10cm, available from e.g. https://nearspacelabs.com/ https://nearspacelabs.com/ (using stratospheric balloons), or in 2025 from https://albedo.com/ https://albe

10cm, available from e.g. https://nearspacelabs.com/ https://nearspacelabs.com/ (using stratospheric balloons), or in 2025 from https://albedo.com/ https://albedo.com/ (using satellites).