NICER observation list: Target ID 254201

4U 1957+11 is one of the few persistently active black hole candidates. Although we do not know its mass, distance, or inclination, the fact that it is apparently always in a thermal-dominated state with extremely high disk temperature, yet very low normalization, suggests a very rapidly rotating black hole. Furthermore, it has an extremely low column, allowing an extremely good view of the soft X-ray spectrum accessible to NICER. Its high disk temperature also places the peak of the disk spectrum in the bandpass of both NICER and NuSTAR. Thus, it becomes an ideal test bed of modern disk atmosphere models. We propose a series of joint NICER/NuSTAR observations that we will analyze as a whole, in order to measure this system's unknown black hole parameters.