  Even among the most irradiated gas giants, so-called ultra-hot Jupiters,
KELT-9b stands out as the hottest planet thus far discovered with a dayside
temperature of over 4500K. At these extreme irradiation levels, we expect an
increase in heat redistribution efficiency and a low Bond albedo owed to an
extended atmosphere with molecular hydrogen dissociation occurring on the
planetary dayside. We present new photometric observations of the KELT-9 system
throughout 4 full orbits and 9 separate occultations obtained by the 30cm space
telescope CHEOPS. The CHEOPS bandpass, located at optical wavelengths, captures
the peak of the thermal emission spectrum of KELT-9b. In this work we
simultaneously analyse CHEOPS phase curves along with public phase curves from
TESS and Spitzer to infer joint constraints on the phase curve variation,
gravity-darkened transits, and occultation depth in three bandpasses, as well
as derive 2D temperature maps of the atmosphere at three different depths. We
find a day-night heat redistribution efficiency of $\sim$0.3 which confirms
expectations of enhanced energy transfer to the planetary nightside due to
dissociation and recombination of molecular hydrogen. We also calculate a Bond
albedo consistent with zero. We find no evidence of variability of the
brightness temperature of the planet, excluding variability greater than 1%
(1$\sigma$).
