Sub-millimeter observations of the terrestrial atmosphere during an Earth flyby of the MIRO sounder on the Rosetta spacecraft

Abstract

Sub-millimeter spectra recorded by the MIRO sounder aboard the Rosetta spacecraft have been used at the time of an Earth flyby (November 2007) to check the consistency and validity of the instrumental data. High-resolution spectroscopic data were recorded in 8 channels in the vicinity of the strong water line at 557 GHz, and in a broad band continuum channel at 570 GHz. An atmospheric radiative transfer code (ARTS) and standard terrestrial atmospheres have been used to simulate the expected observational results. Differences with the MIRO spectra suggest an anomaly in the behavior of four spectroscopic channels. Further technical investigations have shown that a large part of the anomalies are associated with an instability of one of the amplifiers. The quality of the MIRO data has been further tested by inverting the spectra with an atmospheric inversion tool (Qpack) in order to derive a mesospheric temperature profile. The retrieved profile is in good agreement with the one inferred from the Earth Observing System Microwave Limb Sounder (EOS-MLS). This work illustrates the interest of validating instruments aboard planetary or cometary spacecraft by using data acquired during Earth flybys.

New measurements of D/H on Mars using EXES aboard SOFIA

“…4) corresponds to an altitude level of 14 km (consistent with the flight altitude of SOFIA in March 2016) and a pressure of 0.11 bar at this level. The water mixing ratio ranges from 3 × 10 −5 at the first level to 5 × 10 −6 5 km above this level, in agreement with standard models of the terrestrial atmosphere (Jimenez et al 2013). In order to fit the observed spectrum at the center of the 1387.5 cm −1 H 2 O band where the terrestrial transmission is expected to be null, we removed the offset due presumably to scattered light or to incomplete sky subtraction (the same effect was observed in our April 2014 observation).…”

Simulation of submillimetre atmospheric spectra for characterising potential ground-based remote sensing observations

“…It shares observation time between astronomy mode and terrestrial mode and has been instrumental in observing atmospheric constituents such as ClO, N 2 O, HNO 3 , O 3 , water vapour and ice clouds Ekström et al, 2007). A similar approach was employed by the Microwave Instrument for the Rosetta Orbiter (MIRO) on the Rosetta spacecraft, which was temporarily diverted from its primary purpose to rendezvous with the 67P/Churyumov-Gerasimenko comet, in order to measure the terrestrial atmosphere during a scheduled Earth flyby (Jiménez et al, 2013). Data recorded in MIRO's channels centred at 183, 190, 557 and 562 GHz were used to test the instruments performance against expected results from radiative transfer models and measurements from the Earth Observing System Microwave Limb Sounder (EOS MLS).…”

Response to reviewer 2 comments on “Simulation of sub-millimetre atmospheric spectra for characterizing potential ground-based remote sensing observations”

“…It shares observation time between astronomy mode and terrestrial mode and has been instrumental in observing atmospheric constituents such as ClO, N 2 O, HNO 3 , O 3 , water vapour and ice clouds (Urban et al, 2005;Ekström et al, 2007). A similar approach was employed by the Microwave Instrument for the Rosetta Orbiter (MIRO) on the Rosetta spacecraft, which was temporarily diverted from its primary purpose to rendezvous with the 67P/Churyumov-Gerasimenko comet, in order to measure the terrestrial atmosphere during a scheduled Earth flyby (Jiménez et al, 2013). Data recorded in MIRO's channels centred at 183, 190, 557 and 562 GHz were used to test the instruments performance against expected results from radiative transfer models and measurements from the Earth Observing System Microwave Limb Sounder (EOS MLS).…”