70 research outputs found
Method for Deriving Telescope Specifications for Earth-Detecting Coronagraphs and Its Use in Prioritizing Technology Development Investments
Different potential exoplanet mission concepts require different enabling and enhancing technologies. Decisions regarding prioritizing the development of these technologies can be made using a Science-Driven Systems-Engineering framework. The white paper makes the following specific recommendations. (1) Any potential telescope/coronagraph combination should develop a wavefront stability error budget using the method described in this white paper. That error budget will inform discussions about what technology development will be needed to enable the mission. (2) Enhancing and enabling technologies requiring investment include: low noise reaction wheels or control moment gyros; micro-thruster technology; active vibration isolation; materials and design practice for making lightweight stiff structures and optical components; 200-hertz wavefront sensing and control; 500-hertz sub-picometer-precision edge sensor and position actuators; non-destructive process to quantify CTE (Coefficient of Thermal Expansion) homogeneity of 4-meter class mirrors to an uncertainty of plus or minus 1 parts per billion per degree Kelvin over a 100 by 100 sampling; laser gauge positional metrology system; and predictive active thermal control
Footprint of construction errors on the structural damages
The majority of structural failures are attributable to errors in construction. This problem exists in all countries, but it is more frequent in developing communities. This study focuses on construction errors of structures in Tehran, the capital city of Iran. In this study, eighty-eight buildings have been investigated during the construction phase. These buildings have been categorized into ten types and have been distributed in twenty-two suburbs. Results showed that the buildings of Tehran can suffer from at least forty-nine major construction problems. In addition, for the first time, this research has introduced the following three terms in relation to prioritizing of construction errors: Relative Importance Factor (RIF), Priority Index (PI) and Structural Importance Index (SII). As a part of the conclusions, the results showed one hundred percent of investigated buildings are affected dramatically by the “use of untrained workers” and “lack of sampling or wrong sampling” too. In this regard, the RIF and PI of each “Lack of sampling or wrong sampling” and “use of untrained workers” are 100 and 1, respectively. Also, suburb 3 has the best construction conditions while suburb 10 has the worst
HabEx Telescope WFE Stability Specification Derived from Coronagraph Starlight Leakage
HabEx is a space-based 4-meter diameter telescope with ultraviolet (UV), optical, and near-infrared (near-IR) imaging and spectroscopy capabilities. Three driving science goals during its five-year primary mission: 1. To seek out nearby worlds and explore their habitability.; 2. To map out nearby planetary systems and understand the diversity of the worlds they contain.; 3. To carry out observations that open up new windows on the universe from the UV through near-IR
Effect of Space Telescope Primary Mirror Segment Errors on Coronagraph Instrument Performance
No abstract availabl
Simulating reflected light coronagraphy of Earth-like exoplanets with a large IR/O/UV space telescope: impact and calibration of smooth exozodiacal dust
Observing Earth-like exoplanets orbiting within the habitable zone of
Sun-like stars and studying their atmospheres in reflected starlight requires
contrasts of in the visible. At such high contrast,
starlight reflected by exozodiacal dust is expected to be a significant source
of contamination. Here, we present high-fidelity simulations of coronagraphic
observations of a synthetic Solar System located at a distance of 10 pc and
observed with a 12 m and an 8 m circumscribed aperture diameter space telescope
operating at 500 nm wavelength. We explore different techniques to subtract the
exozodi and stellar speckles from the simulated images in the face-on, the 30
deg inclined, and the 60 deg inclined case and quantify the remaining
systematic noise as a function of the exozodiacal dust level of the system. We
find that in the face-on case, the exozodi can be subtracted down to the photon
noise limit for exozodi levels up to zodi using a simple toy model
for the exozodiacal disk, whereas in the 60 deg inclined case this only works
up to zodi. We also investigate the impact of larger wavefront errors
and larger system distance, finding that while the former have no significant
impact, the latter has a strong (negative) impact. Ultimately, we derive a
penalty factor as a function of the exozodi level and system inclination that
should be considered in exoplanet yield studies as a realistic estimate for the
excess systematic noise from the exozodi.Comment: 20 pages, 9 figures, accepted for publication in A
HabEx Telescope WFE Stability Specification Derived from Coronagraph Starlight Leakage
No abstract availabl
Method for deriving optical telescope performance specifications for Earth-detecting coronagraphs
Direct detection and characterization of extrasolar planets has become possible with powerful new coronagraphs on ground-based telescopes. Space telescopes with active optics and coronagraphs will expand the frontier to imaging Earth-sized planets in the habitable zones of nearby Sun-like stars. Currently, NASA is studying potential space missions to detect and characterize such planets, which are dimmer than their host stars by a factor of 10¹⁰. One approach is to use a star-shade occulter. Another is to use an internal coronagraph. The advantages of a coronagraph are its greater targeting versatility and higher technology readiness, but one disadvantage is its need for an ultrastable wavefront when operated open-loop. Achieving this requires a system-engineering approach, which specifies and designs the telescope and coronagraph as an integrated system. We describe a systems engineering process for deriving a wavefront stability error budget for any potential telescope/coronagraph combination. The first step is to calculate a given coronagraph’s basic performance metrics, such as contrast. The second step is to calculate the sensitivity of that coronagraph’s performance to its telescope’s wavefront stability. The utility of the method is demonstrated by intercomparing the ability of several monolithic and segmented telescope and coronagraph combinations to detect an exo-Earth at 10 pc
Method for deriving optical telescope performance specifications for Earth-detecting coronagraphs
Direct detection and characterization of extrasolar planets has become possible with powerful new coronagraphs on ground-based telescopes. Space telescopes with active optics and coronagraphs will expand the frontier to imaging Earth-sized planets in the habitable zones of nearby Sun-like stars. Currently, NASA is studying potential space missions to detect and characterize such planets, which are dimmer than their host stars by a factor of 10¹⁰. One approach is to use a star-shade occulter. Another is to use an internal coronagraph. The advantages of a coronagraph are its greater targeting versatility and higher technology readiness, but one disadvantage is its need for an ultrastable wavefront when operated open-loop. Achieving this requires a system-engineering approach, which specifies and designs the telescope and coronagraph as an integrated system. We describe a systems engineering process for deriving a wavefront stability error budget for any potential telescope/coronagraph combination. The first step is to calculate a given coronagraph’s basic performance metrics, such as contrast. The second step is to calculate the sensitivity of that coronagraph’s performance to its telescope’s wavefront stability. The utility of the method is demonstrated by intercomparing the ability of several monolithic and segmented telescope and coronagraph combinations to detect an exo-Earth at 10 pc
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