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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 NTRS1993

Performance of high resolution decoding with Multi-Anode Microchannel Array detectors

The Multi-Anode Microchannel Array (MAMA) is a microchannel plate based photon counting detector with applications in ground-based and space-based astronomy. The detector electronics decode the position of each photon event, and the decoding algorithm that associates a given event with the appropriate pixel is determined by the geometry of the anode array. The standard MAMA detector has a spatial resolution set by the anode array of 25 microns, but the MCP pore resolution exceeds this. The performance of a new algorithm that halves the pixel spacing and improves the pixel spatial resolution is described. The new algorithm does not degrade the pulse-pair resolution of the detector and does not require any modifications to the detector tube. Measurements of the detector's response demonstrate that high resolution decoding yields a 60 percent enhancement in spatial resolution. Measurements of the performance of the high resolution algorithm with a 14 micron MAMA detector are also described. The parameters that control high resolution performance are discussed. Results of the application of high resolution decoding to speckle interferometry are presented.

Kasle, David B.↗
NASA NTRS1995

Stellar Interferometer Technology Experiment (SITE)

The MIT Space Engineering Research Center and the Jet Propulsion Laboratory stand ready to advance science sensor technology for discrete-aperture astronomical instruments such as space-based optical interferometers. The objective of the Stellar Interferometer Technology Experiment (SITE) is to demonstrate system-level functionality of a space-based stellar interferometer through the use of enabling and enhancing Controlled-Structures Technologies (CST). SITE mounts to the Mission Peculiar Experiment Support System inside the Shuttle payload bay. Starlight, entering through two apertures, is steered to a combining plate where it is interferred. Interference requires 27 nanometer pathlength (phasing) and 0.29 archsecond wavefront-tilt (pointing) control. The resulting 15 milli-archsecond angular resolution exceeds that of current earth-orbiting telescopes while maintaining low cost by exploiting active optics and structural control technologies. With these technologies, unforeseen and time-varying disturbances can be rejected while relaxing reliance on ground alignment and calibration. SITE will reduce the risk and cost of advanced optical space systems by validating critical technologies in their operational environment. Moreover, these technologies are directly applicable to commercially driven applications such as precision matching, optical scanning, and vibration and noise control systems for the aerospace, medical, and automotive sectors. The SITE team consists of experienced university, government, and industry researchers, scientists, and engineers with extensive expertise in optical interferometry, nano-precision opto-mechanical control and spaceflight experimentation. The experience exists and the technology is mature. SITE will validate these technologies on a functioning interferometer science sensor in order to confirm definitely their readiness to be baselined for future science missions.

Crawley, Edward F.↗
NASA NTRS1996

Recommendations for Technology Development and Validation Activities in Support of the Origins Program

The Office of Space Science (OSS) has initiated mission concept studies and associated technology roadmapping activities for future large space optical systems. The scientific motivation for these systems is the study of the origins of galaxies, stars, planetary systems and, ultimately, life. Collectively, these studies are part of the 'Astronomical Search for Origins and Planetary Systems Program' or 'Origins Program'. A series of at least three science missions and associated technology validation flights is currently envisioned in the time frame between the year 1999 and approximately 2020. These would be the Space Interferometry Mission (SIM), a 10-meter baseline Michelson stellar interferometer; the Next Generation Space Telescope (NGST), a space-based infrared optimized telescope with aperture diameter larger than four meters; and the Terrestrial Planet Finder (TPF), an 80-meter baseline-nulling Michelson interferometer described in the Exploration of Neighboring Planetary Systems (ExNPS) Study. While all of these missions include significant technological challenges, preliminary studies indicate that the technological requirements are achievable. However, immediate and aggressive technology development is needed. The Office of Space Access and Technology (OSAT) is the primary sponsor of NASA-unique technology for missions such as the Origins series. For some time, the OSAT Space Technology Program has been developing technologies for large space optical systems, including both interferometers and large-aperture telescopes. In addition, technology investments have been made by other NASA programs, including OSS; other government agencies, particularly the Department of Defense; and by the aerospace industrial community. This basis of prior technology investment provides much of the rationale for confidence in the feasibility of the advanced Origins missions. In response to the enhanced interest of both the user community and senior NASA management in large space optics, OSAT is moving to improve the focus of its sensor, spacecraft, and interferometer/telescope technology programs on the specific additional needs of the OSS Origins Program. To better define Origins mission technology and facilitate its development, OSAT and OSS called for a series of workshops with broad participation from industry, academia and the national laboratory community to address these issues. Responsibility for workshop implementation was assigned jointly to the two NASA field centers with primary Origins mission responsibility, the Goddard Space Flight Center and the Jet Propulsion Laboratory. The Origins Technology Workshop, held at Dana Point, California between June 4 and 6, 1996 was the first in the series of comprehensive workshops aimed at addressing the broad technological needs of the Origins Program. It was attended by 64 individuals selected to provide technical expertise relevant to the technology challenges of the Origins missions. This report summarizes the results of that meeting. A higher level executive summary was considered inappropriate because of the potential loss of important context for the recommendations. Subsequent to the Origins Technology Workshop and prior to publication of this report, NASA Headquarters reorganized the activities of the Of fice of Space Access and Technology. It appears likely that responsibility for the technology programs recommended in this document will move to the Office of Space Science.

Capps, Richard W.↗
NASA NTRS2003

Precision Pointing for the Laser Interferometry Space Antenna Mission

This viewgraph presentation discusses requirements for control systems in the design and production of space-based telescopes. Specific topics covered include: pointing control methods, wavefront control methods, vibration control methods and thermal control methods. Control systems on the Hubble Space Telescope and the James Webb Space Telescope are reviewed. Control system requirements for future space telescopes are also mentioned.

Hyde, T. Tupper↗
NASA NTRS1999

ARISE: A Challenging 25-m Space Antenna Design

ARISE (Advanced Radio Interferometry between Space and Earth). Future scientific and communications missions are conceptualizing using very large reflector antennas in space. The antenna dimensions are targeted from lOm to 25m beyond. Frequencies coveting L-band through W-band are being considered. these challenging missions, one may refer to ARISE (Advanced Radio Interferometry between Space and Earth), which is projected to utilize a 25-m dual Gregorian optics operating from 8 GHz to 86 Gl-lz . An artist's renditions Gregorian antenna concept is shown . The objective of this mission is to create a space-based VLBI system (integrated with ground based antennas) for high resolution mapping of black holes. Successful realization of ARISE necessitates development of several technologies . The most crucial technology is that of the deployable 25-m reflector that must work at frequencies as high as 43 and 86 GHz. The current baseline selection for ARISE is an inflatable antenna, under development for several other applications in communications and remote sensing.

Rahmat-Samii, Yahya↗
NASA NTRS2004

Formation Control for the MAXIM Mission

Over the next twenty years, a wave of change is occurring in the space-based scientific remote sensing community. While the fundamental limits in the spatial and angular resolution achievable in spacecraft have been reached, based on today s technology, an expansive new technology base has appeared over the past decade in the area of Distributed Space Systems (DSS). A key subset of the DSS technology area is that which covers precision formation flying of space vehicles. Through precision formation flying, the baselines, previously defined by the largest monolithic structure which could fit in the largest launch vehicle fairing, are now virtually unlimited. Several missions including the Micro-Arcsecond X-ray Imaging Mission (MAXIM), and the Stellar Imager will drive the formation flying challenges to achieve unprecedented baselines for high resolution, extended-scene, interferometry in the ultraviolet and X-ray regimes. This paper focuses on establishing the feasibility for the formation control of the MAXIM mission. MAXIM formation flying requirements are on the order of microns, while Stellar Imager mission requirements are on the order of nanometers. This paper specifically addresses: (1) high-level science requirements for these missions and how they evolve into engineering requirements; and (2) the development of linearized equations of relative motion for a formation operating in an n-body gravitational field. Linearized equations of motion provide the ground work for linear formation control designs.

Luquette, Richard J.↗
NASA NTRS2006

Results from SIM's Thermo-Opto-Mechanical (TOM3) Testbed

Future space-based optical interferometers, such as the Space Interferometer Mission Planet Quest (SIM), require thermal stability of the optical wavefront to the level of picometers in order to produce astrometric data at the micro-arc-second level. In SIM, the internal path of the interferometer will be measured with a small metrology beam whereas the starlight fringe position is estimated from a large concentric annular beam. To achieve the micro-arc-second observation goal for SIM, it is necessary to maintain the optical path difference between the central and the outer annulus portions of the wavefront of the front-end telescope optics to a few tens of picometers. The Thermo-Opto-Mecha nical testbed (TOM3) was developed at the Jet Propulsion Laboratory to measure thermally induced optical deformations of a full-size flight-like beam compressor and siderostat, the two largest optics on SIM, in flight-like thermal environments. A Common Path Heterodyne Interferometer (COPHI) developed at JPL was used for the fine optical path difference measurement as the metrology sensor. The system was integrated inside a large vacuum chamber in order to mitigate the atmospheric and thermal disturbances. The siderostat was installed in a temperature-controlled thermal shroud inside the vacuum chamber, creating a flight-like thermal environment. Detailed thermal and structural models of the test articles (siderostat and compressor) were also developed for model prediction and correlation of the thermal deformations. Experimental data shows SIM required thermal stability of the test articles and good agreement with the model predictions.

interferometry↗
NASA NTRS2005

Accessing Small Inner Working Angles with a Rotating Sub-Aperture Nuller

A new approach to high contrast observations near bright stars with a single-aperture telescope is discussed, which is based on the idea of a rotating separated-aperture nulling interferometer. The approach can be described as a rotating sub-aperture nuller, because it nulls two or more sub-apertures within a single telescope's pupil, and uses baseline rotation to modulate the signals from off-axis sources in a manner similar to that of potential space-based nulling interferometers. The sub-aperture beams can be combined in a number of ways, including a fiber nuller and a rotational shearing interferometer. Such a rotating nulling coronagraph has two great advantages. First, it can be used on a ground-based telescope to test signal reconstruction approaches pertinent to potential space-based nulling interferometers. Moreover, it also has the potential to enable ground-based coronagraphic observations of faint off-axis companions very close to bright stars.

coronagraphy↗
NASA NTRS2007

Interferometry from Space

Space-based interferometric observatories will be challenging projects, equal at least to that of building the Great Observatories (the Hubble Space Telescope (HST), Spitzer Space Telescope (SST), Chandra X-ray Observatory, and the Gamma Ray Observatory), if not the Pyramids of Eygpt - but they represent the next logical step in examining our Universe at substantially higher angular resolution. Increasing our resolving power by factors of 100 or more (as is needed to make meaningful improvements in this observational arena) over existing facilities such as HST and SST requires mirror diameters (100's to 1000's of meters) much larger than can be supported by single or segmented mirrors - and thus the design and construction of sparse aperture, inteferometric arrays such as those described herein will be required. But just imagine the rewards of being able to see, for the first time, the surfaces of other stars, the location and type of extrasolar planets and even pictures of those same planets, the inner workings of Active Galactic Nuclei, the close-in details of supernovae explosions, black hole event horizons, and the infrared universe at the same resolution of the UV-optical Hubble Deep Fields. As a slight variation on the "Star Trek: Enterprise" theme song might say, it'll be a "long road, getting from here to there", but it will one well-worth taking.

Carpenter, Kenneth↗
NASA NTRS2008

LISA: Astrophysics Out to z Approximately 10 with Low-Frequency Gravitational Waves

This viewgraph presentation reviews the Laser Interferometer Space Antenna (LISA). LISA os a joint ESA-NASA project to design, build and operate a space-based gravitational wave detector. The 5 million Kilometer long detector will consist of three spacecraft orbiting the Sun in a triangular formation. Space-Time strains induced by gravitational waves are detected by measuring changes in the separation of fiducial masses with laser interferometry. LISA is expected to detect signals from merging massive black holes, compact stellar objects spiraling into super massive black holes in galactic nuclei, thousands of close binaries of compact objects in the Milky way and possible backgrounds of cosmological origin.

Stebbins, Robin T.↗
NASA NTRS2010

A Transportable Gravity Gradiometer Based on Atom Interferometry

A transportable atom interferometer-based gravity gradiometer has been developed at JPL to carry out measurements of Earth's gravity field at ever finer spatial resolutions, and to facilitate high-resolution monitoring of temporal variations in the gravity field from ground- and flight-based platforms. Existing satellite-based gravity missions such as CHAMP and GRACE measure the gravity field via precise monitoring of the motion of the satellites; i.e. the satellites themselves function as test masses. JPL's quantum gravity gradiometer employs a quantum phase measurement technique, similar to that employed in atomic clocks, made possible by recent advances in laser cooling and manipulation of atoms. This measurement technique is based on atomwave interferometry, and individual laser-cooled atoms are used as drag-free test masses. The quantum gravity gradiometer employs two identical atom interferometers as precision accelerometers to measure the difference in gravitational acceleration between two points (Figure 1). By using the same lasers for the manipulation of atoms in both interferometers, the accelerometers have a common reference frame and non-inertial accelerations are effectively rejected as common mode noise in the differential measurement of the gravity gradient. As a result, the dual atom interferometer-based gravity gradiometer allows gravity measurements on a moving platform, while achieving the same long-term stability of the best atomic clocks. In the laboratory-based prototype (Figure 2), the cesium atoms used in each atom interferometer are initially collected and cooled in two separate magneto-optic traps (MOTs). Each MOT, consisting of three orthogonal pairs of counter-propagating laser beams centered on a quadrupole magnetic field, collects up to 10(exp 9) atoms. These atoms are then launched vertically as in an atom fountain by switching off the magnetic field and introducing a slight frequency shift between pairs of lasers to create a moving rest frame for the trapped atoms. While still in this moving-frame molasses, the laser frequencies are further detuned from the atomic resonance (while maintaining this relative frequency shift) to cool the atom cloud's temperature to 2 K or below, corresponding to an rms velocity of less than 2 cm/s. After launch, the cold atoms undergo further state and velocity selection to prepare for atom interferometry. The atom interferometers are then realized using laser-induced stimulated Raman transitions to perform the necessary manipulations of each atom, and the resulting interferometer phase is measured using laser-induced fluorescence for state-normalized detection. More than 20 laser beams with independent controls of frequency, phase, and intensity are required for this measurement sequence. This instrument can facilitate the study of Earth's gravitational field from surface and air vehicles, as well as from space by allowing gravity mapping from a low-cost, single spacecraft mission. In addition, the operation of atom interferometer-based instruments in space offers greater sensitivity than is possible in terrestrial instruments due to the much longer interrogation times available in the microgravity environment. A space-based quantum gravity gradiometer has the potential to achieve sensitivities similar to the GRACE mission at long spatial wavelengths, and will also have resolution similar to GOCE for measurement at shorter length scales.

Yu, Nan↗
NASA NTRS2010

LISA Technology Development and Risk Reduction at NASA

The Laser Interferometer Space Antenna (LISA) is a joint ESA-NASA project to design, build and operate a space-based gravitational wave detector based on a laser interferometer. LISA relies on several technologies that are either new to spaceflight or must perform at levels not previously demonstrated in a spaceflight environment. The ESA-led LISA Pathfinder mission is the main effort to demonstrate LISA technology. NASA also supports complementary ground-based technology development and risk reduction activities. This presentation will report the status of NASA work on micronewton thrusters, the telescope, the optical pointing subsystem and mission formulation. More details on some of these topics will be given in posters. Other talks and posters will describe NASA-supported work on the laser subsystem, the phasemeter, and aspects of the interferometry. Two flight-qualified clusters of four colloid micronewton thrusters, each capable of thrust Levels between 5 and 30 microNewton with a resolution less than 0.l microNewton and a thrust noise less than 0.1 microNewton/vHz (0.001 to 4 Hz), have been integrated onto the LISA Pathfinder spacecraft. The complementary ground-based development focuses on lifetime demonstration. Laboratory verification of failure models and accelerated life tests are just getting started. LISA needs a 40 cm diameter, afocal telescope for beam expansion/reduction that maintains an optical pathlength stability of approximately 1 pm/vHz in an extremely stable thermal environment. A mechanical prototype of a silicon carbide primary-secondary structure has been fabricated for stability testing. Two optical assemblies must point at different distant spacecraft with nanoradian accuracy over approximately 1 degree annual variation in the angle between the distant spacecraft. A candidate piezo-inchworm actuator is being tested in a suitable testbed. In addition to technology development, NASA has carried out several studies in support of the mission formulation. The results of systems engineering work on flight software, avionics and reliability will be summarized.

Stebbins, Robin T.↗
NASA NTRS2007

Starlight Nulling Technology at the Jet Propulsion Laboratory

The current interests in extra-solar planet detection and space-based and ground-based interferometry for astronomical observations has led to the development of a number of nulling instrument designs at the Jet Propulsion Laboratory (JPL) and elsewhere. This paper summarizes briefly JPL's efforts in nulling interferometry to date and consists of illustrations of some key nulling activities. Basic layouts of nulling testbeds are described and key applications discussed.

Terrestrial Planet Finder↗
NASA NTRS2012

Developing Wide-Field Spatio-Spectral Interferometry for Far-Infrared Space Applications

Interferometry is an affordable way to bring the benefits of high resolution to space far-IR astrophysics. We summarize an ongoing effort to develop and learn the practical limitations of an interferometric technique that will enable the acquisition of high-resolution far-IR integral field spectroscopic data with a single instrument in a future space-based interferometer. This technique was central to the Space Infrared Interferometric Telescope (SPIRIT) and Submillimeter Probe of the Evolution of Cosmic Structure (SPECS) space mission design concepts, and it will first be used on the Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII). Our experimental approach combines data from a laboratory optical interferometer (the Wide-field Imaging Interferometry Testbed, WIIT), computational optical system modeling, and spatio-spectral synthesis algorithm development. We summarize recent experimental results and future plans.

Leisawitz, David↗
NASA NTRS2010

Systems Engineering and Application of System Performance Modeling in SIM Lite Mission

The SIM Lite Astrometric Observatory will be the first space-based Michelson interferometer operating in the visible wavelength, with the ability to perform ultra-high precision astrometric measurements on distant celestial objects. SIM Lite data will address in a fundamental way questions such as characterization of Earth-mass planets around nearby stars. To accomplish these goals it is necessary to rely on a model-based systems engineering approach - much more so than most other space missions. This paper will describe in further detail the components of this end-to-end performance model, called "SIM-sim", and show how it has helped the systems engineering process.

Exoplanet↗