Impact of an axial non-confocal antenna on the on-orbit lasercom receiver analyzed by the simplified combination method of ray tracing and diffraction theory

For an on-orbit lasercom receiver, the space thermal environment, microgravity environment and the adjustment error will deform the optical antenna, distorting the received wavefront and deteriorating the system performance. The axial non-confocal antenna is a deformed antenna caused by the despace of the secondary or primary mirror. Based on the simplified combination method of ray tracing and diffraction theory (simplified CMRD, or SCMRD), the calculation model of the normalized intensity distribution (NID) and the normalized received power (NRP) is established for an axial non-confocal antenna. The numerical results show that, the axial non-confocal antenna will flatten the received light spot, causing interruption of the communication link and deterioration of the bit error rate (BER) performance. The quantitative relations of the NID versus the axial non-confocal distance and the NRP versus the axial non-confocal distance would provide a reference for optical design, structural design, thermal design, assembly and adjustment accuracy design and detector selection. Besides, the numerical results are compared to those calculated by the wavefront fitting method and CMRD. The pros and cons of all methods are discussed. This work would advance the development of extending the SCMRD to analyze other deformed antennas’ impact on an on-orbit lasercom receiver.