  We present near-infrared Ks-band photometry bracketing the secondary eclipse
of the hot Jupiter TrES-2b using the Wide-field Infrared Camera on the
Canada-France-Hawaii Telescope. We detect its thermal emission with an eclipse
depth of 0.062 +/- 0.012% (5-sigma). Our best-fit secondary eclipse is
consistent with a circular orbit (a 3-sigma upper limit on the eccentricity, e,
and argument or periastron, omega, of |ecos(omega)| < 0.0090), in agreement
with mid-infrared detections of the secondary eclipse of this planet. A
secondary eclipse of this depth corresponds to a day-side Ks-band brightness
temperature of TB = 1636 +/- 88 K. Our thermal emission measurement when
combined with the thermal emission measurements using Spitzer/IRAC from
O'Donovan and collaborators suggest that this planet exhibits relatively
efficient day to night-side redistribution of heat and a near isothermal
dayside atmospheric temperature structure, with a spectrum that is well
approximated by a blackbody. It is unclear if the atmosphere of TrES-2b
requires a temperature inversion; if it does it is likely due to chemical
species other than TiO/VO as the atmosphere of TrES-2b is too cool to allow
TiO/VO to remain in gaseous form. Our secondary eclipse has the smallest depth
of any detected from the ground at around 2 micron to date.
