39 research outputs found
Interferometer
An interferometer of relatively simple design which is tilt compensated, and which facilitates adjustment of the path lengths of split light beams is described. The interferometer includes a pair of plate-like elements with a dielectric coating and an oil film between them, that forms a beamsplitter interface, and with a pair of reflector surfaces at the ends of the plates. A pair of retroreflectors are positioned so that each split beam component is directed by a retroreflector onto one of the reflector surfaces and is then returned to the beamsplitter interface, so that the reflector surfaces tilt in a direction and amount that compensates for tilting of the beamsplitter interface
Interferometer
A high resolution interferometer is described. The interferometer is insensitive to slight misalignment of its elements, avoids channeling in the spectrum, generates a maximum equal path fringe contrast, produces an even two sided interferogram without critical matching of the wedge angles of the beamsplitter and compensator wedges, and is optically phase tunable. The interferometer includes a mirror along the path of each beam component produced by the beamsplitter, for reflecting the beam component from the beamsplitter, for reflecting the beam component from the beamsplitter to a corresponding retroreflector and for reflecting the beam returned by the retroreflector back to the beamsplitter. A wedge located along each beam component path, is large enough to cover the retroreflector, so that each beam component passes through the wedge during movement towards the retroreflector and away therefrom
Probing Interstellar Dust With Space-Based Coronagraphs
We show that space-based telescopes such as the proposed Terrestrial Planet
Finder Coronagraph will be able to detect the light scattered by the
interstellar grains along lines of sight passing near stars in our Galaxy. The
relative flux of the scattered light within one arcsecond of a star at 100 pc
in a uniform interstellar medium of 0.1 H atoms cm^-3 is about 10^-7. The halo
increases in strength with the distance to the star and is unlikely to limit
the coronagraphic detection of planets around the nearest stars. Grains passing
within 100 AU of Sun-like stars are deflected by radiation, gravity and
magnetic forces, leading to features in the scattered light that can
potentially reveal the strength of the stellar wind, the orientation of the
stellar magnetic field and the relative motion between the star and the
surrounding interstellar medium.Comment: Accepted for publication in ApJ Supplement
ExoPlanet Optics: conceptual design processes for stealth telescopes
In this paper we examine several contrast-degrading static signature sources present in current terrestrial exoplanet Lyot Coronagraph/Telescope optical systems. These are: - Unnecessary optical surfaces, which increase cost, absorption, scatter, wavefront control and alignment issues. A suggested solution is to make every effort to investigate innovative solutions to reduce the number of optical surfaces during the early design phase. Consider free-form optics. - Diffraction from secondary support systems and classical hexagon segmented apertures, which masks the low IWA terrestrial exoplanets. A suggested mitigation is to investigate curved secondary support systems and a pinwheel architecture for the deployable primary aperture. - Polarization Fresnel and form birefringence aberrations, which distort the system PSF, introduce absorption, scatter and wavefront control issues. Mitigation is to reduce all ray-angles of incidence to a minimum, investigate zero-loss polarization compensation wavefront technology, and investigate metal thin film deposition processes required to minimize form birefringence in large-area high-reflectivity coatings. - Small-angle specular or resolved angle scattered light, which places a narrow halo of incoherent light around the base of the PSF. There is no requirement on mirror smooth-surface scatter. Investigate the physical source of the small angle scatter and develop mirror polishing and thin film deposition processes to minimize scatter
Rapid-prototyping a tabletop integral field spectrograph
We successfully rapid-prototyped a mostly off-the-shelf, partially 3D-printed pathfinder version of an integral field spectrograph (IFS) in order to compress the design/build/test schedule of a final, mostly-custom IFS, by accelerating the start date of data pipeline development, thus allowing this development to progress in parallel with the design, procurement, fabrication, and alignment of the final IFS version. This parallel-path development schedule enabled us to successfully design, build, align, test, and extract a data cube from the new IFS within only 1 year, even in the face of several design setbacks. We have begun using the now-functional IFS for development of IFS sensing and control algorithms, and have also begun implementing motorized alignment upgrades that enable the systematic characterization of the tolerance (or required compensation) of its data cube extraction to misaligned images, in support of NASA's WFIRST and PISCES IFS. © 2019 SPIE
Wide-Field InfrarRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA 2015 Report
This report describes the 2014 study by the Science Definition Team (SDT) of
the Wide-Field Infrared Survey Telescope (WFIRST) mission. It is a space
observatory that will address the most compelling scientific problems in dark
energy, exoplanets and general astrophysics using a 2.4-m telescope with a
wide-field infrared instrument and an optical coronagraph. The Astro2010
Decadal Survey recommended a Wide Field Infrared Survey Telescope as its top
priority for a new large space mission. As conceived by the decadal survey,
WFIRST would carry out a dark energy science program, a microlensing program to
determine the demographics of exoplanets, and a general observing program
utilizing its ultra wide field. In October 2012, NASA chartered a Science
Definition Team (SDT) to produce, in collaboration with the WFIRST Study Office
at GSFC and the Program Office at JPL, a Design Reference Mission (DRM) for an
implementation of WFIRST using one of the 2.4-m, Hubble-quality telescope
assemblies recently made available to NASA. This DRM builds on the work of the
earlier WFIRST SDT, reported by Green et al. (2012) and the previous WFIRST-2.4
DRM, reported by Spergel et. (2013). The 2.4-m primary mirror enables a mission
with greater sensitivity and higher angular resolution than the 1.3-m and 1.1-m
designs considered previously, increasing both the science return of the
primary surveys and the capabilities of WFIRST as a Guest Observer facility.
The addition of an on-axis coronagraphic instrument to the baseline design
enables imaging and spectroscopic studies of planets around nearby stars.Comment: This report describes the 2014 study by the Science Definition Team
of the Wide-Field Infrared Survey Telescope mission. 319 pages; corrected a
misspelled name in the authors list and a typo in the abstrac
Technology for a Mid-IR Flagship Mission to Characterize Earth-like Exoplanets
The exploration of Earth-like exoplanets will be enabled at mid-infrared wavelengths
through technology and engineering advances in nulling interferometry and precision formation
flying. Nulling interferometry provides the dynamic range needed for the detection of
biomarkers. Formation flying provides the angular resolution required in the mid-infrared to
separately distinguish the spectra of planets in multi-planet systems. The flight performance
requirements for nulling have been met and must now be validated in a flight-like environment.
Formation-flying algorithms have been demonstrated in the lab and must now be validated in
space. Our proposed technology program is described