arXiv subjects

Steve Osterman

Publications and source records attributed to Steve Osterman.

8 recordsLinked to original sources

arXiv2026

The Wide Field Imager (WFI) Instruments for the Polarimeter to Unify the Corona and Helliosphere (PUNCH)

We describe the design, hardware integration, and calibration performance of the Wide-Field Imager (WFI) instruments for the Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission. The WFI instruments are a trio of visible-light heliospheric imagers that, together, view the outer corona and solar wind from under 3.5° to over 47° from the Sun, via sunlight that is Thomson-scattered from free electrons. In flight, the WFIs are arranged so that their collective fields of view form an approximately symmetric trefoil on the sky, comprising three circular-truncated square fields spaced 120° apart in position angle. The WFIs work with the NFI instrument, described elsewhere, to implement the full PUNCH field spanning all solar position angles, at elongations from 1.5° to 47° from disk center. WFI is implemented using dioptric (lens) optics and deep multi-stage baffles that attenuate solar, planetary, and lunar stray light sufficiently for ground processing to reveal the faint signal for the primary science. WFI measures both total brightness (tB) and polarized brightness (pB), via an on-board polarizing filter wheel (PFW) and charge-coupled device (CCD) camera that share a common design with those of the NFI instrument.

astro-ph.IM↗

arXiv2019

Stellar Spectroscopy in the Near-infrared with a Laser Frequency Comb

The discovery and characterization of exoplanets around nearby stars is driven by profound scientific questions about the uniqueness of Earth and our Solar System, and the conditions under which life could exist elsewhere in our Galaxy. Doppler spectroscopy, or the radial velocity (RV) technique, has been used extensively to identify hundreds of exoplanets, but with notable challenges in detecting terrestrial mass planets orbiting within habitable zones. We describe infrared RV spectroscopy at the 10 m Hobby-Eberly telescope that leverages a 30 GHz electro-optic laser frequency comb with nanophotonic supercontinuum to calibrate the Habitable Zone Planet Finder spectrograph. Demonstrated instrument precision <10 cm/s and stellar RVs approaching 1 m/s open the path to discovery and confirmation of habitable zone planets around M-dwarfs, the most ubiquitous type of stars in our Galaxy.

astro-ph.EP↗

arXiv2014

The Habitable-zone Planet Finder Calibration System

We present the design concept of the wavelength calibration system for the Habitable-zone Planet Finder instrument (HPF), a precision radial velocity (RV) spectrograph designed to detect terrestrial-mass planets around M-dwarfs. HPF is a stabilized, fiber-fed, R$\sim$50,000 spectrograph operating in the near-infrared (NIR) z/Y/J bands from 0.84 to 1.3 microns. For HPF to achieve 1 m s$^{-1}$ or better measurement precision, a unique calibration system, stable to several times better precision, will be needed to accurately remove instrumental effects at an unprecedented level in the NIR. The primary wavelength calibration source is a laser frequency comb (LFC), currently in development at NIST Boulder, discussed separately in these proceedings. The LFC will be supplemented by a stabilized single-mode fiber Fabry-Perot interferometer reference source and Uranium-Neon lamp. The HPF calibration system will combine several other new technologies developed by the Penn State Optical-Infrared instrumentation group to improve RV measurement precision including a dynamic optical coupling system that significantly reduces modal noise effects. Each component has been thoroughly tested in the laboratory and has demonstrated significant performance gains over previous NIR calibration systems.

astro-ph.IM↗

arXiv2013

Generation of a 650 nm - 2000 nm Laser Frequency Comb based on an Erbium-Doped Fiber Laser

We present a laser frequency comb based upon a 250 MHz mode-locked erbium-doped fiber laser that spans more than 300 terahertz of bandwidth, from 660 nm to 2000 nm. The system generates 1.2 nJ, 70 fs pulses at 1050 nm by amplifying the 1580 nm laser light in Er:fiber, followed by nonlinear broadening to 1050 nm and amplification in Yb:fiber. Extension of the frequency comb into the visible is achieved by supercontinuum generation from the 1050 nm light. Comb coherence is verified with cascaded f-2f interferometry and comparison to a frequency stabilized laser.

physics.optics↗

arXiv2012

A near infrared frequency comb for Y+J band astronomical spectroscopy

Radial velocity (RV) surveys supported by high precision wavelength references (notably ThAr lamps and I2 cells) have successfully identified hundreds of exoplanets; however, as the search for exoplanets moves to cooler, lower mass stars, the optimum wave band for observation for these objects moves into the near infrared (NIR) and new wavelength standards are required. To address this need we are following up our successful deployment of an H band(1.45-1.7μm) laser frequency comb based wavelength reference with a comb working in the Y and J bands (0.98-1.3μm). This comb will be optimized for use with a 50,000 resolution NIR spectrograph such as the Penn State Habitable Zone Planet Finder. We present design and performance details of the current Y+J band comb.

astro-ph.IM↗

arXiv2012

Demonstration of On-Sky Calibration of Astronomical Spectra using a 25 GHz near-IR Laser Frequency Comb

We describe and characterize a 25 GHz laser frequency comb based on a cavity-filtered erbium fiber mode-locked laser. The comb provides a uniform array of optical frequencies spanning 1450 nm to 1700 nm, and is stabilized by use of a global positioning system referenced atomic clock. This comb was deployed at the 9.2 m Hobby-Eberly telescope at the McDonald Observatory where it was used as a radial velocity calibration source for the fiber-fed Pathfinder near-infrared spectrograph. Stellar targets were observed in three echelle orders over four nights, and radial velocity precision of \sim10 m/s (\sim6 MHz) was achieved from the comb-calibrated spectra.

physics.optics↗

arXiv2011

The Cosmic Origins Spectrograph

The Cosmic Origins Spectrograph (COS) is a moderate-resolution spectrograph with unprecedented sensitivity that was installed into the Hubble Space Telescope (HST) in May 2009, during HST Servicing Mission 4 (STS-125). We present the design philosophy and summarize the key characteristics of the instrument that will be of interest to potential observers. For faint targets, with flux F_lambda ~ 1.0E10-14 ergs/s/cm2/Angstrom, COS can achieve comparable signal to noise (when compared to STIS echelle modes) in 1-2% of the observing time. This has led to a significant increase in the total data volume and data quality available to the community. For example, in the first 20 months of science operation (September 2009 - June 2011) the cumulative redshift pathlength of extragalactic sight lines sampled by COS is 9 times that sampled at moderate resolution in 19 previous years of Hubble observations. COS programs have observed 214 distinct lines of sight suitable for study of the intergalactic medium as of June 2011. COS has measured, for the first time with high reliability, broad Lya absorbers and Ne VIII in the intergalactic medium, and observed the HeII reionization epoch along multiple sightlines. COS has detected the first CO emission and absorption in the UV spectra of low-mass circumstellar disks at the epoch of giant planet formation, and detected multiple ionization states of metals in extra-solar planetary atmospheres. In the coming years, COS will continue its census of intergalactic gas, probe galactic and cosmic structure, and explore physics in our solar system and Galaxy.

astro-ph.IM↗

arXiv2010

Observing with HST below 1150Å: Extending the Cosmic Origins Spectrograph Coverage to 900Å

The far-ultraviolet (FUV) channel of the Cosmic Origins Spectrograph (COS) is designed to operate between 1130Å and 1850Å, limited at shorter wavelengths by the reflectivity of the MgF2 protected aluminum reflective surfaces on the Optical Telescope Assembly and on the COS FUV diffraction gratings. However, because the detector for the FUV channel is windowless, it was recognized early in the design phase that there was the possibility that COS would retain some sensitivity at shorter wavelengths due to the first surface reflection from the MgF2 coated optics. Preflight testing of the flight spare G140L grating revealed ~5% efficiency at 1066Å, and early on-orbit observations verified that the COS G140L/1230 mode was sensitive down to at least the Lyman limit with 10-20 cm^2 effective area between 912Å and 1070Å, and rising rapidly to over 1000 cm2 beyond 1150Å. Following this initial work we explored the possibility of using the G130M grating out of band to provide coverage down to 900Å. We present calibration results and ray trace simulations for these observing modes and explore additional configurations that have the potential to increase spectroscopic resolution, signal to noise, and observational efficiency below 1130Å.

astro-ph.IM↗