Limits imposed on millimeter and sub-millimeter wave limb sounders by continuum emissions

MASTER SOPRANO and PIRAMHYD are scenarios for future satellite borne limb sounders investigated by the European Space Agency They are planned to operate in the millimeter and submillime ter spectral range allowing the retrieval of atmospheric mixing ratio pro les of several molecular species One criterion for the scienti c value of such an instrument is the altitude range where the retrieval of mixing ratios is possible The present work is a characterization of the low altitude limits of the retrieval ranges of all three instruments The most important limiting factor at low altitudes is the high continuum background mainly due to water vapor but also due to oxygen and nitrogen