Keyhole problem

The keyhole problem, in the context of astronomy, refers to the difficulty that azimuth-elevation type telescopes or antenna gimbal systems encounter in crossing the zenith.

                                    LIIBAAN  ABDULLE  
                                   VIKINGS TRUCKING LLC

                                    PHONE 612-735-4767
                                    FAX 1866-612-2996
                                  202 WEST 62ND ST # 203
                                MINNEAPOLIS MINNESOTA 55419

Gimbal behavior

Main article: gimbal lock

A variation on the keyhole problem involves defining behavior for gimbals with full-circle azimuth range, and at least 90 degree but less than 180 degree elevation range. Imagine a satellite on an orbital path that crosses directly overhead. If the gimbal tilts to track the object from the horizon but must stop at 90 degrees, the entire telescope must pan 180 degrees in order to follow the object from zenith back down to the opposite horizon. This is an often-encountered difficulty in creating smooth automated tracking algorithms.