arXiv subjects

Sean Bryan

Publications and source records attributed to Sean Bryan.

At least 19 recordsLinked to original sources

arXiv2026

An Open Source RFSoC-based Readout Electronics System for Arrays of Kinetic Inductance Detectors and Superconducting Resonators

We present a novel readout electronics system for large arrays of superconducting electromagnetic resonators, such as kinetic inductance detectors (KIDs), based on a Radio Frequency System on Chip (RFSoC) architecture. Each channel in the readout system is designed for frequency division multiplexing of up to 1024 high quality factor resonances placed on a single microwave transmission line at unique frequencies within a 512 MHz bandwidth. We describe the design of the digital and analog signal processing chains for the implementation of a two-channel 2048-resonator system on the Xilinx ZCU111 RFSoC evaluation board in combination with a custom intermediate frequency (IF) system to convert the RFSoC band to higher frequencies up to 4 GHz. We also detail an associated software interface that provides a range of tools commonly utilized for characterizing KID resonators and for operating them as part of a photometric millimeter-wave imager. We additionally provide noise characterizations of the individual readout components, along with the complete readout system in isolation and in operation to readout KID resonators.

physics.ins-det↗

arXiv2026

Tracing the Boundary of the South Atlantic Anomaly Region with SPHEREx Transient Flagging Rates

The NASA SPHEREx satellite was launched in 03/2025 to survey the full sky between 0.75 - 5.0 um. The image processing of SPHEREx H2RG detectors includes real-time flagging of transient events during integration. SPHEREx follows a polar orbit passing over the South Atlantic Anomaly (SAA) zone multiple times daily, where the transient counts reach as high as >80% of pixels, depleting the pixel inventory for further analysis. The science pipeline flags all exposures taken while in the SAA for re-observation, as well as any with >10% transients regardless of the spacecraft location. After six months, ~1.5% of the exposures outside of the pre-defined SAA zone were flagged. While some exposures are adjacent to the edge of the SAA, the majority appear to trace the geomagnetic field near the poles. Given the importance of the SAA to designing and operating space instruments, in this paper we present the SAA boundary traced by SPHEREx transient flags as a reference for future mission.

astro-ph.IM↗

arXiv2026

Observations of Atmospheric Helium and Oxygen with SPHEREx

We present measurements of near-infrared (NIR) terrestrial airglow produced by helium and oxygen in the exosphere as observed by SPHEREx. Using eight months of survey data obtained from a 680 km low-Earth orbit, emission from HeI $\lambda$10830, OI $\lambda$8446, and OI $\lambda$11287 is mapped with both global spatial and multi-season temporal coverage. These measurements are obtained along upward looking lines of sight as part of the astrophysical survey, in contrast to conventional nadir-viewing Earth remote sensing, which probes the behavior of low-density material in the thermo- and exosphere. We describe an analytical framework to extract atmospheric emission lines in the presence of astrophysical backgrounds including stars, resolved galaxies, and the diffuse Zodiacal light. The resulting global measurements reveal temporal variability over the survey period and systematic dependencies on geographic location. We interpret these variations in the context of the variable Solar illumination and seasonal effects. SPHEREx, an astrophysical space observatory, is demonstrated to be a promising new platform for monitoring NIR airglow and investigating its coupling to Solar activity and global geophysical processes.

physics.ao-ph↗

arXiv2026

CubeSounder: Low SWaP-C 180 GHz Radiometer for Atmospheric Sensing Tested on High Altitude Balloons

Microwave sounding is the leading driver of global numerical weather forecasting, but is limited by the scalability of such instruments. With modern machining and commercial microwave components, it is now possible to design low size, weight, power, and cost (SWaP-C) microwave spectrometers while maintaining wide bandwidth performance. Here we report on the status of CubeSounder, a spectrometer tailored for water vapor radiometry that utilizes passive wave guide filter banks. After developing a prototype and high altitude balloon payload, we demonstrated CubeSounder on commercial stratospheric balloon flights. We report on our design process, especially the simulation and fabrication of the custom millimeter-wave filter banks. We also report the initial results of the data collected from the balloon flights.

eess.SP↗

arXiv2025

Spaceflight KID Readout Electronics for PRIMA

We present the design and testing of a prototype multiplexing kinetic inductance detector (KID) readout electronics for the PRobe far-Infrared Mission for Astrophysics (PRIMA) space mission. PRIMA is a Probe-class astrophysics mission concept that will answer fundamental questions about the formation of planetary systems, the co-evolution of stars and supermassive black holes in galaxies, and the rise of heavy elements and dust over cosmic time. The readout electronics for PRIMA must be compatible with operation at Earth-Sun L2 and capable of multiplexing more than 1000 detectors over 2.5 GHz bandwidth while consuming around 30 W per readout chain. The electronics must also be capable of switching between the two instruments, which have different readout bands: the hyperspectral imager (PRIMAger, 2.6-4.9 GHz) and the spectrometer (FIRESS, 0.4-2.4 GHz). The PRIMA readout electronics use high-heritage SpaceCube digital electronics with a build-to-print SpaceCube Mini v3.0 board using a radiation-tolerant Kintex KU060 field programmable gate array (FPGA) and a custom high-speed digitizer board, along with RF electronics that provide filtering and power conditioning. We present the driving requirements for the system, as well as the hardware, firmware, software, and system-level design that meets those requirements.

astro-ph.IM↗

arXiv2025

Readout of Microwave Kinetic Inductance Detector (MKID) Arrays for Habitable Worlds Observatory Using a Polyphase Filterbank Algorithm

The Habitable Worlds Observatory (HWO), a nextgeneration ultraviolet/optical/infrared space telescope, will require detector technologies capable of supporting substantially larger pixel-count arrays than those flown on previous missions. Microwave Kinetic Inductance Detectors (MKIDs) provide a scalable solution through microwave multiplexing and have already been demonstrated in balloon-borne instruments using Field-Programmable Gate Arrays (FPGAs) for real-time signal processing. A central element of MKID readout is the Polyphase Filter Bank (PFB) spectrometer, which converts digitized timedomain signals into finely resolved frequency channels for subsequent analysis. To meet the demands for broader bandwidths and higher spectral resolution driven by emerging science goals, efficient FPGA-based implementations of the PFB are essential. This work presents current results from a fixed-point digital design methodology for deploying the PFB architecture on spacequalified FPGAs. The approach emphasizes efficient resource utilization and numerical precision while satisfying stringent performance constraints, enabling scalable, high-resolution spectral processing for future space observatories and remote sensing applications.

astro-ph.IM↗

arXiv2025

KID Detector Readout Electronics Development for Habitable Worlds Observatory

We present the status and goals of the readout electronics system we are developing to support the detector arrays in the coronagraph instrument on the NASA Habitable Worlds Observatory (HWO) mission currently in development. HWO aims to revolutionize exoplanet exploration by performing direct imaging and spectroscopy of 25 or more habitable exoplanets, and to resolve a broad range of astrophysics science questions as well. Since exoplanet yield depends critically on the detector dark count rate, as we show in this paper, the ambitious goals of HWO require arrays of single-photon energy-resolving detectors. We argue that Kinetic Inductance Detectors (KIDs) are best suited to meet these requirements. To support the detectors required for HWO and future far-IR missions, at the required power consumption and detector count, we are developing a radiation-tolerant reconfigurable readout system for both imaging and energy-resolving single photon KID detector arrays. We leverage an existing RFSoC-based system we built for NASA balloons that has a power consumption of 30 Watts and reads out 2000-4000 detectors (i.e. 7-15 mW/pixel), and move to a radiation tolerant Kintex Ultrascale FPGA chip to bring low-power wide bandwidth readout to a space-qualified platform for the first time. This improves significantly over previous spaceflight systems, and delivers what is required for NASA's future needs: ~100,000 pixels with less than 1 kW total power consumption. Overall, the system we are developing is a significant step forward in capability, and retires many key risks for the Habitable Worlds Observatory mission.

astro-ph.IM↗

arXiv2025

Optimized Observation Sequencing in Low-Earth Orbit with the SPHEREx Survey Planning Software

SPHEREx is a NASA infrared astronomy mission that launched on March 12th, 2025 and is operating successfully in low-Earth orbit (LEO). The mission is currently observing the entire sky in 102 spectral channels in four independent all-sky surveys and also achieves enhanced coverage in two deep fields. This data will resolve key science questions about the early universe, galaxy formation, and the origin of water and biogenic molecules. In this paper, we describe the survey planning software (SPS) that enables SPHEREx to observe efficiently while mitigating a range of operational challenges in LEO. Our optimal target selection algorithm achieves the required high coverage in both the All-Sky and Deep Surveys. The algorithm plans observations to stay within our time-varying allowable pointing zone, interleaves required data downlink passes, and mitigates outages due to the South Atlantic Anomaly and other events. As demonstrated by the sky coverage achieved in the first SPHEREx public data release, our approach is performing well in flight. The SPHEREx SPS is a key new capability that enables the mission to deliver groundbreaking science from LEO.

astro-ph.IM↗

arXiv2025

Development of Space Qualified Signal Processing Readout Electronics for HabWorlds and Origins Space Telescope Detector and Arrays

The Habitable Worlds Observatory (HWO) -- a flagship ultraviolet/optical/infrared space telescope recommended by the National Academies' Pathways to Discovery in Astronomy and Astrophysics -- will require detector technologies capable of supporting significantly larger pixel-count arrays than previous missions. Microwave Kinetic Inductance Detectors (MKIDs), naturally suited to microwave multiplexing readout, are already in use across several balloon-borne missions with FPGA based systems. To transition this capability to space, we are developing a radiation-hardened detector readout system that builds directly on the technical and environmental requirements defined by the PRIMA mission. PRIMA serves as a critical pathfinder, informing the radiation tolerance, resource constraints, and on-board processing capabilities needed for HWO. In this work, we present our current results on algorithm implementation, hardware architecture, and firmware development using the radiation-hardened AMD Kintex Ultrascale FPGA, aligning with PRIMA's stringent specifications to ensure compatibility with future space-based observatories like HWO.

astro-ph.IM↗

arXiv2024

SPHEREx: NASA's Near-Infrared Spectrophotmetric All-Sky Survey

SPHEREx, the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and ices Explorer, is a NASA MIDEX mission planned for launch in 2024. SPHEREx will carry out the first all-sky spectral survey at wavelengths between 0.75 micron and 5 micron with spectral resolving power ~40 between 0.75 and 3.8 micron and ~120 between 3.8 and 5 micron At the end of its two-year mission, SPHEREx will provide 0.75-to-5 micron spectra of each 6.2"x6.2" pixel on the sky - 14 billion spectra in all. This paper updates an earlier description of SPHEREx presenting changes made during the mission's Preliminary Design Phase, including a discussion of instrument integration and test and a summary of the data processing, analysis, and distribution plans.

astro-ph.IM↗

arXiv2023

Robust Joint Estimation of Galaxy Redshift and Spectral Templates using Online Dictionary Learning

We present a novel approach to analyzing astronomical spectral survey data using our non-linear extension of an online dictionary learning algorithm. Current and upcoming surveys such as SPHEREx will use spectral data to build a 3D map of the universe by estimating the redshifts of millions of galaxies. Existing algorithms rely on hand-curated external templates and have limited performance due to model mismatch error. We address these limitations by developing a new algorithm that jointly estimates both the underlying spectral features in common across the entire dataset, as well as the redshift of each galaxy. To do this, we significantly extend an existing online dictionary learning algorithm, and apply this approach to redshift estimation for the first time. Our new approach scales well to large datasets since we only process a single spectrum in memory at a time. Our algorithm performs better than a state-of-the-art existing algorithm when analyzing a mock SPHEREx dataset, achieving a normalized median absolute deviation (NMAD) of 0.18% and a catastrophic error rate of 0.40% when analyzing noiseless data. Our algorithm also performs well over a wide range of signal to noise ratios (S/N), delivering sub-percent NMAD and catastrophic error above median S/N of 20. We released our algorithm publicly and it is available on github.

astro-ph.IM↗

arXiv2022

Snowmass 2021 CMB-S4 White Paper

This Snowmass 2021 White Paper describes the Cosmic Microwave Background Stage 4 project CMB-S4, which is designed to cross critical thresholds in our understanding of the origin and evolution of the Universe, from the highest energies at the dawn of time through the growth of structure to the present day. We provide an overview of the science case, the technical design, and project plan.

astro-ph.CO↗

arXiv2022

Snowmass2021 CMB-HD White Paper

CMB-HD is a proposed millimeter-wave survey over half the sky that would be ultra-deep (0.5 uK-arcmin) and have unprecedented resolution (15 arcseconds at 150 GHz). Such a survey would answer many outstanding questions about the fundamental physics of the Universe. Major advances would be 1.) the use of gravitational lensing of the primordial microwave background to map the distribution of matter on small scales (k~10 h Mpc^(-1)), which probes dark matter particle properties. It will also allow 2.) measurements of the thermal and kinetic Sunyaev-Zel'dovich effects on small scales to map the gas density and velocity, another probe of cosmic structure. In addition, CMB-HD would allow us to cross critical thresholds: 3.) ruling out or detecting any new, light (< 0.1 eV) particles that were in thermal equilibrium with known particles in the early Universe, 4.) testing a wide class of multi-field models that could explain an epoch of inflation in the early Universe, and 5.) ruling out or detecting inflationary magnetic fields. CMB-HD would also provide world-leading constraints on 6.) axion-like particles, 7.) cosmic birefringence, 8.) the sum of the neutrino masses, and 9.) the dark energy equation of state. The CMB-HD survey would be delivered in 7.5 years of observing 20,000 square degrees of sky, using two new 30-meter-class off-axis crossed Dragone telescopes to be located at Cerro Toco in the Atacama Desert. Each telescope would field 800,000 detectors (200,000 pixels), for a total of 1.6 million detectors.

astro-ph.CO↗

arXiv2020

The Atacama Large Aperture Submillimetre Telescope (AtLAST)

The coldest and densest structures of gas and dust in the Universe have unique spectral signatures across the (sub-)millimetre bands ($\nu \approx 30-950$~GHz). The current generation of single dish facilities has given a glimpse of the potential for discovery, while sub-mm interferometers have presented a high resolution view into the finer details of known targets or in small-area deep fields. However, significant advances in our understanding of such cold and dense structures are now hampered by the limited sensitivity and angular resolution of our sub-mm view of the Universe at larger scales. In this context, we present the case for a new transformational astronomical facility in the 2030s, the Atacama Large Aperture Submillimetre Telescope (AtLAST). AtLAST is a concept for a 50-m-class single dish telescope, with a high throughput provided by a 2~deg - diameter Field of View, located on a high, dry site in the Atacama with good atmospheric transmission up to $\nu\sim 1$~THz, and fully powered by renewable energy. We envision AtLAST as a facility operated by an international partnership with a suite of instruments to deliver the transformative science that cannot be achieved with current or in-construction observatories. As an 50m-diameter telescope with a full complement of advanced instrumentation, including highly multiplexed high-resolution spectrometers, continuum cameras and integral field units, AtLAST will have mapping speeds hundreds of times greater than current or planned large aperture ($>$ 12m) facilities. By reaching confusion limits below L$_*$ in the distant Universe, resolving low-mass protostellar cores at the distance of the Galactic Centre, and directly mapping both the cold and the hot (the Sunyaev-Zeldovich effect) circumgalactic medium of galaxies, AtLAST will enable a fundamentally new understanding of the sub-mm Universe.

astro-ph.IM↗

arXiv2020

CMB-S4: Forecasting Constraints on Primordial Gravitational Waves

CMB-S4---the next-generation ground-based cosmic microwave background (CMB) experiment---is set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the Universe, from the highest energies at the dawn of time through the growth of structure to the present day. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semi-analytic projection tool, targeted explicitly towards optimizing constraints on the tensor-to-scalar ratio, $r$, in the presence of Galactic foregrounds and gravitational lensing of the CMB. This framework is unique in its direct use of information from the achieved performance of current Stage 2--3 CMB experiments to robustly forecast the science reach of upcoming CMB-polarization endeavors. The methodology allows for rapid iteration over experimental configurations and offers a flexible way to optimize the design of future experiments given a desired scientific goal. To form a closed-loop process, we couple this semi-analytic tool with map-based validation studies, which allow for the injection of additional complexity and verification of our forecasts with several independent analysis methods. We document multiple rounds of forecasts for CMB-S4 using this process and the resulting establishment of the current reference design of the primordial gravitational-wave component of the Stage-4 experiment, optimized to achieve our science goals of detecting primordial gravitational waves for $r > 0.003$ at greater than $5\sigma$, or, in the absence of a detection, of reaching an upper limit of $r < 0.001$ at $95\%$ CL.

astro-ph.CO↗

arXiv2020

CMB-HD: Astro2020 RFI Response

CMB-HD is a proposed ultra-deep (0.5 uk-arcmin), high-resolution (15 arcseconds) millimeter-wave survey over half the sky that would answer many outstanding questions in both fundamental physics of the Universe and astrophysics. This survey would be delivered in 7.5 years of observing 20,000 square degrees, using two new 30-meter-class off-axis cross-Dragone telescopes to be located at Cerro Toco in the Atacama Desert. Each telescope would field 800,000 detectors (200,000 pixels), for a total of 1.6 million detectors.

astro-ph.CO↗

arXiv2019

CMB-S4 Decadal Survey APC White Paper

We provide an overview of the science case, instrument configuration and project plan for the next-generation ground-based cosmic microwave background experiment CMB-S4, for consideration by the 2020 Decadal Survey.

astro-ph.IM↗

arXiv2019

The Simons Observatory: Astro2020 Decadal Project Whitepaper

The Simons Observatory (SO) is a ground-based cosmic microwave background (CMB) experiment sited on Cerro Toco in the Atacama Desert in Chile that promises to provide breakthrough discoveries in fundamental physics, cosmology, and astrophysics. Supported by the Simons Foundation, the Heising-Simons Foundation, and with contributions from collaborating institutions, SO will see first light in 2021 and start a five year survey in 2022. SO has 287 collaborators from 12 countries and 53 institutions, including 85 students and 90 postdocs. The SO experiment in its currently funded form ('SO-Nominal') consists of three 0.4 m Small Aperture Telescopes (SATs) and one 6 m Large Aperture Telescope (LAT). Optimized for minimizing systematic errors in polarization measurements at large angular scales, the SATs will perform a deep, degree-scale survey of 10% of the sky to search for the signature of primordial gravitational waves. The LAT will survey 40% of the sky with arc-minute resolution. These observations will measure (or limit) the sum of neutrino masses, search for light relics, measure the early behavior of Dark Energy, and refine our understanding of the intergalactic medium, clusters and the role of feedback in galaxy formation. With up to ten times the sensitivity and five times the angular resolution of the Planck satellite, and roughly an order of magnitude increase in mapping speed over currently operating ("Stage 3") experiments, SO will measure the CMB temperature and polarization fluctuations to exquisite precision in six frequency bands from 27 to 280 GHz. SO will rapidly advance CMB science while informing the design of future observatories such as CMB-S4.

astro-ph.IM↗