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The Thermal and Near-Infrared Sensor for Carbon Observation Fourier-Transform Spectrometer-2 (TANSO-FTS-2) onboard the Japanese Greenhouse gases Observing SATellite-2 (GOSAT-2) observes a wide spectral region of the atmosphere, from the ShortWave-InfraRed (SWIR) to longwave Thermal InfraRed radiation (TIR) with 0.2cm-1 spectral intervals. The TANSO-FTS-2 has operated nominally since Feb 2019, and the atmospheric radiance spectra it has acquired have been released to the public. This paper describes an updated model for spectral radiance calibration and its validation. The model applies to the version 210210 TIR products of the TANSO-FTS-2 and integrates polarization sensitivity correction for the internal optics and the scanner mirror thermal emission. These correction parameters are characterized by an optimization which depends on the difference between the spectral radiance of the TANSO-FTS-2 and coincident nadir observation data from the Infrared Atmospheric Sounding Interferometer (IASI) on METOP-B. To validate the updated spectral radiance product against other satellite products, temporally and spatially coincident observation points were considered for Simultaneous Nadir Overpass (SNO) from February 2019 to March 2021 from the Atmospheric Infrared Sounder (AIRS) on Aqua, IASI on METOP-B, and TANSO-FTS on GOSAT. The agreement of brightness temperatures between the TANSO-FTS-2 and AIRS and IASI was better than 0.3 K (1𝜎) from 180 K to 330 K for the 680 cm-1 CO2 channel. The brightness temperatures between the TANSO-FTS-2 and TANSO-FTS of version v230231, which implemented a new polarization reflectivity of the pointing mirror and was released in June 2021, generally agree from 220 K to 320 K. However, there is a discrepancy at lower brightness temperatures, pronounced for CO2 channels at high latitudes. To characterize the spectral radiance bias for along-track and cross-track angles, a 2-Orthogonal Simultaneous Off-Nadir Overpass (2O-SONO) is now done for the TANSO-FTS-2 and IASI, the TANSO-FTS-2 and AIRS, and the TANSO-FTS-2 and TANSO-FTS. The 2O-SONO comparison results indicate that the TIR product for the TANSO-FTS-2 has a bias that exceeds 0.5 K in the CO2 channel for scenes with forward and backward viewing angles greater than 20°. These multi satellite sensor and multi-angle comparison results suggest that the calibration of spectral radiance for the TANSO-FTS-2 TIR, version v210210, is superior to that of the previous version in its consistency of multi-satellite sensor data. In addition, the paper identifies the remaining challenging issues in current TIR products. [ABSTRACT FROM AUTHOR]

A global database of infrared (IR) land surface emissivity is introduced to support more accurate retrievals of atmospheric properties such as temperature and moisture profiles from multispectral satellite radiance measurements. Emissivity is derived using input from the Moderate Resolution Imaging Spectroradiometer (MODIS) operational land surface emissivity product (MOD11). The baseline fit method, based on a conceptual model developed from laboratory measurements of surface emissivity, is applied to fill in the spectral gaps between the six emissivity wavelengths available in MOD11. The six available MOD11 wavelengths span only three spectral regions (3.8-4, 8.6, and 11-12 [micro]m), while the retrievals of atmospheric temperature and moisture from satellite IR sounder radiances require surface emissivity at higher spectral resolution. Emissivity in the database presented here is available globally at 10 wavelengths (3.6, 4.3, 5.0, 5.8, 7.6, 8.3, 9.3, 10.8, 12.1, and 14.3 [micro]m) with 0.05[degrees] spatial resolution. The wavelengths in the database were chosen as hinge points to capture as much of the shape of the higher-resolution emissivity spectra as possible between 3.6 and 14.3 [micro]m. The surface emissivity from this database is applied to the IR regression retrieval of atmospheric moisture profiles using radiances from MODIS, and improvement is shown over retrievals made with the typical assumption of constant emissivity.

The National Polar-Orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Testbed (NAST) consists of two passive collocated cross-track scanning instruments, an infrared interferometer (NAST-I) and a microwave radiometer (NAST-M), that fly onboard high-altitude aircraft such as the NASA ER-2 at an altitude near 20 km. NAST-I provides relatively high spectral resolution (0.25-[cm.sup.-1]) measurements in the 645-2700-[cm.sup.-1] spectral region with moderate spatial resolution (a linear resolution equal to 13% of the aircraft altitude at nadir) cross-track scanning. We report the methodology for retrieval of atmospheric temperature and composition profiles from NAST-I radiance spectra. The profiles were determined by use of a statistical eigenvector regression algorithm and improved, as needed, by use of a nonlinear physical retrieval algorithm. Several field campaigns conducted under varied meteorological conditions have provided the data needed to verify the accuracy of the spectral radiance, the retrieval algorithm, and the scanning capabilities of this instrumentation. Retrieval examples are presented to demonstrate the ability to reveal fine-scale horizontal features with relatively high vertical resolution. OCIS codes: 010.0010, 010.1280, 280.0280.

During the period of 26 October 1989 through 6 December 1989 a unique complement of measurements was made at the University of Wisconsin - Madison to study the radiative properties of cirrus clouds. Simultaneous observations were obtained from a scanning lidar, two interferometers, a high spectral resolution lidar, geostationary and polar orbiting satellites, radiosonde launches, and a whole-sky imager. This paper describes the experiment, the instruments deployed, and, as an example, the data collected during one day of the experiment.

The Japanese Greenhouse gases Observing SATellite-2 (GOSAT-2), in orbit since 29 October 2018, follows up the GOSAT mission, itself in orbit since 23 January 2009. GOSAT-2 monitors carbon dioxide and methane in order to increase our understanding of the global carbon cycle. It simultaneously measures carbon monoxide emitted from fossil fuel combustion and biomass burning, and permits identification of the amount of combustion-related carbon. To do this, the satellite utilizes the Thermal and Near Infrared Sensor for Carbon Observation Fourier-Transform Spectomer-2 (TANSO-FTS-2). This spectrometer detects gas absorption spectra of solar radiation reflected from the Earth's surface in the shortwave-infrared (SWIR) region as well as the emitted thermal infrared radiation (TIR) from the ground and the atmosphere. TANSO-FTS-2 can measure the oxygen A band (0.76 um), weak and strong CO2 bands (1.6 um and 2.0 um), weak and strong CH4 bands (1.6 um and 2.3 um), a weak CO band (2.3 um), a mid-wave TIR band (5.5-8.4 um) and a long-wave TIR band (8.4-14.3 um) with 0.2 cm-1 spectral resolution. TANSO-FTS-2 is equipped with a solar diffuser target, a monochromatic light source, and a black body for spectral radiance calibration. These calibration sources permit characterization of time-dependent instrument changes in orbit. The onboard-recalibrated instrumental parameters are considered in operational level-1 processing and released as TANSO-FTS-2 level-1 version 102102 products, which were officially released on 25 May 2020. This paper provides an overview of the TANSO-FTS-2 instrument, the level-1 processing, and the first-year on-orbit performance. To validate the spectral radiance calibration during the first year of operation, the spectral radiance of the version 102102 product is compared at temporally coincident and spatially collocated points from February 2019 to March 2020 with TANSO-FTS on GOSAT for SWIR, and with AIRS on AQUA and IASI on METOP-B for TIR. The spectral radiances measured by TANSO-FTS and TANSO-FTS-2 agree within 2 % of the averaged bias and 0.5 % standard deviation for SWIR bands. The agreement of brightness temperature between TANSO-FTS-2 and AIRS, IASI, is better than 0.5 % in the range from 220 K to 320 K. GOSAT-2 not only provides seamless global CO2 and CH4 observation but also observes local emissions and uptake with an additional CO channel, fully customized sampling patterns, higher signal-to-noise ratios, and wider pointing angles than GOSAT. [ABSTRACT FROM AUTHOR]