Cryogenic focus measurement system for a wide-field infrared space telescope
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1.
California Institute of Technology
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2.
Jet Propulsion Lab
Abstract
We describe a technique for measuring focus errors in a cryogenic, wide-field, near-infrared space telescope. The measurements are made with a collimator looking through a large vacuum window, with a reflective cold filter to reduce the background thermal infrared loading on the detectors and optics. The vacuum window and cold filter introduce a wavefront error that we characterize using an autocollimating microscope. For the 200 mm diameter aperture f/3 space telescope SPHEREx, we achieve a focus position measurement with a ∼15µm systematic and a ∼5µm statistical error.
Copyright and License
© 2024 Optica Publishing Group.
Acknowledgement
We thank Darren Dowell, Kenneth Mannat, Hien Nguyen, and Marco Viero for productive discussions regarding the collimator design and for helpful comments on the manuscript. The research described in this paper was carried out at the California Institute of Technology under a contract with the National Aeronautics and Space Administration.
Funding
National Aeronautics and Space Administration (80NM0018D0004).
Conflict of Interest
The authors declare no conflicts of interest.
Data Availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
Additional details
- National Aeronautics and Space Administration
- 80NM0018D0004
- Accepted
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2024-04-27Accepted paper
- Available
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2024-04-24Published online
- Caltech groups
- Astronomy Department
- Publication Status
- Published