Dual Quadrature Phasemeter for Space-Based Interferometry

TL;DR

This paper introduces a dual quadrature phasemeter with wider bandwidth and improved phase tracking for space-based laser interferometry, enabling more flexible and accurate satellite measurements.

Contribution

It presents a novel dual quadrature phasemeter design that overcomes bandwidth limitations and allows phase tracking without optical frequency shifters in space geodesy.

Findings

Phase tracking error less than 10 microcycles/√Hz.

Overcomes bandwidth limitations of conventional phasemeters.

Enables new optical configurations for space geodesy.

Abstract

This letter presents a dual quadrature phasemeter, an implementation of a phase-locked loop designed to track the phase of homodyne and heterodyne inter-satellite laser links. The dual quadrature phasemeters use dual quadrature optical detection to enable an alternate phase readout scheme that operates with wider bandwidths and on signals with carrier frequency differences down to DC. Analytical modeling demonstrates that dual quadrature phasemeters overcome the bandwidth limitations of conventional phasemeters. Numerical simulations of noise linearity tests found that the phase tracking error of the dual quadrature phasemeter is less than 10 microcycle/$\sqrt{\text{Hz}}$ in the presence of non-linear cyclic errors. The dual quadrature phasemeter enables exploration of a new optical configuration for retroreflector-based space geodesy missions with architecture similar to that implemented in GRACE-FO. One such alternate configuration is proposed that is capable of tracking satellite separation without requiring a frequency offset between local and incoming light, eliminating the need for optical frequency shifters.