NICER observation list: Target ID 675601

X-ray reflection in accreting black holes occurs in the inner region of the accretion disk, and physical modeling of the spectral and timing properties of this emission enables measurement of the black hole mass and spin. The unique combination of NuSTAR s hard and NICER s soft coverage provides the broad bandpass, high count rates and energy and timing resolution required to constrain models of the time averaged energy spectrum and the reverberation lag energy spectrum on different timescales. We propose to observe any black hole transient, known or unknown, exceeding 30 mCrab during the bright hard state for 30 ks with a simultaneous NuSTAR and NICER observation in order to access unprecedented characterization of black hole spin and mass.