Complete Catalog of Laser Locking Configurations for LISA

TL;DR

This paper systematically catalogs all feasible laser locking configurations for LISA, aiding in optimal frequency planning for its gravitational wave detection mission.

Contribution

It introduces an automated method to explore, validate, and classify all possible laser locking schemes, expanding beyond previous algorithmic solutions.

Findings

Identified 36 non-frequency-swapping configurations.

Found 72 frequency-swapping configurations.

Provided a comprehensive catalog for operational scenarios.

Abstract

The Laser Interferometer Space Antenna (LISA) will enable direct observations of low-frequency gravitational waves, offering unprecedented insight into astrophysical and cosmological phenomena. LISA's heterodyne interferometric measurement system requires phase-locking five of its six onboard lasers with tunable frequency offsets to ensure that all beatnotes remain within the metrology system's operational range, despite Doppler-induced frequency shifts. The selection of these offset frequencies -- collectively forming a frequency plan -- is a complex optimization problem constrained by the spacecraft's orbital dynamics and instrument limitations. While previous work established an algorithmic solution for deriving time-dependent frequency plans, this study takes a complementary approach by systematically analyzing and cataloging all possible laser locking configurations. We present an automated method to explore, validate, and classify viable locking schemes, identifying 36 unique non-frequency-swapping configurations and 72 additional frequency-swapping configurations for an arbitrary choice of primary laser. This exhaustive classification provides a foundation for frequency planning across the full range of operational scenarios.