Signatures of orbital motion in strongly curved space-time of accreting black holes via the upcoming X-ray missions

We explore the appearance of an observable signal generated by extended accretion tori with a contribution from localized radiating hot spots moving along quasi-elliptic trajectories near the innermost stable circular orbit (ISCO) in the Schwarzschild spacetime. Our on-going effort is aimed to compare the capabilities of observatories operating during the past two decades (represented by the Rossi X-ray Timing Explorer, RXTE) versus two future instruments -- Advanced Telescope for High-Energy Astrophysics (Athena) and The enhanced X-ray Timing and Polarimetry mission (eXTP). We conclude that the spectral and timing abilities of the proposed observatories can greatly help to distinguish between the different physical models, significantly beyond the current state of the art.