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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

The Visible Nulling Coronagraph--Progress Toward Mission and Technology Development

This paper describes a space mission for visible direct detection and spectroscopy of Earth like extrasolar planets using a nulling coronagraph instrument behind a moderately sized (approximately 4m) telescope in space. In our design, a 4 beam nulling interferometer is synthesized from the telescope pupil, producing a deep null proportional to theta (sup 4) which is then filtered by a coherent array of single mode fibers to suppress the residual scattered light. With diffraction limited telescope optics and similar quality components in the optical train (lambda/20), suppression of the starlight to 10 (exp -10) is achievable. We describe key features of the basic analysis, show how this effects a space mission design, present latest results of laboratory measurements demonstrating achievable null depth and component development, and discuss future key technical milestones.

coronagraph↗
NASA NTRS2008

Dilute Aperture Visible Nulling Coronagraph Imaging (DAViNCI)

The presentation focuses on instrument and mission overview, science case, Team X study, and technology status. Topics include DAViNCI study milestones, number of targets versus inner working angle, planet orbit and IWA, combiner/nuller instrument, DAViNCI Team X costs, technology status and near future plans, and deep laser null 1.23 x 10(exp -7) suppression. Summary points are: dilute aperture concept advantages, lower cost than a comparable 7-8m coronagraph working at 2 lambda/D, technology progress prior to 2008 was seriously limited by available funding but showed 1e-y suppression (2006) of laser light needed for 1e-9 to approximately 1e-10 contrast, and current technology effort is off to a fast date with a demonstration of less than 100pm wavefront measurement in Nov 08.

coronagraphs↗
NASA NTRS2008

Path Length Control in a Nulling Coronagraph with a MEMS Deformable Mirror and a Calibration Interferometer

We report progress on a nulling coronagraph intended for direct imaging of extrasolar planets. White light is suppressed in an interferometer, and phase errors are measured by a second interferometer. A 1020-pixel MEMS deformable mirror in the first interferometer adjusts the path length across the pupil. A feedback control system reduces deflections of the deformable mirror to order of 1 nm rms.

MEMS adaptive optics↗
NASA NTRS2011

Deep UV to NIR Space Telescopes and Exoplanet Coronagraphs: A Trade Study on Throughput, Polarization, Mirror Coating Options and Requirements

The NASA Exoplanet program and the Cosmic Origins program are exploring technical options to combine the visible to NIR performance requirements of a space coronagraph with the general astrophysics requirements of a space telescope covering the deep UV spectrum. Are there compatible options in terms of mirror coatings and telescope architecture to satisfy both goals? In this paper, we address some of the main concerns, particularly relating to polarization in the visible and throughput in the UV. Telescope architectures employing different coating options compatible with current technology are considered in this trade study.

coronagraph↗
NASA NTRS2015

Demonstrating Broadband Billion-to-One Contrast with the Visible Nulling Coronagraph

The key to broadband operation of the Visible Nulling Coronagraph (VNC) is achieving a condition of quasi- achromatic destructive interference between combined beams. Here we present efforts towards meeting this goal using Fresnel rhombs in each interferometric arm as orthogonally aligned half wave phase retarders. The milestone goal of the demonstration is to achieve 1 × 10−9 contrast at 2/D over a 40 nm bandpass centered at 633 nm. Rhombs have been designed and fabricated, and a multi-step approach to alignment using coarse positioners for each rhomb and pair has been developed to get within range of piezo stages used for fine positioning. The previously demonstrated narrowband VNC sensing and control approach that uses a segmented deformable mirror is being adapted to broadband to include fine positioning of the piezo-mounted rhombs, all demonstrated in a low-pressure environment.

Visible Nulling Coronagraph (VNC)↗
NASA NTRS1970

Coronagraphic solar limb data, 7 March 1970

Solar limb photographic, isodensity and isophotal data for eclipse of 7 March 1970 from coronagraph observations, noting coronal green line and prominence activity

Cain, S. D.↗
NASA NTRS1973

Space application of SEC vidicons - The OSO 7 coronagraph.

An externally occulted Lyot coronagraph employing a digitized SEC vidicon detection system is a prime experiment aboard the NASA Orbiting Solar Observatory 7 (OSO 7). Continuing daily operation since the 29 September 1971 launch has produced more than 2200 pictures of the solar white light corona covering the region between 3 R and 10 R. Important advantages of the SEC vidicon in this application are its ability to integrate an electron image and store it for long periods prior to readout. Special applications of digital techniques are employed in stepping and pulsing the readout electron beam, thereby realizing the detector's inherent qualities of high resolution and large dynamic range.

Brueckner, G.↗
NASA NTRS1973

Astronaut operations requirements document for the White Light Coronagraph experiment s-052 for the Apollo Telescope Mount

Information necessary for successful performance of the observer's function in the White Light Coronagraph portion of the Apollo Telescope Mount experiments is presented. The pre-flight, in-flight, and post-flight operations required to perform the S-052 experiment are described. A discussion of the scientific objectives of the experiment and a description of the hardware are provided.

Ross, C. L.↗
NASA NTRS1975

Coronagraph particulate measurements. Skylab flight experiment T025

Major results of the Skylab T025 Coronagraph experiment designed to monitor the particulate contamination about the spacecraft and to study the earth's atmospheric aerosol distribution are presented. A model for comet outbursts based on the properties of amorphous ice and ground based narrow-band and white light photography of comet Kohoutek ten days to perihelion are included. The effect of atmospheric refraction on the analysis of the T025 atmospheric data was also investigated.

Greenberg, J. M.↗
NASA NTRS1976

Initial results from the High Altitude Observatory white light coronagraph on Skylab - A progress report

Frequent periodic observations by the white-light coronagraph allow an examination of coronal variations over a broad range of temporal scales. Examples of the slowest and most rapid variations are presented. An example of extremely slow coronal variations is the gradual evolution - to a large equatorial streamer - in association with a marked decrease in solar activity, as the total magnetic flux in one hemisphere decreased. Another example is given of a long-lived quasi-stable coronal streamer, apparently associated with a stable filament channel; comparison of this streamer with coronal potential-magnetic-field computations show little correlation. Some results on coronal transients - the most rapid variations observed - are summarized. Characteristic masses and energies involved in mass-ejection transients, their temporal and spatial distributions, their associations with surface phenomena and possible interplanetary signatures, and their role in coronal evolution are briefly noted.

Macqueen, R. M.↗
NASA NTRS1977

Measurement of stray radiance in the High Altitude Observatory's Skylab coronagraph

The paper outlines two techniques used for determining the instrumental stray radiance from orbital results obtained with the Skylab white light coronagraph. The first technique employs images of the lunar disk made near the time of solar eclipse to compare the apparent contrasts of maria and highlands recorded by the coronograph with those of previous studies and then determine the magnitude of the stray radiance and its variation along a radius. The second method determines the azimuthal variation of the stray radiance by measuring the change in the net radiance of a point in the coronal images as the image is rotated.

Csoeke-Poeckh, A.↗
NASA NTRS1977

Coronagraphic technique to infer the nature of the Skylab particulate environment

Photographs taken with the High Altitude Observatory's White Light Coronagraph (Skylab experiment S052) are shown to contain information on the sizes and velocities of contaminant particulates around Skylab. Sizes as small as 5 micron (radius) are derived for particles as far away as 200 m from the spacecraft. The random error in the size derivation is about 30%, and no particle larger than 120 micron was observed. Transverse velocities are determined to within 0.08 m/sec and radial velocities to within 9 m/sec. The S052 data bank contains about 3500 contaminated frames from which the nature of the Skylab environment can be inferred.

Schuerman, D. W.↗
NASA NTRS1979

Computer assisted performance tests of the Lyman Alpha Coronagraph

Preflight calibration and performance tests of the Lyman Alpha Coronagraph rocket instrument in the laboratory, with the experiment in its flight configuration and illumination levels near those expected during flight were successfully carried out using a pulse code modulation telemetry system simulator interfaced in real time to a PDP 11/10 computer system. Post acquisition data reduction programs developed and implemented on the same computer system aided in the interpretation of test and calibration data.

Parkinson, W. H.↗
NASA NTRS1980

CCD camera systems and support electronics for a White Light Coronagraph and X-ray XUV solar telescope

Two instruments, a White Light Coronagraph and an X-ray XUV telescope built into the same housing, share several electronic functions. Each instrument uses a CCD as an imaging detector, but due to different spectral requirements, each uses a different type. Hardware reduction, required by the stringent weight and volume allocations of the interplanetary mission, is made possible by the use of a microprocessor. Most instrument functions are software controlled with the end use circuits treated as peripherals to the microprocessor. The instruments are being developed for the International Solar Polar Mission.

Harrison, D. C.↗
NASA NTRS1981

A systems approach to mechanisms for a white light coronagraph X-ray XUV telescope

A combined instrument package containing nine mechanisms was designed and developed for the international solar polar mission (ISPM). This complement of instruments, commonly called the CXX, is the only imaging system on either the NASA or ESA spacecraft and consists of a white light coronagraph mounted parallel to a combined X-ray and extreme ultra-violet (XUV) telescope. Requirements for and implementation of mechanisms in the CXX instrument are discussed.

R Mastronardi↗