CELESTA stands for CERN Latchup Experiments Student sAtellite and will be the first CERN-driven microsatellite. Between June and September 2016, it successfully passed its System Requirements Review and has now entered Phase B. During the review, the technical and programmatic feasibility of the CELESTA concept was validated. The review also highlighted the need to consolidate the payload design through a functional test between the prototype payload cards and the on-board data handling during irradiation. The test was successfully performed mid-October 2016 at the CHARM facility at CERN.