Matthew G. Kowalewski

Ozone monitoring instrument calibration

The Ozone Monitoring Instrument (OMI) was launched on July 15, 2004 on the National Aeronautics and Space Administrations Earth Observing System Aura satellite. The OMI instrument is an ultraviolet-visible imaging spectrograph that uses two-dimensional charge-coupled device detectors to register both the spectrum and the swath perpendicular to the flight direction with a 115/spl deg/ wide swath, which enables global daily ground coverage with high spatial resolution. This paper presents the OMI design and discusses the main performance and calibration features and results.

Characterization of errors in the use of integrating-sphere systems in the calibration of scanning radiometers

Laboratory measurements were performed to characterize the geometrical effects in the calibration of the NASAs cloud absorption radiometer (CAR). The measurements involved three integrating sphere sources (ISSs) operated at different light levels and experimental setups to determine radiance variability. The radiance gradients across the three ISS apertures were 0.2%-2.6% for different visible, near-infrared, and shortwave infrared illumination levels but <15% in the UV. Change in radiance with distance was determined to be 2%-20%, being highest in the UV. Radiance variability due to the edge effects was found to be significant; as much as 70% due to the sphere aperture and <10% due to the CAR telescopes secondary mirror.

Performance and Calibration of the Nadir Suomi-NPP Ozone Mapping Profiler Suite From Early-Orbit Images

The Ozone Mapping Profiler Suite (OMPS) was launched aboard the Suomi National Polar-orbiting Partnership spacecraft on October 28, 2011. A successful thorough Early Orbit Checkout (EOC) enabled the current Intensive Calibration and Validation stage. We present our analyses and results of OMPS Nadir early-orbit sensor performance and calibration. We collected and analyzed data from both nominal and diagnostic activities via orbital measurements of detector dark current, sensor linearity, and solar irradiance. Our results demonstrate that the OMPS Nadir sensors smoothly transitioned from ground to orbit by meeting or exceeding sensor level requirements. The orbital measurements agree with the predicted values determined during the prelaunch calibration and characterization of OMPS. Our results also suggest that the effects of charge coupled device (CCD) lattice damage due to energetic particle hits onto the CCD must be accounted for in the dark current calibration.

Remote sensing capabilities of the Airborne Compact Atmospheric Mapper

The Airborne Compact Atmospheric Mapper (ACAM) was designed and built at the NASA Goddard Space Flight Center (GSFC) as part of an effort to provide cost-effective remote sensing observations of tropospheric and boundary layer pollutants and visible imagery for cloud and surface information. ACAM has participated in three campaigns to date aboard NASAs Earth Science Project Office (ESPO) WB-57 aircraft. This paper provides an overview of the instrument design and summarizes its ability to determine the minimal measurable slant-column concentration of nitrogen dioxide (NO2) as well as exploring the calibration stability of commercially available miniature spectrometers.

The on-ground calibration of the ozone monitoring instrument from a scientific point of view

The Ozone Monitoring Instrument is an UV-Visible imaging spectrograph using two-dimensional CCD detectors to register both the spectrum and the swath perpendicular to the flight direction. This allows having a wide swath (114 degrees) combined with a small ground pixel (nominally 13 x 24 km2). The instrument is planned for launch on NASA’s EOS-AURA satellite in January 2004. The on-ground calibration measurement campaign of the instrument was performed May-October 2002, data is still being analyzed to produce the calibration key data set. The paper highlights selected topics from the calibration campaign, the radiometric calibration, spectral calibration including a new method to accurately calibrate the spectral slitfunction and results from the zenith sky measurements and gas cell measurements that were performed with the instrument.

Earth Observations from DSCOVR EPIC Instrument

The NOAA Deep Space Climate Observatory (DSCOVR) spacecraft was launched on February 11, 2015, and in June 2015 achieved its orbit at the first Lagrange point or L1, 1.5 million km from Earth towards the Sun. There are two NASA Earth observing instruments onboard: the Earth Polychromatic Imaging Camera (EPIC) and the National Institute of Standards and Technology Advanced Radiometer (NISTAR). The purpose of this paper is to describe various capabilities of the DSCOVR/EPIC instrument. EPIC views the entire sunlit Earth from sunrise to sunset at the backscattering direction (scattering angles between 168.5° and 175.5°) with 10 narrowband filters: 317, 325, 340, 388, 443, 552, 680, 688, 764 and 779 nm. We discuss a number of pre-processingsteps necessary for EPIC calibration including the geolocation algorithm and the radiometric calibration for each wavelength channel in terms of EPIC counts/second for conversion to reflectance units. The principal EPIC products are total ozone O3amount, scene reflectivity, erythemal irradiance, UV aerosol properties, sulfur dioxide SO2 for volcanic eruptions, surface spectral reflectance, vegetation properties, and cloud products including cloud height. Finally, we describe the observation of horizontally oriented ice crystals in clouds and the unexpected use of the O2 B-band absorption for vegetation properties.

High-resolution NO2 observations from the Airborne Compact Atmospheric Mapper: Retrieval and validation

Nitrogen dioxide (NO2) is a short-lived atmospheric pollutant that serves as an air quality indicator, and is itself a health concern. The Airborne Compact Atmospheric Mapper (ACAM) was flown on board the NASA UC-12 aircraft during the DISCOVER-AQ Maryland field campaign in July 2011. The instrument collected hyperspectral remote sensing measurements in the 304-910 nm range, allowing day-time observations of several tropospheric pollutants, including nitrogen dioxide (NO2), at an unprecedented spatial resolution of 1.5 × 1.1 km2. Retrievals of slant column abundance are based on the Differential Optical Absorption Spectroscopy (DOAS) method. For the Air Mass Factor (AMF) computations needed to convert these retrievals to vertical column abundance, we include high resolution information for the surface reflectivity by using bidirectional reflectance distribution function (BRDF) data from the Moderate Resolution Imaging Spectroradiometer (MODIS). We use high-resolution simulated vertical distributions of NO2 from the Community Multiscale Air Quality (CMAQ) and Global Modeling Initiative (GMI) models to account for the temporal variation in atmospheric NO2 to retrieve middle- and lower-tropospheric NO2 columns (NO2 below the aircraft). We compare NO2 derived from ACAM measurements with in-situ observations from NASAs P-3B research aircraft, total column observations from the ground-based Pandora spectrometers, and tropospheric column observations from the space-based OMI instrument. The high-resolution ACAM measurements not only give new insights into our understanding of atmospheric composition and chemistry through observation of sub-sampling variability in typical satellite and model resolutions, but they also provide opportunities for testing algorithm improvements for forthcoming geostationary air quality missions.

Deriving aerosol parameters from absolute UV sky radiance measurements using a Brewer double spectrometer

A Brewer MKIII double spectrophotometer has been modified to measure direct sun and sky radiance from 303nm to 363nm for the purpose of measuring aerosol optical depth, Angstrom parameter, and single scattering albedo. Results from a detailed instrument calibration showed that there is a temperature dependence of -0.3% per degree Celsius, the field of view was 2.6° full width half maximum, and the wavelength calibration was accurately determined using a dye-LASER. Using both integrating sphere and lamp-diffuser plate combinations, absolute diffuse radiometric calibration was performed and converted into direct calibration using the measured field of view. Aerosol optical depth and Angstrom parameter were measured on 4 clear sky days in June 2003 at Greenbelt, Maryland and compared to AERONET-data at the same location. The average difference in the aerosol optical depth at 340nm was smaller than 0.02. A depolarizing element was inserted in the Brewers optical path to reduce the very pronounced polarization sensitivity, and additional polarized filters were added to explore the possibility to obtain additional aerosol information. Because of a defect in the depolarizer, the current residual polarization is 5%, which has to be reduced to less than 1% to derive additional aerosol parameters from sky radiance measurements.

Remote sensing capabilities of the GEO-CAPE airborne simulator

The Geostationary Coastal and Air Pollution Events (GEO-CAPE) Airborne Simulator (GCAS) was designed and built at the NASA Goddard Space Flight Center (GSFC) as a technology demonstration instrument for the atmospheric science study group of GEO-CAPE and potential validation instrument for NASA’s Tropospheric Emissions: Monitoring Pollution (TEMPO) mission. GCAS was designed to make high altitude remote sensing observations of tropospheric and boundary layer pollutants, coastal and ocean water leaving radiances, and visible imagery for cloud and surface information. The instrument has participated in one flight campaign in Houston, TX as part of the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) in September 2013. An overview of the instrument’s design, characterization, and preliminary slant column retrievals of nitrogen dioxide (NO2) and ozone (O3) during the DISCOVER-AQ campaign will be provided in this paper.

EOS-aura Ozone Monitoring Instrument in-flight performance and calibration

In-flight performance and calibration results of the Ozone Monitoring Instrument OMI, successfully launched on 15 July 2004 on the EOS-AURA satellite, are presented and discussed. The radiometric calibration in comparison to the high-resolution solar irradiance spectrum from the literature convolved with the measured spectral slit function is presented. A correction algorithm for spectral shifts originating from inhomogeneous ground scenes (e.g. clouds) is discussed. Radiometric features originating from the on-board reflection diffusers are discussed, as well as the accuracy of the calibration of the instruments viewing properties. It is shown that the in-flight performance of both CCD detectors shows evidence of particle hits by trapped high-energetic protons, which results in increased dark currents and increase in the Random Telegraph Signal (RTS) behaviour.