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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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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

The StarLight Space Interferometer: Optical design and performance modeling

The StarLight mission aimed to place the first formation flying optical interferometer into space in year 2006. Utilizing two spacecraft to form a long baseline Michelson interferometer, it would measure white light fringes on a number of partially resolved stars of magnitudes >5 in the wavelength range 600 to 1000nm. The interferometer baseline is variable between 30 and 125 m, and also has a fixed 1 m mode. The spacecraft are flown in a parabolic geometry which requires an optical delay line to build up more than 14m of delay on one arm of the interferometer. To obtain high fringe visibility, starlight wavefront, pointing and intensity must be preserved through 22 reflections from mirrors and beamsplitters. The alignment of a total of 27 optics is maintained through careful thermal design and the use of two actuated mirrors on each arm. This paper describes the optical layout in depth, including the beam combiner design which allows star tracking, optical system alignment and fringe formation on a single CCD. The effects of diffraction of the starlight transferred from a distant spacecraft and from optical surface imperfections are modeled. Other contributors to the visibility budget and the resulting variation of fringe visibility across the focal plane are discussed .

StarLight↗
NASA NTRS1991

Optical interferometer testbed

Viewgraphs on optical interferometer testbed presented at the MIT Space Research Engineering Center 3rd Annual Symposium are included. Topics covered include: space-based optical interferometer; optical metrology; sensors and actuators; real time control hardware; controlled structures technology (CST) design methodology; identification for MIMO control; FEM/ID correlation for the naked truss; disturbance modeling; disturbance source implementation; structure design: passive damping; low authority control; active isolation of lightweight mirrors on flexible structures; open loop transfer function of mirror; and global/high authority control.

Blackwood, Gary H.↗
NASA NTRS1996

Astrophysical Adaptation of Points, the Precision Optical Interferometer in Space

POINTS (Precision Optical INTerferometer in Space) would perform microarcsecond optical astrometric measurements from space, yielding submicroarcsecond astrometric results from the mission. It comprises a pair of independent Michelson stellar interferometers and a laser metrology system that measures both the critical starlight paths and the angle between the baselines. The instrument has two baselines of 2 m, each with two subapertures of 35 cm; by articulating the angle between the baselines, it observes targets separated by 87 to 93 deg. POINTS does global astrometry, i.e., it measures widely separated targets, which yields closure calibration, numerous bright reference stars, and absolute parallax. Simplicity, stability, and the mitigation of systematic error are the central design themes. The instrument has only three moving-part mechanisms, and only one of these must move with sub-milliradian precision; the other two can tolerate a precision of several tenths of a degree. Optical surfaces preceding the beamsplitter or its fold flat are interferometrically critical; on each side of the interferometer, there are only three such. Thus, light loss and wavefront distortion are minimized. POINTS represents a minimalistic design developed ab initio for space. Since it is intended for astrometry, and therefore does not require the u-v-plane coverage of an imaging, instrument, each interferometer need have only two subapertures. The design relies on articulation of the angle between the interferometers and body pointing to select targets; the observations are restricted to the 'instrument plane.' That plane, which is fixed in the pointed instrument, is defined by the sensitive direction for the two interferometers. Thus, there is no need for siderostats and moving delay lines, which would have added many precision mechanisms with rolling and sliding parts that would be required to function throughout the mission. Further, there is no need for a third interferometer, as is required when out-of-plane observations are made. An instrument for astrometry, unlike those for imaging, can be compact and yet scientifically productive. The POINTS instrument is compact and therefore requires no deployment of precision structures, has no low-frequency (i.e., under 100 Hz) vibration modes, and is relatively easy to control thermally. Because of its small size and mass, it is easily and quickly repointed between observations. Further, because of the low mass, it can be economically launched into high Earth orbit which, in conjunction with a solar shield, yields nearly unrestricted sky coverage and a stable thermal environment.

Reasenberg, Robert D.↗
NASA NTRS1992

The Mount Wilson optical interferometer: The first automated instrument and the prospects for lunar interferometry

Before contemplating an optical interferometer on the Moon one must first review the accomplishments achieved by this technology in scientific applications for astronomy. This will be done by presenting the technical status of optical interferometry as achieved by the Mount Wilson Optical Interferometer. The further developments needed for a future lunar-based interferometer are discussed.

Johnston, Ken J.↗
NASA NTRS1990

Lunar optical interferometer

Various design configurations of a lunar optical interferometer are examined to determine the interaction of science objectives and the architecture of an instrument that will have 10 microarcsec imaging resolution and 0.1 microarcsec astrometric accuracy. The imaging of the central energy source of AGNs, the discovery of earth-like planets around nearby stars, and the measurement of the proper motion of extragalactic objects to determine the isotropy of the Hubble expansion are some of the observations possible with a lunar interferometer. This interferometer with kilometric baselines and large collecting area will be able to make astronomical observations with angular resolution and sensitivity many orders of magnitude beyond orbital based or earth based instruments.

Shao, M.↗
NASA NTRS1991

Quantitative assessment of the science return from an orbiting, imaging, optical interferometer

Imaging simulations were performed with the filled Mills cross orbiting, imaging, optical interferometer proposed by Synnott et al. (1990) in order to determine its capabilities in the area of spatial resolution, dynamic range, and sensitivity. Astronomical objects have been chosen as candidate program sources to determine whether this interferometer design can accomplish research goals relating to the objects.

Meier, David L.↗
NASA NTRS1986

Fiber-optic interferometer using frequency-modulated laser diodes

This paper describes an electrically passive fiber-optic interferometer which uses dual frequency-modulated laser diodes. Experimental results show that this type of interferometer can attain a displacement range of 100 micron with subnanometer resolution. This technique can serve as the basis for a number of high-precision fiber-optic sensors.

Beheim, G.↗
NASA NTRS1993

Spacecraft and Mission Design for the Precision Optical INTerferometer in Space (POINTS)

This paper describes key features of the instrument, spacecraft, and mission design for the Precision Optical INTerferometer in Space (POINTS), which have evolved through studies at the Jet Propulsion Laboratory during the last few years. This paper complements others in theis volume that describe the POINTS instrument, its scientific objectives, and specific engineering concerns.

flight-system↗
NASA NTRS1993

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.↗
NASA NTRS1996

Integrated Optical Interferometers with Micromachined Diaphragms for Pressure Sensing

Optical pressure sensors have been fabricated which use an integrated optical channel waveguide that is part of an interferometer to measure the pressure-induced strain in a micromachined silicon diaphragm. A silicon substrate is etched from the back of the wafer leaving a rectangular diaphragm. On the opposite side of the wafer, ring resonator and Mach-Zehnder interferometers are formed with optical channel waveguides made from a low pressure chemical vapor deposited film of silicon oxynitride. The interferometer's phase is altered by pressure-induced stress in a channel segment positioned over the long edge of the diaphragm. The phase change in the ring resonator is monitored using a link-insensitive swept frequency laser diode, while in the Mach-Zehnder it is determined using a broad band super luminescent diode with subsequent wavelength separation. The ring resonator was found to be highly temperature sensitive, while the Mach-Zehnder, which had a smaller optical path length difference, was proportionally less so. The quasi-TM mode was more sensitive to pressure, in accord with calculations. Waveguide and sensor theory, sensitivity calculations, a fabrication sequence, and experimental results are presented.

DeBrabander, Gregory N.↗
NASA NTRS1991

Optical system design for a Lunar Optical Interferometer

The moon offers particular advantages for interferometry, including a vacuum environment, a large stable base on which to assemble multi-kilometer baselines, and a cold nighttime temperature to allow for passive cooling of optics for high IR sensitivity. A baseline design for a Lunar Optical Interferometer (LOI) which exploits these features is presented. The instrument operates in the visible to mid-IL region, and is designed for both astrometry and synthesis imaging. The design uses a Y-shaped array of 12 siderostats, with maximum arm lengths of about 1 km. The inner siderostats are monitored in three dimensions from a central laser metrology structure to allow for high precision astrometry. The outer siderostats, used primarily for synthesis imaging, exploit the availability of bright reference stars in order to determine the instrument geometry. The path delay function is partitioned into coarse and fine components, the former accomplished with switched banks of range mirrors monitored with an absolute laser metrology system, and the latter with a short cat's eye delay line. The back end of the instrument is modular, allowing for beam combiners for astrometry, visible and IR synthesis imaging, and direct planet detection. With 1 m apertures, the instrument will have a point-source imaging sensitivity of about 29 mag; with the laser metrology system, astrometry at the microarcsecond level will be possible.

Colavita, M. M.↗
DOE OSTI2022

Increasing Baselines and Precision of Optical Interferometers Using Two-Photon Interference

Observations using interferometers provide sensitivity to features of images on angular scales much smaller than any single telescope, on the order of Δθ ~ λ/b where b is the interferometric baseline. Present-day optical interferometers are essentially classical, interfering single photons with themselves. However, there is a new wave of interest in interferometry using multiple photons, whose mechanisms are inherently quantum mechanical, which offer the prospects of increased baselines and finer resolutions among other advantages. We will discuss recent ideas and results for quantum-assisted interferometry using the resource of entangled pairs, and specifically a two-photon amplitude technique aimed at improved precision in astrometry.

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