Research on trajectory planning of On-The-Fly observing for the active feed receiver in FAST

On-The-Fly (OTF) observing is one of the five kinds of operation mode owned by Five-hundred-meter Aperture Spherical Radio Telescope (FAST). In order to guarantee the active feed receiver move stably during the OTF observation, its trajectory planning was dealt with in this paper. Considering the trajectory in local coordinate system is complex, the paper planned its trajectory planning in the equatorial coordinate system. For the Earth´s rotation, in order to guarantee the active feed receiver to start smoothly from a standstill and to soft-stop stably in the specified time when scanning along the declination, the right ascension and declination were planned with the double S velocity profile at the same time. The resulting trajectory is ensured the continuation in position, velocity and acceleration under local coordinate system, meanwhile, considering the execute ability of the mechanism, the trajectory respect specified limits in velocity, acceleration and jerk. An example and the comparison between the original trajectory and the planned trajectory are given to illustrate the advantage of the presented approach.