Opto-mechanical modeling of the Herschel Space Telescope at ESA/ESTEC

Abstract

In this paper the opto-mechanical modeling of the Herschel infrared space telescope at ESA/ESTEC is presented. The aim of the paper is to give an overview of all modeling activities that took place between 2006 and 2010. In 2006 ESA commissioned a Tiger Team to review the discrepancy between the prediction and measurement of the change in telescope back focal length of the Herschel infrared space telescope. The understanding of the discrepancy was essential since the telescope did not have a refocusing mechanism and hence had to be shimmed to the focus position at cryogenic operational temperature. A team of 16 engineers and scientists collocated at ESA/ESTEC to review the finite element models, optical models and test data used for the prediction of the telescope back focal length. The methodology of prediction, the uncertainties and the obtained results were critically assessed. The team used various modeling techniques including paraxial optical models, first order linear thermal expansion models, full system and metrology ray tracing, deterministic and stochastic thermo-elastic finite element analyses. The opto-mechanical analysis techniques, assumptions and results are discussed. In addition the impact of new measurements of coefficients of thermal expansion, performed after shimming of the telescope flight model, are addressed.

Thermal-structural-optical integrated analysis of low temperature infrared athermal collimation system

“…In the realm of infrared technology, athermal optical-mechanical structures composed of SiC material-known for its low thermal expansion coefficient and high thermal conductivity-have gained widespread usage [13][14][15] . The complete collimation system is constructed from SiC material to ensure consistent dimensional stability under low temperatures.…”

Review on thermal and mechanical challenges in the development of deployable space optics

“…This is not necessarily the operating temperature of the structure. Some telescopes have a certain temperature range required to operate, such as thermal IR telescopes, 45 while others are indifferent to it, but their temperature is defined primarily by their environment. Therefore, it is of primary importance to utilize the correct temperature to linearize the thermal expansion behavior of the material.…”

Optical Conceptual Design for the Giant Magellan Telescope Multi-Object Astronomical and Cosmological Spectrograph

“…According to Heijmans et al (2018), a solution proposed in the literature to integrate optomechanical analysis, which involves the coupling of the structural, thermal, and optical simulation tools in a multi-disciplinary process, is commonly referred to as Structural-Thermal-Optical Performance or STOP analysis. Customized STOP analysis is currently used in large aerospace projects (Fransen et al, 2011;Gracey et al, 2016), but there are also commercial solutions, such as Sigfit, FRED Optical Engineering Software, Lensmechanix among others (Heijmans et al, 2018;Genberg et al, 2017). Although the STOP analysis is part of the optomechanical engineering responsibilities (optomechanical engineering is an application of mechanical engineering principles to design, fabricate, assemble, test, and deploy an optical system that meets operational performance requirements), we decided to develop an in-house methodology for FEA-Zemax integration to satisfy the immediate needs and budget constraints for the conceptual design of GMACS.…”