Aug 2026· Space Telescopes and Instrumentation 2026: Optical, Infrared, and Millimeter Wave· 0 citations· 14 references
Physics
TL;DR
ADORA provides a flexible framework for studying astrometric extraction, calibration-bias diagnosis, and future SHERA requirements, and Pixel-position errors across the tested range remain near the matched-model recovery scale indicating robustness to certain detector calibration errors.
Abstract
Searching for Habitable Exoplanets with Relative Astrometry (SHERA) is a proposed Small Explorer mission concept designed to measure the separation of nearby binary stars at microarcsecond-class precision. Recovering this signal requires separating astrophysical motion from coupled changes in pointing, plate scale, wavefront error, spectral response, and detector calibration. We present the Astrometric Differentiable Optics and Retrieval Algorithm (ADORA), an image-domain framework that combines a three-plane differentiable physical-optics model with a layered astrometric inference algorithm. The forward model includes a diffractive pupil, mirror-specific wavefront error and beamwalk, polychromatic source and throughput models, and configurable detector effects. Per-frame registration states are treated locally and eliminated through Schur reduction before the slower astrometric and instrument state is updated in a prior-whitened Fisher eigenbasis. Five-minute matched-model simulations show no detected separation bias at the current Monte Carlo depth and approximately 11 uas realization-to-realization scatter. A SHERA target sweep reveals a more-than-fivefold variation in astrometric information between Alpha Centauri and 61 Cygni, motivating future target-dependent accumulation and update cadence. High-order-wavefront knowledge error can drive the retrieval toward a strongly biased astrometric solution while leaving the local posterior sigma nearly unchanged, demonstrating that statistical curvature alone does not capture unmodeled bias. Pixel-position errors across the tested range remain near the matched-model recovery scale indicating robustness to certain detector calibration errors. ADORA provides a flexible framework for studying astrometric extraction, calibration-bias diagnosis, and future SHERA requirements.
High-resolution spacecraft images provide important astrometric constraints for orbit refinement, but measurements of resolved bodies are often limited by labor-intensive control-point selection and the difficulty of achieving consistent reductions over large image archives. We present an automated shape-model-based astrometric pipeline for Phobos and apply it to Mars Express Super Resolution Channel (SRC) images. For each exposure, a synthetic image is rendered from a high-resolution 3D shape model under the nominal spacecraft-target-Sun geometry. Feature correspondences between the observed and synthetic images are established using SuperPoint and SuperGlue, followed by RANSAC filtering. The matched synthetic-image keypoints are then associated with surface points through ray-shape intersection. The geometric adjustment fixes the adopted body orientation, spacecraft state, and corrected camera pointing and estimates only two effective plane-of-sky position offsets using the exact perspective-projection model. These offsets are used to derive the center-of-figure position of Phobos. We first test the method on an image set previously analysed with a control-point approach and obtain comparable astrometric performance. We then extend the analysis to a larger SRC dataset spanning 2007-2025 and obtain 1113 successful measurements. Relative to the JPL MAR099 ephemeris, the resulting observed-minus-computed residuals have mean values of 0.186 km in $\alpha \times cos(\delta)$ and 0.053 km in $\delta$, with corresponding standard deviations of 0.609 km and 0.583 km. These results demonstrate that the proposed pipeline provides a practical approach to large-scale, homogeneous astrometric reduction of archival spacecraft images of Phobos, with potential application to other resolved bodies.
Wangxin Lai, Qing-Feng Zhang, Rui Zhang et al.· 0 citations
Space telescopes maintain optical alignment through periodic, resource-intensive wavefront calibration, leaving the optical state unobserved between corrections. We propose treating onboard engineering telemetry as an opportunistic wavefront sensor. Specifically, the high-cadence thermal and pointing signals already recorded by the James Webb Space Telescope may suffice to recover spatially resolved optical path difference at nanometer precision, without dedicated measurements. Our framework uses a two-stage gradient boosting regressor. It predicts optical path difference residuals for each mirror segment in a low-dimensional principal component basis. The model is trained and evaluated using data captured on-orbit during six months. Based on this limited data, optical path difference inference has high statistical significance in 13 out of 18 mirror segments. In 6 mirror segments, the model achieves explained variance above 50\%. These results demonstrate feasibility for telemetry-driven wavefront estimation, as a low-overhead sensing modality. The study suggests a potential to support continuous monitoring and calibration scheduling for large segmented observatories.
Lahav Buzi, Y. Schechner, A. Levis et al.· 0 citations
(Photometry and Astrometry of Point Sources), a fully automated Python-based pipeline for photometric reduction with integrated astrometric calibration, is introduced, supporting the homogeneous reduction of stellar and moving Solar System objects, independent of telescope aperture or detector type.
Orhan Erece, Yücel Kılıç· Astronomy & Astrophysics· 1 citation
We present PhotoIFU, a workflow that uses deep multi-band imaging as a low-resolution photometric integral field unit. Applied to PSF-matched JWST/NIRCam imaging, PhotoIFU treats each spatial pixel as a coarse SED element and fits the pixel SEDs with Prospector to map resolved stellar-population and ISM-related properties. We apply this approach to three galaxies at $z=1.3$--3.7 in JADES: two systems with extended ionized line emission and one post-starburst galaxy with an exceptionally strong neutral outflow. Pixel-by-pixel SED fitting gives maps of stellar-mass surface density, specific star formation rate, dust attenuation, gas-phase metallicity, and recent star-formation history. We find that regions selected from the extended-emission or outflow geometry occupy distinct parts of the resolved SED-property distribution compared with the full host. In the systems with extended ionized emission, these regions are generally less dusty, consistent with ionized emission being observed along dust-poor, low-column-density pathways through the host. In the neutral-outflow system, the selected regions show enhanced recent star formation, suggesting that compact rejuvenation may mark the aftermath of an earlier energetic phase. These results show that galactic outflows and extended emission-line structures can be spatially associated with measurable differences in resolved host-galaxy stellar populations and ISM-related properties. PhotoIFU provides an imaging-based method for resolved SED mapping of feedback-related structures in larger galaxy samples where full spectroscopic integral-field mapping is unavailable.
Yongda Zhu, M. Rieke, Courtney Carreira et al.· 0 citations
The detection of Earth-like exoplanets via astrometry necessitates centroiding precision at the 0.3 microarcsec level, thereby imposing stringent constraints on the focal plane geometry of space telescopes. The AGATE focal plane instrument, a proposed component of the NASA Habitable Worlds Observatory (HWO), aims to achieve this objective through the calibration of the intra-pixel response function of CMOS detectors to an accuracy of 50 micropixel (220 nm The present paper proposes a Young's fringes-based calibration method, derived from those employed by JPL and IPAG, for the purpose of mapping the pixel response barycenter offsets across the detector. Using a Pyxalis GIGAPYX-4600 CMOS sensor, we demonstrate via simulations and laboratory measurements that (1) a precision of 500 micropixel is achievable with 10,000 frames (current setup); (2) inter-pixel capacitance crosstalk and fringe hyperbolicity are dominating the errors at small and large scales, respectively; and, (3) an iterative inverse problem approach with a hyperbolic fringe model is proposed to overcome paraxial approximation limits for 1 Gpix focal planes. These results pave the way for on-board calibration of HWO's astrometric instrument, ensuring the sub-microarcsec precision required for exo-Earth detection.
Hugo Rousset, É. Thiébaut, Chloé Rey et al.· X-Ray, Optical, and Infrared...· 0 citations
Launching in 2027, the Nancy Roman Grace Space Telescope (Roman) has the potential to directly image exoplanets in reflected light for the first time. Roman imaging will introduce new constraints on exoplanet orbital parameters, since reflected-light intensity depends on orbital phase. In this Note, we discuss an addition to the open-source Python package orbitize!, which allows users to model exoplanet orbits using joint constraints from astrometry and photometric variations due to orbital phase. To investigate the impact of adding photometric data into the orbital model, we simulated realistic measurements of partial orbits, both including and excluding photometry in our model, and computed orbital posteriors. We found that fitting both astrometry and photometry improves posterior precision relative to fitting astrometry alone. This effect was more pronounced for higher-signal noise ratio (SNR) images; for example, photometric data with SNR = 10 yielded 33% improvement in inclination precision when including photometry, while SNR = 3 data yielded only 12% improvement.
Farrah Molina, Sarah Blunt, Jason J. Wang· Research Notes of the AAS· 0 citations