Alignment-and-metrological facility for fine adjustment of antenna linear and angular position during spacecraft assembly

The paper discusses issues involved in fine adjustment of the linear and angular position of antenna system reflectors on a spacecraft (SC) during its assembly using an alignment-and-metrology facility that has been developed, which consists of a 6-DOF pointing device and a laser coordinate measurement tracker. Achieving the specified linear and angular positions of antenna system elements in the SC datum reference frame, reducing human effort and time needed to perform this processing operation is an important task when building a spacecraft. To address this problem, a procedure was developed and tried out during an actual SC assembly consisting in the joint use of the 6-DOF pointing device Hexapod PM-mkm-P and the high-precision laser tracker Leica AT 403 for measuring the coordinates. An algorithm was developed for hardware/software interfacing between elements of the alignment-and-metrology facility, which provides iterative linear and angular positioning of the antenna reflectors in a closed loop with a feedback. The paper discusses sources of errors and the way to minimize their effect on the operation of various types of pointing using continuous monitoring by means of an external measuring system. The developed alignment-and-metrology facility provided high-precision spatial positioning of antenna elements in the SC coordinate system, which made it possible to rule out any errors by operator/installation worker during alignment and significantly reduce the time needed to perform the said operation. Key words: spacecraft, antenna alignment, 6-DOF hexapod-type platform with parallel kinematics, Gough-Stewart platform, laser coordinate measuring system.