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  • American Institute of Physics (AIP)  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2512-2518 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe the design of two telescope pointing systems for remote optical sensing of the stratosphere from a balloon-borne gondola. The telescope pointing accuracy is ±0.02° in elevation, from a gondola which has static and dynamic tilts up to ±3°. Each system consists of a telescope, an elevation control subsystem, and a pitch-stabilized single-axis reference platform. The Mark I unit has performed successfully on each of its two balloon flights, for a total of over 16 h in the stratosphere; the Mark II unit is currently under construction. The single-axis platform is referenced to a rate-integrating gyroscope and an inclinometer for high- and low-frequency pitch-angle variations, respectively. The Mark I platform is supported by ball bearings, driven by a brush-contact torque motor, and is subject to a small, permanent pitch angle error which depends directly on the gyro drift rate. The Mark II platform uses flex-pivot supports, a brushless motor, and for even a relatively large gyro drift rate, is designed to asymptotically approach zero angular offset error.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2519-2522 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The balloon flight performance of the Mark I single-axis platform and telescope is presented. Three performance indicators are examined: inclinometer output, gyro output, and infrared detector signal. We find that the gondola itself experiences periodic angular disturbances with maximum amplitudes in the 0.1°–2.0° range, with peaks occurring at periods of about 1, 2, 7, 20, and 250 s. The 2- and 20-s oscillations are identified with simple and compound pendulum motions, while the 250-s oscillations are speculated to be caused by atmospheric waves. Maximum platform deviations from the horizontal are in the 0.002°–0.02° range, well within the 0.02° design goal, except in the 250-s regime where amplitudes are occasionally several times larger than the design goal because of horizontal atmospheric accelerations. We find that the system meets our basic goal of providing a stable pointing direction within an uncertainty which is much less than the 0.3° telescope beam diameter.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
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