Roman Space Telescope at the 237th AAS Meeting

January 10-15, 2021 (Virtual Meeting)

Oral Splinter Sessions

  • Exploring the Transient and Variable Universe with the Roman Space Telescope
    (Tuesday, January 12, 4:10–5:40 p.m. EST)
    The Nancy Grace Roman Space Telescope is a NASA space mission in implementation for launch in the mid 2020s. With a wide field of view of 0.28 sq deg, excellent sensitivity and infrared bandpass, the Roman Space Telescope will provide unique opportunities in time domain and multi-messenger astrophysics. This session will cover a broad sampling of the science topics that can be addressed by Roman observations in the time domain from variable sources in our galaxy to extragalactic transients.

  • Exploring the Milky Way with the Nancy Grace Roman Space Telescope
    (Thursday, January 14, 4:10–5:40 p.m. EST)
    The Nancy Grace Roman Space Telescope is a NASA space mission intended for launch in the mid 2020s. With a wide field of view of 0.28 sq deg, excellent sensitivity and infrared bandpass, Roman will provide unique opportunities to study our Galaxy. This session will cover a broad range of topics ranging from star formation, stellar evolution, the Galactic center, and the structure of the Milky Way.

Town Hall: Nancy Grace Roman Town Hall

  • Opportunities with the Nancy Grace Roman Space Telescope
    (Friday, January 15, 1:20–2:20 p.m. EST)

    The Nancy Grace Roman Space Telescope (formerly WFIRST) is a NASA flagship mission planned for launch in the mid 2020s. Roman will perform breakthrough science in dark energy cosmology, exoplanet microlensing, and NIR sky surveys with its Wide Field Instrument. Roman will also feature the Coronagraph Instrument (CGI), a technology demonstration that will directly image and take spectra of exoplanetary systems using several novel technologies together for the first time in space. This session will cover the status of the project and upcoming opportunities for community involvement in planning and executing the science and technology demonstration aspects of Roman.

Oral Session Talks

  • Cosmology with the Nancy Grace Roman Space Telescope prism - T. L. Astraatmadja (STScI) et al.
    (Thursday, January 14, 12:00–12:10 p.m. EST)
    The Nancy Grace Roman Space Telescope, to be launched in mid-2020s, will be equipped with a Wide Field Instrument (WFI) that consist of seven imaging filters covering 750--2000~nm, a slitless grism and prism for spectroscopy, and eighteen 4k x 4k H4RG HgCdTe detectors that comprises the focal plane array covering a field of view of 0.28 square degrees. The Roman cosmology program, aimed to elucidate on the nature of dark energy, will use WFI to conduct high-latitude surveys of galaxies and lensing, as well Type Ia Supernova (SN Ia) surveys. As a part of our efforts to understand the improvements that the prism can bring to SN Ia cosmology and to understand the sources of systematic uncertainties that may appear, we use spectra templates to simulate SNe spectra through the Roman Space Telescope optical path using the most current characterization of the optical system and detectors. We use realistic noise model based on the known properties of the detector. We analyze the resulting noisy-spectra and evaluate how well we can recover the parameters of supernovae given the statistical and systematic uncertainties as well as observing strategies. A prediction of the overall Dark Energy Task Force figure of merit will also be presented. We find that space-based SN Ia spectroscopy using the slitless prism provides additional information that could not be obtained using imaging alone. This includes not only a better estimate of the redshifts but also improved SNe classification (typing and sub-typing). Systematic uncertainties present in imaging-only surveys are also addressed in prism observations.

  • Why The Nancy Grace Roman Space Telescope WFI instrument should have a Ks bandpass - R. Chary (Caltech, Pasadena, CA.)
    (Thursday, January 14, 12:10–12:20 p.m. EST)
    The Nancy Grace Roman Space Telescope will have a wide field imaging instrument, the WFI, with detectors sensitive to ~2.5 microns but no filter beyond 2 microns. The telescope will be passively cooled to 260K which results in the thermal background dominating the noise at the long wavelength end of the observable wavelength range. A carefully chosen bandpass centered at 2.1 microns with R~6-10 will however, enable surveys that will run at least ten times faster than any ground-based survey to similar depth at corresponding wavelengths. Furthermore, it will have a factor of ~2 better spatial resolution and higher Strehl ratios than a ground-level adaptive optics (GLAO) system in typical conditions. The potential depths achievable with this wavelength coverage over wide areas, compared to Euclid and Subaru/ULTIMATE will reveal pristine stellar populations at the end of the cosmic dark ages at z~17, and characterize the earliest epochs of dust production by measuring the rest-frame ultraviolet slopes of galaxies at z~15. This will allow for timely spectroscopic follow-up with the James Webb Space Telescope. At lower redshifts, by sampling longer wavelengths where the nebular emission increasingly dominates over the stellar photospheric emission, it will provide better constraints on photometric redshifts for samples of galaxies used for weak lensing, and provide a bandpass with a better-sampled point spread function and smaller spectral variations. This will allow us to independently measure weak lensing shear more precisely, with improved galactic shape noise at z > 1. Galactic surveys will also benefit from a Ks bandpass due to the reduced dust extinction and the improved sensitivity to cooler stars as discussed in Stauffer et al. (2018; arXiv:1806.00554).

iPoster-Plus Session

  • The Nancy Grace Roman Space Telescope - J. McEnery (NASA/GSFC)
    (Wednesday, January 13, 4:10–4:20 p.m. EST)
    The Nancy Grace Roman Space Telescope is a NASA space mission in development for launch in the mid 2020s. It has a 2.4 m telescope, wide-field IR instrument operating in the 0.48 - 2.0 micron range and an exoplanet imaging coronagraph instrument operating in the 400 - 1000 nm range. With a wide field of view of 0.28 sq deg, excellent sensitivity and infrared bandpass, Roman will provide unique opportunities for cosmology, exoplanet studies and a wide range of astrophysics from its near-IR surveys. In this presentation we will describe the capabilities and potential science return from the Roman Space Telescope.

  • Science Operations and Support for the Wide-Field Instrument for the Nancy Grace Roman Space Telescope - A. Petric et al. (STScI)
    (Wednesday, January 13, 4:20–4:30 p.m. EST)
    The Space Telescope Science Institute (STScI) will serve as the Science Operations Center for NASA's Nancy Grace Roman Space Telescope (formerly WFIRST), expected to launch in 2025. The Roman Space Telescope will provide HST-like spatial resolution in the infrared but with a field-of-view nearly 100 times larger than HST. Even for single pointings, these faster optics will provide data sets comparable to large survey missions with previous generation space-based observatories. In addition, wide-field slitless spectroscopy capabilities (grism/prism) will allow for characterization of multiple classes of galaxies from nearby dwarf galaxies to the host of the most massive BH at high redshif. Taken together, these capabilities provide the community with a powerful survey-focused observatory, enabling ambitious cosmology to ISM studies. We will discuss the role of STScI in the instrument calibrations, observation, data archiving, commissioning, and community support. We highlight strategies for user support and data access to enhance synergies across missions, wavelengths, and to promote access and equity.

  • Flatfield Calibrations with Astrophysical Sources for the Nancy Grace Roman Space Telescope’s Coronagraphic Instrument - E. R. Maier (University of Arizona) et al.
    (Wednesday, January 13, 4:30–4:40 p.m. EST)
    The Nancy Grace Roman Space Telescope Coronagraph Instrument (CGI) is a high-contrast imager, polarimeter, and spectrometer that will enable the study of exoplanets and circumstellar disks at visible wavelengths (~550 - 850 nm) at contrasts 2 - 3 orders of magnitude better than can currently be achieved by ground-based direct imaging facilities. To capitalize on this sensitivity, precise flux calibration will be required. CGI, like other space-based missions, will use on-orbit flat fields to measure and correct for phenomena that impact the measured QE. However, CGI does not have internal lamp sources, and the potential hardware solution of adding a diffuser did not meet performance or cost requirements. Therefore we have developed a method to perform flat field calibrations using observations of extended planetary sources such as Uranus and Neptune, using a combination of rastering CGI's Fast Steering Mirror (FSM), tiling the planet across the field of view (FOV), and matched-filter image processing. Here we outline the process and present the results of simulations using images of Uranus and Neptune from the Hubble Space Telescopes Wide Field Camera 3 (WFC3), in WFC3 filters approximate to CGI's Band 1 and Band 4. The simulations are performed over the un-vignetted FOVs for CGI's direct imaging (DI) and polarimetric modes. We model QE effects in 3 different spatial frequency regimes including 1) high spatial frequency detector pixel-to-pixel QE variations, 2) medium spatial frequency "measles" caused by particle deposition on the detector or other focal-plane optics post-launch, and 3) low spatial frequency detector fringing caused by self-interference due to internal reflections in the detector substrate as well as low spatial frequency vignetting at the edges of CGI's FOV. We show that this process can correct for these QE variations to the required precision of 0.6% per resolution element with >20% margin in both the imaging and polarimetric modes in Bands 1 and 4 using either Uranus or Neptune.

  • Count Rate Non-linearity and the Dark Energy Figure of Merit with the Roman Space Telescope - S. Deustua (STScI) et al.
    (Wednesday, January 13, 4:40–4:50 p.m. EST)
    The Nancy Grace Roman Space Telescope, is a flagship NASA mission. Science investigations with its Wide Field Imager (WFI) include dark energy and cosmology investigations via a high galactic latitude imaging and spectroscopic and Type Ia supernovae (SNe Ia) surveys. The WFI’s field of view has 100 times the area of HST imaged on 18 H4RG HgCdTe detectors. These semi-conductor detectors have an inherently non-linear response to light. One such artifact is count-rate non-linearity (CRNL),where the detector’s response depends on the flux of the incoming light. CRNL physics is still not well understood; the current hypothesis ascribes the effect to charge traps in the semiconductor (Mosby et al. 2020). At present, we assume a per pixel, wavelength dependent model where CRNL is proportional to a power law of the incoming flux.
    The nature of this effect makes faint sources appear fainter and bright sources seem brighter. If uncorrected, CRNL limits the accuracy and confidence in the SNe Ia and weak lensing measurements of dark energy. To enable on-orbit measurement and tracking of the CRNL, Roman’s WFI carries a Relative Calibration System (RCS) that allows selecting the intensity and wavelength of light illuminating the focal plane. In the direct illumination mode flat fields at six levels of intensity can be acquired. In lamp-on/lamp-off (LOLO) mode, the detectors are simultaneously illuminated by the RCS while observing an astronomical scene.
    Here we present the results of a study of the effects on the dark energy figure of merit (FoM) if the Relative Calibration System capabilities are reduced or increased from the original baseline, thus affecting the characterization of CRNL. A higher FoM value implies greater constraints on the dark energy parameters of interest; we only consider the effect of CRNL. We determine the FoM given a set of filter combinations in direct illumination (DI) and lamp-on/lamp-off (LOLO), relative to the baseline. We find that DI in the six SN/Deep-field filters (RZY JHF) or LOLO in the six SN/deep-field filters or DI in three filters (RZJ) plus LOLO in two (WF) meet the FoM requirement.

NASA Webinars

  • Exoplanet Science with the Nancy Grace Roman Space Telescope - Aki Roberge (NASA HQ)
    (Monday, January 11, 12:00–12:30 p.m. EST)

  • Wide Field Survey Science with the Nancy Grace Roman Space Telescope - Dominic Benford (NASA HQ)
    (Wednesday, January 13, 5:00–5:30 p.m. EST)