End-to-End Science Performance Assessment of the VenSpec-H Instrument for EnVision

VenSpec-H is the high-resolution infrared spectrometer of the ESA EnVision mission, dedicated to the investigation of the composition and dynamics of Venus’ atmosphere. In support of the Phase B2/iPDR activities, an end-to-end science performance assessment framework has been developed to evaluate the capability of the instrument to meet its science objectives under representative observing conditions.The analysis combines high-resolution radiative transfer simulations, instrument-level modelling and retrieval simulations based on the Optimal Estimation Method (OEM). Atmospheric spectra are generated using the ASIMUT-ALVL radiative transfer and retrieval suite and processed through the VenSpec-H instrument simulator (VHIS), which accounts for the instrument spectral response, optical throughput and detector noise contributions.The study investigates the radiometric and scientific performance of the instrument for both dayside and nightside observations across the different spectral bands. Key performance metrics include signal-to-noise ratio (SNR), retrieval uncertainties and information content diagnostics such as the Degrees of Freedom for Signal (DOFS). The analysis also explores the sensitivity of the retrieval performance to atmospheric conditions, radiance levels and instrument assumptions.Special attention was given to the retrieval of isotopic species related to the water history of Venus. The results show that the capability to retrieve these weak atmospheric signals strongly depends on the atmospheric conditions and radiance levels. This demonstrates the importance of using realistic atmospheric scenarios and advanced retrieval diagnostics when assessing the scientific capabilities of future planetary missions.The results indicate the overall capability of the current VenSpec-H design to achieve the targeted science performance under the considered reference scenarios. In addition, the study highlights the importance of end-to-end retrieval analyses and information-content diagnostics to properly interpret the retrieval capability for weak atmospheric species and varying observing conditions.This work provides a consolidated framework for future performance analyses and establishes the basis for subsequent investigations involving broader atmospheric variability, refined instrument modelling and optimisation of the observing strategy. The VenSpec-H experiment is led by the Royal Belgian Institute for Space Aeronomy (BIRA-IASB) with co-ILS teams from Switzerland (ETHZ), Portugal (IA), Spain (IAA), the Netherlands (SRON), and the Czech Republic (JHIPC). The project acknowledges funding by: the Belgian Science Policy Office (BELSPO) under PEA nº400012813 and nº4000144206; the Swiss Space office (SSO) under PEA nº4000138690, nº4000138246, and nº400013824; Fundação para a Ciência e a Tecnologia (FCT) through the research grant UID/04434/2025; the Spanish Space Agency (AEE) under grants PID2021-126365NB-C21 and PID2021-126365NA-C22; the Czech national funding under PEA nº4000147310 and Czech Science Foundation Project No. 24-12656K; and the European Space Agency (ESA) under the EnVision Project. Belgium, Switzerland, Portugal, and the Czech Republic acknowledge the financial and contractual coordination by the ESA Prodex Office.