Simulation of CrIS Radiances Accounting for Realistic Properties of the Instrument Responsivity That Result in Spectral Ringing Features

This paper provides a procedure for the simulation of radiances from the U. S. National Oceanic and Atmospheric Administration (NOAA) Cross-track Infrared Sounder (CrIS) Fourier Transform Spectrometer to include spectral ringing effects caused by the finite-band, non-flat instrument spectral response to incident radiation. A simulation using a line-by-line radiative transfer model is performed to illustrate the magnitude of the effect and to indicate which spectral channels are likely to be impacted. Comparisons with CrIS observations are made to show that for most channels this effect is negligibly small compared to errors in the radiative transfer calculations but for the longwave edge of the CrIS longwave band and a few other regions, the brightness temperature ringing is significant. While the ringing artifact described in this paper may appear to be removed when Hamming apodization is applied, as is done for the assimilation of CrIS data into Numerical Weather Prediction (NWP) models, it is still present, and its influence reappears if the spectral correlation induced by apodization is properly handled to preserve the information content that derives from high spectral resolution. Inclusion of the instrument responsivity in calculated spectra to properly mimic the observed spectra as defined here eliminates artifacts from this type of ringing. Users of CrIS radiances should consider whether this effect is important for their application

Far Infrared Emissivity Estimates of Various Sample Types from the Ground-Based Absolute Radiance Interferometer

This data is published to be companion to the peer-reviewed paper submitted to Earth and Space Science named “Ground-Based Far Infrared Emissivity Measurements Using the Absolute Radiance Interferometer”. This paper describes the data collection process and emissivity derivation technique in detail. The data included here are the single channel and microwindow emissivities which have been derived from the PC-noise-filtered ARI radiance measurements from the 2022 measurement campaign

The University of Wisconsin Space Science and Engineering Center Absolute Radiance Interferometer (ARI): Instrument Overview and Radiometric Performance

Spectrally resolved thermal radiances measured from orbit with extremely high absolute accuracy (\u3c 0.1 K, k = 3, brightness temperature at scene temperature) constitute a critical observation for future climate benchmark missions. The FTS approach is well suited for the combined requirement of ultra-high accuracy and broad spectral coverage at high spectral resolution. FTS technology inherently provides broad spectral coverage with a small number of detectors, a very well defined instrument line shape (ILS) that can be easily monitored and measured, and the spectral resolution required for accurate line shape and position determination and to accurately calibrate the spectral scale using well-known atmospheric absorption lines. The challenge in the IR FTS sensor development for a climate benchmark measurement mission is to achieve this ultra-high accuracy with a design that can be flight qualified, has long design life, and is reasonably small, simple, and affordable. In this area, our approach is to make use of components with strong spaceflight heritage (direct analogs with high TRL) combined into a functional package for detailed performance testing. The required simplicity is achievable due to the large differences in the sampling and noise requirements for the benchmark climate measurement from those of the typical remote sensing infrared sounders for weather research or operations. An instrument overview and summary of the radiometric performance of the Absolute Radiance Interferometer (ARI) at the University of Wisconsin Space Science and Engineering Center (UW-SSEC) will be presented

Performance of CrIS on Suomi – NPP

This presentation will review various recent analyses and results of early checkout activities to characterize the performance of CrIS on the NPP satellite

The Heated Halo for Space-Based Blackbody Emissivity Measurement

The accuracy of radiance measurements with space-based infrared spectrometers is contingent on the quality of the calibration subsystem, as well as knowledge of its uncertainty. Upcoming climate benchmark missions call for measurement uncertainties better than 0.1 K (k=3) in radiance temperature for the detection of spectral climate signatures. Blackbody cavities impart the most accurate calibration for spaceborne infrared sensors, provided that their temperature and emissivity is traceably determined on-orbit. The On-Orbit Absolute Radiance Standard (OARS) has been developed at the University of Wisconsin to meet the stringent requirements of the next generation of infrared remote sensing instruments. It provides on-orbit determination of both traceable temperature and emissivity for calibration blackbodies. The Heated Halo is the component of the OARS that provides a robust and compact method to measure the spectral emissivity of a blackbody in situ. A carefully baffled thermal source is placed in front of a blackbody in an infrared spectrometer system, and the combined radiance of the blackbody and Heated Halo reflection is observed. Knowledge of key temperatures and the viewing geometry allow the blackbody cavity spectral emissivity to be calculated. We present the results from the Heated Halo methodology implemented with a new Absolute Radiance Interferometer (ARI), which is a prototype space-based infrared spectrometer designed for climate benchmarking. We show the evolution of the technical readiness level of this technology and we compare our findings to models and other experimental methods of emissivity determination

Update on the Validation of TES L2 Data Products

An update on the validation of Tropospheric Emission Spectrometer (TES) data products are provided