NICER observation list: Target ID 470201

With its excellent hard X-ray sensitivity, energy resolution, and timing, NuSTAR has revolutionized our view of BH accretion, particularly through studies of Compton scattering and relativistic reflection. But we still have yet to attain a fully self-consistent model of the accretion flow, in part because of the difficulty of constraining seed photons: thermal emission from cool, faint disks. With the launch of NICER in June 2017, we took a great step forward. NICER is to soft X-rays what NuSTAR is to hard X-rays, and together they can produce incredibly tight constraints on the geometry of the inner disk, corona, and their interactions. We propose 5x20 ks coordinated observations of a black hole transient with NuSTAR and NICER (5x10 ks) to exploit their groundbreaking capabilities.