Ground tests and computer simulations about satelittes charging effects require the definition of worst-case environment spectra representative of those encountered in orbit. For this, it is necessary to take into account the entire energy spectrum having an effect on both the gradient voltage build-up or mitigation on dielectrics and the absolute potential for each satellite. Section II deals with the methodology and the criteria used to define worst-case environments, based on the physics of plasma material interaction, including the radiation induced conductivity. (RIC) We have computed different classes of fluxes, all based on six LANL flight data for a period over 15 years. Section II presents how electron differential fluxes are extracted from LANL measurements, taking into account spacecraft potentials, including specific and necessary corrections Then we also take into account the dose effect which affects the conductivity of all exposed dielectrics. Section III specifies different environments considered as possible worstcase environments, following the approach given in Section I. This paper finally presents a synthesis of the spectra obtained and gives perspectives for their use for ground tests and for numerical assessment of worst-case spacecraft surface charging. Section IV provides a summary of the outcome of this paper, including impacts on experimental and numerical estimations of the charging risk in GEO.