THE HALOGEN OCCULTATION EXPERIMENT

The Halogen Occultation Experiment (HALOE) was launched on the Upper A tmosphere Research Satellite (UARS) spacecraft September 12, 1991, and after a period of outgassing, it began science observations October 1 1. The experiment uses solar occultation to measure vertical profiles of O3, HCl, HF, CH4, H2O, NO, NO2, aerosol extinction, and temperature versus pressure with an instantaneous vertical field of view of 1.6 k m at the Earth limb. Latitudinal coverage is from 80-degrees-S to 80-d egrees-N over the course of 1 year and includes extensive observations of the Antarctic region during spring. The altitude range of the meas urements extends from about 15 km to almost-equal-to 60-130 km, depend ing on channel. Experiment operations have been essentially flawless, and all performance criteria either meet or exceed specifications. Int ernal data consistency checks, comparisons with correlative measuremen ts, and qualitative comparisons with 1985 atmospheric trace molecule s pectroscopy (ATMOS) results are in good agreement. Examples of pressur e versus latitude cross sections and a global orthographic projection for the September 21 to October 15, 1992, period show the utility of C H4, HF, and H2O as tracers, the occurrence of dehydration in the Antar ctic lower stratosphere, the presence of the water vapor hygropause in the tropics, evidence of Antarctic air in the tropics, the influence of Hadley tropical upwelling, and the first global distribution of HCl , HF, and NO throughout the stratosphere. Nitric oxide measurements ex tend through the lower thermosphere.