James Webb Space Telescope Optical Simulation Testbed II. Design of a Three-Lens Anastigmat Telescope Simulator

TL;DR

The paper presents the design of a tabletop optical simulation testbed that replicates JWST's wavefront sensing and control physics using a three-lens anastigmat system, enabling realistic testing at visible wavelengths.

Contribution

It introduces a novel three-lens anastigmat optical system that simulates JWST's TMA design at optical wavelengths for wavefront control testing.

Findings

The design achieves image quality comparable to JWST NIRCam at 633 nm.

Linearity of aberration modes is similar to traditional TMA designs.

The testbed supports development of linear-control alignment strategies.

Abstract

The James Webb Space Telescope (JWST) Optical Simulation Testbed (JOST) is a tabletop experiment designed to reproduce the main aspects of wavefront sensing and control (WFSC) for JWST. To replicate the key optical physics of JWST's three-mirror anastigmat (TMA) design at optical wavelengths we have developed a three-lens anastigmat optical system. This design uses custom lenses (plano-convex, plano-concave, and bi-convex) with fourth-order aspheric terms on powered surfaces to deliver the equivalent image quality and sampling of JWST NIRCam at the WFSC wavelength (633~nm, versus JWST's 2.12~micron). For active control, in addition to the segmented primary mirror simulator, JOST reproduces the secondary mirror alignment modes with five degrees of freedom. We present the testbed requirements and its optical and optomechanical design. We study the linearity of the main aberration modes (focus, astigmatism, coma) both as a function of field point and level of misalignments of the secondary mirror. We find that the linearity with the transmissive design is similar to what is observed with a traditional TMA design, and will allow us to develop a linear-control alignment strategy based on the multi-field methods planned for JWST.