  We present an analysis of Sun-as-a-star observations from four different
high-resolution, stabilized spectrographs -- HARPS, HARPS-N, EXPRES, and NEID.
With simultaneous observations of the Sun from four different instruments, we
are able to gain insight into the radial velocity precision and accuracy
delivered by each of these instruments and isolate instrumental systematics
that differ from true astrophysical signals. With solar observations, we can
completely characterize the expected Doppler shift contributed by orbiting
Solar System bodies and remove them. This results in a data set with measured
velocity variations that purely trace flows on the solar surface. Direct
comparisons of the radial velocities measured by each instrument show
remarkable agreement with residual intra-day scatter of only 15-30 cm/s. This
shows that current ultra-stabilized instruments have broken through to a new
level of measurement precision that reveals stellar variability with high
fidelity and detail. We end by discussing how radial velocities from different
instruments can be combined to provide powerful leverage for testing techniques
to mitigate stellar signals.
