About HALOE

Overview

The Halogen Occultation Experiment (HALOE) was launched on the Upper Atmosphere Research Satellite (UARS) spacecraft September 12, 1991, and after a period of outgassing, it began science observations October 11, 1991. The experiment uses solar occultation to measure vertical profiles of O3, HCl, HF, CH4, H2O, NO, NO2, aerosol extinction at 4 infrared wavelenths, and temperature versus pressure with an instantaneous vertical field of view of 1.6 km at the Earth's limb. Latitudinal coverage is from 80°S to 80°N over the course of 1 year and includes extensive observations of the Antarctic region during spring. The altitude range of the measurements extends from about 15 km to 60-130 km, depending on the species. Nitric oxide measurements extend through the lower thermosphere. Experiment operations have been essentially flawless, and all performance criteria either meet or exceed specifications. Internal data consistency checks, comparisons with correlative measurements including satellite, in situ and ground based observations are in good agreement. Examples of pressure versus latitude cross sections and a global orthographic projection for the September 21 to October 15, 1992, period show the utility of CH4, HF, and H2O as tracers, the occurrence of desiccation throughout the southern hemisphere, 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.

Science Goals

• Improve understanding of stratospheric ozone depletion due to ClOy, NOy, and HOy by collecting and analyzing global data on key chemical species, including: O3, HCl, CH4, H2O, NO, NO2, and CO2 (T,P)
• Study the CFC impact on ozone by conducting simultaneous measurements of: HCl and HF
• Analyze the global distribution and temporal behavior of vertical aerosol extinction coefficient profiles at eight infrared wavelengths

Science Objectives

• Study dynamics of polar and other atmospheric regions using HALOE tracers CH4, HF, and H2O
• Use trends in HCl and HF to study the relative importance of anthropogenic versus natural chlorine sources
• Develop and prepare a climatology of HALOE measured stratospheric gases and aerosols
• Carry out stratospheric chemistry studies (especially ClOy and NOx) including effects of heterogeneous chemistry
• Analyze the H2O and total hydrogen budget using HALOE H2O and CH4 data in the stratosphere and mesosphere
• Conduct studies to identify and assess stratosphere/troposphere exchange
• Test diurnal photochemistry using HALOE NO and NO2 results
• Analyze in detail the development and recovery of the Antarctic ozone hole
• Describe the changing Pinatubo aerosol morphology for several years after the eruption (June 12, 1991)