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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

Design and Fabrication of Metamaterial Anti-reflection Coatings for the Simons Observatory

The Simons Observatory (SO) will be a cosmic microwave background (CMB) survey experiment with three small-aperture telescopes and one large-aperture telescope, which will observe from the Atacama Desert in Chile. In total, SO will field over 60,000 transition-edge sensor (TES) bolometers in six spectral bands centered between 27 and 280 GHz in order to achieve the sensitivity necessary to measure or constrain numerous cosmological quantities, as outlined in The Simons Observatory Collaboration et al. (2019). These telescopes require 33 highly transparent, large aperture, refracting optics. To this end, we developed mechanically robust, highly efficient, metamaterial anti-reflection (AR) coatings with octave bandwidth coverage for silicon optics up to 46 cm in diameter for the 22-55, 75-165, and 190-310 GHz bands. We detail the design, the manufacturing approach to fabricate the SO lenses, their performance, and possible extensions of metamaterial AR coatings to optical elements made of harder materials such as alumina.

Joseph E. Golec↗
NASA NTRS2002

Science Planning for Multi-Spacecraft Coordinated Observations

Fulfilling the promise of an era of great observatories, NASA now has more than three space-based astronomical telescopes operating in different wavebands. This situation provides astronomers with a unique opportunity to simultaneously observe with multiple observatories. Yet scheduling multiple observatories simultaneously is highly inefficient when compared to single observatory observations. Thus, programs using multiple observatories are limited not due to scientific restrictions, but due to operational inefficiencies. Each year, a number of proposals are accepted by a space-based observatory for conduction of astronomical observations and gathering of science data for the study of galactic events. Since each space-based observatory uses a set of instruments designed to operate in specific energy regions, most such studies are conducted by submitting observation proposals to multiple observatories, with requests to coordinate among themselves. To assure that the proposed observations can be scheduled, each observatory's staff has to check that the observations are valid and meet all the constraints for their own observatory; in addition, they have to verify that the observations satisfy the constraints of the other observatories. Thus, coordinated observations require painstaking manual collaboration among the observatory staff at each observatory. In order to exploit new paradigms for observatory operation, the Goddard Space Flight Center's Advanced Architectures and Automation Branch has developed a prototype tool called the Visual Observation Layout Tool (VOLT). The main objective of VOLT is to provide a visual tool to automate the science planning of coordinated observations for multiple spacecraft, as well as to increase the scheduling probability of observations. However, VOLT is also useful for single observatory planning to optimize observatory control. Three space-based missions are interested in using VOLT (the Hubble Space Telescope, the Chandra X-Ray Observatory, and the Far Ultraviolet Spectroscopic Explorer). The VOLT team members have collaborated with these missions to gather requirements and obtain feedback on their mission planning processes. VOLT has been developed as a cross-platform Java client application for use by scientists and observatory science planning staff to visualize scheduling options and constraints. It also supports a lightweight graphical user interface for remote viewing via a Web front end. Additionally, it uniquely supports the ability to interact with multiple, diverse scheduling packages in order to determine windows of opportunity for observations and visually portray the constraints of each observation request. VOLT enables science data capture scenarios which are currently either impossible, or which require extensive time and manpower to coordinate amongst multiple observatories. it supports early detection of planning conflicts by generating coordinated solutions based on observatory schedulability and constraints. The project development approach has included frequent prototype demonstrations to our interested missions to obtain feedback after each release of the software. We will present an overview of our lessons learned in infusing the VOLT tool into the operations of the missions we have collaborated with and a brief demonstration of the software.

Maks, Lori↗
NASA NTRS1993

Effect of jet engine exhaust on SOFIA straylight performance

The Stratospheric Observatory For Infrared Astronomy (SOFIA) is being designed at NASA's Ames Research Center as a replacement for the Kuiper Airborne Observatory (KAO). A 2.5-m Nasmyth telescope will be mounted in a Boeing 747 SP and flown at 41,000 ft, above most of the H2O in the earth's atmosphere. In the original SOFIA design, the telescope is located in front of the wings, as it is in the KAO. An alternative design with the telescope placed behind the wings is being studied as part of an effort to reduce cost and weight. In this location, the emission from the engines and the hot H2O molecules in the exhaust become significant straylight sources. The engines and exhaust radiate into the telescope cavity, and illuminate the primary and tertiary mirrors at low telescope elevation angles. The APART/PADE program was used to analyze the straylight at the SOFIA focal plane as a function of wavelength and telescope elevation angle. The emission from the engines and exhaust gas is compared to that from the earth and the telescope itself. Based on the results of this analysis, the SOFIA telescope has been moved behind the wings.

St. Clair Dinger, Ann↗
NASA NTRSDate not supplied

Design and Predicted Performance of 4-m Baseline Habitable-Zone Exoplanet Observatory Telescope

The Habitable Exoplanet Observatory Mission (HabEx) is one of four missions which NASA is studying. Its goal is to directly image and spectroscopically characterize planets in the habitable zone around nearby sun-like stars. Additionally, HabEx would perform a broad range of general astrophysics science enabled by 115 to 1700 nm spectral range and 3x3 arc-minute FOV instruments. Critical to achieving its science goals is a large, ultra-stable UV/Optical/Near-IR (UVOIR) telescope. The baseline HabEx telescope is a 4-meter off-axis unobscured three-mirror-anastigmatic, diffraction limited at 400 nm with wavefront stability on the order of a few 10s of picometers. This paper summarizes how science driven systems engineering (using science requirements to derive engineering specifications) resulting in the opto-mechanical design of the HabEx baseline optical telescope assembly. And, how Structural Thermal Optical Performance (STOP) modeling predicts tolerance compliance.

H Philip Stahl↗
NASA NTRS2004

Spitzer Space Telescope mission design

This paper gives a description of the mission design, launch, orbit, and navigation results for the Spitzer space telescope mission. The Spitzer telescope was launched by the Delta II Heavy launch vehicle into a heliocentric Earth trailing orbit. This orbit is flown for the first time and will be used by several future astronomical missions such as Kepler, SIM, and LISA. This paper describes the launch strategy for a winter versus a summer launch and how it affects communications. It also describes how the solar orbit affects the design and operations of the Observatory. It describes the actual launch timeline, launch vehicle flight performance, and the long term behavior of the as flown orbit. It also provides the orbit knowledge from in-flight navigation data.

Mission Design↗
NASA NTRS1990

An intensified CCD detector using the phosphor TPB

The Research Amplifying Imaging Detector consists of a microchannel plate image intensifier with a thin coating (3500-10,000 A) of the phosphor tetraphenyl-butadiene (TPB) on the entrance window to convert EUV radiation to visible, and coupled via a lens to a CCD detector. This design allows great flexibility in selecting the pixel size and field of view, with a simple mechanical design. The phosphor appears to be quite rugged, with no degradation having appeared during several months of testing both in and out of vacuum. Tests have been made at visible and EUV (304 A) wavelengths of the following performance aspects: EUV spectral sensitivity, spatial resolution (both of components and of the system as a whole), noise, linearity, and dynamic range. An improved detector for the Coronal Diagnostic Spectrometer experiment on the Solar Heliospheric Observatory satellite is being presently designed.

Thompson, William T.↗
NASA NTRS1989

An astronomy camera for low background applications in the 1.0 to 2.5 micron spectral region

A description is given of a low-background astronomy camera system based on a short wavelength (1.0-2.5 micron) 128 x 128 focal plane array. The camera is designed to accept either a HgCdTe array for the 1-2.5 micron spectral region or an InSb array for the 3-5 micron spectral region. A cryogenic folded optical system is utilized to control excess stray light along with a cold eight-position filter wheel for spectral filtering. The camera head and electronics will also accept a 256 x 256 focal plane. Engineering evaluation of the system and two engineering runs at the JPL Table Mountain Observatory have been completed. System design, engineering performance, and sample imagery are presented.

Kaki, Said A.↗
NASA NTRS2020

The Habitable Exoplanet Observatory (HabE) Mission Concept

The Habitable Exoplanet Observatory (HabEx), was one of four candidate flagship missions studied in detail by NASA, which were submitted for consideration to the 2020 Decadal Survey in Astronomy and Astrophysics for possible launch in the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable spacebased telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx was designed to be the Great Observatory of the 2030s and beyond, with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR.

Warfield, Keith↗
NASA NTRS1998

Radial Velocity Detection of Extra-Solar Planetary Systems

The McDonald Observatory Planetary Search (MOPS) was designed to search for Jovian-mass planets in orbit around solar-type stars by making high-precision measurements of the Radial Velocity (RV) of a star, to attempt to detect the reflex orbital motion of the star around the star-planet barycenter. In our solar system, the velocity of the Sun around the Sun-Jupiter barycenter averages 12.3 m/ s. The MOPS survey started operation in September 1987, and searches 36 bright, nearby, solar-type dwarfs to 10 m/s precision. The survey was started using telluric O2 absorption lines as the velocity reference metric. Observations use the McDonald Observatory 2.7-m Harlan Smith Telescope coude spectrograph with the six-foot camera. This spectrograph configuration isolates a single order of the echelle grating on a Texas Instruments 800 x 800 CCD. The telluric line method gave us a routine radial velocity precision of about 15 m/s for stars down to about 5-th magnitude. However, the data obtained with this technique suffered from some source of long-term systematic errors, which was probably the intrinsic velocity variability of the terrestrial atmosphere, i.e. winds. In order to eliminate this systematic error and to improve our overall measurement precision, we installed a stabilized I2 gas absorption cell as the velocity metric for the MOPS in October 1990. In use at the telescope, the cell is placed directly in front of the spectrograph entrance slit, with starlight passing through the cell. The use of this sealed stabilized I2 cell removes potential problems with possible long-term drifts in the velocity metric. The survey now includes a sample of 36 nearby F, G, and K type stars of luminosity class V or IV-V.

Cochran, William D.↗
NASA NTRS2006

The Suzaku High Resolution X-ray Spectrometer

The high resolution X-Ray Spectrometer (XRS) has been designed to provide the Suzaku Observatory with very high spectral resolution, non-dispersive spectroscopy from 0.3 to 12 keV. This energy range encompasses the most diagnostically-rich part of the x-ray band. The sensor consists of a 32 channel array of x-ray of microcalorimeters, each with an energy resolution of about 6 eV. The very low temperature required for operation of the array (60 mK) is provided by a four-stage cooling system containing a single stage ADR, superfluid He Cryostat, solid Ne Dewar, and a single-stage Stirling-cycle cooler. The Suzaku/XRS is the first orbiting x-ray microcalorimeter spectrometer and has been designed to last more than three years in orbit. The early verification phase of the mission demonstrated that the instrument was working properly and that the cryogen consumption rate was low enough to ensure a mission lifetime exceeding 3 years. However, the liquid He cryogen was completely vaporized two weeks after opening the dewar guard vacuum vent. The problem has been traced to inadequate venting of the dewar He and Ne gases out of the spacecraft into space. In this paper we present the design of the XRS instrument and describe the in-flight performance.

Kelley, Richard L.↗
NASA NTRS2012

SOFIA: Flying the Telescope

The primary focus of this paper is how the flight test team for the Stratospheric Observatory For Infrared Astronomy (SOFIA) re-cast an extensive developmental test program to meet key milestones while simultaneously ensuring safe certification of the airframe and delivery of an operationally relevant platform, ultimately saving the overall program from financial demise. Following a brief introduction to the observatory and what it is designed to do, SOFIAs planned developmental test program is summarized, including analysis and design philosophy, envelope expansion, model validation and airframe certification. How NASA used lessons learned from other aircraft that employed open cavities in flight is explained as well as how and why the chosen design was selected. The approach to aerodynamic analysis, including bare airframe testing, wind tunnel testing, computational fluid dynamics and finite element modeling proved absolutely critical. Despite a solid analytical foundation, many unknowns remained. History provides several examples of disastrous effects on both systems and flight safety if cavity design is not approached properly. For these reasons, an extensive test plan was developed to ensure a safe and thorough build-up for envelope expansion, airframe certification and early science missions. Unfortunately, as is often the case, because of chronic delays in overall program execution, severe schedule and funding pressures were present. If critical milestones were not met, domestic as well as international funding was in serious jeopardy, and the demise of the entire program loomed large. Concentrating on rigorous model validation, the test team challenged certification requirements, increased test efficiency and streamlined engineering analysis. This resulted in the safe reduction of test point count by 72%, meeting all program milestones and a platform that soundly satisfied all operational science requirements. Results from early science missions are shown and a proof of concept mission for which SOFIA was opportunely positioned is showcased. Success on this time-critical mission to observe a rare astronomical event proved the usefulness of an airborne observatory and the value in waiting for the capability provided by SOFIA. Finally, lessons learned in the test program are presented with emphasis on how lessons from previous aircraft and successful test programs were applied to SOFIA. Effective application of these lessons was crucial to the success of the SOFIA flight test program. SOFIA is an international cooperative program between NASA and the German Space Agency, DLR. It is a 2.5 meter (100-inch) telescope mounted in a Boeing 747SP aircraft used for astronomical observations at altitudes above 35,000 feet. SOFIA will accommodate a host of scientific instruments from the international science community and has a planned operational lifespan of more than 20 years.

Asher, Troy A.↗
NASA NTRS1994

SOFIA Optical Design for the Aft Configuration

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a planned NASA facility consisting of an infrared telescope of 2.5 meter system aperture flying in a modified Boeing 747. It will have an image diameter of 1.5 arc seconds, an operating wavelength range from visible through 1 millimeter, an 8 arc minute field of view, and a chopping secondary. the configuration is a Cassegrian with a diagonal tertiary to direct the beam to a Nasmyth focus. The new choice of a location aft of the wings allows the primary mirror to have about an f/1.4 focal ratio, which is preferable to f/1.1 previously planned for the forward location.

Davis, Paul K.↗
NASA NTRS2007

STEREO Mission Design Implementation

STEREO (Solar-TErrestrial RElations Observatory) is the third mission in the Solar Terrestrial Probes program (STP) of the National Aeronautics and Space Administration (NASA) Science Mission Directorate Sun-Earth Connection theme. This paper describes the successful implementation (lunar swingby targeting) of the mission following the first phasing orbit to deployment into the heliocentric mission orbits following the two lunar swingbys. The STEREO Project had to make some interesting trajectory decisions in order to exploit opportunities to image a bright comet and an unusual lunar transit across the Sun.

Guzman, Jose J.↗
NASA NTRS1977

Design, fabrication and expected performance of the HEAO-B X ray telescope

The X-ray telescope of the second High Energy Astronomy Observatory (HEAO-B) is described. The design consists of four concentric paraboloid/hyperboloid pairs. Focal length is 3.44 meters, paraboloid diameters vary from 580-336 mm, grazing angles vary from 70 to 40 arcmin for paraxial rays, segment lengths are 511 mm. The reflecting surfaces are nickel-coated fused quartz and the resolution is limited by assembly errors (for small field angles) and design aberrations (for large field angles). The local slope, roundness, and surface roughness are identified as the primary optical tolerances connected with the individual elements.

Van Speybroeck, L. P.↗
NASA NTRS2000

Design and Plans for a Wide-Field Imaging Interferometry Testbed

Future scientific observatories for NASA will utilize interferometry to image astronomical sources. Interferometry is particularly needed in the far-infrared and sub-millimeter because the long wavelength drives large baselines in order to achieve reasonable spatial resolution. However, the requirement to cover a wide field of view with interferometry has not been demonstrated. Because of this, we have been funded by NASA to develop a testbed for demonstrating wide field imaging interferometry that will also allow us to evaluate the system issues associated with this type of observatory. This paper will describe the drivers for this testbed, the design of this testbed, and the actual tests and algorithms we plan to run and demonstrate.

Feinberg, Lee D.↗
DOE OSTI2020

The Large-Eddy Simulation (LES) Atmospheric Radiation Measurement (ARM) Symbiotic Simulation and Observation (LASSO) Activity for Continental Shallow Convection

The U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) user facility recently initiated the Large-Eddy Simulation (LES) ARM Symbiotic Simulation and Observation (LASSO) activity focused on shallow convection at ARM’s Southern Great Plains (SGP) atmospheric observatory in Oklahoma. LASSO is designed to overcome an oft-shared difficulty of bridging the gap from point-based measurements to scales relevant for model parameterization development, and it provides an approach to add value to observations through modeling. LASSO is envisioned to be useful to modelers, theoreticians, and observationalists needing information relevant to cloud processes. LASSO does so by combining a suite of observations, LES inputs and outputs, diagnostics, and skill scores into data bundles that are freely available, and by simplifying user access to the data to speed scientific inquiry. The combination of relevant observations with observationally constrained LES output provides detail that gives context to the observations by showing physically consistent connections between processes based on the simulated state. A unique approach for LASSO is the generation of a library of cases for days with shallow convection combined with an ensemble of LES for each case. The library enables researchers to move beyond the single-case-study approach typical of LES research. The ensemble members are produced using a selection of different large-scale forcing sources and spatial scales. Since large-scale forcing is one of the most uncertain aspects of generating the LES, the ensemble informs users about potential uncertainty for each date and increases the probability of having an accurate forcing for each case.

54 ENVIRONMENTAL SCIENCES↗