The HyperScout-H hyperspectral imager (HS-H) is one of the payloads aboard ESA's Hera spacecraft, launched in October 7, 2024. It is produced by cosine* and its primary objective is to provide a detailed characterization of the near-Earth binary asteroid system (65803) Didymos-Dimorphos, following the impact of NASA's DART mission [1, 2]. HS-H is a versatile, dual-purpose payload, functioning as a hyperspectral imager that captures both images and spectral data within the 0.65 - 0.95 μm wavelength range covered by 25 filters that are distributed along the detector on 5 by 5 macropixels. This work is focused on the in-flight observations of HS-H during the cruise phase. These were performed between October 2024 and March 2025, during the commissioning, early cruise phases of the mission, and the Mars swing-by.The commissioning activities included imaging the Earth-Moon system, acquiring bias and dark images, and observing several star fields, including various observations of Vega and Aldebaran stars. The goal of these observations was to validate the instrument's functionality and cross-check the calibration performed in the laboratory [3].The sequence of Earth - Moon images demonstrates that the full photometric range of the instrument was tested using varying exposure times as presented in Figure 1, where we can see Earth's images at different exposure times. The star exposures of Vega and Aldebaran confirm the expected behavior of the Point Spread Function and validate the detector's linear response regime. Three images of Aldebaran (a K5III star) at different exposure times are shown in Figure 2. Radiometric calibration was verified within a 10% margin, consistent with the accuracy limitations of the method.Figure 1. Earth images obtained by HS-H are displayed with the number of pixels on each axis indicated. The images are organized based on their exposure time and the moment they were captured. The dark/white levels are set according to the instrument's dynamic range (grayscale color bar at the top), i.e. from 0 to 4095 Digital Numbers (DNs).Figure 2: Linearity test images for Aldebaran at different wavelengths of the central pixel and exposure times as shown in the plots. The images correspond to three different frames, showing the increase in detected signal with exposure time. The grayscale color bar on the right indicates the pixel intensity in DNs. To further validate the instrument's radiometric accuracy, we perform a cross-calibration using hyperspectral observations of Mars. By targeting well-characterized surface features (e.g. Huygens crater) and comparing the extracted spectra with established datasets (e.g. CRISM@MRO), we asses both spectral and radiometric consistency. The reflectance spectrum shown in Figure 3 is extracted from a region of interest inside the Huygens crater of Mars. The in-flight observations successfully validated the instrument's functionality and helped improve the radiometric and spectral calibrations, ensuring readiness for scientific operations. These early results are a solid foundation for its upcoming observations of the Didymos-Dimorphos system.Figure 3. HS-H image of Huygens crater on Mars with an annotated Region of Interest (ROI), indicated by the white square, used for spectral extraction. The inset plot displays the normalized reflectance spectrum (dots) and a third degree polynomial fit (continuos line). The blue color of Mars observed in near-infrared resulted from a coloring algorithm that uses shifted colors with blue channel at 650 - 750 nm and red channel at 850 - 950 nm. [1] P. Michel et al. The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) Didymos. , 3(7):160, July 2022.[2] Andrew S. Rivkin et al.. The double asteroid redirection test (dart): Planetary defense investigations and requirements. The Planetary Science Journal, 2(5):173, aug 2021.[3] Popescu, M., de León, J., Goldberg, H., Kovács, G., Krämer Ruggiu, L., Nagy, B., Prodan, G. P., Grieger, B., Kohout, T., Licandro, J., Karatekin, Ö., Esposito, M., and Küppers, M.: Hyperspectral imaging of meteorites using the HyperScout-H instrument, Europlanet Science Congress 2024, Berlin, Germany, 8-13 Sep 2024, EPSC2024-586, https://doi.org/10.5194/epsc2024-586, 2024.* https://www.cosine.nl/