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NASA NTRS2011

X-Ray Optics for the 2020s

Three factors characterize an X-ray optics technology: angular resolution, effective area per unit mass, and production cost per unit effective area. In general, these three factors are always in conflict with one another. Every telescope that has flown so far represents an astronomically useful compromise of these factors. Of three operating X-ray telescopes, Chandra has been optimized for angular resolution (0.5); Suzaku for effective area per unit mass; and both were optimized in its own way to minimize production cost. Optics for the decade of2020 requires a combination of Chandra's angular resolution and Suzaku's effective area per unit mass. In this talk I will briefly review X -ray optics fabrication techniques that have been used in the past three decades and then present my expectations for the 2020s. In particular I will propose a couple of new techniques that should be investigated for making lightweight and high resolution X-ray optics.

Zhang, William↗

NASA NTRS2011

Dual Electron Spectrometer for Magnetospheric Multiscale Mission: Results of the Comprehensive Tests of the Engineering Test Unit

The Magnetospheric Multiscale mission (MMS) is designed to study fundamental phenomena in space plasma physics such as a magnetic reconnection. The mission consists of four spacecraft, equipped with identical scientific payloads, allowing for the first measurements of fast dynamics in the critical electron diffusion region where magnetic reconnection occurs and charged particles are demagnetized. The MMS orbit is optimized to ensure the spacecraft spend extended periods of time in locations where reconnection is known to occur: at the dayside magnetopause and in the magnetotail. In order to resolve fine structures of the three dimensional electron distributions in the diffusion region (reconnection site), the Fast Plasma Investigation's (FPI) Dual Electron Spectrometer (DES) is designed to measure three dimensional electron velocity distributions with an extremely high time resolution of 30 ms. In order to achieve this unprecedented sampling rate, four dual spectrometers, each sampling 180 x 45 degree sections of the sky, are installed on each spacecraft. We present results of the comprehensive tests performed on the DES Engineering & Test Unit (ETU). This includes main parameters of the spectrometer such as energy resolution, angular acceptance, and geometric factor along with their variations over the 16 pixels spanning the 180-degree tophat Electro Static Analyzer (ESA) field of view and over the energy of the test beam. A newly developed method for precisely defining the operational space of the instrument is presented as well. This allows optimization of the trade-off between pixel to pixel crosstalk and uniformity of the main spectrometer parameters.

Avanov, Levon A.↗

DOE OSTI2020

Version 4 of the CRU TS monthly high-resolution gridded multivariate climate dataset

CRU TS (Climatic Research Unit gridded Time Series) is a widely used climate dataset on a 0.5° latitude by 0.5° longitude grid over all land domains of the world except Antarctica. It is derived by the interpolation of monthly climate anomalies from extensive networks of weather station observations. Here we describe the construction of a major new version, CRU TS v4. It is updated to span 1901–2018 by the inclusion of additional station observations, and it will be updated annually. The interpolation process has been changed to use angular-distance weighting (ADW), and the production of secondary variables has been revised to better suit this approach. This implementation of ADW provides improved traceability between each gridded value and the input observations, and allows more informative diagnostics that dataset users can utilise to assess how dataset quality might vary geographically.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2020

Planck intermediate results

We present the NPIPE processing pipeline, which produces calibrated frequency maps in temperature and polarization from data from the Planck Low Frequency Instrument (LFI) and High Frequency Instrument (HFI) using high-performance computers. NPIPE represents a natural evolution of previous Planck analysis efforts, and combines some of the most powerful features of the separate LFI and HFI analysis pipelines. For example, following the LFI 2018 processing procedure, NPIPE uses foreground polarization priors during the calibration stage in order to break scanning-induced degeneracies. Similarly, NPIPE employs the HFI 2018 time-domain processing methodology to correct for bandpass mismatch at all frequencies. In addition, NPIPE introduces several improvements, including, but not limited to: inclusion of the 8% of data collected during repointing manoeuvres; smoothing of the LFI reference load data streams; in-flight estimation of detector polarization parameters; and construction of maximally independent detector-set split maps. For component-separation purposes, important improvements include: maps that retain the CMB Solar dipole, allowing for high-precision relative calibration in higher-level analyses; well-defined single-detector maps, allowing for robust CO extraction; and HFI temperature maps between 217 and 857 GHz that are binned into 0'.9 pixels (Nside = 4096), ensuring that the full angular information in the data is represented in the maps even at the highest Planck resolutions. The net effect of these improvements is lower levels of noise and systematics in both frequency and component maps at essentially all angular scales, as well as notably improved internal consistency between the various frequency channels. Based on the NPIPE maps, we present the first estimate of the Solar dipole determined through component separation across all nine Planck frequencies. The amplitude is (3366.6 ± 2.7) μK, consistent with, albeit slightly higher than, earlier estimates. From the large-scale polarization data, we derive an updated estimate of the optical depth of reionization of τ = 0.051 ± 0.006, which appears robust with respect to data and sky cuts. There are 600 complete signal, noise and systematics simulations of the full-frequency and detector-set maps. As a Planck first, these simulations include full time-domain processing of the beam-convolved CMB anisotropies. The release of NPIPE maps and simulations is accompanied with a complete suite of raw and processed time-ordered data and the software, scripts, auxiliary data, and parameter files needed to improve further on the analysis and to run matching simulations.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2019

The Simons Observatory: science goals and forecasts

The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. We describe the scientific goals of the experiment, motivate the design, and forecast its performance. SO will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands centered at: 27, 39, 93, 145, 225 and 280 GHz. The initial configuration of SO will have three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. Our key science goals are to characterize the primordial perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. The small aperture telescopes will target the largest angular scales observable from Chile, mapping ≈ 10% of the sky to a white noise level of 2 μK-arcmin in combined 93 and 145 GHz bands, to measure the primordial tensor-to-scalar ratio, r, at a target level of σ(r)=0.003. The large aperture telescope will map ≈ 40% of the sky at arcminute angular resolution to an expected white noise level of 6 μK-arcmin in combined 93 and 145 GHz bands, overlapping with the majority of the Large Synoptic Survey Telescope sky region and partially with the Dark Energy Spectroscopic Instrument. With up to an order of magnitude lower polarization noise than maps from the Planck satellite, the high-resolution sky maps will constrain cosmological parameters derived from the damping tail, gravitational lensing of the microwave background, the primordial bispectrum, and the thermal and kinematic Sunyaev-Zel'dovich effects, and will aid in delensing the large-angle polarization signal to measure the tensor-to-scalar ratio. In conclusion, the survey will also provide a legacy catalog of 16,000 galaxy clusters and more than 20,000 extragalactic sources.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2019

High resolution measurement of tagged two-neutron energy and angle correlations in 252-Cf (sf)

Spontaneous fission events emit prompt neutrons correlated with one another in emission angle and energy. Measurements of these correlations can shed light on the partitioning of the excitation energy between the fragments, even if they are not directly measured. Purpose: We explore the relationship in energy and angle between correlated prompt neutrons emitted from 252 Cf spontaneous fission. Methods: Measurements with the Chi-Nu array provide experimental data for coincident neutrons tagged with a fission chamber signal with 10° angular resolution and 1-ns timing resolution for time-of-flight energy calculations. The experimental results are compared to simulations produced by the fission event generators cgmf, freya, and mcnpx-polimi ipol(1) = 1. Results: We find that the measurements and the simulations all exhibit anisotropic neutron emission, although differences between fission event generators are evident. In conclusion, this work shows that the dependence of detected neutron energy on the energy of another neutron detected in coincidence, although weak, is non-negligible, indicating that there may be correlations in energy between two neutrons emitted in the same fission event..

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

NASA NTRS1978

Evaluation of radiation interference in the Voyager Sun Sensor's cadmium sulfide detector

The simulation of radiation interference effects and the results of a radiation interference test on two Voyager Sun Sensor prototype detector assemblies are reported. The derivation of test levels and requirements are discussed and show that cobalt 60 gamma radiation is an effective and practical simulator of the ionization dose rate effects induced by high-energy electron flux incident on the spacecraft at a rate of 3.7 x 10 to the 8th e/sq cm-sec (10 rad(Si)/s) during closest approach to Jupiter. The test results provide information that is used to confirm an analytic correlation, and to predict satisfactory performance of a spacecraft sun sensing device having stringent angular resolution requirements. The measured detector response shows that at dose rates incident on the detector elements of 2 rad(Si)/sec, which is four times that expected during Jupiter encounter, the radiation-induced angle error is almost an order of magnitude less than that allowed by the acceptance criteria.

Clarke, T. C.↗

NASA NTRS2017

Reduced-Scale Transition-Edge Sensor Detectors for Solar and X-Ray Astrophysics

We have developed large-format, close-packed X-ray microcalorimeter arrays fabricated on solid substrates, designed to achieve high energy resolution with count rates up to a few hundred counts per second per pixel for X-ray photon energies upto 8 keV. Our most recent arrays feature 31-micron absorbers on a 35-micron pitch, reducing the size of pixels by about a factor of two. This change will enable an instrument with significantly higher angular resolution. In order to wire out large format arrays with an increased density of smaller pixels, we have reduced the lateral size of both the microstrip wiring and the Mo/Au transition-edge sensors (TES). We report on the key physical properties of these small TESs and the fine Nb leads attached, including the critical currents and weak-link properties associated with the longitudinal proximity effect.

Arrays↗

NASA NTRS2019

The Simons Observatory: science goals andforecasts

The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. We describe the scientific goals of the experiment, motivate the design, and forecast its performance. SO will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands centered at: 27, 39, 93, 145, 225 and 280 GHz. The initial configuration of SO will have three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. Our key science goals are to characterize the primordial perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. The small aperture telescopes will target the largest angular scales observable from Chile, mapping ≈ 10% of the sky to a white noise level of 2 μK-arcmin in combined 93 and 145 GHz bands, to measure the primordial tensor-to-scalar ratio, r, at a target level of σ(r)=0.003. The large aperture telescope will map ≈ 40% of the sky at arcminute angular resolution to an expected white noise level of 6 μK-arcmin in combined 93 and 145 GHz bands, overlapping with the majority of the Large Synoptic Survey Telescope sky region and partially with the Dark Energy Spectroscopic Instrument. With up to an order of magnitude lower polarization noise than maps from the Planck satellite, the high-resolution sky maps will constrain cosmological parameters derived from the damping tail, gravitational lensing of the microwave background, the primordial bispectrum, and the thermal and kinematic Sunyaev-Zel'dovich effects, and will aid in delensing the large-angle polarization signal to measure the tensor-to-scalar ratio. The survey will also provide a legacy catalog of 16,000 galaxy clusters and more than 20,000 extragalactic sources.

Peter Ade↗

NASA NTRS1985

The sun and nearby stars - Microwave observations at high resolution

High-resolution microwave observations are providing new insights into the nature of active regions and eruptions on the sun and nearby stars. The strength, evolution, and structure of magnetic fields in coronal loops can be determined by multiple-wavelength observations with the Very Large Array. Flare models ccan be tested with Very Large Array snapshot maps, which have angular resolutions of better than 1 second of arc in time periods as short as 10 seconds. Magnetic changes that precede solar eruptions on time scales of tens of minutes involve primarily emerging coronal loops and the interactions of two or more loops. Magnetic reconnection at the interface of two closed loops may accelerate electrons and trigger the release of microwave energy in the coronal parts of the magnetic loops. Nearby main-sequence stars of late spectral type emit slowly varying microwave radiation and stellar microwave bursts that show striking similarities to those of the sun.

Kundu, M. R.↗

DOE OSTI2025

Development of Thin Gap GEM-µRWELL Hybrid Detectors at Jefferson Lab

Over the past few decades, Micro Pattern Gaseous Detector (MPGD) technologies have been increasingly adopted as tracking detector options in High Energy and Nuclear Physics experiments thanks to their good spatial resolution, high-rate capability, stability and more importantly their ability for large area coverage at a relatively low cost compared to the alternative. The thin gap GEM-µRWELL hybrid detector is the latest addition to the MPGD family, that was introduced to vastly improve the spatial resolution capability of gaseous trackers when deployed in the barrel region to cover large angular acceptance of the central tracker in a collider experiment. In this talk, I will re-introduce the concept and motivation for the development of thin gap GEM-µRWELL hybrid technology with an emphasis on the initial studies that establish the proof-of-concept of the technology. I will then discuss the more recent results from latest beam test campaign at Jefferson Lab in May 2025 to study detector efficiency performance with various gas mixtures. I will also briefly present the ongoing activities to develop large area thin gap GEM-µRWELL tracking detectors for the ePIC experiment of the future Electron Ion Collider as well as the exploration of the technology to provide large area tracking options to the muon system of experiments at a future Higgs Factory Collider such as the FCC-ee for example. Finally, I will conclude with some perspectives on new ideas under exploration to develop the next generation of thin gap MPGD technologies with enhanced timing and spatial resolution capabilities

Gnanvo, Kondo [Thomas Jefferson National Accelerat↗

NASA NTRS2006

Electromagnetic Properties of Filled, Pixellated Arrays

Filled arrays of bolometers are currently being employed for use in astronomy from the far-infrared through millimeter parts of the electromagnetic spectrum. Because of the large range of wavelengths for which this is applicable, the number of modes supported by a bolometric pixel will vary according to specific application. Withington et al. (2003) have built a formalism for treating the electromagnetic properties of such bolometers by propagating the second order statistical properties of the radiation through a canonical optical system. In this work, we use this formalism to construct beam pattern images of square pixels for various ratios of p/lambda where p is the pixel size and lambda is the wavelength. In the low mode limit, the diffraction effects cause the beam pattern to be circular with a quadrupole dependence of Stokes Q and U. High mode cases approach the geometric limit. The polarization in these cases can be seen to trace the pixel edges. The effective size of the beam has a direct impact on the inter-pixel coupling and sets the number of independent detectors in an astronomical focal plane. This technique illustrates and quantifies the relationship between pixel size and angular resolution limits for a given wavelength and telescope. This is especially true in the limit of low p/lambda. In this case, the diffraction due to pixelization is non-negligible for the calculation of the overall angular resolution of the telescope. In addition, for instruments that are polarization sensitive, this method also provides a quantitative method for determining the contribution of the instrument to the measured polarization.

Chuss, David T.↗

NASA NTRS2009

An Investigation of Differential Deposition for Figure Corrections in Full-Shell Grazing-Incidents X-Ray Optics

We are investigating differential deposition as a way of correcting small figure errors inside full-shell grazing-incidence x-ray optics. The optics in our study are fabricated using the electroformed-nickel-replication technique, and the figure errors arise from fabrication errors in the mandrel, from which the shells are replicated, as well as errors induced during the electroforming process. Combined, these give sub-micron-scale figure deviations which limit the angular resolution of the optics to approx. 10 arcsec. Sub-micron figure errors can be corrected by selectively depositing (physical vapor deposition) material inside the shell. The requirements for this filler material are that it must not degrade the ultra-smooth surface finish necessary for efficient x-ray reflection (approx. 5 A rms), and must not be highly stressed. In addition, a technique must be found to produce well controlled and defined beams within highly constrained geometries, as some of our mirror shells are less than 3 cm in diameter.

Gubarev, Mikhail V.↗

NASA NTRS2014

Toward Large-Area Sub-Arcsecond X-Ray Telescopes

The future of x-ray astronomy depends upon development of x-ray telescopes with larger aperture areas (approx. = 3 square meters) and fine angular resolution (approx. = 1 inch). Combined with the special requirements of nested grazing-incidence optics, the mass and envelope constraints of space-borne telescopes render such advances technologically and programmatically challenging. Achieving this goal will require precision fabrication, alignment, mounting, and assembly of large areas (approx. = 600 square meters) of lightweight (approx. = 1 kilogram/square meter areal density) high-quality mirrors at an acceptable cost (approx. = 1 million dollars/square meter of mirror surface area). This paper reviews relevant technological and programmatic issues, as well as possible approaches for addressing these issues-including active (in-space adjustable) alignment and figure correction.

ODell, Stephen L.↗

NASA NTRS2008

Climate Model Evaluation using New Datasets from the Clouds and the Earth's Radiant Energy System (CERES)

There are some in the science community who believe that the response of the climate system to anthropogenic radiative forcing is unpredictable and we should therefore call off the quest . The key limitation in climate predictability is associated with cloud feedback. Narrowing the uncertainty in cloud feedback (and therefore climate sensitivity) requires optimal use of the best available observations to evaluate and improve climate model processes and constrain climate model simulations over longer time scales. The Clouds and the Earth s Radiant Energy System (CERES) is a satellite-based program that provides global cloud, aerosol and radiative flux observations for improving our understanding of cloud-aerosol-radiation feedbacks in the Earth s climate system. CERES is the successor to the Earth Radiation Budget Experiment (ERBE), which has widely been used to evaluate climate models both at short time scales (e.g., process studies) and at decadal time scales. A CERES instrument flew on the TRMM satellite and captured the dramatic 1998 El Nino, and four other CERES instruments are currently flying aboard the Terra and Aqua platforms. Plans are underway to fly the remaining copy of CERES on the upcoming NPP spacecraft (mid-2010 launch date). Every aspect of CERES represents a significant improvement over ERBE. While both CERES and ERBE measure broadband radiation, CERES calibration is a factor of 2 better than ERBE. In order to improve the characterization of clouds and aerosols within a CERES footprint, we use coincident higher-resolution imager observations (VIRS, MODIS or VIIRS) to provide a consistent cloud-aerosol-radiation dataset at climate accuracy. Improved radiative fluxes are obtained by using new CERES-derived Angular Distribution Models (ADMs) for converting measured radiances to fluxes. CERES radiative fluxes are a factor of 2 more accurate than ERBE overall, but the improvement by cloud type and at high latitudes can be as high as a factor of 5. Diurnal cycles are explicitly resolved by merging geostationary satellite observations with CERES and MODIS. Atmospheric state data are provided from a frozen version of the Global Modeling and Assimilation Office- Data Assimilation System at the NASA Goddard Space Flight Center. In addition to improving the accuracy of top-of-atmosphere (TOA) radiative fluxes, CERES also produces radiative fluxes at the surface and at several levels in the atmosphere using radiative transfer modeling, constrained at the TOA by CERES (ERBE was limited to the TOA). In all, CERES uses 11 instruments on 7 spacecraft all integrated to obtain climate accuracy in TOA to surface fluxes. This presentation will provide an overview of several new CERES datasets of interest to the climate community (including a new adjusted TOA flux dataset constrained by estimates of heat storage in the Earth system), show direct comparisons between CERES ad ERBE, and provide a detailed error analysis of CERES fluxes at various time and space scales. We discuss how observations can be used to reduce uncertainties in cloud feedback and climate sensitivity and strongly argue why we should NOT "call off the quest".

Loeb, Norman G.↗

NASA NTRS2008

High-Resolution N-Band Observations of the Nova Rs Ophiuchi: First Science with the Keck Interferometer Nuller

We report new observations of the nova RS Ophiuchi using the Keck Interferometer Nulling Instrument (KIN), approximately 3.8 days following the most recent outburst that occurred on 2006 February 12. These observations represent the first scientific results from the KIN, which operates in N-band from 8 to 12.5 microns. The nulling technique is the sparse aperture equivalent of the conventional coronagraphic technique used in filled aperture telescopes. By fitting the unique KIN inner and outer spatial regime data, we have obtained an angular size of the mid-infrared continuum of 6.2,4.0, or 5.4 mas for a disk profile, Gaussian profile, and shell profile respectively. The data show evidence of enhanced neutral atomic hydrogen emission and atomic metals including silicon located in the inner spatial regime near the white dwarf relative to the outer regime. There are also nebular emission lines and evidence of hot silicate dust in the outer spatial region, centered at approximately 2.5E14 cm from the WD, that are not found in the inner regime. The nova flash in the outer spatial regime evidently excited these features before the blast wave reached these regions. These identifications support the following interpretation. The dust appears to be present between outbursts and was not created during the outburst event. We further discuss the present results in terms of a unifying model of the system that includes an increase in density in the plane of the orbit of the two stars created by a spiral shock wave caused by the motion of the stars through the cool wind of the red giant star. These data show the power and potential of the nulling technique which has been developed for the detection of Earthlike planets around nearby stars for the Terrestrial Planet Finder Mission and Darwin missions.

Danchi, William↗

NASA NTRS1991

Measurements of radar backscatter from an artificial tree - An indication of azimuthal variations and polarization sensitivity of trees

Measurements of radar backscatter from an artificial tree were made in the laboratory at 6 and 10 GHz at horizontal incidence. The system had a resolution cylinder 18 cm in diameter and 11 cm long, so about half of the tree (30.5 cm high) was within the beam. The mean returned power from the target with leaves was always higher than that from the target without leaves, as expected. The signal faded with an exponential distribution when the artificial tree was rotated about its trunk, with no angular trend apparent. When the leaves were present, tilted polarizations gave results favoring an angle corresponding with that of the branches. When leaves were absent, the trunk of the tree dominated the radar backscatter at all polarizations.

Moore, R. K.↗

NASA NTRS2001

A High Resolution Study of the X-Ray Emission From 3C400.2

The ROSAT HRI observation of 3C400.2 was conducted and the data have been received by the PI. The data have been processed using the Extended Source Analysis SW (ESAS) developed by Steve Snowden for the analysis of extended objects with ROSAT. The ESAS SW models and subtracts the particle background of the ROSAT HRI which is the dominant contributor to the non-cosmic background in the HRI. The background-subtracted image was smoothed with an adaptive-smoothing algorithm in order to enhance faint structure but also to maintain the superb angular resolution of the HRI where a sufficient number of counts were available. We have also used the ESAS SW to analyze the existing archival PSPC data. We have generated background-subtracted and merged images from the multiple PSPC observations. In the future, we will conduct a detailed comparison between the HRI and PSPC images. In addition, we plan to use the existing archival ASCA data to better determine the spectrum as a function of position in the remnant. The PI has not been able to finish the analysis and write the paper due to his demands on his time supporting operations of the Chandra X-ray Observatory. The PI will have more time in the coming year and hopes to finish the analysis.

Plucinsky, Paul↗