The most prominent feature of radiation from a body with extreme
acceleration is the kinematics necessary for its observation. One
needs *two* coordinate frames: one for the accelerated source, the
other for the inertial observer. It is vital that these two frames be
aligned properly (as in Figure 12) so that
the geometrical clock of one frame is (one-way) commensurable with the
clock of the other. This commensurability locks the two frames into a
conjoint coordinate frame with an event horizon between them.

This conjointness opens vistas which are closed to the familiar inertial frames with their respective lattice work of free-float clocks and rods Taylor and Wheeler (1992). An obvious example is the measurement of the acceleration radiation scattered by a dipole oscillator as it accelerates through the e.m. field in its Minkowski vacuum state. The augmented Larmor formula applied to this oscillator yields the result that it scatters black body radiation with 100% spectral fidelity relative to the inertially expanding reference frame.