Optimal frequency plan for LISA pre-science operations using verification binaries

TL;DR

This paper evaluates different locking schemes for the LISA mission's pre-science phase, analyzing their impact on guaranteed sources and instrument calibration, and finds that the non-swap locking scheme is optimal for calibration and reduces inclination bias.

Contribution

It introduces a comparative analysis of locking schemes for LISA's pre-science operations, highlighting the advantages of the non-swap scheme for calibration and bias reduction.

Findings

Non-swap locking scheme is optimal for instrument calibration.

Differences in TDI output are within 10% for various locking schemes.

Similar amplitudes in TDI streams reduce inclination bias.

Abstract

The future Laser Interferometer Space Antenna (LISA) mission, which has successfully passed Mission Formulation phase, is in planning to be launched in 2030s. One of the ubiquitous LISA sources are the white-dwarf binaries (WDB) of which $\sim$40 are guaranteed sources as of now, making LISA unique in comparison to its ground-based counterpart. The current hardware design in planning necessitates a thorough check to determine whether the various locking schemes influence the guaranteed sources' signals significantly in order to re-consider that what is hard-coded in the phasemeter before launch for pre-science operations phase. Comparison of the phasemeter output of a face-on (V407Vul) binary and an edge-on (ZTFJ1539) binary indicates that the non-swap locking scheme, N2a, is optimal for instrument calibration. Additionally, the influence of the $\sim 7$ min orbital period edge-on source in two of the locking schemes yields a difference of maximum $\leq 10\%$ at the Time Delay Interferometry (TDI) output for data stream of one day. Simplified analyses show that neither of the locking schemes is favoured in the post-processing level. We find similar amplitudes in the TDI output stream for the face-on system V407Vul and the edge-on system ZTFJ1539 which leads to a significantly smaller inclination bias for the non-swap locking scheme. Additionally, a larger amplitude for edge-on systems will benefit most verification systems as the population of verification systems is biased towards edge-on systems as they are easier to detect in electromagnetic data.