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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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Experimental demonstration of wavefront control with shaped pupils. Contrast level is maintained across different wavelengths and 10% broadband light. Further improvements in contrast believed to have been possible with more time and parameter optimizations.
Direct detection of planets around nearby stars requires the development of high-contrast imaging techniques because of the high difference between their respective fluxes. This led us to test a new coronagraphic approach based on the use of phase mask instead of dark occulting ones. Combined with high-level wavefront correction on an unobscured off-axis section of a large telescope, this method allows imaging very close to the star. Calculations indicate that for a given ground-based on-axis telescope, use of such an off-axis coronagraph provides a near-neighbor detection capability superior to that of a traditional coronagraph utilizing the full telescope aperture. Setting up a laboratory experiment working in near infrared allowed us to demonstrate the principle of the method, and a rejection of 2000:1 has already been achieved.
This viewgraph presentation reviews the Adaptive Cross-Correlation (ACC) Algorithm for extended scene-Shack Hartmann wavefront (WF) sensing. A Shack-Hartmann sensor places a lenslet array at a plane conjugate to the WF error source. Each sub-aperture lenslet samples the WF in the corresponding patch of the WF. A description of the ACC algorithm is included. The ACC has several benefits; amongst them are: ACC requires only about 4 image-shifting iterations to achieve 0.01 pixel accuracy and ACC is insensitive to both background light and noise much more robust than centroiding,
This slide presentation reviews the sensitivity studies on the Phase-Induced Amplitude Apodization (PIAA), or pupil mapping using the High-Contrast Imaging Testbed (HCIT). PIAA is a promising technique in high-dynamic range stellar coronagraph. This presentation reports on the investigation of the effects of the phase and rigid-body errors of various optics on the narrowband contrast performance of the PIAA/HCIT hybrid system. The results have shown that the 2-step wavefront control method utilizing 2-DMs is quite effective in compensating the effects of realistic phase and rigid-body errors of various optics
This paper presents lessons learned over the course of several space telescope mission and instrument developments spanning two decades. These projects involved astronomical telescopes developed by the National Aeronautics and Space Administration (NASA) and were designed to further our understanding of the Universe. It is hoped that the lessons drawn from these experiences may be of use to future mission developers.
An analytical description of the scattered light from a 10 meter diameter Diffractive Optical Element lens-based telescope operating at 1 micron wavelength has been formulated.
This paper presents an overview of the ACTDP program including programmatic objectives and timelines, and conceptual details of the cooler concepts under development.
We report on the laboratory demonstration of an active linear metrology scheme using two separate lasers.
The Space Interferometry Mission (SIM) is NASA's first space science interferometer, and will enable fundamental new discoveries in both galactic and extra-galactic astronomy, including cosmic distance scale...It demonstrates several key technologies...