VenSpec-U is one of the three channels of the VenSpec suite onboard the ESA’s mission Envision to Venus, whose launch is foreseen in 2031. It is a UV spectrometer operating in the 190-380 nm range aiming at analyzing the sulfured gases in the high atmosphere of Venus by absorption spectroscopy and investigating the unknown “UV absorber”, thus contributing to answer one of the key questions the Envision mission will address: “How has Venus’ climate become so hostile”. VenSpec-U, developed under LATMOS (Guyancourt, France) PI-ship, is part of the spectrometer suite named ”VenSpec” led by DLR (Berlin, Germany). This manuscript provides an overview of the current instrument design, at the time of the end of phase B1/early phase B2.
Friederike Wolff, Jörn Helbert, Giulia Alemanno, Emmanuel Marcq, Ann-Carine Vandaele, Sévrine Robert, Louisa Maria Lara, Andreas Nathues, Vanderlei Cunha Parro, Sandrine Bertran, Justin Erwin, Gisbert Peter, Benjamin Lustrement, Eddy Neefs, Roderick de Cock, Till Hagelschuer, Lisa Hafemeister, Jose Maria Castro, Pablo Gutierrez-Marques
VenSpec is an instrument-suite composed of three spectrometers sharing a central control unit. Tied together by the common goal of exploring the different layers of Venus from the surface to the upper atmosphere in a holistic manner, three instrument lead scientists from Germany (DLR), France (LATMOS) and Belgium (BIRA-IASB) have joined forces. From the outset of the phase A study a collaborative work environment has been put in place to enable synergistic scientific planning and development work from the initial conceptual design throughout the actual instrument development and leading up to the operations and analysis of scientific returns. This paper addresses the challenges the consortium has faced in the process of guiding geographically, financially and institutionally separated projects towards a common goal with as little organizational overhead to the teams as possible. In the case of VenSpec, the scientific aspiration of working together via a common science team was set down at the beginning of the project: the consortium was consolidated by assuring each party full access to all scientific data produced by any instrument and also by connecting them physically to a common central control unit. This enables the consortium to act as a single entity towards the European Space Agency as well as the prime industrial contractor when beneficial while giving each party the freedom to act independently of each other for those aspects of scientific planning or technical development in which harmonization is not required. This paper lays out how the VenSpec consortium is organized and explains how close collaboration and the leveraging of synergies can be balanced with independent activities and individual and tailored strategies.
The dual-channel UV spectrometer VenSpec-U onboard ESA’s next mission to Venus, EnVision, will study the upper layer of the atmosphere located above the clouds. It aims to characterise the chemical composition, with a focus on the sulphured gases (SO2 and SO) and the identification of the unknown UV absorber, and will also monitor the dynamical processes such as gravity waves and convection cells. In this article, we are interested in knowing how the instrumental design allows to comply with requirements arising from these scientific objectives. This study is based on the radiative transfer model (RTM) developed for SPICAV/Venus-Express data analysis, that is used to retrieve of atmospheric features from radiance factor spectra, which will be derived from VenSpec- U’s measurements of Venus’ radiance. We will then study the sensitivity of the model to various error sources: random errors or biases. For the first ones, we assess the impacts of the Signal-to-Noise Ratio on the uncertainties of the inverse RTM outputs, in order to check that the required uncertainties are achieved for the main science goals. Limits in terms of SNR can also be defined in order to ensure the compliance with the specifications. We then present the approach implemented for the characterisation of systematic errors: the Effective Spectral Radiometric Accuracy (ESRA) requirement is used to estimate the impact of a bias on the accuracy of the retrieved science products based on the spectral characteristics of the biased spectra. After identifying some bias sources that could occur in VenSpec-U’ case, combinations are considered in order to study potential compensations and estimate allowable envelopes of residual error levels for each kind.
In this paper, we describe the concept of the Venus InfraRed Atmospheric Linker (VIRAL) spectrometer for investigation of the composition and structure of the planetary atmosphere at the top and above the cloud layer of Venus onboard the Venus Orbiter Mission announced by the Indian Space Research Organization (ISRO). VIRAL includes two channels, an infrared echelle spectrometer channel and an ultra-high resolution heterodyne interferometer channel. Here, we present the concept of the echelle channel only. The instrument is designed to perform solar occultation, providing an optimal photon yield combined with a superior spectral resolving power that exceeds 20,000. VIRAL echelle spectrometer will cover the wavelength range from 2.3 to 4.3 μm, and achieve high vertical resolution (with a footprint of about 1 km at the limb) to allow the detailed altitude profiling of the Venusian upper atmosphere with its composition and structure. We present the instrument concept, its preliminary optical design and science objectives of the experiment.
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