Satellite detectors are sensitive to energetic particles in the Van Allen radiation belts, and EVE is no exception. SDO was launched Feb. 11, 2010 from KSC and EVE was turned on today. During its first orbit with power, EVE’s Lyman-alpha photodiode had very low dark signal while at GEO altitudes (about 36000 km) but has larger signal at the lower altitudes. Why? EVE is designed with shielding to protect its detectors from the energetic electrons that dominate at GEO altitudes, but EVE sees the energetic protons that dominate in the Van Allen radiation belts that are lower in atltitude than GEO. Over the next couple of weeks, SDO will be transitioning from a highly ellipitical GEO transfer orbit into a circular GEO orbit.
August 16, 2023