Raunak Agarwal, Markus A. Wenzel, Simon Baur, Jonas Zimmer, George Harvey, Jackie Ma. Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers). 2026.

We report on the on-ground stray light calibration of the hyperspectral Environmental Mapping and Analysis Program (EnMAP) satellite mission, which was successfully launched into space on April 1, 2022. EnMAP’s optical payload consists of a visible and near-infrared (VNIR) (420–1000 nm) and a short wavelength infrared (SWIR) (900–2450 nm) imaging spectrometer. Using a custom-built light source and a collimator, we determined the diffuse stray light by measuring the point spread functions (PSFs) at 12 spatial and 15 (11 VNIR, 4 SWIR) spectral positions with a dynamic range between eight and nine orders of magnitude. Additionally, we measured the out-of-field stray light in along-track direction over an angular range of ±0.2°, resulting in an along-track response function (AltRF) for each spectrometer unit with a dynamic range of$\sim 10^{7}$. To reduce memory usage and computational time, we use a binned stray light extraction matrix to correct the diffuse stray light. The along-track out-of-field stray light of individual frames is corrected by subtracting preceding and following frames that are weighted with the AltRF. Finally, we show with simulations the impact of both types of stray light on a test scene and evaluate the performance of the presented correction methods in the same manner.

Spaceborne imaging spectroscopy is undergoing a rapid expansion with a new generation of missions in recent years. Following the Hyperion (2000) and HICO (2009) missions, new spaceborne imaging spectroscopy missions have recently started operating: DESIS (2018), PRISMA (2019), HISUI (2019) and more recently EnMAP (2022) and EMIT (2022). These missions face the common challenge of providing accurate spectral and radiometric results over a wide spectral range. This requires accurate instrument calibration and the validation of the results obtained. In this contribution, we provide an overview of the calibration and validation (CalVal) activities in the EnMAP mission, and we present the CalVal results that were obtained as part of the commissioning phase (April - October 2022).