7,450 research outputs found
The Palomar Testbed Interferometer
The Palomar Testbed Interferometer (PTI) is a long-baseline infrared
interferometer located at Palomar Observatory, California. It was built as a
testbed for interferometric techniques applicable to the Keck Interferometer.
First fringes were obtained in July 1995. PTI implements a dual-star
architecture, tracking two stars simultaneously for phase referencing and
narrow-angle astrometry. The three fixed 40-cm apertures can be combined
pair-wise to provide baselines to 110 m. The interferometer actively tracks the
white-light fringe using an array detector at 2.2 um and active delay lines
with a range of +/- 38 m. Laser metrology of the delay lines allows for servo
control, and laser metrology of the complete optical path enables narrow-angle
astrometric measurements. The instrument is highly automated, using a
multiprocessing computer system for instrument control and sequencing.Comment: ApJ in Press (Jan 99) Fig 1 available from
http://huey.jpl.nasa.gov/~bode/ptiPicture.html, revised duging copy edi
Better 3D Inspection with Structured Illumination Part I: Signal Formation and Precision
For quality control in the factory, 3D-metrology faces increasing demands for
high precision and for more space-bandwidth-speed-product SBSP (number of
3D-points/sec). As a potential solution, we will discuss
Structured-Illumination Microscopy (SIM). We distinguish optically smooth and
rough surfaces and develop a theoretical model of the signal formation for both
surface species. This model is exploited to investigate the physical limits of
the precision and to give rules to optimize the sensor parameters for best
precision or high speed. This knowledge can profitably be combined with fast
scanning strategies, to maximize the SBSP, which will be discussed in paper
part II.Comment: 7 pages, 5 figures, submitted to Applied Optics on April 17, 201
ProtoDESI: First On-Sky Technology Demonstration for the Dark Energy Spectroscopic Instrument
The Dark Energy Spectroscopic Instrument (DESI) is under construction to
measure the expansion history of the universe using the baryon acoustic
oscillations technique. The spectra of 35 million galaxies and quasars over
14,000 square degrees will be measured during a 5-year survey. A new prime
focus corrector for the Mayall telescope at Kitt Peak National Observatory will
deliver light to 5,000 individually targeted fiber-fed robotic positioners. The
fibers in turn feed ten broadband multi-object spectrographs. We describe the
ProtoDESI experiment, that was installed and commissioned on the 4-m Mayall
telescope from August 14 to September 30, 2016. ProtoDESI was an on-sky
technology demonstration with the goal to reduce technical risks associated
with aligning optical fibers with targets using robotic fiber positioners and
maintaining the stability required to operate DESI. The ProtoDESI prime focus
instrument, consisting of three fiber positioners, illuminated fiducials, and a
guide camera, was installed behind the existing Mosaic corrector on the Mayall
telescope. A Fiber View Camera was mounted in the Cassegrain cage of the
telescope and provided feedback metrology for positioning the fibers. ProtoDESI
also provided a platform for early integration of hardware with the DESI
Instrument Control System that controls the subsystems, provides communication
with the Telescope Control System, and collects instrument telemetry data.
Lacking a spectrograph, ProtoDESI monitored the output of the fibers using a
Fiber Photometry Camera mounted on the prime focus instrument. ProtoDESI was
successful in acquiring targets with the robotically positioned fibers and
demonstrated that the DESI guiding requirements can be met.Comment: Accepted versio
Rocket studies of solar corona and transition region
The XSST (X-Ray Spectrometer/Spectrograph Telescope) rocket payload launched by a Nike Boosted Black Brant was designed to provide high spectral resolution coronal soft X-ray line information on a spectrographic plate, as well as time resolved photo-electric records of pre-selected lines and spectral regions. This spectral data is obtained from a 1 x 10 arc second solar region defined by the paraboloidal telescope of the XSST. The transition region camera provided full disc images in selected spectral intervals originating in lower temperature zones than the emitting regions accessible to the XSST. A H-alpha camera system allowed referencing the measurements to the chromospheric temperatures and altitudes. Payload flight and recovery information is provided along with X-ray photoelectric and UV flight data, transition camera results and a summary of the anomalies encountered. Instrument mechanical stability and spectrometer pointing direction are also examined
Advanced optical microscopies for materials: new trends
Podeu consultar el llibre complet a: http://hdl.handle.net/2445/32166This article summarizes the new trends of Optical Microscopy applied to Materials, with examples of applications that illustrate the capabilities of the
technique
The Wide Field Imaging Interferometry Testbed
We are developing a Wide-Field Imaging Interferometry Testbed (WIIT) in
support of design studies for NASA's future space interferometry missions, in
particular the SPIRIT and SPECS far-infrared/submillimeter interferometers.
WIIT operates at optical wavelengths and uses Michelson beam combination to
achieve both wide-field imaging and high-resolution spectroscopy. It will be
used chiefly to test the feasibility of using a large-format detector array at
the image plane of the sky to obtain wide-field interferometry images through
mosaicing techniques. In this setup each detector pixel records interferograms
corresponding to averaging a particular pointing range on the sky as the
optical path length is scanned and as the baseline separation and orientation
is varied. The final image is constructed through spatial and spectral Fourier
transforms of the recorded interferograms for each pixel, followed by a
mosaic/joint-deconvolution procedure of all the pixels. In this manner the
image within the pointing range of each detector pixel is further resolved to
an angular resolution corresponding to the maximum baseline separation for
fringe measurements.
We present the motivation for building the testbed, show the optical,
mechanical, control, and data system design, and describe the image processing
requirements and algorithms. WIIT is presently under construction at NASA's
Goddard Space Flight Center.Comment: 7 pages, 3 figures, IEEE Aerospace Conference 200
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