The Radiance Differences between Wavelength and Wavenumber Spaces in Convolving Hyperspectral Infrared Sounder Spectrum to Broadband for Intercomparison

Converting the hyperspectral infrared (IR) sounder radiance spectrum to broadband is a common approach for intercomparison/calibration. Usually the convolution is performed in wavenumber space. However, numerical experiments presented here indicate that there are brightness temperature (BT) differences between wavelength and wavenumber spaces in convolving hyperspectral IR sounder spectrum to broadband. The magnitudes of differences are related to the spectral region and the width of the spectral response functions (SRFs). In addition, the central wavelength and central wavenumber should be determined separately in wavelength and wavenumber spaces, respectively; they cannot be converted to each other directly for broadband BT calculations. There exist BT differences (BTDs) between interpolating the resolution of SRF to hyperspectral IR sounder spectrum, and vice versa, for convolution. This study provides clarity on convolution, central wavelength/wavenumber determination, and spectral resolution matching between broadband SRFs and hyperspectral IR sounder radiances for intercomparison/calibration

COBE's search for structure in the Big Bang

The launch of Cosmic Background Explorer (COBE) and the definition of Earth Observing System (EOS) are two of the major events at NASA-Goddard. The three experiments contained in COBE (Differential Microwave Radiometer (DMR), Far Infrared Absolute Spectrophotometer (FIRAS), and Diffuse Infrared Background Experiment (DIRBE)) are very important in measuring the big bang. DMR measures the isotropy of the cosmic background (direction of the radiation). FIRAS looks at the spectrum over the whole sky, searching for deviations, and DIRBE operates in the infrared part of the spectrum gathering evidence of the earliest galaxy formation. By special techniques, the radiation coming from the solar system will be distinguished from that of extragalactic origin. Unique graphics will be used to represent the temperature of the emitting material. A cosmic event will be modeled of such importance that it will affect cosmological theory for generations to come. EOS will monitor changes in the Earth's geophysics during a whole solar color cycle