  We study the uncoupled space-time fractional operators involving
time-dependent coefficients and formulate the corresponding inverse problems.
Our goal is to determine the variable coefficients from the exterior partial
measurements of the Dirichlet-to-Neumann map. We exploit the integration by
parts formula for Riemann-Liouville and Caputo derivatives to derive the Runge
approximation property for our space-time fractional operator based on the
unique continuation property of the fractional Laplacian. This enables us to
extend early unique determination results for space-fractional but time-local
operators to the space-time fractional case.
