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| Paper: |
High Precision Astrometry for the HWO High Resolution Imager |
| Monograph: |
11, HWO25 Proceedings Part II: Mission Framework, Technology, and Broader Contributions |
| Page: |
319 |
| Authors: |
Eduardo Bendek, B. Scott Gaudi, and Kaz Gary |
| DOI: |
10.26624/UXEM1048 |
| Abstract: |
Accurately measuring exoplanet masses is essential to address priority topics for the Habitable Worlds Observatory, such as detecting and assessing the habitability of nearby Earth analogs. Measuring Earth analogs exoplanet masses to ∼10% is necessary \citep{damiano2025Mass_uncert} to break the degeneracy between some true bio-signatures and lifeless atmospheres. Stellar astrometry can detect exoplanets and it is the only technique that can unambiguously measure their masses. However, measuring the masses of Earth analogs around FGK stars out to ∼10pc requires sub-microarcsecond astrometric accuracy, which is beyond the capabilities of current instrumentation. The main limiting factor is optical distortions caused by the motion of the optical elements. Previously, a solution to calibrate changes in the distortion field has been proposed using diffraction fiducials created by a pattern imprinted on the telescope's primary mirror. While we have shown that this solution can effectively mitigate the optical distortions, it does increase the diffracted light that might affect other astrophysical science cases. We propose to enhance high-precision astrometry for exoplanet detection using the Habitable Worlds Observatory High-Resolution Imager (HRI) instrument. For that we propose to implement an optional high-precision astrometry mode using a switchable diffractive pupil at the entrance of the HRI. This optical element would create diffraction features that will propagate through the camera and map optical distortions on the focal plane, allowing for distortion calibration and enhancing the astrometric accuracy of the observatory. |
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