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Results for “MIRROR POINT”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Design of a mirror pointing and occulting mechanism for the Ultraviolet Coronagraph Spectrometer (UVCS)

The Mirror and Occulter Mechanism (MOM), a lightweight stable optical assembly which is a critical component to the Ultraviolet Coronagraph Spectrometer to be flown on the European SOHO spacecraft, is discussed. The MOM combines the functions of precision mirror pointing and occultation of stray light into a single package. The mirror mechanism and occulter mechanism designs are described and development testing and life testing activities are discussed.

Highman, Clifton O.↗
NASA NTRS1990

Driving and latching of the Starlab pointing mirror doors

The Starlab Experiment, a major SDIO technology initiative, is an attached payload which will be delivered into Earth orbit aboard NASA's Space Shuttle in 1991. Starlab will generate and aim an 80 cm diameter laser beam into space through a large opening in the structure which houses the pointing mirror. Two doors, each somewhat larger than a desktop, cover the opening when the laser optics system is nonoperational. Latch Mechanism Assemblies hold the doors shut during liftoff and ascent and, again, during Orbiter reentry. Each door is powered by a Door Drive System during the many open/close cycles between various experiments. The design, testing, and resultant failure modes of these mechanisms are examined.

Beaven, Herbert R., Jr.↗
NASA NTRS1998

Development of a mirror pointing mechanism for an atmospheric gas measurement instrument

Development of the Open Path Tunable Infrared Monitor of the Atmosphere (OPTIMA) instrument involved designing a pair of motion systems that could maintain a precise alignment and spatial distance between two mirrors installed on the NASA DC-8 research laboratory aircraft. This is the first airborne optical instrument that allows direct measurement of the gases in the freestream airflow on the exterior of the aircraft. One mirror is mounted within a specially constructed open port cavity in the cabin of the aircraft and the second is mounted 6 meters away on top of the inboard port side (number 2) engine pylon. Three co-aligned laser beams are reflected between the two mirrors 64 times in a Herriott pattern. The resulting sample path length of 384 meters is used to perform a spectral absorption analysis of the airflow between the mirrors. To compensate for normal wing movement and engine oscillations both mirrors were designed as continuously driven mechanisms to maintain alignment within allowable limits. The motion systems of the two mirror assemblies provide five degrees of freedom and are designed to maintain a pointing accuracy within seven arc-sec with a response frequency in excess of 10 Hz. The pylon motion system incorporates controlled pitch and yaw movement. The fuselage motion system compensates for pitch variation as well as linear translation for focal length and vertical aiming of the laser beam via a controlled beam guidance mechanism.

Graham, Michael↗
NASA NTRS1998

Development of a Mirror Pointing Mechanism for an Atmospheric Gas Measurement Instrument

Development of the Open Path Tunable Infrared Monitor of the Atmosphere (OPTIMA) instrument involved designing a pair of motion systems that could maintain a precise alignment and spatial distance between two mirrors installed on the NASA DC-8 research laboratory aircraft. This is the first airborne optical instrument that allows direct measurement of the gases in the freestream airflow on the exterior of the aircraft. One mirror is mounted within a specially constructed open port cavity in the cabin of the aircraft and the second is mounted 6 meters away on top of the inboard port side (number 2) engine pylon. Three co-aligned laser beams are reflected between the two mirrors 64 times in a Herriott pattern. The resulting sample path length of 384 meters is used to perform a spectral absorption analysis of the airflow between the mirrors. To compensate for normal wing movement and engine oscillations both mirrors were designed as continuously driven mechanisms to maintain alignment within allowable limits. The motion systems of the two mirror assemblies provide five degrees of freedom and are designed to maintain a pointing accuracy within seven arc-sec with a response frequency in 6xcess of 10 Hz. The pylon motion system incorporates controlled pitch and yaw movement. The fuselage motion system compensates for pitch variation as well as linear translation for focal length and vertical aiming of the laser beam via a controlled beam guidance mechanism.

Graham, Michael↗
NASA NTRS1971

A note on the effect of reflected solar radiation on airborne and ground measurements in the thermal infrared

The magnitude of thermal solar radiation reflected from water surfaces is considered. It is shown both theoretically and by field observation that, for instruments with small fields of view, the reflected thermal solar radiation can contribute significantly to the measured energy. Comparison of thermal scanner data taken from aircraft at a 16 deg azimuth angle from the mirror point of the sun over the open ocean with data taken at a 164 deg anzimuth angle from the mirror point of the sun at the same angle from nadir is indicative of a difference of 2.8 K in the equivalent black body radiation temperature. Observations taken from a surface vessel into sunglint 80 deg from nadir are indicative of an equivalent black body radiation temperature that is 34 K warmer than the temperature obtained at a similar nadir angle away from the sunglint.

Whitehead, V. S.↗
NASA NTRS1990

Wave-particle interactions for relativistic electrons in a recirculation acceleration model

Evidence is presented for the presence of a multistep process, leading to relativistic electron populations, in the magnetospheres of earth and Jupiter. After an initial injection of a spectrally soft electron component in the outer magnetosphere, inward radial diffusion acts to accelerate the electrons perpendicular to the local magnetic field; strong wave-particle interactions deep in the magnetosphere is of primary significance in the pitch-angle scattering of electrons, thereby lowering their mirror points. An additional model element of critical significance, again involving wave-particle interactions, is energy-preserving outward transport near the mirror points where the field strength is large and trans-L distances are small.

Baker, D. N.↗
NASA NTRS1977

The photometry of flat, basaltic surfaces

A photometer was developed and successfully operated to obtain photometric measurements on several flat, particulate surfaces of basalt for coplanar scattering geometries. The test materials were two size ranges each of two different basalts with significantly different albedos. The measurements include a range of phase angles from 30 to 80 degrees and were obtained by varying the angles of incidence and emission such that the phase angle remained constant. The data were used elsewhere in the verification of the Meador-Weaver photometric function and are presented here in the form of Minnaert plots. In this form the data offered the first support for the accuracy of the Meador-Weaver photometric function because of a deviation of the data from a straight line trend at larger departures from the mirror point geometry. This trend is predicted by the Meador-Weaver function but not by the Minnaert function. The failure of photometric data to support the Minnaert function was not evident in earlier measurements because of the restriction of planetary data to small departures from the mirror point geometry and to small values of the phase angle.

Weaver, W. R.↗
NASA NTRS1992

Estimation of surface heat and moisture fluxes over a prairie grassland. I - In situ energy budget measurements incorporating a cooled mirror dew point hygrometer

Attention is focused on in situ measurements taken during FIFE required to support the development and validation of a biosphere model. Seasonal time series of surface flux measurements obtained from two surface radiation and energy budget stations utilized to support the FIFE surface flux measurement subprogram are examined. Data collection and processing procedures are discussed along with the measurement analysis for the complete 1987 test period.

Smith, Eric A.↗
NASA NTRS2006

Instrument Pointing Control System for the Stellar Interferometry Mission - Planet Quest

This paper describes the high precision Instrument Pointing Control System (PCS) for the Stellar Interferometry Mission (SIM) - Planet Quest. The PCS system provides front-end pointing, compensation for spacecraft motion, and feedforward stabilization, which are needed for proper interference. Optical interferometric measurements require very precise pointing (0.03 as, 1-(sigma) radial) for maximizing the interference pattern visibility. This requirement is achieved by fine pointing control of articulating pointing mirrors with feedback from angle tracking cameras. The overall pointing system design concept is presentcd. Functional requirements and an acquisition concept are given. Guide and Science pointing control loops are discussed. Simulation analyses demonstrate the feasibility of the design.

control↗
NASA NTRS1975

A wide angle search technique for a 10.6 micron ladar

A ladar (laser radar) sensor designed around a pulsed passively Q-switched CO2 laser, capable of a efficient and rapid scans with a narrow beam over a wide field of view, is considered for surveillance and tracking applications in space. The output is a train of narrow pulses with a controllable pulse repetition rate. A resonant vibrating mirror in back of a classical Gregorian telescope, and a plane pointing mirror in front for beam steering, are used in scanning. Scan pulse sequences are described and illustrated. The 10.6 micron ladar set is under consideration as baseline sensor for various space rendezvous and docking applications.

Levinson, S.↗
NASA NTRS2018

Technologies and Operations for High Voltage Corona Detection with UAVs

Autonomous UAV transmission line inspection served as a reference mission for NASA demonstration of UAV deployment for economic benefit; this paper reports corona sensing advances in development of that reference mission. Unmanned aerial vehicles can serve as a platform for autonomous sensing and location of high voltage coronal discharge. Simple processing of commercial corona camera imagery can automate discharge localization and documentation. Inexpensive ultraviolet point sensors can sense discharge when carried close to the defect with a UAV. Augmented with a parabolic mirror, point sensor range can be increased to a safe inspection standoff distance, at the cost of a narrowed field of view. Results from a test flight of an augmented UV sensor are described. The imaging approach is superior in sensitivity and acquisition time, while the point sensor approach has superior size, weight, cost and durability advantages.

Moore, Andrew J.↗
NASA NTRS1991

Precision pointing control for an orbital earth observing system

The design concept developed for the pointing system of the high-resolution imaging spectrometer (HIRIS) which will be flown on one of NASA's earth observing system platforms is presented. The instrument is an F/5.4-aperture spectrometer with a focal length of 1222 mm, and it uses a precision two-axis gimballed mirror pointing system to image and track targets. Pointing accuracy of better than 585 arcsec (peak-to-peak), and pointing jitter of less than 2.65 arcsec in 33 ms are ensured through the use of gimbal position and basebody rate sensors. A state-space controller implemented with a digital computer is used to provide a position loop bandwidth of 1 Hz and a rate loop bandwidth of 7 Hz. An overview of the system design and flight hardware is given, the development of the controller architecture is addressed, and a simulation assessment of the pointing system that takes into consideration issues such as nonlinear effects, sensor noise, and noncollocated sensors and actuators in a flexible structure is discussed.

Robeck, Linda S.↗