TEPEE/GReAT is an experiment aimed at testing the principle of equivalence at a level of accuracy equal to 5 parts in 1015 by means of a differential acceleration detector free falling inside a co-moving, cryogenic, evacuated capsule,
released from a stratospheric balloon. The detector is spun about a horizontal axis during the fall in order to modulate the equivalence principle violation signal at the
spin frequency. Thanks to the recent funding of the Italian side, the project is ready to enter its second phase. The main activities related to detector prototype (both
non-cryogenic and cryogenic versions) development and testing, free-fall tests, signal extraction from noise (in particular related to the common-mode rejection factor) and flight model requirements are discussed
