Microwave temperature and pressure measurements with the Odin satellite: I. Observational method

Abstract

Abstract:The Odin satellite is equipped with millimetre and sub-millimetre receivers for observations of several molecular lines in the middle and upper atmosphere of our planet (∼25-100 km, the particular altitude range depending on the species) for studies in dynamics, chemistry, and energy transfer in these regions. The same receivers are also used to observe molecules in outer space, this being the astrophysical share of the project. Among the atmospheric lines that can be observed, we find two corresponding to molecular oxygen (118.75 GHz and 487.25 GHz). These lines can be used for retrievals of the atmospheric temperature vertical profile. In this paper, we describe the radiative-transfer modeling for O 2 in the middle and upper atmosphere that we will use as a basis for the retrieval algorithms. Two different observation modes have been planned for Odin, the three-channel operational mode and a high-resolution mode. The first one will determine the temperature and pressure on an operational basis using the oxygen line at 118.75 GHz, while the latter can be used for measurements of both O 2 lines, during a small fraction of the total available time for aeronomy, aimed at checking the particular details of the radiative transfer near O 2 lines at very high altitudes (>70 km). The Odin temperature measurements are expected to cover the altitude range ∼30-90 km. PACS Nos.: 07.57Mj, 94.10Dy, 95.75Rs Résumé : Le satellite Odin est équipé de détecteurs millimétriques et sous-millimétriques pour observer plusieurs raies moléculaires dans les parties moyenne et supérieure de l'atmosphère (25-100 km, le domaine en altitude dépendant des molécules étudiées) afin d'étudier la dynamique, la chimie et les transferts d'énergie dans ces régions. Ces mêmes détecteurs peuvent être orientés vers l'espace dans le volet astrophysique de la mission. Parmi

Atmospheric transmission at microwaves (ATM): an improved model for millimeter/submillimeter applications

“…2) Symmetric rotor in electronic state (12) where is the electronic spin operator, is the orbital rotational angular moment, and , , and are rotational constants. 3) Asymmetric rotors: We use the Watson-type Hamiltonian [16] according to the notation appearing in [17].…”

“…Polarization can be produced by different mechanisms: emission of paramagnetic molecules such as O under the effect of the geomagnetic field, radiation scattering by hydrometeors, or reflection on a Fresnel-like (ocean) surface. These mechanisms are also treated in the ATM model but have been ([10]- [12] Zeeman effect ) or will be discussed elsewhere ( [13] scattering by hydrometeors ). Here we discuss only unpolarized radiative transfer through a clear sky.…”

Molecular Line Parameters for the “MASTER” (Millimeter Wave Acquisitions for Stratosphere/Troposphere Exchange Research) Database

“…On the other hand, continuum emission from water and dry air limits this advantage. At present stratospheric limb sounding has already been demonstrated successfully by instruments like the microwave limb sounder (MLS) on the upper atmosphere research satellite (UARS) (Lahoz et al, 1994;Eluszkiekicz et al, 1996 Livesey et al, 2003 andreferences therein) and more recently by the sub millimeter radiometer (SMR) on board the Odin satellite since February 2001 Eriksson et al, 2002;Merino et al, 2002;Pardo et al, 2002;Ridal et al, 2002;Urban et al, 2004). Also the NASA's Earth observation system microwave limb sounder (EOS-MLS) was launched in 2004.…”

Reinvestigation of pressure broadening parameters at 60-GHz band and single 118.75GHz oxygen lines at room temperature

“…The EOS MLS apparatus focus on temperature and pressure sensing using the line at 118-GHz [3]. And 118.75-GHz fix-tuned HEMT preamplifier has been installed in recently launched satellite ODIN to allow very sensitive searches for interstellar O 2 [4] and used for retrievals of the atmospheric temperature vertical profile [5].…”

“…Advantages of the RAD spectrometer were recording of the true absorption profiles of the lines by means of amplitude modulation with signal-to-noise ratio (SNR) better than 100, which was demonstrated earlier in studying rotational spectrum of oxygen molecule [6,7]. Improving of accuracy of the broadening parameters is important for more accurate modeling of experimental lineshapes for retrieval of atmospheric temperature profiles [5].…”