Roscoe is a new, more compact version of the NASA GSFC Cloud Physics Lidar that has flown on multiple NASA high altitude aircraft over the past two decades. While utilizing the same proven measurement technique of coupling a high repetition rate laser with photon-counting detection, Roscoe differs from CPL in two significant ways.  First, it is designed to simultaneously observe both upwards and downwards from the aircraft, to enable studies of stratospheric aerosols above flight altitude as well as below.  It is, essentially, two small CPL instruments in one package, one pointing nadir and one pointing zenith.  Second, it operates at only 1064 and 355 nm (not 532 nm) to satisfy eye-safety considerations for airborne operation.  Roscoe measures depolarization at both wavelengths to characterize the phase of the cloud and aerosol particles detected.