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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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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Supervised Autonomous Assembly to Create and Evolve Persistent Assets

Supervised autonomous assembly (SAA) will create a paradigm shift in the planning and design of future persistent assets (PAs), both in near zero-g environments and on planetary surfaces. SAA refers to an autonomy approach that has the benefits of autonomous assembly as well as the benefits provided by a supervisor (operator) who is available to resolve unexpected situations. SAA provides both increased design freedom as well as reduced programmatic risk. SAA enables evolution of future PAs over decades as in-space operations transition from single purpose missions to creation of PAs, such as laboratories and experimental stations which more closely resembling terrestrial laboratories that can easily adapt and evolve to new missions leveraging repeated visits to the PA. The ability to evolve enables PAs to rapidly respond to changing objectives resulting from new questions as our understanding improves. A recently initiated National Aeronautics and Space Administration (NASA) project in the Space Technology Mission Directorate (STMD) Game Changing Development (GCD) Program called the Precision Assembled Space Structure (PASS), leverages the advantages of SAA to develop technologies that enable efficient creation and evolution of hexagonal topologies; both planar (example: fuel depots) and curved (examples: telescopes and shelters). PASS will be used to provide context for the philosophy and concepts discussed as well as the decision and selections made. PASS objectives are: a) Develop confidence in SAA and on-orbit servicing, assembly and manufacturing (OSAM) technologies by executing a test campaign that uses a path-to-flight autonomous precision assembly process directly applicable to future space telescopes. b) Test autonomous technologies including automated path planning and error recovery, to emphasize a robust approach that relies on generic robots and special purpose tools. c) Validate critical component models using a digital twin that includes the assembled primary mirror support structure and assembly process. A digital twin is a high-fidelity simulation of the asset capable of predicting the on-orbit performance. The paper concludes after identifying the critical need for a modest assembly flight experiment to validate and develop confidence in the SAA paradigm, thus accelerating adoption of the benefits described. SAA is a game changing paradigm that enhances the ability of an organization to infuse new technology through rapid evolution of PAs while leveraging OSAM technologies.

Structural Modeling↗
NASA NTRS2009

JWST OTE Development Status

This slide presentation reviews the status of the optical telescope element (OTE) for the James Webb Space Telescope (JWST). Information about the cryotests that have been performed, and the test of the Primary Mirror Segment Assembly (PMSA) is included. Also views of the progress on the secondary, tertiary Mirror Segment Assembly and the fine steering motor are included. Information is included about the status of other structures. The critical design audit (CDA) of the OTE is scheduled for October of 2009.

Keski-Kuha, Ritva↗
NASA NTRS1982

Thematic Mapper. Volume 2: Flight model preshipment review

The various systems of the Thematic Mapper are reviewed and a comparison of measured and specified performance is given. Test methodologies are described. The specific instrument systems discussed include the power supply assembly, scan mirror, electronics module, focal plane assembly, radiometer, and radiation cooler.

Source record↗
NASA NTRSDate not supplied

Design for Minimum Casualty Area – The IXPE Case

The Imaging X-Ray Polarimetry Explorer (IXPE) is a new international space observatory in NASA’s Small Explorer program, designed in a collaboration between the Italian Space Agency and NASA’s Marshall Space Flight Center, and built by Ball Aerospace. IXPE has an expected launch in November 2021, to a 600-km altitude equatorial orbit. IXPE is an astrophysics mission using three telescope assemblies to measure the polarization of cosmic X-rays. Each assembly is composed of a mirror module assembly (MMA) with 24 nested nickel-cobalt cylindrical shells and a unique, polarization-sensitive, gas pixel detector (GPD) within the detector unit (DU). As a NASA mission, IXPE must adhere to the orbital debris mitigation requirements specified in NASA Standard 8719.14 [1]; in the present work, we will only discuss reentry human casualty risk. As initially designed, the IXPE observatory exceeded NASA’s casualty risk threshold. IXPE does not include a propulsion system to perform a controlled reentry at the end of mission to mitigate the ground casualty risk. To reduce the risk from the uncontrolled reentry of this observatory, the IXPE design team worked with the NASA Orbital Debris Program Office to reduce the debris casualty area through design-for-demise and containment methods. The flight design of IXPE is now compliant with the ground casualty risk requirement at a casualty probability of 1:13,100 compared to a casualty requirement of better than 1:10,000.

C Ostrom↗
NASA NTRS1989

The flexure assembly design for the SIRTF one-meter primary mirror

A titanium flexure assembly for the Space Infrared Telescope Facility (SIRTF) 1-m primary mirror has been designed to accommodate: (1) the cryogenic cool-down effect on the optical performance of the mirror, (2) the Shuttle launch-load environment, and (3) the support-baseplate manufacturing tolerances. Numerous iterations involving a multidimensional design space search led to an assembly design that provides the stiffness and strength in the vertical (optical axis) and tangential directions to accommodate launch loads, but is compliant radially to accommodate cryogenic cool down. A 'folded back' titanium flexure system was required because of the differential thermal contraction of the aluminum telescope baseplate support and the fused-silica mirror. This unique and innovative flexure assembly represents a totally passive mechanism for accommodating the design launch loads, cryogenic cool down, and out-of-plane baseplate effects.

Richard, R. M.↗
NASA NTRS1995

Particle fallout/activity sensor

A particle fallout/activity sensor measures relative amounts of dust or other particles which collect on a mirror in an area to be monitored. The sensor includes a sensor module and a data acquisition module, both of which can be operated independently of one another or in combination with one another. The sensor module includes a housing containing the mirror, an LED assembly for illuminating the mirror and an optical detector assembly for detecting light scattered off of the mirror by dust or other particles collected thereon. A microprocessor controls operation of the sensor module's components and displays results of a measurement on an LCD display mounted on the housing. A push button switch is also mounted on the housing which permits manual initiation of a measurement. The housing is constructed of light absorbing material, such as black delrin, which minimizes detection of light by the optical detector assembly other than that scattered by dust or particles on the mirror. The data acquisition module can be connected to the sensor module and includes its own microprocessor, a timekeeper and other digital circuitry for causing the sensor module to make a measurement periodically and send the measurement data to the data acquisition module for display and storage in memory for later retrieval and transfer to a separate computer. The time tagged measurement data can also be used to determine the relative level of activity in the monitored area since this level is directly related to the amount of dust or particle fallout in the area.

Curtis, Ihlefeld M.↗
NASA NTRS1983

Double arch mirror study. Part 1: Preliminary engineering report

In the proposed design, the NASA AMES 20-in double arch mirror is supported by three clamp and flexure assemblies. The mirror clamp consists of a T-shaped Invar-36 member that goes into a similarly shaped socket in the back of the mirror. The mirror socket is made oversize and contacts the clamp only along the conical surface. The clamp is preloaded by a spring washer and pulls the mirror into contact with the flexure. The clamp is then inserted into the mirror socket through a cutout, is rotated 90 deg, and is then pinned in place. Loading conditions considered in socket design are discussed as well as stress in the socket and clamp. Flexure geometry and stress are examined as well as the effects of flexure error and of mirror cell error.

Vukobratovich, D.↗
NASA NTRS2012

Wavefront Calibration Testing of the James Webb Space Telescope Primary Mirror Center of Curvature Optical Assembly

The James Webb Space Telescope (JWST) Optical Telescope Element (OTE) consists of a 6.6 meter clear aperture, all-reflective, three-mirror anastigmat!. The 18-segment primary mirror (PM) presents unique and challenging assembly, integration, alignment and testing requirements. A full aperture center of curvature optical test is performed in cryogenic vacuum conditions at the integrated observatory level to verify PM performance requirements. Two wavefront calibration tests are utilized to verify the low and Mid/High spatial frequency performance ofthe test system. In this paper the methods and results of the wavefront calibration tests are presented.

Olczak, Gene↗
NASA NTRS2007

JWST Lightweight Mirror TRL-6 Results

Mirror technology for a Primary Mirror Segment Assembly (PMSA) is a system of components: reflective coating; polished optical surface; mirror substrate; actuators, mechanisms and flexures; and reaction structure. The functional purpose of a PMSA is to survive launch, deploy and align itself to form a 25 square meter collecting area 6.5 meter diameter primary mirror with a 131 nm rms wavefront error at temperatures less than 50K and provide stable optical performance for the anticipated thermal environment. At the inception of JWST in 1996, such a capability was at a Technology Readiness Level (TRL) of 3. A highly successful technology development program was initiated including the Sub-scale Beryllium Mirror Demonstrator (SBMD) and Advanced Mirror System Demonstrator (AMSD) projects. These projects along with flight program activities have matured mirror technology for JWST to TRL-6. A directly traceable prototype (and in some cases the flight hardware itself) has been built, tested and operated in a relevant environment.

Stahl, H. Philip↗
NASA NTRS2023

Assembly of the FOXSI-4 Mirror Modules

The Focusing Optics X-ray Solar Imager 4 (FOXSI 4) is a heliophysics sounding rocket experiment that is currently in its fourth launch campaign. The payload is comprised of seven 2 m focal length X-ray telescopes, which each consist of a grazing incidence mirror module that focuses x-rays onto an imaging detector. For this fourth flight, Marshall Space Flight Center (MSFC) designed, built, and tested three new high-angular-resolution optics. This paper describes the design and assembly of the FOXSI 4 mirror modules.

Stephen D. Bongiorno↗
NASA NTRS2013

Improvements of VIIRS and MODIS Solar Diffuser and Lunar Calibration

Both VIIRS and MODIS instruments use solar diffuser (SD) and lunar observations to calibrate their reflective solar bands (RSB). A solar diffuser stability monitor (SDSM) is used to track the SD on-orbit degradation. On-orbit observations have shown similar wavelength-dependent SD degradation (larger at shorter VIS wavelengths) and SDSM detector response degradation (larger at longer NIR wavelengths) for both VIIRS and MODIS instruments. In general, the MODIS scan mirror has experienced more degradation in the VIS spectral region whereas the VIIRS rotating telescope assembly (RTA) mirrors have seen more degradation in the NIR and SWIR spectral region. Because of this wavelength dependent mirror degradation, the sensor's relative spectral response (RSR) needs to be modulated. Due to differences between the solar and lunar spectral irradiance, the modulated RSR could have different effects on the SD and lunar calibration. In this paper, we identify various factors that should be considered for the improvements of VIIRS and MODIS solar and lunar calibration and examine their potential impact. Specifically, we will characterize and assess the calibration impact due to SD and SDSM attenuation screen transmission (uncertainty), SD BRF uncertainty and onorbit degradation, SDSM detector response degradation, and modulated RSR resulting from the sensor's optics degradation. Also illustrated and discussed in this paper are the calibration strategies implemented in the VIIRS and MODIS SD and lunar calibrations and efforts that could be made for future improvements.

VIIRS↗
NASA NTRS2011

Metrology of IXO Mirror Segments

For future x-ray astrophysics mission that demands optics with large throughput and excellent angular resolution, many telescope concepts build around assembling thin mirror segments in a Wolter I geometry, such as that originally proposed for the International X-ray Observatory. The arc-second resolution requirement posts unique challenges not just for fabrication, mounting but also for metrology of these mirror segments. In this paper, we shall discuss the metrology of these segments using normal incidence metrological method with interferometers and null lenses. We present results of the calibration of the metrology systems we are currently using, discuss their accuracy and address the precision in measuring near-cylindrical mirror segments and the stability of the measurements.

Chan, Kai-Wing↗
NASA NTRSDate not supplied

High Speed Interferometry for James Webb Space Telescope Testing

High speed interferometry (HSI) was one of the enabling technologies to the successful development and testing of the James Webb Space Telescope (JWST) optical system that consists of a 6.5 meter diameter, segmented, lightweight primary mirror and lightweight carbon fiber composite structure. This paper reviews the interferometry that was used first to demonstrate that the lightweight mirror and lightweight composite structure technologies were ready for JWST and later to verify performance of the fully assembled primary mirror and the telescope at cryogenic temperature. The tools and techniques developed for JWST are being advanced to benefit future missions that require stable mirrors, precision metering structures, active controls and diagnostic metrology.

B Saif↗
NASA NTRS2008

Engineering Design Unit Primary Mirror Segment

The James Webb Space Telescope Primary Mirror Engineering Design Unit (EDU) recently demonstrated the final manufacturing process at L-3-SSG/Tinsley in Richmond, California. Shown in the picture below, the EDU is a prototype 1.4 meter diameter Beryllium mirror that is identical to the 18 flight mirror segments and is used to check out all mirror manufacturing processes prior to the actual flight mirror processing. This recent result gives confidence that all manufacturing processes are in place to figure the 18 flight mirrors. Lessons learned from the EDU have been applied to the flight mirrors improving the performance and processing time and all 18 flight mirrors are well along in their processing at L3-SSG/Tinsley. As a result of completing the final manufacturing demonstration, the EDU mirror was sent to Ball Aerospace in Boulder, Colorado where it is now undergoing integration with the hexapod mount assembly and optical testing checkout. After integration to mount assemblies, flight mirrors will be sent for cryogenic (50 degrees Kelvin) optical testing where the cryogenic distortions will be measured. After cryogenic testing, mirrors will eventually be returned to Tinsley for final cryogenic polishing. During final cryogenic polishing, the inverse of the measured cryogenic distortions will be polished into the mirror to assure the mirror works at it's cryogenic operating temperature. Once cryogenic polishing is completed to final specifications, the mirror will be coated and sent for final cryogenic testing.

Alongi, Chris↗
NASA NTRS2007

JWST Mirror Technology Development Results

Mirror technology is a critical enabling capability for the James Webb Space Telescope (JWST). JWST requires a Primary Mirror Segment Assembly (PMSA) that can survive launch, deploy and align itself to form a 25 square meter collecting area 6.5 meter diameter primary mirror with a 131 nm rms wavefront error at temperatures less than 50K and provide stable optical performance. At the inception of JWST in 1996, such a capability did not exist. A highly successful technology development program was initiated including the Sub-scale Beryllium Mirror Demonstrator (SBMD) and Advanced Mirror System Demonstrator (AMSD) projects. These projects along with flight program activities have matured and demonstrated mirror technology for JWST. Directly traceable prototypes or flight hardware has been built, tested and operated in a relevant environment. This paper summarizes that technology development effort.

Stahl, H. Philip↗
NASA NTRS2006

Precision Linear Actuators for the Spherical Primary Optical Telescope Demonstration Mirror

The Spherical Primary Optical Telescope (SPOT) is an ongoing research effort at Goddard Space Flight Center developing wavefront sensing and control architectures for future space telescopes. The 03.5 m SPOT telescope primary mirror is comprised20f 6, 0.86 m hexagonal mirror segments arranged in a single ring, with the central segment missing . The mirror segments are designed for laboratory use and are not light-weighted to reduce cost. Each primary mirror segment is actuated and has tip, tilt, and piston rigid body motions. Additionally, the radius of curvature of each mirror segment may be varied mechanically3. To provide these degrees of freedom, the SPOT mirror segment assembly requires linear actuators capable of 10 nm resolution over a total stroke of 5 mm. These actuators must withstand high static loads as they must support the mirror segment, which has a mass of approx.100 kg. A stepper motor driving a differential satellite roller screw was designed to meet these demanding requirements. Initial testing showed that the actuator is capable of sub-micron repeatability over the entire 6mm range, and was limited by 100-200 nm measurement noise levels present in the facility. Further testing must be accomplished in an isolated facility with a measurement noise floor of < 5 nm. Such a facility should be ready for use at GSFC in the early summer of 2006, and will be used to better characterize this actuator.

Budinoff, Jason↗