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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2020

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, isa NASA MIDEX mission planned for launch in 2024. SPHEREx will carry out the first all-sky spectral survey at wavelengths between 0.75μm and 5μm with spectral resolving power ~40 between 0.75 and 3.8μm and ~120 between 3.8 and 5μm At the end of its two-year mission, SPHEREx will provide 14 billion 0.75-to-5μm spectra of each 6."2 x 6."2 pixel on the sky. 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 flow and a summary of the data processing, analysis, and distribution plans.

Zemcov, Michael↗
NASA NTRSDate not supplied

Improving the Transient Sensitivity of AMEGO-X Using Single-site Events

AMEGO-X is a Compton/pair gamma-ray telescope, submitted to NASA's 2021 MIDEX AO, which will image and survey the medium-energy gamma-ray sky between 100 keV and 1 GeV. It is designed to detect and characterize gamma-ray emission from multi-messenger sources. On short time scales (<100s), including information from single-site events (photoelectric effect interactions) significantly increases AMEGO-X's sensitivity and lowers its energy threshold down to 25 keV. In this presentation, we will present AMEGO-X's sensitivity to transient events such as gamma-ray bursts and magnetar giant flares, and discuss the improvements due to the inclusion of single-site events. We will also discuss AMEGO-X's ability to localize transient sources and alert the community for follow-up observations.

Henrike Fleischhack↗
NASA NTRSDate not supplied

Overview of NASA’s Science Mission Directorate Small Satellites Programs and Advances in Transformative Science Measurements with Small Satellites

Small satellites have become an accepted platform for enabling high-quality science measurements and observations. NASA missions have leveraged advances in sensor miniaturization, technology innovations, and new small satellite mission architectures to support high spatial and temporal measurements, continuity measurements, and constellations in response to science objectives described in NASA’s Decadal Surveys. Across six divisions of the Science Mission Directorate (SMD), over 12 years, SMD has funded 88 CubeSat/ SmallSat Missions and 59 Studies to date. Currently, SMD has 53 small spacecraft science missions (87spacecraft) in implementation or formulation. This paper provides the background of efforts to promote the implementation of small satellites within NASA as a balanced portfolio for the agency’s science, technology, and exploration goals. We include analysis of SmallSat awards and trends funded by SMD through Research Opportunities in Space and Earth Sciences (ROSES), Small Innovative Missions for Planetary Exploration (SIMPLEx), and Small Explorer (SMEX) and Medium Explorer (MIDEX) calls over the last 12years. The data source of this assessment is a subset of the NASA SmallSat Coordination Group Database, a collection of all known funded NASA SmallSat and CubeSat missions and studies. This paper also provides an overview of small satellite programs and selected missions from SMD’s divisions: Astrophysics, Heliophysics, Earth Science, and Planetary Science, and describes SMD’s efforts in fostering an incremental and continuous path to achieve high-priority science through transformative science measurements. This paper recognizes the latest observations and trends of the NASA CubeSat / SmallSat Science missions with masses ranging between 1kg to 500kg.

Small Satellites, SMD SmallSat, CubeSat,↗
NASA NTRSDate not supplied

Advances in Transformative Science Measurements with Small Satellites

Small satellites have become an accepted platform for enabling high-quality science measurements and observations. NASA missions have leveraged advances in sensor miniaturization, technology innovations, and new small satellite mission architectures to support high spatial and temporal measurements, continuity measurements, and constellations in response to science objectives described in NASA’s Decadal Surveys. Across six divisions of the Science Mission Directorate (SMD), over 12 years, SMD has funded 88 CubeSat/ SmallSat Missions and 59 Studies to date. Currently, SMD has 53 small spacecraft science missions (87spacecraft) in implementation or formulation. This paper provides the background of efforts to promote the implementation of small satellites within NASA as a balanced portfolio for the agency’s science, technology, and exploration goals. We include analysis of SmallSat awards and trends funded by SMD through Research Opportunities in Space and Earth Sciences (ROSES), Small Innovative Missions for Planetary Exploration (SIMPLEx), and Small Explorer (SMEX) and Medium Explorer (MIDEX) calls over the last 12years. The data source of this assessment is a subset of the NASA SmallSat Coordination Group Database, a collection of all known funded NASA SmallSat and CubeSat missions and studies. This paper also provides an overview of small satellite programs and selected missions from SMD’s divisions: Astrophysics, Heliophysics, Earth Science, and Planetary Science, and describes SMD’s efforts in fostering an incremental and continuous path to achieve high-priority science through transformative science measurements. This presentation recognizes the latest observations and trends of the NASA CubeSat / SmallSat Science missions with masses ranging between 1kg to 500kg.

Small Satellites, SMD SmallSat, CubeSat↗
NASA NTRS2022

The Event Horizon Explorer Mission Concept

The Event Horizon Explorer (EHE) is a mission concept to extend the Event Horizon Telescope via anadditional space-based node. We provide highlights and overview of a concept study to explore the feasibility ofsuch a mission. We present science goals and objectives, which include studying the immediate environment aroundsupermassive black holes, and focus on critical enabling technologies and engineering challenges. We provide anassessment of their technological readiness and overall suitability for a NASA Medium Explorer (MIDEX) class mission.

Peter Kurczynski↗
NASA NTRSDate not supplied

STAR-X: Survey and Time-domain Astrophysical Research eXplorer

STAR-X is a MIDEX mission proposed to NASA in December 2021. Comprising an X-ray telescope (XRT) provided by GSFC and MIT, a UV telescope (UVT) provided by the University of Colorado, and a spacecraft (SC) provided by Ball Aerospace, STAR-X is designed to conduct time-domain survey and to respond rapidly to transient events discovered by other observatories such as LIGO, Rubin LSST, Roman WFIRST, and SKA. The key features of the XRT are its excellent PSF (2.5 arc-seconds half-power diameter), large effective area (1,800 cm2 at 1 keV), and large field of view (1 deg2), making it more than an order of magnitude more capable and more sensitive than Chandra and Swift/XRT to conduct survey and to find and study transient sources. The UVT has a 30-cm aperture with 5 filters covering the 160nm to 340nm band, providing simultaneous spectral coverage with the XRT and enabling reverberation mapping of accretion disk geometries around black holes. The SC is highly autonomous and is capable of fast slewing, enabling efficient raster scans and time-domain surveys. In particular, in combination with a state-of-the-art mission operations center at the University of Colorado, the SC can respond to targets of opportunity within 2 hours 90% of the time. With its nearly equatorial low-earth orbit, STAR-X’s telescopes will have low particle background, enabling them to have unprecedented sensitivity for measuring faint diffuse emissions from clusters of galaxies. STAR-X is a timely response to Astro2020’s recommendation for a space-based, sustaining time-domain and multi-messenger program.

William W. Zhang↗
NASA NTRSDate not supplied

HelioSwarm: The Swarm is the Observatory

HelioSwarm will transform our understanding of space plasma turbulence by being the first-of-its-kind simultaneous, multiscale observatory comprising multiple spacecraft. HelioSwarm was competitively selected under the Heliophysics Explorers Program 2019 Medium-Class Explorer (MIDEX) Announcement of Opportunity. The central powered-ESPA hub spacecraft is co-orbited by eight SmallSat Node spacecraft, together moving through a High Earth Orbit to obtain data in various solar wind regimes. The mission architecture is that of hub-and-spoke, with the larger hub serving as a communications relay between the nodes and DSN. Mission operations, management, and technical oversight are provided by NASA Ames Research Center; the spacecraft are provided by Northrop Grumman and BCT. The instrument suite includes foreign-contributed instruments and U.S. ones, all under the oversight of University of New Hampshire (which is also the Principal Investigator’s home institution and Science Operations Center). The mission timeline from launch through conclusion of the one-year science mission is provided along with a summarized concept of operations, with particular emphasis on placing the nodes in their proper relative orbit loops to form the geometry needed for science collection at apogee. A brief discussion of how a combination of legacy tools and custom-created swarm analysis tools are used to design the swarm and sort and visualize the collected science data and telemetry in context is provided. Finally, an exploration of the pathfinding nature of HelioSwarm and some implications for future large scientific swarms is offered.

Heliophysics↗
NASA NTRS2022

UV Spectropolarimetry With Polstar: Protoplanetary Disks

Polstar is a proposed NASA MIDEX mission that carries a high resolution UV spectropolarimeter capable of measure all four Stokes parameters onboard a 60 cm telescope. The mission has been designed to pioneer the field of time-domain UV spectropolarimetry. Time domain UV spectropolarimetry offers the best resource to determine the geometry and physical conditions of protoplanetary disks from the stellar surface to <5 AU.We detail two key objectives that a dedicated time domain UV spectropolarimetry survey, such as that enabled by Polstar or a similar mission concept, could achieve: 1) Test the hypothesis that magneto-accretion operating in young planet-forming disks around lower-mass stars transitions to boundary layer accretion in planet-forming disks around higher mass stars; and 2) Discriminate whether transient events in the innermost regions of planet-forming disks of intermediate mass stars are caused by inner disk misalignments or from stellar or disk emissions.

John P Wisniewski↗
NASA NTRS2022

Ultraviolet Spectropolarimetry with Polstar: Using Polstar to Test Magnetospheric Mass-Loss Quenching

Polstar is a proposed NASA MIDEX space telescope that will provide high-resolution, simultaneous full-Stokes spectropolarimetry in the far ultraviolet, together with low-resolution linear polarimetry in the near ultraviolet. This observatory offers unprecedented capabilities to obtain unique information on the magnetic and plasma properties of the magnetospheres of hot stars. We describe an observing program making use of the known population of magnetic hot stars to test the fundamental hypothesis that magnetospheres should act to rapidly drain angular momentum, thereby spinning the star down, whilst simultaneously reducing the net mass-loss rate. Both effects are expected to lead to dramatic differences in the evolution of magnetic vs. non-magnetic stars.

M. E. Shultz↗
NASA NTRS2022

Bayesian Rules of Thumb: Robust Uncertainty Quantification in Early Project Cost Estimation

Systems engineers often make use of cost Rules ofThumb in order to estimate cost during early phases of projectformulation. These Rules of Thumb typically take the form ofa sequence of percentages over which a total cost is allocatedacross NASA WBS elements. Rules of Thumb can then be usedto extrapolate cost from one or more known WBS elements tothe remaining unknown WBS elements, assisting early projectformulation architecture studies (such as those in JPL’s Team Xand A Team).A number of issues can arise when generating and using costRules of Thumb. For example, many records of project costsconsist of incomplete data. Typical methods of dealing withincomplete cost allocation data include (a) ignoring missionswith incomplete data, or (b) taking averages of the non-zero percentagesacross missions, but both of these methods can result inbiased estimates if the existence of incomplete data correlateswith total mission cost or any particular WBS element. Anothercommon example is cost reported in one or more incorrect WBSelements. This is especially prevalent in smaller missions whereit is more common for engineers to perform tasks that fall underthe purview of multiple WBS elements.Furthermore, a Rule of Thumb estimate is typically reported asa point estimate; there is no reported uncertainty around thepercentages used to generate an allocation. Even in the rarecase in which confidence intervals around mean percentages areprovided, there may be positive or negative correlations betweenWBS elements which can skew estimates.Here we attempt to address these problems by formulatingprobabilistic Rules of Thumb in which a distribution of allocationschemes, rather than a single allocation scheme, is generated.We use a bootstrap imputation method to simultaneouslyaccount for uncertainty in the missing data while using allavailable information contained in the dataset. The imputeddatasets are then input into a multivariate Bayesian modelwhich accounts for correlations between WBS elements andproperly accounts for uncertainty in the final Rule of Thumbpercentages and predictions. We describe the mathematicalmodel and provides snippets of R code utilizing the brms(Bayesian Regression Models using Stan) package. To illustratethis model, we generate a Bayesian Level 2 WBS Cost Rule ofThumb for MIDEX (Medium-Class Explorers) missions withdata extracted from NASA’s CADRe. We then compare thismethod’s performance with the classical Rule of Thumb method.

Hooke, Melissa A↗
NASA NTRSDate not supplied

HelioSwarm: The Swarm is the Observatory

The HelioSwarm Mission will transform our understanding of space plasma turbulence by being the first-of-its-kind simultaneous, multiscale observatory comprising multiple spacecraft. HelioSwarm was competitively selected under the Heliophysics Explorers Program 2019 Medium-Class Explorer (MIDEX) Announcement of Opportunity. The central powered-ESPA Hub spacecraft is co-orbited by eight SmallSat Node spacecraft, together moving through a High Earth Orbit to obtain data in various solar wind regimes. The mission architecture is that of hub-and-spoke, with the larger hub serving as a communications relay between the Nodes and DSN. Mission operations, management, and technical oversight are provided by NASA Ames Research Center; the spacecraft are provided by Northrop Grumman and BCT. The instrument suite includes foreign-contributed instruments and U.S. ones, all under the oversight of University of New Hampshire (which is also the Principal Investigator’s home institution and Science Operations Center). The mission timeline from launch through conclusion of the one-year science mission is provided along with a summarized concept of operations, with particular emphasis on placing the Nodes in their proper relative orbit loops to form the geometry needed for science collection at apogee. A brief discussion of how a combination of legacy tools and custom-created swarm analysis tools are used to design the swarm and sort and visualize the collected science data and telemetry in context is provided. Finally, an exploration of the pathfinding nature of HelioSwarm and some implications for future large scientific swarms is offered.

Heliophysics↗
NASA NTRSDate not supplied

A New Linear Polarizer Design for Application in the Far-Ultraviolet Spectral Range

New mission concepts that are under consideration by NASA (such as the Polstar MIDEX mission concept) call for the design and implementation of Far Ultraviolet (FUV) polarizer technologies that have not been developed yet. A team that includes members from the NASA Goddard Space Flight Center (GSFC), Arizona State University (ASU), and Woodruff Consulting, worked on the design and development of a polarizer design that may produce extinction ratios higher than have ever been reported before in the FUV spectral range (100-200 nm). This polarizer consists of transmitting linearly polarized light through a series of reflections from a combination of two silicon carbide (SiC) and two lithium fluoride (LiF) crystals positioned at angles of incidence (relative to surface normal) close to the LiF Brewster’s angle. The performance of this polarizer concept was fabricated and tested with an existing McPherson 225 Vacuum Ultraviolet (VUV) spectrometer located in the Optics Branch at NASA-GSFC. Initial testing has shown that in the FUV spectral range, this design can produce state-of-the-art extinction ratios at the Hydrogen Lyman-Alpha (Ly-α) wavelength of 121.6 nm. A polarizer with such a performance has never been reported and it signifies a breakthrough in FUV polarization technology. The levels of effectiveness paired with the design’s compact design allows for a new polarizer capability that would one day be implemented in a future spectropolarimetry space mission. In addition, this polarizer concept could potentially be used to characterize the optical properties of new mirror coatings that will be used in a future Habitable World Observatory (HWO) mission concept as proposed by the 2020 Decadal Survey.2

Far Ultraviolet (FUV), polarimetry, instrumentatio↗
NASA NTRSDate not supplied

Linear Polarizer Design for Application in the Far-Ultraviolet Spectral Range

New mission concepts that are under consideration by NASA (such as the Polstar MIDEX mission concept) call for the design and implementation of Far Ultraviolet (FUV) polarizer technologies that have not been developed yet. A team that includes members from the NASA Goddard Space Flight Center (GSFC), Arizona State University (ASU), and Woodruff Consulting, worked on the design and development of a polarizer design that may produce extinction ratios higher than have ever been reported before in the FUV spectral range (100-200 nm). This polarizer consists of transmitting linearly polarized light through a series of reflections from a combination of two silicon carbide (SiC) and two lithium fluoride (LiF) crystals positioned at angles of incidence (relative to surface normal) close to the LiF Brewster’s angle. The performance of this polarizer concept was fabricated and tested with an existing McPherson 225 Vacuum Ultraviolet (VUV) spectrometer located in the Optics Branch at NASA-GSFC. Initial testing has shown that in the FUV spectral range, this design can produce state-of-the-art extinction ratios at the Hydrogen Lyman-Alpha (Ly-α) wavelength of 121.6 nm. A polarizer with such a performance has never been reported and it signifies a breakthrough in FUV polarization technology. The levels of effectiveness paired with the design’s compact design allows for a new polarizer capability that would one day be implemented in a future spectropolarimetry space mission. In addition, this polarizer concept could potentially be used to characterize the optical properties of new mirror coatings that will be used in a future Habitable World Observatory (HWO) mission concept as proposed by the 2020 Decadal Survey.2

Far Ultraviolet (FUV), polarimetry, instrumentatio↗
NASA NTRS2002

NGSS: the next generation sky survey

The Next Generation Sky Survey (NGSS) is a Medium Explorer currently in Phase A study, with launch planned for 2007. NGSS will map the entire sky with unprecedented sensitivity from 3.5 to 23 microns.

infrared↗
NASA NTRS2022

Understanding Structure in Line-Driven Stellar Winds Using Ultraviolet Spectropolarimetry in the Time Domain

The most massive stars are thought to lose a significant fraction of their mass in a steady wind during the main-sequence and blue supergiant phases. This in turn sets the stage for their further evolution and eventual supernova, and preconditions the surrounding medium for all following events, with consequences for ISM energization, chemical enrichment, and dust formation. Understanding these processes requires accurate observational constraints on the mass-loss rates of the most luminous stars, which can also be used to test theories of stellar wind driving. In the past, mass-loss rates have been characterized via collisional emission processes such as optical Hα and free-free radio emission, but these so-called “density squared” diagnostics require correction in the presence of widespread clumping. Recent observational and theoretical evidence points to the likelihood of a ubiquitously high level of such clumping in hot-star winds, but quantifying its effects requires a deeper understanding of the complex dynamics of radiatively driven winds and their stochastic instabilities. Furthermore, large-scale structures initiating in surface anisotropies and propagating throughout the wind can also affect wind driving and alter mass-loss diagnostics. Time series spectroscopy of high resonance-line opacity in the UV, capable of high resolution and high signal-to-noise, are required to better understand these complex dynamics, and more accurately determine mass-loss rates. The proposed Polstar mission (Scowen et al. 2022, this volume) provides the necessary resolution at the Sobolev (∼10 km s −1 ) or sound-speed (∼20 km s −1 ) scale, for over three dozen bright galactic massive stars with signal-to noise an order of magnitude above that of the celebrated MEGA campaign (Massa et al. 1995) of the International Ultraviolet Explorer (IUE), via continuous observations that track propagating structures through the winds in real time. Supporting geometric constraints are provided by the polarimetric capabilities present in all the datasets of such a mission.

Polstar – NASA MIDEX↗
NASA NTRS2022

Ultraviolet Spectropolarimetry: on the Origin of Rapidly Rotating B Stars

UV spectroscopy and spectropolarimetry hold the key to understanding certain aspects of massive stars that are largely inaccessible (or exceptionally difficult) with optical or longer wavelength observations. As we demonstrate, this is especially true for the rapidly-rotating Be and Bn stars, owing to their high temperatures, geometric asymmetries, binary properties, evolutionary history, as well as mass ejection and disks (in the case of Be stars). UV spectropolarimetric observations are extremely sensitive to the photospheric consequences of rapid rotation (i.e. oblateness, temperature, and surface gravity gradients), far beyond the reach of optical wavelengths. Our polarized radiative-transfer modelling predicts that with low-resolution UV spectropolarimetry covering 120–300 nm, and with a reasonable SNR, the inclination angle of a rapid rotator can be determined to within 5 degrees, and the rotation rate to within 1%. The origin of rapid rotation in Be/n stars can be explained by either single-star or binary evolution, but their relative importance is largely unknown. Some Be stars have hot sub-luminous (sdO) companions, which at an earlier phase transferred their envelope (and with it mass and angular momentum) to the present-day rapid rotator. Although sdO stars are small and relatively faint, their flux peaks in the UV making this the optimal observational wavelength regime. Through spectral modelling of a wide range of simulated Be/n+sdO configurations, we demonstrate that high-resolution high-signal-to-noise ratio UV spectroscopy can detect an sdO star even when ∼1,000 times fainter in the UV than its Be/n star companion. This degree of sensitivity is needed to more fully explore the parameter space of Be/n+sdO binaries, which so far has been limited to about a dozen systems with relatively luminous sdO stars. We suggest that a UV spectropolarimetric survey of Be/n stars is the next step forward in understanding this population. Such a dataset would, when combined with population synthesis models, allow for the determination of the relative importance of the possible evolutionary pathways traversed by these stars, which is also crucial for understanding their future evolution and fate.

Ultraviolet astronomy↗