arXiv subjects

Milo Langker

Publications and source records attributed to Milo Langker.

4 recordsLinked to original sources

arXiv2026

Model-Based Retrieval of Four Years of JWST/NIRCam Wavefronts

The fidelity of data recovered by the James Webb Space Telescope (JWST) depends on precise monitoring of the mirror segments' surfaces and alignment. To this end, every few days the observatory takes pairs of defocused images of a reference star with its NIRCam instrument; a closed-source phase retrieval package is then employed to infer the wavefront. We here present camino (Computational Aberration Modelling and Inference for NIRCam Observations), an open-source algorithm to model NIRCam built in JAX using the differentiable Fresnel optics code dLUX and regularised maximum likelihood inference that has been conditioned on the entire archive of NIRCam wavefront sensing data. We typically improve the reduced chi-squared in fits to the defocused data from 60-65 to 12-13. We reconstruct the wavefront history of JWST from the beginning of science operations to early 2026. This open source implementation operates in parallel to the current STScI phase retrieval algorithm, allowing access by the broader scientific community to high-accuracy wavefront estimation and enabling its direct integration into science-analysis workflows. This represents a major step towards the ultimate goal of predictive calibration methods based on physics-based forward modelling, obviating the need for time-consuming observation of contemporaneous dedicated reference stars.

astro-ph.IM↗

arXiv2026

Spectral Information Content of Diffraction-Limited Images

High-resolution optical imaging is fundamentally limited by diffraction, which imprints wavelength-dependent structure onto the point spread function (PSF) of the optical system. This intrinsic chromaticity implies that in addition to spatial structure, images encode spectral information. We develop the theory of this spectral information content and provide strategies for its optimal extraction with calculations of Fisher information. We show that polychromatic PSF formation can be expressed as a convolution in logarithmic coordinates and define the corresponding spectral transfer function. We derive this function for the Airy disk and find algebraic decay in spectral log-frequency, implying the existence of arbitrarily fine spectral structure in the ideal, noiseless PSF. We use a differentiable forward model to numerically construct the spectral information eigenbasis and quantify the spectroscopic capability of diffraction-limited imaging across a range of noise and detector systematics. We demonstrate injection and recovery of the constrained spectral modes in a realistic simulated example and compare these results with previously reported methods. Our information-theoretic framework provides a generalisable method for spectral characterisation of PSFs spanning a variety of imaging contexts.

astro-ph.IM↗

arXiv2026

Astrometric detection of rocky exoplanets from inexpensive space platforms

The detection of orbiting exoplanets by way of astrometric monitoring of the host star to reveal gravitationally induced reflex motion requires extreme precision and measurement stability when targeting Earth-mass objects. Despite this, astrometry is widely regarded as the most promising avenue for the most desired of all targets: true Earth analogue systems in the solar neighbourhood. Formerly thought to require flagship class investment, recently several smaller concepts such as the TOLIMAN and SHERA missions have shown that detections are possible, at least in principle, from more modest space platforms. A key enabling feature is that these missions exploit narrow-angle astrometry. Observing only multiple star systems where the target provides its own astrometric reference greatly alleviates the challenges confronted by traditional astrometry with its reliance on distant, faint field stars. This principle underlies the TOLIMAN mission, for which progress and status is reported. However, only a tiny handful of nearby star systems are suited to such a TOLIMAN-like architecture. This paper discusses speculative optical concepts featuring ultra-stable telescopes of modest (<0.5m) aperture designed for astrometric monitoring of isolated single stars at the micro-arcsecond scales required for the discovery of Earth mass objects orbiting sun-like stars in temperate orbits. In simulation, highly sought-after neighbourhood systems such as Epsilon Eridani and Tau Ceti can be exhaustively searched for rocky planets with dedicated observing campaigns spanning several years, all from relatively inexpensive orbital platforms.

astro-ph.IM↗

arXiv2026

The TOLIMAN mission: A low-cost space telescope for high precision narrow-angle astrometry

The TOLIMAN project is engaged with the construction, launch and operation of a low-cost space telescope of unorthodox optical design. Its primary science goal targets an exhaustive search for temperate-orbit rocky planets around either star in the alpha Centauri AB binary within our nearest-neighbor star system. Despite their favorable proximity and brightness, the detection of terrestrial exoplanets around such nearby Sun-like stars remains problematic for contemporary instrumental approaches. By performing narrow-angle astrometric monitoring of binary stars at extreme precision, any exoplanets will betray their presence by way of gravitationally-induced perturbations on the binary orbit. Recovery of this signal is challenging for it amounts to only a few microarcseconds of angular deflection (at best), and so is normally thought to require a large (meter-class) instrument. By implementing an innovative optical and signal encoding architecture, the TOLIMAN space telescope aims to recover such signals with a telescope aperture of only 12.5cm. This paper gives an overview of key features of the mission; in particular the concepts underlying the optics to enable image registration at the extreme levels of precision required. An outline is also provided, sketching further mission components and systems incorporated into the 16U CubeSat spacecraft bus in which the science payload is housed - all of which are now under construction.

astro-ph.IM↗