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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 NTRS2011

Mid-Infrared Imaging of Exo-Earths: Impact of Exozodiacal Disk Structures

The characterization of Earth-like extrasolar planets in the mid-infrared is a significant observational challenge that could be tackled by future space-based interferometers. The presence of large amounts of exozodiacal dust around nearby main sequence stars represents however a potential hurdle to obtain mid-infrared spectra of Earth-like planets. Whereas the disk brightness only affects the integration time, the emission of resonant dust structures mixes with the planet signal at the output of the interferometer and could jeopardize the spectroscopic analysis of an Earth-like planet. Fortunately, the high angular resolution provided by space-based interferometry is sufficient to spatially distinguish most of the extended exozodiacal emission from the planetary signal and only the dust located near the planet significantly contributes to the noise level. Considering modeled resonant structures created by Earth-like planets, we address in this talk the role of exozodiacal dust in two different cases: the characterization of Super-Earth planets with single space-based Bracewell interferometers (e.g., the FKSI mission) and the characterization of Earth-like planets with 4-telescope space-based nulling interferometers (e.g., the TPF-I and Darwin projects). In each case, we derive constraints on the disk parameters that can be tolerated without jeopardizing the detection of Earth-like planets

Defrere, Denis↗
NASA NTRS2012

HCIT Broadband Contrast Performance Sensitivity Studies

One of the important milestones of the TPF Coronagraph project is to demonstrate the ability to predict the performance sensitivities of the system at levels consistent with exo-planet detection requirement. We want to gain some general understanding about the potentials and the limitations of the current single-Deformable-Mirror (DM) High-contrast imaging testbed (HCIT) system through modeling and simulations. Specifically, we want to understand the effects of some common errors on the EFC-based control of e-field over a half dark-hole region and broadband contrast. Investigated errors include: (1) Absorbing particles on a flat-mirror (2) Defects on the Occulter surface (3) Dead actuators on the DM. We also investigated the effects of control bandwidth on the broadband contrast. We used a MACOS-based simulation algorithm which (1) combines a ray trace, diffraction model, & a broadband wavefront control algorithm (2) is capable of performing full three-dimensional near-field diffraction analysis

exoplanets↗
NASA NTRS2013

High-Voltage Clock Driver for Photon-Counting CCD Characterization

A document discusses the CCD97 from e2v technologies as it is being evaluated at Goddard Space Flight Center's Detector Characterization Laboratory (DCL) for possible use in ultra-low background noise space astronomy applications, such as Terrestrial Planet Finder Coronagraph (TPF-C). The CCD97 includes a photoncounting mode where the equivalent output noise is less than one electron. Use of this mode requires a clock signal at a voltage level greater than the level achievable by the existing CCD (charge-coupled-device) electronics. A high-voltage waveform generator has been developed in code 660/601 to support the CCD97 evaluation. The unit generates required clock waveforms at voltage levels from -20 to +50 V. It deals with standard and arbitrary waveforms and supports pixel rates from 50 to 500 kHz. The system is designed to interface with existing Leach CCD electronics.

Baker, Robert↗
NASA NTRS2014

OCCAMS: Optically Controlled and Corrected Active Meta-Material Space Structures

Telescopes require sub-wavelength figure (shape) error in order to achieve acceptable Strehl ratios. Traditional methods of achieving this require rigid and therefore heavy mirrors and reaction structures as well as proportionally heavy and expensive spacecraft busses and launch vehicles. This effectively limits the diameter and therefore resolution and collecting area of space optics. Large diameter telescopes must either be heavy or actively controlled. Space telescopes of the size proposed for missions such as TPF (Terrestrial Planet Finder), TPI (Terrestrial Planet Imager), etc. will likely require large active primaries and structures and corrective optics to implement downstream wavefront control. We propose a novel viable enabling technology. High resolution space imaging requires the production of lightweight large aperture optics subject to design tradespace constraints based on nanometer physical tolerances, low system aerial density, high control authority, suitable thermal and mechanical properties, deployment capability, launch vehicle volume constraints, as well as production cost and schedule risk mitigation. Segmented systems impose additional requirements on segment alignment, wavefront phasing, and telescope mass with increased edge diffraction. Photons weigh nothing. Why must even small space telescopes "weigh" tons? Our team is working to demonstrate that they do not, by leveraging 15 years of effort and a novel advanced concept.The ultimate research goal is to refine technology to produce a mission capable ultra-lightweight membrane optic whose shape can be remotely controlled using a laser beam. Using our novel optically-controlled molecular actuators allows substitution of optically-induced control for rigidity and mirror mass. In analogy with noise-canceling headphones, this technique also potentially provides a way to excite vibratory modes to couple with and damp out normal modes of oscillation induced by slewing, other motion and thermal changes, thus allowing a robust response to repointing of a large aperture.

Astronomy↗
NASA NTRS2003

Mid-infrared nuller for Terrestrial Planet Finder: design progress and results

Nulling interferometry shows promise as a technique enabling investigation of faint objects such as planets and exo-zodiacal dust around nearby stars. At Jet Propulsion Laboratory, a nulling beam combiner based on a design built for the Keck Observatory in Hawaii has been used to pursue deep and stable narrowband nulls. We describe the design and layout of the Modified Mach Zehnder TPF nuller, and the results achieved in the laboratory to date. We report the stabilized 900,000 nulls achieved using a CO2 laser, and discuss the performance limitations and way forward to the deep, broadband nulls required for a space-borne nulling interferometer mission. We show briefly the results from Keck breadboard experiments: broadband transient nulls centered around 10.6 micron have been achieved ranging between 17500 at 18% bandwidth and 7500:1 at 29% bandwidth.

Serabyn, E.↗
NASA NTRS2020

ATSA- A Cold, Active Telescope for Space Astronomy

The National Academies’ Decadal Survey telescope studies have produced mission design concepts that plotpathways into the future to follow on from Hubble, Spitzer, JWST and NGRST. Considering the results of theLUVOIR and HabEx studies in particular, it is clear that segmented mirrors will eventually be needed to providevery large apertures in space and that this architecture presents both a scientific opportunity and an engineeringchallenge. Furthermore, while HabEx and LUVOIR cover a great deal of spectrum, both fall short of the mid-IRregion where general astronomy and astrophysics can be undertaken that would be impossible from terrestrialobservatories and where there also exist spectral features of interest in the search for life. A telescope with similarcapabilities to Habex/LUVOIR but also capable of exoplanet work in spectral regions up to 5 µm would largelybridge the gap between those proposals and TPF-I (which would have operated from about 7 µm upwards), andis therefore worthy of study. The Active Telescope for Space Astronomy (ATSA) design study presents a possiblearchitecture and is moderately sized (6 m) to enable the use of both starshade and coronagraph technologies.While the segment gaps of a segmented primary mirror present a challenge for coronagraphy, the architecturedoes allow direct wavefront control at each segment of that mirror, enabling a great degree of control at theprimary source of contrast degradation. While active systems (for example, deformable mirrors on WFIRSTCGI) are being incorporated into telescope designs today, a fully active mirror system needs further developmentfor a future mission. With this concept in mind, and intending to build on the LUVOIR and HabEx studies, wediscuss the elements of a cooled telescope design enabling both general astrophysics and exoplanet studies fromthe near UV through to the near-IR.

Steeves, John↗
NASA NTRS2003

How many Earths are enough?

In this paper, I discuss some of the parameters that bound the size of the TPF/Darwin sample and outline a science program to improve our knowledge so that we can make timely decisions about the scope and expense of TPF/Darwin.

TPF Darwin↗
NASA NTRS2003

Design and test of a 2m x 4m DART system

A 2 meter by 4 meter DART (dual anamorphic reflector telescope) system has been designed and fabricated using thin stretched mesh reflectors. This report documents the structural configuration, test preparation, test results, and analysis correlation.

TPF Terrestrial Planet Finder life detection extra↗
NASA NTRS2004

Recommended architectures for the Terrestrial Planet Finder

The primary conclusion from an intensive, two year period of study is that with suitable technology investment, starting now, a mission to detect terrestrial planets around nearby stars could be launched within a decade.

Terrestrial Planet Finder TPF↗