported to the instrument. They are then passed through a laser beam and the light scattered by individual particles is measured. Particle size is related to the scattered light. The data reduction for the FCAS II takes into account the water which is evaporated from the particle in sampling and the effects of anisokinetic sampling (Jonsson et al., 1995).

The FCAS II and its predecessors have provided accurate aerosol size distribution measurements throughout the evolution of the volcanic cloud produced by the eruption of Mt. Pinatubo. (Wilson et al., 1993). Near co-incidences between FCAS II and SAGE II measurements show good agreement between optical extinctions calculated from FCAS size distributions and extinctions measured by SAGE II.

Accuracy: The instrument has been calibrated with monodisperse aerosol carrying a single charge. The FCAS III and the electrometer agree to within 10%. Sampling errors may increase the uncertainty but a variety of comparisons suggests that total uncertainties in aerosol surface are near 30% (Jonsson, et al., 1995).

Precision: The precision equals 1/ÖN where N is the number of particles counted. In many instances the precision on concentration measurements may reach 7% for 0.1 Hz data. If better precision is desired, it is necessary only to accumulate over longer time intervals.

Response Time: Data are processed at 0.1 Hz. However, the response time depends upon the precision required to detect the change in question. Small changes may require longer times to detect. Plume measurements may be processed with 1 s resolution.

Weight: Approximately 50 lbs.