Abstract
The NOMAD instrument has been designed to best fulfil the science objectives of the ExoMars Trace Gas Orbiter mission that will be launched in 2016. The instrument is a combination of three channels that cover the UV, visible and IR spectral ranges and can perform solar occultation, nadir and limb observations. In this series of two papers, we present the optical models representing the three channels of the instrument and use them to determine signal to noise levels for different observation modes and Martian conditions. In this first part, we focus on the UVIS channel, which will sound the Martian atmosphere using nadir and solar occultation viewing modes, covering the 200-650nm spectral range. High SNR levels (>1000) can easily be reached for wavelengths higher than 300nm both in solar occultation and nadir modes when considering binning. Below 300nm SNR are lower primarily because of the lower signal and the impact of atmospheric absorption.
Highlights
NOMAD (Nadir and Occultation for MArs Discovery) is one of four instruments on board the ExoMars Trace Gas Orbiter [1], scheduled for launch in January 2016 and to begin nominal science mission around Mars in late 2017
We focus on the ultraviolet/visible channel (UVIS) channel, which will sound the Martian atmosphere using nadir and solar occultation viewing modes, covering the 200-650nm spectral range
The incoming light is the solar radiance attenuated by the absorption by the atmosphere along the Line of Sight (LOS) which is defined from the centre of the Sun to the aperture of the instrument
Summary
NOMAD (Nadir and Occultation for MArs Discovery) is one of four instruments on board the ExoMars Trace Gas Orbiter [1], scheduled for launch in January 2016 and to begin nominal science mission around Mars in late 2017. It consists of a suite of three high-resolution spectrometers [2, 3] – UVIS (Ultraviolet-Visible), SO (Solar Occultation) and LNO Global coverage will extend between ± 74° latitude with an Instantaneous Field of View (IFOV) of 0.5x17km on the surface This channel can make occultation measurements should the SO channel fail. In this paper we will focus on the UVIS channel model, while in the companion paper [6], the models and results for the IR channels will be presented and discussed
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