On the distribution of mesospheric molecular hydrogen inferred from HALOE measurements of H₂O and CH₄

The Halogen Occultation Experiment (HALOE) is in orbit on NASA's Upper Atmosphere Research Satellite (UARS), and has been used to make measurements of a number of stratospheric and mesospheric constituents since October 1991. These include, amongst others, water vapour, H 2 O, and methane, CH 4 , two principal components of the total hydrogen budget of the middle atmosphere. The third main component is molecular hydrogen, H 2 , which is not measurable by HALOE or any other UARS sensor. By making the assumption that the total hydrogen content of the middle atmosphere is a conserved quantity, and that these three constituents dominate the budget, it is possible to infer the H 2 fields in the mesosphere from the HALOE H 2 O and CH 4 measurements.