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  • 1
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    A cryogenic scan mechanism for use in Fourier transform spectrometers (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This paper describes the requirements, design, assembly and testing of the linear Scan Mechanism (SM) of the Composite Infrared Spectrometer (CIRS) Instrument. The mechanism consists of an over constrained flexible structure, an innovative moving magnet actuator, passive eddy current dampers, a Differential Eddy Current (DEC) sensor, Optical Limit Sensors (OLS), and a launch lock. Although all the components of the mechanism are discussed, the flexible structure and the magnetic components are the primary focus. Several problems encountered and solutions implemented during the development of the scan mechanism are also described.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA. Johnson Space Center, The 29th Aerospace Mechanisms Symposium; p 316-333
    Format: application/pdf
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  • 2
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    ATLAS Beam Steering Mechanism (BSM) Lessons Learned (2016)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: This paper describes the design, testing, and lessons learned during the development of the Advanced Topographic Laser Altimeter System (ATLAS) Beam Steering Mechanism (BSM). The BSM is a 2 degree-of-freedom tip-tilt mechanism for the purpose of pointing a flat mirror to tightly control the co-alignment of the transmitted laser and the receiver telescope of the ATLAS instrument. The high resolution needs of the mission resulted in sub-arcsecond pointing and knowledge requirements, which have been met. Development of the methodology to verify performance required significant effort. The BSM will fly as part of the Ice, Cloud, and Elevation Satellite II Mission (ICESat II), which is scheduled to be launched in 2017. The ICESat II primary mission is to map the Earth's surface topography for the determination of seasonal changes of ice sheet thickness and vegetation canopy thickness to establish long-term trends.
    Keywords: Mechanical Engineering
    Type: 43rd Aerospace Mechanisms Symposium; 1-14; NASA/CP-2016-219090
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  • 3
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    A Spaceflight Magnetic Bearing Equipped Optical Chopper with Six-Axis Active Control (1998)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper describes the development of an ETU (Engineering Test Unit) rotary optical chopper with magnetic bearings. An ETU is required to be both flight-like, nearly identical to a flight unit without the need for material certifications, and demonstrate structural and performance integrity. A prototype breadboard design previously demonstrated the feasibility of meeting flight performance requirements using magnetic bearings. The chopper mechanism is a critical component of the High Resolution Dynamics Limb Sounder (HIRDLS) which will be flown on EOS-CHEM (Earth Observing System-Chemistry). Particularly noteworthy are the science requirements which demand high precision positioning and minimal power consumption along with full redundancy of coils and sensors in a miniature, lightweight package. The magnetic bearings are unique in their pole design to minimize parasitic losses and utilize collocated optical sensing. The motor is of an unusual disk-type ironless stator design. The ETU design has evolved from the breadboard design. A number of improvements have been incorporated into the ETU design. Active thrust control has been added along with changes to improve sensor stability, motor efficiency, and touchdown and launch survivability. It was necessary to do all this while simultaneously reducing the mechanism volume. Flight-like electronics utilize a DSP (Digital Signal Processor) and contain all sensor electronics and drivers on a single five inch by nine inch circuit board. Performance test results are reported including magnetic bearing and motor rotational losses.
    Keywords: Optics
    Type: Magnetic Bearings; Aug 05, 1998 - Aug 07, 1998; Cambridge, MA; United States
    Format: text
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  • 4
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    A Spaceflight Magnetic Bearing Equipped Optical Chopper with Six-Axis Active Control (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper describes the development of an ETU (Engineering Test Unit) rotary optical chopper with magnetic bearings. An ETU is required to be both flight-like, nearly identical to a flight unit without the need for material certifications, and demonstrate structural and performance integrity. A prototype breadboard design previously demonstrated the feasibility of meeting flight performance requirements using magnetic bearings. The chopper mechanism is a critical component of the High Resolution Dynamics Limb Sounder (HIRDLS) which will be flown on EOS-CHEM (Earth Observing System-Chemistry). Particularly noteworthy are the science requirements which demand high precision positioning and minimal power consumption along with full redundancy of coils and sensors in a miniature, lightweight package. The magnetic bearings are unique in their pole design to minimize parasitic losses and utilize collocated optical sensing. The motor is of an unusual disk-type ironless stator design. The ETU design has evolved from the breadboard design. A number of improvements have been incorporated into the ETU design. Active thrust control has been added along with changes to improve sensor stability, motor efficiency, and touchdown and launch survivability. It was necessary to do all this while simultaneously reducing the mechanism volume. Flight-like electronics utilize a DSP (Digital Signal Processor) and contain all sensor electronics and drivers on a single five inch by nine inch circuit board. Performance test results are reported including magnetic bearing and motor rotational losses.
    Keywords: Mechanical Engineering
    Type: Magnetic Bearings; Aug 05, 1998 - Aug 07, 1998; Cambridge, MA; United States
    Format: application/pdf
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  • 5
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    New Understanding of Hubble Space Telescope Gyro Current Increase Led to a Method to Save a Failing Gyro (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Throughout the history of the Hubble Space Telescope (HST) program, gyro current increases have been observed to occur, oftentimes leading to gyro failure. The explanation was that debris from the surfaces of the gas bearings, with only 50 millionths on an inch clearance, resulted in rotor restriction, which increased friction, torque, and current. However, the rotor restriction theory never could account for the fact that a restart of the gyro would restore the current back to nominal. An effort was made to understand this puzzling gyro behavior after two HST gyros exhibited increased current within the same week in November 2015. A review board was created to resolve these anomalies and generate operational procedures to potentially extend gyro life.
    Keywords: Mechanical Engineering
    Type: GSFC-E-DAA-TN43390 , European Space Mechanisms and Tribology Symposium; Sep 20, 2017 - Sep 22, 2017; Hatfield; United Kingdom
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  • 6
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    New Understanding of Hubble Space Telescope Gyro Current Increase Led to a Method to Save a Failing Gyro Presentation (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Throughout the history of the Hubble Space Telescope (HST) program, gyro current increases have been observed to occur, often times leading to gyro failure. The explanation was that debris from the surfaces of the gas bearings, with only 1.27 micron clearance, resulted in rotor restriction, which increased friction, torque, and current. However, the rotor restriction theory never could account for the fact that a restart of the gyro would restore the current back to nominal. An effort was made to understand this puzzling gyro behavior after two HST gyros exhibited increased current within the same week in November 2015. A review board was created to resolve these anomalies and generate operational procedures to potentially extend gyro life. A new understanding of gyro current behavior led to implementation of a method that could potentially save a failing gyro.
    Keywords: Mechanical Engineering
    Type: GSFC-E-DAA-TN44387 , European Space Mechanisms and Tribology Symposium (ESMATS); Sep 20, 2017 - Sep 22, 2017; Hatfield, UK; United States
    Format: application/pdf
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  • 7
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    ATLAS Beam Steering Mechanism Lessons Learned (2016)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: This paper describes the design, testing, and lessons learned during the development of the Advanced Topographic Laser Altimeter System (ATLAS) Beam Steering Mechanism (BSM). The BSM is a 2 degree-of-freedom tip-tilt mechanism for the purpose of pointing a flat mirror to tightly control the co-alignment of the transmitted laser and the receiver telescope of the ATLAS instrument. The high resolution needs of the mission resulted in sub-arcsecond pointing and knowledge requirements, which have been met. Development of the methodology to verify performance required significant effort. The BSM will fly as part of the Ice, Cloud, and Elevation Satellite II Mission (ICESat II), which is scheduled to be launched in 2017. The ICESat II primary mission is to map the earth's surface topography for the determination of seasonal changes of ice sheet thickness and vegetation canopy thickness to establish long-term trends.
    Keywords: Lasers and Masers; Electronics and Electrical Engineering
    Type: GSFC-E-DAA-TN30122 , Aerospace Mechanisms Symposium; May 04, 2016 - May 06, 2016; Santa Clara, CA; United States
    Format: application/pdf
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  • 8
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    Shaft Position Optical Sensor (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The present invention is an optical sensor that senses the movement of a shaft. Detection of radial movement is made when a portion of light incident on the shaft sensor-target is blocked. For detection of axial movement, a disk with flat surface is mounted and used to block a portion of light. The variation in the amount of light allowed to pass through is a measure of the position of the shaft. As proposed by this invention, significant improvement is made with respect to sensitivity and linearity of the system when the light is permanently partially blocked. To accomplish this goal this invention adds a boss to the system. To eliminate possible drift of system performance due to LED degradation or temperature variation, a feedback feature is added to the system.
    Keywords: Optics
    Format: text
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  • 9
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    Combination radial and thrust magnetic bearing (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A combination radial and thrust magnetic bearing is disclosed that allows for both radial and thrust axes control of an associated shaft. The combination radial and thrust magnetic bearing comprises a rotor and a stator. The rotor comprises a shaft, and first and second rotor pairs each having respective rotor elements. The stator comprises first and second stator elements and a magnet-sensor disk. In one embodiment, each stator element has a plurality of split-poles and a corresponding plurality of radial force coils and, in another embodiment, each stator element does not require thrust force coils, and radial force coils are replaced by double the plurality of coils serving as an outer member of each split-pole half.
    Keywords: Mechanical Engineering
    Format: application/pdf
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  • 10
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    Low loss pole configuration for multi-pole homopolar magnetic bearings (2001)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A new pole configuration for multi-pole homopolar bearings proposed in this invention reduces rotational losses caused by eddy-currents generated when non-uniform flux distributions exist along the rotor surfaces. The new homopolar magnetic bearing includes a stator with reduced pole-to-pole and exhibits a much more uniform rotor flux than with large pole-to-pole gaps. A pole feature called a pole-link is incorporated into the low-loss poles to provide a uniform pole-to-pole gap and a controlled path for pole-to-pole flux. In order to implement the low-loss pole configuration of magnetic bearings with small pole-to-pole gaps, a new stator configuration was developed to facilitate installation of coil windings. The stator was divided into sector shaped pieces, as many pieces as there are poles. Each sector-shaped pole-piece can be wound on a standard coil winding machine, and it is practical to wind precision layer wound coils. To achieve maximum actuation efficiency, it is desirable to use all the available space for the coil formed by the natural geometric configuration. Then, the coils can be wound in a tapered shape. After winding, the sectored-pole-pieces are installed into and fastened by bonding or other means, to a ring of material which encloses the sectored-pole-pieces, forming a complete stator.
    Keywords: Mechanical Engineering
    Format: application/pdf
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