Abstract

The LIMS experiment was launched on the Nimbus 7 satellite to sound the upper atmosphere composition and structure. Broadband earth horizon radiance profiles were measured in the infrared and later ground-processed to infer vertical profiles of temperature and the mixing ratios of O₃, H₂O, NO₂, and HNO₃. A key to successful retrieval of information from the radiances is a fast radiative transfer code that will allow sufficient iterations and provide essentially line-by-line transmittance calculation accuracy. The LIMS radiances were calculated using the emissivity growth approximation (EGA) technique, which is based on use of a precalculated data base developed for a wide range of temperature and pressure. This method was used in combination with an onion peeling retrieval technique that does not rely on a prior statistical knowledge. The HALOE experiment will be launched on the UARS satellite in late 1989 to measure vertical profiles of stratosphere O₃, HCI, HF, CH₄, H₂O, NO, and NO₂. Unlike LIMS, HALOE uses solar occultation measurements made by both broadband and gas filter correlation radiometry. Retrievals using the correlation measurements require high spectral resolution calculations, and the process can be very time-consuming and expensive in an iterative approach. The FIALOE processing will use a combination of the LIMS EGA method and a fast narrowband line-by-line method to provide the required speed and accuracy in the radiative transfer calculations. The onion peeling retrieval approach and another scheme, which uses information from all tangent altitudes simultaneously, are currently being evaluated.

© 1985 Optical Society of America