The capability to measure absolute fission rates per nucleus at a remote laboratory site [the Coupled Fast Reactivity Measurement Facility (CFRMF) at Aerojet Nuclear Company] has been established to a precision level of better than ±1% and was sustained at that level for a period of two years. Double fission ionization chambers and solid-state track recorders were used in a series of irradiations designed to calibrate fission activation detectors used for reactor fuels and materials dosimetry. The array of reference and working fissionable deposits involved in the measurements included five isotopes: 239Pu, 235U, 238 U, 237Np, and 234U. Isotopic masses for the fissionable deposits were determined from interrelated components of mass assay: (a) relative and absolute alpha counting, (b) fission comparison counting in thermal-neutron beams, (c) mass spectrometry, and (d) quantitative deposition employing solutions of known fissionable element concentration. Absolute accuracies for the fission rates per nucleus measured in CFRMF are in the range of ±1.5 to ±2.5% and are dominated by uncertainties in the fissionable deposit masses. Fission cross-section ratios for the CFRMF central spectrum are (1.000 : 1.145 ± 0.017 : 0.0485 ± 0.0007 : 0.354 ± 0.008) for (235U: 239Pu: 238U: 237Np), respectively.