The Cross-track Infrared Sounder (CrIS) on board the Suomi National Polar-Orbiting Partnership (S-NPP) Satellite, NOAA-20, and future Joint Polar Satellite System (JPSS) satellites J2 to J4 provide the hyperspectral infrared observations for profiling atmospheric temperature, moisture and greenhouse gases globally. In this study, the J2 CrIS prelaunch spectral calibration parameters including detector focal plane geometry (FOV size and offset angles, referred to as instrument line shape (ILS)) and Neon lamp effective wavelength are derived from the thermal vacuum (TVAC) gas cell test data. These derived parameters are evaluated using the spectral cross-correlation method by comparing with the simulated spectral lines from the line-by-line radiative transfer model (LBLRTM).

Spectra of the earth's thermal emission as measured by the Atmospheric InfraRed Sounder (AIRS), Cross-track Infrared Sounder (CrIS), and Infrared Atmospheric Sounding Interferometer (IASI) hyperspectral sounders are becoming a significant part of the long-term climate record. These instruments have broadly similar spatial sampling, spectral resolution, and band spans. However, the spectral response functions differ in detail, leading to significant differences in observed spectra. To address this, we translate channel radiances from one sounder to another, including simulation of the response functions of the translation target. We make regular use of such translations from AIRS to CrIS and IASI to CrIS and have implemented and tested IASI-to-AIRS and CrIS-to-AIRS translations as well. Our translation from AIRS to CrIS has some novel features. AIRS is a grating spectrometer with a distinct response function for each channel, whereas CrIS is a Michaelson interferometer with a sinc response function after calibration and corrections. We use our detailed knowledge of the AIRS spectral response functions to deconvolve AIRS channel radiances to a resolution-enhanced intermediate representation. This is reconvolved to CrIS or other instrument specifications. The resulting translation is shown to be more accurate than interpolation or regression.

The two main elements of the Atmospheric Infrared Sounder radiative transfer algorithm (AIRS-RTA) are described in this paper: 1) the fast parameterization of the atmospheric transmittances that are used to perform the AIRS physical retrievals and 2) the spectroscopy used to generate the parameterized transmittances. We concentrate on those aspects of the spectroscopy that are especially relevant for temperature and water vapor retrievals. The AIRS-RTA is a hybrid model in that it parameterizes most gases on a fixed grid of pressures, while the water optical depths are parameterized on a fixed grid of water amounts. Water vapor, ozone, carbon monoxide, and methane profiles can be varied, in addition to the column abundance of carbon dioxide.

We investigate ways in which UIO-based conformance testing can fail to catch faults, including single and multiple faults, faults with extra or missing states, and faults at both the test sequence and subsequence levels. Given a particular error and test method, the error is masked if it is not detected by the test method. Many forms of fault masking are possible, and all test methods we have considered exhibit some forms of masking. Faults captured at the test subsequence level may become masked at the sequence level, and vice versa. Fault masking has been used to argue relative merits of various testing methods. Because of the pervasiveness of masking, we cannot use masking alone to argue that one UIO-based test method is superior to another. Information about the density of masked faults among all faults is needed to evaluate a test method.>

The authors consider a protocol specification represented as a fully specified Mealy automata, and the problem of testing an implementation for conformance to such a specification. No single sequence-based test can be completely reliable, if one allows for the possibility of an implementation with an unknown number of extra states. They define a hierarchy of test sequences, parameterized by the length of behaviors under test. For the reset method of conformance testing, they prove that the hierarchy has the property that any fault detected by test i is also detected by test i+1, and show that this sequence of tests converges to a reliable conformance test. For certain bridge sequence methods for constructing test sequences, this result does not always hold. In experiments with several specifications, they observe that given a small number of extra states in an implementation, the sequence of tests converge to a total fault coverage for small values of i, for both reset and bridge sequence methods. They also observe that the choice of characterizing sequence has less effect on fault coverage than the choice of behavior length or number of extra states in the implementation.>