Long-term radiometric accuracy is a fundamental requirement for future measurement of solar and terrestrial atmospheric EUV emissions from space. Since remote sensing of EUV radiation will become an important measuring technique to explore the thermosphere, new methods have to be established to trace calibration changes of EUV instrumentation, too. With the proposed satellite ATON (Egyptian god of the sun) the solar energy input and other important thermospheric/ionospheric parameters (O2, O, O+, N2, N+, NO, H, He, Ne, Tn, X-rays, solar EUV energy, polar energies) shall be measured based on absolute in-flight calibration of solar and airglow instrumentation. The model payload consists of (1) auto-calibrating solar EUV spectrometers, (2) airglow-solar spectrometer, (3) airglow spectrometer (high spectral resolution), (4) EUV photometers (high data statistics), (5) radio beacon experiment and (6) photocathode arrangement (the latter to detect short-lived solar phenomena of aeronomic interest). The basic measuring concept and instrumental details are presented.