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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 325 records · Page 18
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NASA NTRS2013

Team X Report #1401: Exoplanet Coronagraph STDT Study 2013-06

This document is intended to stimulate discussion of the topic described. All technical and cost analyses are preliminary. This document is not a commitment to work, but is a precursor to a formal proposal if it generates sufficient mutual interest. The data contained in this document may not be modified in any way. Cost estimates described or summarized in this document were generated as part of a preliminary, first-order cost class identification as part of an early trade space study, are based on JPL-internal parametric cost modeling, assume a JPL in-house build, and do not constitute a commitment on the part of JPL or Caltech. JPL and Team X add cost reserves for development and operations. Unadjusted estimate totals and cost reserve allocations would be revised as needed in future more-detailed studies as appropriate for the specific cost-risks for a given mission concept.

cost estimating↗
NASA NTRS2010

Low-Cost High-Precision PIAA Optics for High Contrast Imaging with Exo-Planet Coronagraphs

PIAA optics for high contrast imaging present challenges in manufacturing and testing due to their large surface departures from aspheric profiles at the aperture edges. With smaller form factors and consequent smaller surface deformations (<50 microns), fabrication of these mirrors with diamond turning followed by electron beam lithographic techniques becomes feasible. Though such a design reduces the system throughput to approx.50%, it still provides good performance down to 2 lambda/D inner working angle. With new achromatic focal plane mask designs, the system performance can be further improved. We report on the design, expected performance, fabrication challenges, and initial assessment of such novel PIAA optics.

pupil remapping↗
NASA NTRS2015

Lower Limits on Aperture Size for an ExoEarth Detecting Coronagraphic Mission

The yield of Earth-like planets will likely be a primary science metric for future space-based missions that will drive telescope aperture size. Maximizing the exoEarth candidate yield is therefore critical to minimizing the required aperture. Here we describe a method for exoEarth candidate yield maximization that simultaneously optimizes, for the first time, the targets chosen for observation, the number of visits to each target, the delay time between visits, and the exposure time of every observation. This code calculates both the detection time and multiwavelength spectral characterization time required for planets. We also refine the astrophysical assumptions used as inputs to these calculations, relying on published estimates of planetary occurrence rates as well as theoretical and observational constraints on terrestrial planet sizes and classical habitable zones. Given these astrophysical assumptions, optimistic telescope and instrument assumptions, and our new completeness code that produces the highest yields to date, we suggest lower limits on the aperture size required to detect and characterize a statistically motivated sample of exoEarths.

Earth-like planets↗
NASA NTRS2017

Replacing the Polarizer Wheel with a Polarization Camera to Increase the Temporal Resolution and Reduce the Overall Complexity of a Solar Coronagraph

Experiments that require linearly polarized brightness measurements, traditionally have obtained three successive images through a linear polarizer that is rotated through three well-defined angles and the images are combined to get the linearly polarized brightness. This technique requires a mechanism to hold the linear polarizer in place and to precisely turn it through the three angles. Obviously, the temporal resolution is lost in such a scenario, since the three images that are used to derive the linearly polarized brightness are taken at three different times. Specifically, in a dynamic corona that is in constant reshaping of its structures, the linearly polarized brightness image produced in this manner may not yield true values all around the corona. In this regard, with the advent of the polarization camera, the linearly polarized brightness can be measured from a single image. This also eliminates the need for a linear polarizer and the associated rotator mechanisms and can contribute toward lower weight, size, power requirements, overall risk of the instrument, and most importantly, increase the temporal resolution. We evaluate the capabilities of a selected polarization camera and how these capabilities could be tested in a ground experiment conducted in conjunction with a total solar eclipse. The ground experiment requires the measurement of the linearly polarized brightness, also known as K-corona, in a corona that also contains unpolarized brightness, known as F-corona, in order to measure three important physical properties pertaining to coronal electrons, namely, the electron density, electron temperature, and the electron speed.

Reginald, Nelson L.↗
NASA NTRS2018

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.

Space Telescope Technology↗