arXiv subjects

Pao-Yu Wang

Publications and source records attributed to Pao-Yu Wang.

6 recordsLinked to original sources

arXiv2026

The SPHEREx Instrument: Calibration, testing and performance measurements of the NIR 2 spectroscopic surveyor from the laboratory to in-orbit commissioning

The SPHEREx near-infrared space telescope is an all-sky spectroscopic survey mission launched on March 12th, 2025 UTC. In addition to providing the community with a spectral database applicable to a wide range of investigations, it is optimized to address three core science goals: to survey the large scale structure of the Universe for signatures of non-Gaussianity during inflation; to conduct intensity mapping studies of the extragalactic background light for probing the history of galaxy evolution; and to survey the plane of the Milky Way for the prevalence and distribution of water and other biogenic ices. Each of these science goals imposes unique requirements on the performance of the instrument. We detail the design and testing strategies and report the performance results for the full instrument test campaign, ranging from component-level screening to in-orbit tests during the commissioning phase. The instrument, currently operating in full science survey mode, meets all of its driving requirements including optical performance, point source sensitivity, thermal stability and correlated noise minimization.

astro-ph.IM↗

arXiv2025

The SPHEREx Image and Spectrophotometry Processing Pipeline

In this paper, we describe the SPHEREx image and spectrophotometry data processing pipeline, an infrastructure and software system designed to produce calibrated spectral images and photometric measurements for NASA's SPHEREx mission. SPHEREx is carrying out a series of four all-sky spectrophotometric surveys at 6.15 arcsecond resolution in 102 spectral channels spanning 0.75 to 5 microns. The pipeline which will deliver the flux- and wavelength-calibrated data products deriving from these surveys has been developed and is operated by the SPHEREx Science Data Center at Caltech/IPAC in collaboration with the SPHEREx Science Team. Here we describe the framework and modules used in the pipeline, along with the data products, which are available at the NASA/IPAC Infrared Science Archive.

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↗

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↗

arXiv2012

Confronting Phantom Dark Energy with Observations

We confront two types of phantom dark energy potential with observational data. The models we consider are the power-law potential, $V\propto ϕ^μ$, and the exponential potential, $V\propto \exp(λϕ/{M_P})$. We fit the models to the latest observations from SN-Ia, CMB and BAO, and obtain tight constraints on parameter spaces. Furthermore, we apply the goodness-of-fit and the information criteria to compare the fitting results from phantom models with that from the cosmological constant and the quintessence models presented in our previous work. The results show that the cosmological constant is statistically most preferred, while the phantom dark energy fits slightly better than the quintessence does.

astro-ph.CO↗

arXiv2011

Confronting Tracker Field Quintessence with Data

We confront tracker field quintessence with observational data. The potentials considered in this paper include $V(ϕ)\proptoϕ^{-α}$, $\exp(M_{p}/ϕ)$, $\exp(M_{p}/ϕ)-1$, $\exp(βM_{p}/ϕ)$ and $\exp(γM_{p}/ϕ)-1$; while the data come from the latest SN Ia, CMB and BAO observations. Stringent parameter constraints are obtained. In comparison with the cosmological constant via information criteria, it is found that models with potentials $\exp(M_{p}/ϕ)$, $\exp(M_{p}/ϕ)-1$ and $\exp(γM_{p}/ϕ)-1$ are not supported by the current data.

astro-ph.CO↗