arXiv subjects

Ramya Anche

Publications and source records attributed to Ramya Anche.

13 recordsLinked to original sources

arXiv2026

The Roman Coronagraph Community Participation Program: data reduction pipeline design and implementation

The Roman Space Telescope Coronagraph Instrument will demonstrate a series of technologies and techniques to enable the direct detection of reflected-light planets with space-based observatories. To characterize and validate the performance of the Coronagraph Instrument, the Community Participation Program is developing corgidrp, an open-source Python-based data reduction pipeline. The pipeline can process data from the required and best-effort observing modes and their associated calibration sequences into calibrated science-ready data products. We present the software design and implementation of corgidrp and the motivation behind specific design decisions. We describe the software architecture, data flow, processing steps, automation tools, testing framework, and development philosophy. We also outline future development plans in preparation for on-sky data.

astro-ph.IM↗

arXiv2026

The Roman Coronagraph Community Participation Program: trials and triumphs of designing an observing program for a technology demonstration instrument

The Coronagraph Instrument onboard the Nancy Grace Roman Space Telescope serves as a crucial technology pathfinder for the Habitable Worlds Observatory, with on-sky verification of high-contrast imaging techniques and the potential to image a Jupiter analog in reflected light for the first time. Together with the Roman Project Team, the Community Participation Program (CPP) is responsible for target selection, preparatory observations, developing an exposure time calculator, target database, data reduction pipeline, simulation tools, and engagement with the broader community. Here we present an overview of the CPP activities over the past two years with an emphasis on observation planning activities for the initial in-orbit checkout and the first six months of the observation phase. Finally, we present future opportunities for the astronomical community to interact with the data as it becomes public early in the mission.

astro-ph.IM↗

arXiv2026

The Roman Coronagraph Community Participation Program: target database and tools

The Nancy Grace Roman Space Telescope, set to launch in Fall 2026, will carry the Coronagraph Instrument, which will, for the first time, demonstrate high-contrast imaging with active wavefront control in visible wavelengths from space. In preparation for execution of the Coronagraph's commissioning and observing programs, the Roman Coronagraph Community Participation Program (CPP) has developed a target database and associated ecosystem of publicly accessible tools for observation planning and scheduling. The target database includes both stars and known sub-stellar companions and disks that may be observed by the Coronagraph instrument during its primary mission. Targets in the database include planet and disk hosts as well as calibration stars, reference stars, and engineering program targets. The database is designed to operate in conjunction with a variety of tools, including an exposure time calculator, a pointing and keepout calculator, and a reference star selection tool. Here, we describe the current schema and contents of the database and demonstrate how it and its associated tools are being used for observation planning.

astro-ph.IM↗

arXiv2026

The Space Coronagraph Optical Bench (SCoOB): X. Dark zone maintenance

The Space Coronagraph Optical Bench (SCoOB) is a vacuum high contrast imaging testbed designed to demonstrate starlight suppression at optical wavelengths and obtain contrasts better than 10$^{-8}$ in a one-sided dark hole from 3 to 10 $\lambda/D$ using a vector vortex coronagraph (VVC) mask. Some of the recent efforts have been in testing dark zone maintenance (DZM) algorithms which are used to stabilize the contrast in the presence of wavefront drifts and allow for the long integration times required by exoplanet observations. In this work, we discuss the results from simulations with two DZM algorithms - linear dark field control (LDFC) and extended Kalman Filter-based (EKF) DZM. We also report preliminary results from the testbed with LDFC.

astro-ph.IM↗

arXiv2026

Design and modeling of an oblique incidence dichroic mirror for a high contrast imaging system

The proposed Habitable Worlds Observatory (HWO) aims to detect and characterize Earth-like planets around Sun-like stars from the ultraviolet to the infrared using high-contrast imaging. A dichroic mirror is a natural choice for splitting light between multiple wavelength channels in such a system, but the coating must introduce minimal polarization aberrations and chromatic wavefront errors (WFE) to avoid limiting contrast. We present the design of a long-pass dichroic mirror operated at a $7^\circ$ angle of incidence that provides high reflection in the short-wavelength band, high transmission in the long-wavelength band, and a sharp cut-on near 550~nm. A multilayer thin-film design process was used to meet these spectral requirements while reducing polarization aberrations and chromatic WFE sensitivity. Reflected phase optimization was also incorporated to reduce sensitivity to manufacturing-induced layer-thickness variations, which can produce wavelength-dependent WFE and degrade coronagraph performance. The resulting coating-induced WFE was propagated through simulations of a vector vortex coronagraph to assess contrast performance. Simulations predict dark-hole contrast residuals at the $10^{-12}$ level, indicating that the optimized dichroic mirror does not limit coronagraph performance.

astro-ph.IM↗

arXiv2026

The Lazuli Space Observatory: Architecture & Capabilities

The Lazuli Space Observatory is a 3-meter aperture astronomical facility designed for rapid-response observations and precision astrophysics across visible to near-infrared wavelengths (400-1700 nm bandpass). An off-axis, freeform telescope delivers diffraction-limited image quality (Strehl $>$0.8 at 633 nm) to three instruments across a wide, flat focal plane. The three instruments provide complementary capabilities: a Wide-field Context Camera (WCC) delivers multi-band imaging over a 35' $\times$ 12' footprint with high-cadence photometry; an Integral Field Spectrograph (IFS) provides continuous 400-1700 nm spectroscopy at R $\sim$ 100-500 for stable spectrophotometry; and an ExtraSolar Coronagraph (ESC) enables high-contrast imaging expected to reach raw contrasts of $10^{-8}$ and post-processed contrasts approaching $10^{-9}$. Operating from a 3:1 lunar-resonant orbit, Lazuli will respond to targets of opportunity in under four hours--a programmatic requirement designed to enable routine temporal responsiveness that is unprecedented for a space telescope of this size. Lazuli's technical capabilities are shaped around three broad science areas: (1) time-domain and multi-messenger astronomy, (2) stars and planets, and (3) cosmology. These capabilities enable a potent mix of science spanning gravitational wave counterpart characterization, fast-evolving transients, Type Ia supernova cosmology, high-contrast exoplanet imaging, and spectroscopy of exoplanet atmospheres. While these areas guide the observatory design, Lazuli is conceived as a general-purpose facility capable of supporting a wide range of astrophysical investigations, with open time for the global community. We describe the observatory architecture and capabilities in the preliminary design phase, with science operations anticipated following a rapid development cycle from concept to launch. [Abstract abridged]

astro-ph.IM↗

arXiv2025

Optimizing Kilonova Searches: A Case Study of the Type IIb SN 2025ulz in the Localization Volume of the Low-Significance Gravitational Wave Event S250818k

Kilonovae, the ultraviolet/optical/infrared counterparts to binary neutron star mergers, are an exceptionally rare class of transients. Optical follow-up campaigns are plagued by contaminating transients, which may mimic kilonovae, but do not receive sufficient observations to measure the full photometric evolution. In this work, we present an analysis of the multi-wavelength dataset of supernova (SN) 2025ulz, a proposed kilonova candidate following the low-significance detection of gravitational waves originating from the potential binary neutron star merger S250818k. Despite an early rapid decline in brightness, our multi-wavelength observations of SN 2025ulz reveal that it is a type IIb supernova. As part of this analysis, we demonstrate the capabilities of a novel quantitative scoring algorithm to determine the likelihood that a transient candidate is a kilonova, based primarily on its 3D location and light curve evolution. We also apply our scoring algorithm to other transient candidates in the localization volume of S250818k and find that, at all times after the discovery of SN 2025ulz, there are $\geq 4$ candidates with a score comparable to SN 2025ulz, indicating that the kilonova search may have benefited from the additional follow-up of other candidates. During future kilonova searches, this type of scoring algorithm will be useful to rule out contaminating transients in real time, optimizing the use of valuable telescope resources.

astro-ph.HE↗

arXiv2025

The Space Coronagraph Optical Bench (SCoOB): 6. demonstration of Lyot low order wavefront control combined with high order wavefront control using a vortex coronagraph

To reach and maintain high contrast levels, coronagraph instruments will require a combination of low-order and high-order wavefront control techniques to correct for dynamic wavefront error. Efficient low-order wavefront sensing and control (LOWFSC) schemes use the starlight rejected by the coronagraph such that LOWFSC can operate with a relatively bright signal to correct rapid disturbances. Meanwhile, a family of high-order wavefront sensing and control (HOWFSC) techniques utilizing the science camera have been developed to create regions of high contrast known as dark holes. These two control loops must operate simultaneously for dark holes to be maintained over long observation periods. Using a 952 actuator MEMS deformable mirror and a vector vortex coronagraph (VVC) on the Space Coronagraph Optical Bench (SCoOB), we demonstrate a Lyot-based LOWFSC loop operating in combination with a HOWFSC loop. For these experiments, implicit electric field conjugation (iEFC) is the chosen HOWFSC technique, and we demonstrate how this empirical method can be calibrated and deployed while the LOWFSC loop corrects for dynamic wavefront error. We show this combination of LOWFSC and iEFC maintained 1E-8 contrast levels in air.

physics.optics↗

arXiv2025

The Space Coronagraph Optical Bench (SCoOB): 7. design, fabrication, and first light for a self-coherent camera

The 2020 Decadal Survey on Astronomy and Astrophysics tasked future space observatories with the goal of detecting and characterizing a large sample of Earth-like exoplanets. To achieve this, these observatories will require coronagraphs and wavefront control algorithms in order to achieve $10^{-10}$ or better starlight suppression. The Space Coronagraph Optical Bench (SCoOB) is a vacuum compatible testbed at the University of Arizona which aims to advance and mature starlight suppression technologies in a space-like environment. In its current configuration, SCoOB is a charge-6 vector vortex coronagraph outfitted with a Kilo-C microelectromechanical systems deformable mirror capable of achieving sub-$10^{-8}$ dark hole contrast at visible wavelengths using implicit electric field conjugation (iEFC). In this work, we demonstrate the use of a self-coherent camera (SCC) for dark hole digging and maintenance on SCoOB. The SCC introduces a small off-axis pinhole in the Lyot plane which allows some starlight to reach the focal plane and interfere with residual speckles. This enables high-order focal-plane wavefront sensing which can be combined with active wavefront control to null the speckles in a specified region of high contrast known as the dark hole. We discuss considerations for implementation, potential limitations, and provide a performance comparison with iEFC. We also discuss the design optimization and fabrication process for our SCC Lyot stops.

astro-ph.IM↗

arXiv2024

A Generalized Expression for Accelerating Beamlet Decomposition Simulations

Paraxial diffraction modeling based on the Fourier transform has seen widespread implementation for simulating the response of a diffraction-limited optical system. For systems where the paraxial assumption is not sufficient, a class of algorithms has been developed that employs hybrid propagation physics to compute the propagation of an elementary beamlet along geometric ray paths. These "beamlet decomposition" algorithms include the well-known Gaussian Beamlet Decomposition (GBD) algorithm, of which several variants have been created. To increase the computational efficiency of the GBD algorithm, we derive an alternative expression of the technique that utilizes the analytical propagation of beamlets to tilted planes. We then use this accelerated algorithm to conduct a parameter-space search to find the optimal combination of free parameters in GBD to construct the analytical Airy function. The experiment is conducted on a consumer-grade CPU, and a high-performance GPU, where the new algorithm is 34 times faster than the previously published algorithm on CPUs, and 67,513 times faster on GPUs.

physics.optics↗

arXiv2023

Approaches to lowering the cost of large space telescopes

New development approaches, including launch vehicles and advances in sensors, computing, and software, have lowered the cost of entry into space, and have enabled a revolution in low-cost, high-risk Small Satellite (SmallSat) missions. To bring about a similar transformation in larger space telescopes, it is necessary to reconsider the full paradigm of space observatories. Here we will review the history of space telescope development and cost drivers, and describe an example conceptual design for a low cost 6.5 m optical telescope to enable new science when operated in space at room temperature. It uses a monolithic primary mirror of borosilicate glass, drawing on lessons and tools from decades of experience with ground-based observatories and instruments, as well as flagship space missions. It takes advantage, as do large launch vehicles, of increased computing power and space-worthy commercial electronics in low-cost active predictive control systems to maintain stability. We will describe an approach that incorporates science and trade study results that address driving requirements such as integration and testing costs, reliability, spacecraft jitter, and wavefront stability in this new risk-tolerant "LargeSat" context.

astro-ph.IM↗

arXiv2023

Poke: An open-source ray-based physical optics platform

Integrated optical models allow for accurate prediction of the as-built performance of an optical instrument. Optical models are typically composed of a separate ray trace and diffraction model to capture both the geometrical and physical regimes of light. These models are typically separated across both open-source and commercial software that don't interface with each other directly. To bridge the gap between ray trace models and diffraction models, we have built an open-source optical analysis platform in Python called Poke that uses commercial ray tracing APIs and open-source physical optics engines to simultaneously model scalar wavefront error, diffraction, and polarization. Poke operates by storing ray data from a commercial ray tracing engine into a Python object, from which physical optics calculations can be made. We present an introduction to using Poke, and highlight the capabilities of two new propagation physics modules that add to the utility of existing scalar diffraction models. Gaussian Beamlet Decomposition is a ray-based approach to diffraction modeling that allows us to integrate physical optics models with ray trace models to directly capture the influence of ray aberrations in diffraction simulations. Polarization Ray Tracing is a ray-based method of vector field propagation that can diagnose the polarization aberrations in optical systems. Poke has been recently used to study the next generation of astronomical observatories, including the ground-based Extremely Large Telescopes and a 6 meter space telescope early concept for NASA's Habitable Worlds Observatory.

astro-ph.IM↗

arXiv2022

The Space Coronagraph Optical Bench (SCoOB): 1. Design and Assembly of a Vacuum-compatible Coronagraph Testbed for Spaceborne High-Contrast Imaging Technology

The development of spaceborne coronagraphic technology is of paramount importance to the detection of habitable exoplanets in visible light. In space, coronagraphs are able to bypass the limitations imposed by the atmosphere to reach deeper contrasts and detect faint companions close to their host star. To effectively test this technology in a flight-like environment, a high-contrast imaging testbed must be designed for operation in a thermal vacuum (TVAC) chamber. A TVAC-compatible high-contrast imaging testbed is undergoing development at the University of Arizona inspired by a previous mission concept: The Coronagraphic Debris and Exoplanet Exploring Payload (CDEEP). The testbed currently operates at visible wavelengths and features a Boston Micromachines Kilo-C DM for wavefront control. Both a vector vortex coronagraph and a knife-edge Lyot coronagraph operating mode are under test. The optics will be mounted to a 1 x 2 meter pneumatically isolated optical bench designed to operate at 10^-8 torr and achieve raw contrasts of 10^-8 or better. The validation of our optical surface quality, alignment procedure, and first light results are presented. We also report on the status of the testbed's integration in the vaccum chamber.

astro-ph.IM↗