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At least 37 records · Page 2

Development of Flight Hardware for an Inflatable Deployable Antenna Experiment

Space deployable antennas are needed for a variety of applications that include space based very-long-baseline interferometry, mobile communications, active microwave sensing, earth observation radiometry, synthetic aperture radar, spacecraft communications, and DOD space-based radar. Design and development concepts discussed are low cost, reliability, low weight, packaging, precision and stability.

Space Antennas Structures Materials

Controlled structures technology and the design of an optical interferometer spacecraft

The impact of extremely stringent structural control requirements and controlled structures techniques on the overall design of a spacecraft system is examined. A space-based optical interferometer presents a design case that necessitates the application of controlled structures technology. In order for interferometry to succeed, differential pathlengths between the optical components need to be identical within a fraction of a wavelength of the light (about 25 nm for visible light). This high level of precision must be maintained on a large, flexible structure in the face of common spacecraft vibrational disturbances. Aspects of spacecraft design are examined to determine the impact of structural control on the 'normal' design process. Structural control objectives can drive several choices in subsystem component selection and sizing that minimize the vibrational environment.

Nisbet, Andrew M.

Towards satellite tests combining general relativity and quantum mechanics through quantum optical interferometry: progress on the deep space quantum link

The Deep Space Quantum Link (DSQL) is a space-mission concept that aims to explore the interplay between general relativity and quantum mechanics using quantum optical interferometry. This mission concept was formally presented to the United States National Academy of Science Decadal Survey as a research campaign for Fundamental Physics in 2022. Since then, advances have been made in the space-based quantum optical technologies required to conduct a DSQL-type mission. In addition, other research efforts have defined alternative measurement concepts to explore the same scientific questions motivating the DSQL mission. This paper serves as an update to the community on the status of the DSQL mission concept and related research and technology development efforts.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC

Infrared imaging of extrasolar planets

An optical system for direct detection, in the infrared, of planets orbiting other stars is described. The proposed system consists of a large aperture (about 16 m) space-based telescope to which is attached a specialized imaging instrument containing a set of optical signal processing elements to suppress diffracted light from the central star. Starlight suppression is accomplished using coronagraphic apodization combined with rotational shearing interferometry. The possibility of designing the large telescope aperture to be of a deployable, multiarm configuration is examined, and it is shown that there is some sacrifice in performance relative to a filled, circular aperture.

Diner, David J.

Stellar Interferometer Tracking experiment - A proposed technology demonstration experiment

A flight experiment entitled the Stellar Interferometer Tracking Experiment (SITE) is described. The objective of the program is to validate the operation of the primary detector of a space-based optical interferometric telescope and to evaluate how isolation, vibration suppression, and pathlength control enable and enhance instrument operation in the disturbance environment of the Shuttle payload bay. The minimum set of hardware that can perform stellar interferometry is described and the need for nanometer pathlength and arcsecond jitter control is shown. The justification for flight, the experimental benefits, and the applications to future space missions are presented. Results of previous ground experiments that demonstrate the required disturbance rejection are reviewed, and initial estimates of open-loop and required closed-loop performance of the flight experiment are presented.

Blackwood, Gary

Aperture-synthesis interferometry at optical wavelengths

The prospects for applying aperture-synthesis interferometry to the optical domain are reviewed. The radio examples such as the VLA provide a model, since the concepts are equally valid for radio and optical wavelengths. If scientific problems at the milliarc-second resolution level (or better) are to be addressed, a space-based optical array seems to be the only practical alternative, for the same reasons that dictated array development at radio wavelengths. One concept is examined, and speculations are offered concerning the prospects for developing real systems. Phase-coherence is strongly desired for a practical array, although self-calibration and phase-closure techniques allow one to relax the restriction on absolute phase stability. The design of an array must be guided by the scientific problems to be addressed.

Burke, Bernard F.

Frequency stable high power lasers in space

The concept of a laser heterodyne gravity wave antenna that would operate in solar orbit with a one million kilometer path length is discussed. Laser technology that would be appropriate for operation of this space-based gravity wave detector is also discussed. The rapid progress in diode laser coupled with the energy storage and potentially sub-Hertz linewidths of solid state lasers, and the possibility of efficient frequency conversion by nonlinear optical techniques defines a technology that is appropriate for laser interferometry in space. The present status of diode-laser-pumped, solid state lasers is summarized and future progress is projected in areas of linewidth control, high average power, operating efficiency, and operational lifetimes that are essential for space-based applications.

Byer, Robert L.

A low frequency radio array for space

This paper considers the need for and the possibility of constructing and operating a low-frequency array in space, the Low Frequency Space Array (LFSA), which is presently in its developmental phase, to form an entirely space-based synthesis interferometer for high-resolution high-sensitivity sky surveying and source imaging over the frequency range from about 1 to about 30 MHz. It is emphasized that there is a wealth of new astronomical information to be found in the as yet unexplored frequency range below 30 MHz, the wavelengths at which only interferometry is practicable. A possible instrumental concept for an LFSA spacecraft is described together with orbits, hardware, and subsystems.

Weiler, K. W.

A fiber-coupled heterodyne interferometric displacement sensor

Space-based interferometers and large segmented reflectors will require precision metrology with nanometer accuracy for active control systems. This paper summarizes an experimental study of an optical heterodyne interferometer with resolution of about 3 nm. Optical signals are carried to and from the interferometer by optical fibers to avoid thermally loading the reflector panels. Heterodyne detection provides far greater precision than does traditional interferometry.

Nerheim, Noble

Space VLBI Co-Observing Developments in the DSN

The JPL/NASA Deep Space Network (DSN) plans to participate in the upcoming Space VLBI missions by using its 70m antenna time to co-observe with space-based radio telescopes. To enhance this support, the DSN is upgrading its radio astronomy equipment at L- and K-band, its VLBI recorders, and its computers and software for co-observing operations.

telescopes radio astronomy Jet Propulsion Laborato

Detecting gravitational signatures of dark matter with atom gradiometers

We study the purely gravitational signatures of dark matter from the ultralight to the ultraheavy mass range in proposed long-baseline atom gradiometers, focusing on terrestrial designs, such as AION-km and MAGIS-km, as well as space-based concepts, such as MAGIS-space, AEDGE and AEDGE+. Due to its exceptional acceleration sensitivity and depending on astrophysical backgrounds, a detector similar to AEDGE+ could detect a dark matter subcomponent which constitutes 𝒪⁡(10%) of the local dark matter energy density and is populated by compact clumps of mass between 10 6 kg and 10 10 kg (10 −25 ⁢𝑀⊙ ≲ 𝑀 ≲10 −21⁢ 𝑀⊙) in an otherwise unexplored region of dark matter model space. Furthermore, because the gravitational observable depends on the relative gravitational time delay measured by spatially separated atomic clouds, we find that atom gradiometers are parametrically more sensitive than laser interferometers, such as LIGO and LISA, to fast-oscillating spacetime perturbations sourced by energy density and pressure fluctuations of ultralight dark matter. Depending on astrophysical backgrounds, a detector akin to AEDGE+ could probe a DM overdensity of 𝒪⁡(10) times the local dark matter energy density for masses 𝑚 ≲10 −17 eV.

79 ASTRONOMY AND ASTROPHYSICS

Quantum Gravity and Laser Interferometry: Towards Observable Predictions

Understanding quantum gravity remains one of the deepest challenges in modern physics, as direct experimental access to Planck-scale effects is beyond current technological reach. However, recent theoretical advances indicate that quantum fluctuations of spacetime may produce measurable effects in precision experiments, particularly near causal horizons. This opens new avenues for testing quantum gravity phenomena through high-precision measurement techniques. This dissertation develops multiple theoretical models to characterize these effects and examines their potential observational signatures in future gravitational wave interferometers. We begin by investigating the role of quantum fluctuations in near-horizon geometries through the lens of the AdS/CFT correspondence, which provides a powerful framework for understanding the interplay between quantum field theory and general relativity via holographic principles. By modeling stochastic energy-momentum sources in Rindler-AdS spacetime, we demonstrate that vacuum fluctuations transform the Einstein equations into a Langevin-type stochastic differential equation, leading to potentially observable fluctuations in photon traversal times. Extending this approach to Minkowski spacetime, we establish a correspondence between gravitational shockwaves and fluid dynamics, showing that near-horizon perturbations satisfy an equation analogous to that governing incompressible fluids, thereby reinforcing the membrane paradigm and hydrodynamic analogies in the context of the fluid/gravity duality. Furthermore, we construct the covariant phase space of a spherically symmetric causal diamond in Minkowski spacetime, identifying two fundamental charges that govern its evolution. These results provide a foundation for quantizing causal horizons and understanding their microscopic degrees of freedom. Building upon these theoretical developments, we further examine a related stochastic phenomenon: the gravitational wave memory background arising from the cumulative memory steps produced by supermassive black hole mergers. After reviewing the standard stochastic gravitational wave background, gravitational memory effects, and BMS symmetries, we model the stochastic memory background using a Brownian motion framework. We show that while the cumulative memory background initially appears above the sensitivity curve of space-based interferometers like LISA, the realistic subtraction of individually resolvable merger events substantially suppresses the residual signal, making its detection more challenging. This highlights the critical importance of source subtraction when evaluating the detectability of gravitational memory effects. By bridging fundamental theory with experimental prospects, this dissertation contributes to the ongoing effort to uncover the quantum nature of spacetime through precision measurement techniques. Whether through detecting quantum spacetime fluctuations, gravitational memory backgrounds, or probing the symmetries of causal horizons, the pursuit of observable quantum gravity phenomena continues to expand the frontiers of both theory and experiment.

Zhang, Yiwen [Caltech] (ORCID:0000000323559416)

Viscoelastic deformation near active plate boundaries

Model deformations near the active plate boundaries of Western North America using space-based geodetic measurements as constraints are discussed. The first six months of this project were spent gaining familarity with space-based measurements, accessing the Crustal Dynamics Data Information Computer, and building time independent deformation models. The initial goal was to see how well the simplest elastic models can reproduce very long base interferometry (VLBI) baseline data. From the Crustal Dynamics Data Information Service, a total of 18 VLBI baselines are available which have been surveyed on four or more occasions. These data were fed into weighted and unweighted inversions to obtain baseline closure rates. Four of the better quality lines are illustrated. The deformation model assumes that the observed baseline rates result from a combination of rigid plate tectonic motions plus a component resulting from elastic strain build up due to a failure of the plate boundary to slip at the full plate tectonic rate. The elastic deformation resulting from the locked plate boundary is meant to portray interseismic strain accumulation. During and shortly after a large interplate earthquake, these strains are largely released, and points near the fault which were previously retarded suddenly catch up to the positions predicted by rigid plate models. Researchers judge the quality of fit by the sum squares of weighted residuals, termed total variance. The observed baseline closures have a total variance of 99 (cm/y)squared. When the RM2 velocities are assumed to model the data, the total variance increases to 154 (cm/y)squared.

Ward, S. N.

Mission operations system for Russian space Very-Long-Baseline Interferometry mission

A mission operations system developed to meet the unique requirements of the prospective Russian space VLBI mission Radioastron is described. The challenges associated with the Radioastron operations are mainly due to the interrelationship between the space-based telescope and the ground observatories, and the mission's international character. The Radioastron project includes radio observatories located in 17 different countries, tracking facilities in possibly seven different countries, orbit determination centers in Russia and USA, and widely located data processing facilities. In addition, unique scheduling constraints arise from the competing demands placed on the ground observatory time by earth-based VLBI experiments, and the tracking station time by a Japanese space interferometry mission VSOP, which is expected to be in orbit concurrently with Radioastron. A diagram illustrating the organizational structure of the Radioastron project during operations is presented.

Altunin, V. I.

High resolution imaging at Palomar

For the last two years we have embarked on a program of understanding the ultimate limits of ground-based optical imaging. We have designed and fabricated a camera specifically for high resolution imaging. This camera has now been pressed into service at the prime focus of the Hale 5 m telescope. We have concentrated on two techniques: the Non-Redundant Masking (NRM) and Weigelt's Fully Filled Aperture (FFA) method. The former is the optical analog of radio interferometry and the latter is a higher order extension of the Labeyrie autocorrelation method. As in radio Very Long Baseline Interferometry (VLBI), both these techniques essentially measure the closure phase and, hence, true image construction is possible. We have successfully imaged binary stars and asteroids with angular resolution approaching the diffraction limit of the telescope and image quality approaching that of a typical radio VLBI map. In addition, we have carried out analytical and simulation studies to determine the ultimate limits of ground-based optical imaging, the limits of space-based interferometric imaging, and investigated the details of imaging tradeoffs of beam combination in optical interferometers.

Kulkarni, Shrinivas R.

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.

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.

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.