NASA - National Aeronautics and Space Administration

A solar tracking Direct beam Irradiance Airborne Spectrometer (DIAS) is used for calculation of line of sight ozone and wavelength dependent aerosol optical depths.

GAMS/LAABS is a combination of the Gas and Aerosol Measurement System (GAMS) and the Langley Airborne A-Band Spectrometer (LAABS). The instruments are optically co-aligned and use a common pointing system to track the Sun through an aircraft view port. In the field the instrument provides line-of-sight (LOS) O3, NO2, O4, and water vapor measurements using both a SAGE III-like multiple linear regression algorithm and a full spectrum algorithm. Aerosol may also be derived for ‘enhanced’ conditions including polar stratospheric clouds and optically thin cirrus. Using profile data (1-D/2-D) transformed to GAMS/LAABS LOS geometry, quick-look validation/comparison products for SAGE III, AROTAL, AATS-14, SCIAMACHY, and other instruments will be obtained. The data from GAMS/LAABS will make possible crucial evaluations of SAGE III data processing possible following deployment. These activities include SAGE III etaloning/mirror correction validation, O2 spectroscopy and forward model verification, ozone spectroscopy near the O2 A band and 940-nm water vapor features, evaluation of the relative strength of spectroscopic features (e.g., water vapor features at 600 nm and 940 nm) and altitude registration validation using oxygen measurements.

Instrument Details:

Gas and Aerosol Measurement Sensor (GAMS)

o Solar spectrometer with 1024 channels from ~ 430 to 1030 nm
o Provides measurements of LOS transmission spectra and
differential O3, H2O, O2, O4, and aerosol
o Solar imager to monitor scene homogeneity
o Focus on UV-Vis-Near-IR solar occultation only
o Designed to extend the technique into the troposphere
o Built space flight-like spectrometer, telescope, photon-to-bits
boards, & MCM (detector controller).
o COTS imager to establish imager performance requirements

Langley Airborne A-Band Spectrometer (LAABS)

• High spectral resolution (~0.035 nm) grating spectrometer with > 800
channels from ~759 to 771 nm
• Provides measurements of LOS transmission spectra for evaluation of
SAGE III O2 A-band forward model
• Originally developed to support CALIPSO (formerly PICASSO-CENA)
spaceborne A-band spectrometer
• Designed and fabricated by BATC to provide high spectral resolution
(~0.035 nm) radiance measurements in O2 A-band spectral region
(~765 nm)

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.

AATS-14 measures direct solar beam transmission at 14 wavelengths between 354 and 2139 nm in narrow channels with bandwidths between 2 and 5.6 nm for the wavelengths less than 1640 nm and 17.3 nm for the 2139 nm channel. The transmission measurements at all channels except 940 nm are used to retrieve spectra of aerosol optical depth (AOD). In addition, the transmission at 940 nm and surrounding channels is used to derive columnar water vapor (CWV) [Livingston et al., 2008]. Methods for AATS-14 data reduction, calibration, and error analysis have been described extensively, for example, by Russell et al. [2007] and Shinozuka et al. [2011]. AATS-14 measurements of spectral AOD and CWV obtained during aircraft vertical profiles can be differentiated to determine corresponding vertical profiles of spectral aerosol extinction and water vapor density. Such measurements have been used extensively in the characterization of the horizontal and vertical distribution of aerosol optical properties and in the validation of satellite aerosol sensors. For example, in the Aerosol Characterization Experiment-Asia (ACE-Asia), AATS measurements were used for closure (consistency) studies with in situ aerosol samplers aboard the NCAR C-130 and the CIRPAS Twin-Otter aircraft, and with ground-based lidar systems. In ACE-Asia, CLAMS (Chesapeake Lighthouse & Aircraft Measurements for Satellites, 2001), the Extended-MODIS-λ Validation Experiment (EVE), INTEX-A, INTEX-B, and ARCTAS, AATS results have been used in the validation of satellite sensors aboard various EOS platforms, providing important aerosol information used in the improvement of retrieval algorithms for the MISR and MODIS sensors among others.