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EnVision, Europe’s mission to Venus
ESA’s EnVision mission is set to launch to Venus in November 2031, aiming to provide the most comprehensive study of the Earth’s sister planet to date and to retrieve a better view on its history, present activity and climate.
It aims at investigating the planet’s many unsolved mysteries, from the makeup of its interior and possible volcanic activity at the surface, to intriguing processes in its atmosphere dominated by gasses thought to be originating from volcanism. In January 2024, ESA officially approved the EnVision mission, allowing to move forward with its implementation.
VenSpec-H probing Venus’ atmosphere above and below its thick cloud deck
VenSpec-H is a high-resolution infrared spectrometer on-board EnVision, developed under the scientific lead of the Planetary atmospheres division at BIRA-IASB. It will analyse Venus’ atmosphere, measuring gases above the cloud deck during the day and probing deeper layers at night using infrared transparency windows.
Besides studying the atmospheric composition (e.g., H2O, HDO, OCS, CO, HF, SO2, HCl), a key point of interest for VenSpec-H is the pronounced greenhouse effect that dominates the climate of the planet.
In 2023-2024, BIRA-IASB’s Engineering department coordinated the instrument’s technical development, leading a broad international consortium.
VenSpec-H is built around an echelle grating, which converts light from the planet’s nadir direction into a spectrum. To prevent interference from its own thermal radiation, the grating and surrounding optics are cooled to -45 °C during operation. In front of this cold spectrometer, a filter wheel selects the spectral bands of interest. At the rear, a detector, operating at around -135 °C, captures the spectrum, which is processed on board through the instrument’s electronics before transmission to Earth.
Instrument breadboard development and validation
In 2021-2022, a numerical (software) finite element model (FEM) and a thermal geometrical mathematical model (TGMM) were developed, and specialised partners conducted analyses to assess the structural and thermal soundness of the design. In 2023-2024, the engineering team at BIRA-IASB manufactured and assembled a full instrument breadboard in-house. This mechanically and thermally representative hardware model of the instrument enables real-life testing, followed by correlation of the results with the software FEM and TGMM models.
To simulate the mechanical loads experienced during launch, the breadboard underwent vibration testing, which prompted several design refinements. A thermal-vacuum test is scheduled for early 2025.
