Wide-bandwidth observations can experience substantial differences in things like atmospheric optical depth and brightness temperature across the frequency range spanned by the bandwidth. The weather data tabulated within ngehtsim can in principle be used to track these variations across the bandwidth and integrate over them, but ngehtsim currently simply uses the values appropriate for the center of the band.
Wide-bandwidth observations can experience substantial differences in things like atmospheric optical depth and brightness temperature across the frequency range spanned by the bandwidth. The weather data tabulated within ngehtsim can in principle be used to track these variations across the bandwidth and integrate over them, but ngehtsim currently simply uses the values appropriate for the center of the band.