Surveys in space and time are key to answering outstanding questions in astrophysics. The power to study very large numbers of stars, galaxies, and transient events over large portions of the sky and different time scales has repeatedly led to new breakthroughs. The Nancy Grace Roman Space Telescope (Roman), NASA’s next Astrophysics Flagship mission, elevates wide field and time domain survey observations to previously inaccessible scales. Roman carries the Wide Field Instrument (WFI), which provides visible to near-infrared imaging and spectroscopy with an unprecedented combination of field-of-view, spatial resolution, and sensitivity. When combined with a highly stable observatory and efficient operations, the WFI allows surveys never before possible. These observations will lead to new discoveries in cosmology, exoplanets, and a very wide array of other astrophysics topics ranging from high redshift galaxies to small bodies in the solar system. This paper provides an overview of Roman survey science, connects this science to the design of the WFI, and provides a status update on WFI hardware build and test.
We describe our technical approach to developing a space observatory to survey the large-scale distribution of neutral and ionized intergalactic gas during cosmological reionization (the landmark event of “Cosmic Dawn”) from 400 to 800 million years after the Big Bang. To look this far back in time at the large-scale distributions of ionized gases, we use wide-field, narrow-passband surveys for Lyman alpha light from individual galaxies red-shifted to the near-infrared. Wherever this light can be seen, it implies the presence of ionized gas. We are developing a large FOV (0.5-to-1.0-degree) instrument with plate scale on the order of 0.3”/pixel to obtain a comprehensive view of the reionization process over a representative volume of the early universe. To maximize science return, the Reionization Explorer (REX) will be placed in a high orbit. Through disciplined application of design-for-cost principles and a thorough searching for existing designs that can achieve our science objectives, we have developed what could be a game changing approach at advancing our understanding of the formation of the universe on a limited Small Explorer (SMEX) budget by leveraging existing telescope, instrument, and spacecraft designs.
REX is a NASA Astrophysics Small Explorer Mission concept to chart the history of cosmic dawn in unprecedented detail in space and time. REX will identify very young galaxies and black holes by means of their powerful Lyman alpha (Lyα) line emission using about 10 narrow-bandpass filters covering about 100 square degrees. The strong line emission identifies samples of the most actively star-forming early galaxies, believed to be the drivers of reionization. Moreover, mapping the distribution and properties of the Lyman alpha emitting population will reveal the distribution of ionized and neutral gas, because neutral gas scatters Lyman alpha light, rendering them difficult to detect. REX will use an 0.5-1m telescope and 1 square degree field of view, tiled with HgCdTe detectors with development heritage from the Nancy Grace Roman Space Telescope. Its large, flexible filter complement will be used in a point-and-stare mode to identify Lyα emitting galaxies at a range of discrete redshift slices spanning the reionization era. In addition to its core reionization surveys, REX brings a new capability of tracing gas emission over large scales at the peak of star and black formation era. We will find millions of the youngest, least massive galaxies in epochs spanning the most active growth period of the universe. Applications will include ionized gas in nearby and distant galaxies, active galactic nuclei, and galaxy clusters. In summary, the REX survey will have the sensitivity and the area coverage to find the sites of earliest galaxy formation and will have the pixel size to enable good localization for follow up of individual galaxies with JWST and future telescopes.
ULTRASAT is a near-ultraviolet imaging satellite with a wide field of view (200 square degrees) and a planned launch in late 2027. It is an international partnership led by Israel (Israel Space Agency and Weizmann Institute of Science) in partnership with the United States (NASA) and Germany (DESY). ULTRASAT will provide high cadence observations and rapid target-of-opportunity response, providing a powerful capability for time-domain and multimessenger astrophysics (TDAMM), and will have scientific applications from solar system studies to cosmology. This proceedings paper includes the content of a poster presented at the 2024 SPIE Astronomical Telescopes and Instruments meeting, describing briefly the ULTRASAT science drivers and capabilities; NASA’s roles in the ULTRASAT project; and how ULTRASAT fits with NASA scientific priorities. It also includes an expanded summary of the United States Participating Scientist Program for ULTRASAT.
The Roman Space Telescope Grism and Prism assemblies will allow the wide-field instrument (WFI) to perform slitless, multi-object spectroscopy across the complete field of view. These optical elements play a critical role in the High Latitude Wide Area and High Latitude Time Domain Surveys, which are designed to produce robust spectroscopic redshifts for millions of objects over the mission lifetime. To facilitate the characterization of these assemblies, a dedicated test bed was designed and utilized to perform a wide variety of spectroscopic measurements over the full range of operational wavelengths and field angles. Characterized features include, but are not limited to dispersion magnitude, dispersion clocking, encircled energy, total throughput, and bandpass edges. We present the results of this experimental campaign in which the Grism and Prism assemblies met or exceeded many of their design requirements and discuss measurement limitations.
We present a plan to address the calibration needs of the Wide Field Instrument (WFI) on the Wide Field Infrared Space Telescope (WFIRST), for on on-orbit observations and ground testing. The science mission of WFI is based on a combination of large surveys, a Guest Observer program, and a strong archival research program.
The WFIRST Science Requirements Document delineates several data quality and calibration requirements for the Mission. The Calibration Plan aims to be prescriptive and predictive, discussing which observations will be needed and estimating the total time required to carry out such observations. We discuss these requirements from an instrumental perspective, and identify the measurements, observations, and analysis steps needed to achieve the desired calibration and data quality levels, especially in terms of on-orbit observations..
ATLAS (Astrophysics Telescope for Large Area Spectroscopy) Probe is a mission concept for a NASA probe-class space mission with primary science goal the definitive study of galaxy evolution through the capture of 300,000,000 galaxy spectra up to z=7. It is made of a 1.5-m Ritchey-Chretien telescope with a field of view of solid angle 0.4 deg2. The wavelength range is at least 1 μm to 4 μm with a goal of 0.9 μm to 5 μm. Average resolution is 600 but with a possible trade-off to get 1000 at the longer wavelengths. The ATLAS Probe instrument is made of 4 identical spectrographs each using a Digital Micro-mirror Device (DMD) as a multi-object mask. It builds on the work done for the ESA SPACE and Phase-A EUCLID projects. Three-mirror fore-optics re-image each sub-field on its DMD which has 2048 x 1080 mirrors 13.6 μm wide with 2 possible tilts, one sending light to the spectrograph, the other to a light dump. The ATLAS Probe spectrographs use prisms as dispersive elements because of their higher and more uniform transmission, their larger bandwidth, and the ability to control the resolution slope with the choice of glasses. Each spectrograph has 2 cameras. While the collimator is made of 4 mirrors, each camera is made of only one mirror which reduces the total number of optics. All mirrors are aspheric but with a relatively small P-V with respect to their best fit sphere making them easily manufacturable. For imaging, a simple mirror to replace the prism is not an option because the aberrations are globally corrected by the collimator and camera together which gives large aberrations when the mirror is inserted. An achromatic grism is used instead. There are many variations of the design that permit very different packaging of the optics. ATLAS Probe will enable ground-breaking science in all areas of astrophysics. It will (1) revolutionize galaxy evolution studies by tracing the relation between galaxies and dark matter from the local group to cosmic voids and filaments, from the epoch of reionization through the peak era of galaxy assembly; (2) open a new window into the dark universe by mapping the dark matter filaments to unveil the nature of the dark Universe using 3D weak lensing with spectroscopic redshifts, and obtaining definitive measurements of dark energy and modification of gravity using cosmic large-scale structure; (3) probe the Milky Way's dust-shrouded regions, reaching the far side of our Galaxy; and (4) characterize asteroids and other objects in the outer solar systems.
The Star Formation Camera (SFC) is a wide-field (~19'×~15', >280 arcmin2), high-resolution (18 mas pixels) UV/optical
dichroic camera designed for the Theia 4-m space-borne space telescope concept. SFC will deliver diffraction-limited
images at λ > 300 nm in both a blue (190-517nm) and a red (517-1075nm) channel simultaneously. The goal is to
conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births
and life cycles of stars and their planetary systems, and to investigate the range of environments, feedback mechanisms,
and other factors that most affect the outcome of star and planet formation.
Filters for astronomical imaging traditionally have a simple bandpass that admits (more or less equally) all the
photons within some bandwith ▵λ around some central wavelength λ0. However, there are situations where
not all photons are equally desirable. We plan to develop and apply multiband filters for practical astronomical
application. A multiband filter is a bandpass filter whose transmission dips to zero at select, undesired wavelength
ranges. Anticipated applications include (i) OH-suppressing filters, especially in the J band (λc ≈ 1.2μm); (ii)
economy of filter slots through multi-band filters used in series with broad blocking filters; and (iii) efficient
searches for object classes with highly structured spectra. We present the design and anticipated photometric
properties of a prototype reduced-background JR filter, which we plan to buy and test in 2010.
Paul Scowen, Rolf Jansen, Matthew Beasley, Brian Cooke, Shouleh Nikzad, Oswald Siegmund, Robert Woodruff, Daniela Calzetti, Steven Desch, Alex Fullerton, John Gallagher, Sangeeta Malhotra, Mark McCaughrean, Robert O'Connell, Sally Oey, Debbie Padgett, James Rhoads, Aki Roberge, Nathan Smith, Daniel Stern, Jason Tumlinson, Rogier Windhorst
The Star Formation Observatory (SFO) is a 1.65m space telescope that addresses pivotal components in the 2007 NASA
Science Plan, with a primary focus on Cosmic Origins. The design under consideration provides 100 times greater
imaging efficiency and >10 times greater spectroscopic efficiency below 115 nm than existed on previous missions. The
mission has a well-defined Origins scientific program at its heart: a statistically significant survey of local, intermediate,
and high-redshift sites and indicators of star formation, to investigate and understand the range of environments,
feedback mechanisms, and other factors that most affect the outcome of the star and planet formation process. This
program relies on focused capabilities unique to space and that no other planned NASA mission will provide: near-
UV/visible (20-1100 nm) wide-field, diffraction-limited imaging; and high-efficiency, low- and high- resolution (R~40,000) UV (100-175 nm) spectroscopy using far-UV optimized coatings and recent advances in Micro-Channel Plate
(MCP) detector technology. The Observatory imager has a field of view in excess of 17' × 17' (>250 arcmin2) and uses a
dichroic to create optimized UV/blue and red/near-IR channels for simultaneous observations, employing detectors that
offer substantial quantum efficiency gains and that suffer lower losses due to cosmic rays.
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