  We report the first orbital period determination for a Dwarf Nova (DN) in a
glubular cluster: V101 in M5 has a period of 5.796 +- 0.036 hours. We derived
this period from I-band photometry acquired with the Calypso Observatory High
Resolution Camera operating with tip-tilt adaptive optics correction.
Observations from the South African Astronomical Observatory in the V-band were
also analyzed and exhibit a periodic signal of the same period. This orbital
period suggests that V101 has a secondary of mid to late K spectral type with
Mv = +8.2 +- 0.5. The predicted spectral type is consistent with previous
spectral observations in quiescence which show a fairly red continuum. From the
observed minimum brightness of V = 22.5, we derive a distance modulus of (m -
M)v = 14.3 +- 0.5 to the DN which supports V101's membership in the globular
cluster M5. Measurement of the ellipsoidality effect indicates that the orbital
plane of the V101 system is moderately inclined, but not enough to exhibit
eclipses.
