title: Tangent height registration method for the Version 1.4 data retrieval algorithm of the solar occultation sensor ILAS-II.
abstract: The Improved Limb Atmospheric Spectrometer-II (ILAS-II) is a satellite-borne solar occultation sensor onboard the Advanced Earth Observing Satellite-II (ADEOS-II). The ILAS-II succeeded the ILAS. The ILAS-II used four grating spectrometers to observe vertical profiles of gas volume mixing ratios of trace constituents and was also equipped with a Sun-edge sensor to determine tangent heights geometrically with high precision. The accuracy of gas volume mixing ratios depends on the accuracy of the tangent height determination. The combination method is a tangent height registration method that was developed to give appropriate tangent heights for the ILAS-II Version 1.4 data retrieval algorithm. This study describes the method used in the ILAS-II Version 1.4 retrieval algorithm to register tangent heights. The root-sum-square total random error is estimated to be 30 m, and the total systematic error is 180 m at an altitude of 30 km. The influence of the tangent height errors on the vertical profiles of gas volume mixing ratios in ILAS-II Version 1.4 is estimated by using the relative difference. The relative difference for each species is within 7% (20%) for an altitude shift of +/-100 m(+/-300 m).
authors.affiliation: National Institute for Environmental Studies, Tsukuba, Japan. tanaka.tomoaki@nies.go.jp
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Tanaka
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nakajima
authors.forename: Takafumi
authors.initials: T
authors.lastname: Sugita
authors.forename: Mitsumu K
authors.initials: MK
authors.lastname: Ejiri
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Irie
authors.forename: Naoko
authors.initials: N
authors.lastname: Saitoh
authors.forename: Yukio
authors.initials: Y
authors.lastname: Terao
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kawasaki
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Usami
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Yokota
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Sasano