Altius instrument: testing, qualification, and status towards flight

The Altius Mission (Atmospheric Limb Tracker for Investigation of the Upcoming Stratosphere) aims at the development of a limb sounder based on a small satellite concept. The Altius instrument consists of three spectral imagers based on Acousto-Optic Tunable Filters (AOTFs) in the Visible (440-675nm) and NIR (600-1020nm) range, and a cascade of Fabry-Pérot Interferometers (FPI) in the UV (250-355nm) range providing a versatile operational concept with spectral resolutions ranging from 1nm to 10nm. It aims to monitor stratospheric ozone distribution with high vertical resolution for operational services and long-term trend monitoring. The Altius Instrument development is led by OIP N.V with Redwire Space N.V as mission Prime. ALTIUS has now completed the Instrument and System Critical Design Review and is well advanced in the manufacturing of the flight hardware. This paper presents the key technical challenges encountered in the manufacturing, testing and qualification of its key subunits, with special attention to the spectral filters and optical modules. The results that will be presented highlight the engineering trade-offs and design changes that were implemented to ensure compliance to the L0 requirements within the project constraints. Finally, the paper presents the most important lessons learned from the CDR and the qualification activities as well as an overview of the foreseen project milestones towards launch.