NASA's Wide Field Infrared Survey Explorer (WISE), which launched in December 2009, is currently producing an allsky survey in the mid-infrared (2.8 - 26 microns) with far greater sensitivity and resolution than any previous IR survey mission. The ongoing on-orbit calibration of the instrument is performed at the Wise Science Data Center (WSDC), but several of the calibration parameters of interest were best measured on the ground, and have been maintained as part of the on-orbit calibration process. The Utah State University Space Dynamics Laboratory (SDL) built the science payload, and performed a series of ground characterization tests prior to launch. A challenge in a MIDEX mission such as WISE is to balance the various program demands to perform a thorough ground calibration within schedule and budget constraints, while also demonstrating compliance with formal flow-down requirements, and simultaneously verifying that performance has not been degraded during late-program environmental testing. These activities are not always entirely compatible. This paper presents an assessment of ground characterization challenges and solutions that contributed to a successful WISE mission.