The NISTAR ACRs were designed to have a noise floor of less than 10 nW, defined here to be the level at which the signal to noise is equal to one for a single 1 second measurement. The NISTAR electronics have a measurement resolution of 10 milliOhms and internal equivalent noise of less than that. Tests with the flight electronics have yielded results of 7 milliOhms for measurements of a 10 kiloOhm resistor. To date the complete flight instrument has not been tested under cryogenic vacuum test conditions since the flight electronics have yet to be completed. However, tests using commercially available electronics with a similar prototype radiometer to those used in NISTAR have produced results approaching 10 nanoWatts. The prognosis for achieving the science goals of the mission is excellent based on the preliminary results to date.