Large dish mapping with coherent laser radar multilateration

Abstract

Coherent laser radar (CLR) multilateration for mapping a large dish relative to antenna design is discussed. Multilateration is more accurate than typical mapping methods used for analysis of antenna design, such as photogrammetry and tracking interferometers. Two CLR designs are considered: using four independent CLRs, and using a single CLR in which the laser is divided into four channels. The accuracy/cost trade-off shows that the four independent CLRs are about 3 × more accurate than the single four-channel CLR, while the cost is 3 × more. For a laser beam on a 50-m dish, the estimated CLR measurement uncertainty is between 20 and 31 μm, while the average root mean square, including environmental considerations for four independent CLRs, is 28 and 83 μm for the single CLR with four channels. The antenna can be measured at any elevation angle and dynamic measurements are possible. CLR is immune to sunlight, so measurements can be collected during daytime or nighttime. CLR operating wavelength (1500 nm) is sufficiently different from millimeter frequencies, so simultaneous measurements may be possible.