1. A turbulence avoidance operation assist device as an airborne device comprising: a Doppler lidar for detecting the presence of a danger region such as a turbulent region ahead of an aircraft in a flight direction; a unit for representing the danger region as an assembly of rectangular solids when the Doppler lidar recognizes the danger region, and generating a flight trajectory consisting of time-varying variables by a local optimum solution of an avoidance trajectory using a convex quadratic programming method in which deviation from a reference trajectory is the smallest on the basis of an initial estimation solution obtained by a semidefinite programming method; and a unit for reporting, the flight trajectory to a pilot, wherein a size of the rectangular solid of the limiting region is determined by gridding a measurement region corresponding to a resolution of the Doppler lidar, where the measurement region is such that an initial position of a current position of a fuselage is taken as an end surface, and a length in a current flight direction, that is a direction determined by a current flight-path angle and heading angle, a height, and a width thereof are set correspondingly to a measurement range of the resolution of the Doppler lidar.