A Year of Wavefront Sensing with JWST in Flight: Cycle 1 Telescope Monitoring and Maintenance Summary

TL;DR

This paper reports on JWST's optical performance and stability during Cycle 1, highlighting high stability, reduced tilt events, effective mirror corrections, and negligible impact from micrometeoroids, with performance maintained or improved in Cycle 2.

Contribution

It provides the first comprehensive in-flight performance summary of JWST's telescope stability, wavefront control, and impact resilience during its first year.

Findings

Segment alignment stability better than 10 nm RMS

Tilt events decreased significantly and ceased

Mirror corrections effectively maintained wavefront error below 70 nm RMS

Abstract

We summarize JWST's measured telescope performance across science Cycle 1. The stability of segments alignments is typically better than 10 nanometers RMS between measurements every two days, leading to highly stable point spread functions. The frequency of segment "tilt events" decreased significantly, and larger tilt events ceased entirely, as structures gradually equilibrated after cooldown. Mirror corrections every 1-2 months now maintain the telescope below 70 nm RMS wavefront error. Observed micrometeoroid impacts during cycle 1 had negligible effect on science performance, consistent with preflight predictions. As JWST begins Cycle 2, its optical performance and stability are equal to, and in some ways better than, the performance reported at the end of commissioning.