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    Re: Digital Sextant
    From: Dan Allen
    Date: 2002 Apr 1, 16:27 -0800

    Here is the text of the request:
    N02-104                  TITLE: Daytime Electronic Stellar Imaging
    TECHNOLOGY AREAS: Information Systems, Sensors, Electronics, Battlespace
    OBJECTIVE:  Develop a high dynamic range electronic imaging system for imaging 
    and resolving individual stars during daytime with
    sufficient accuracy to enable Automated Celestial Navigation (ACN) systems.
    DESCRIPTION:   The Navy relies heavily on the Global Positioning System (GPS), 
    which is the best navigation system for worldwide,
    day-and-night position determination.  However, it is well known that GPS 
    signals from space are subject to jamming that may render
    the GPS system ineffective for some periods of time.  The Navy's Balanced 
    Navigation Plan calls for the development of alternate
    methods of navigation to mitigate this vulnerability.
    The development of an ACN system would provide an alternative to GPS that is 
    invulnerable to jamming and completely independent of
    man-made constructs such as satellites and transmission stations.   In order 
    to be viable as a complement to GPS, such an ACN system
    must provide accuracies comparable to other modern navigation systems.  This 
    requires imaging individual stars with angular
    resolutions on the order of 3 arcsec or less, exposure times on the order of 
    100 ms or less, both day and night.
    The development of current Charge-Coupled-Device (CCD) arrays has been driven 
    by the commercial market for digital cameras.  Such
    microelectronic devices consist of arrays of sensors on a chip yielding up to 
    a few million pixels.  Current devices don't have the
    required sensitivity or dynamic range to image stars in the presence of strong 
    scattering of visible light in the daytime sky.
    Alternative systems are made using CMOS silicon devices.  This topic calls for 
    the development of new electronic sensor arrays that
    could be based on current CCD or CMOS technology, or use a completely 
    different approach and technology.  The preferred spectral
    region would probably be the near infrared.  The goal is a 
    microelectronics-based array of sensor elements that would be mounted in
    the focal plane of a camera.  An electronic readout would then provide a 
    visual and digital image of the field of view.  Ideally,
    the field of view of such an optical system should be at least 3 degrees.
    PHASE I:  Conduct an assessment of the field of electronic sensors.  Quantify 
    the optical requirements needed to image stars in
    daylight applying whatever digital signal processing and optical filtering 
    that might be required.  The spectral window of operation
    could be adjusted to match the characteristics of the sensor array over a 
    broad range from the near infrared to longer wavelengths.
    Determine a reasonable approach to develop such a sensor array with the 
    required sensitivity and dynamic range to image stars by
    daylight at reasonable data rates for shipboard use.
    PHASE II:  Develop a prototype electronic imaging array for testing and 
    evaluation.  Such a prototype should be fabricated in an
    array of at least 100x100 pixels and characterized for resolution, 
    sensitivity, and dynamic range.  This phase calls for actual
    fabrication of prototype sensor arrays.  The arrays should be evaluated, and 
    their optical performance compared to expectations and
    to the requirements deduced in Phase I.
    PHASE III:  Transition this R&D effort into a commercially viable product.  In 
    addition to the primary goal of an Automated
    Celestial Navigator, prototype devices should be configured for use in law 
    enforcement and other surveillance applications.
    COMMERCIAL POTENTIAL:  The continuing development of electronic imagers should 
    have many applications in the commercial markets.  In
    addition, imagers sensitive in the infrared portion of the spectrum would have 
    numerous applications in crime fighting, drug
    surveillance and interdiction, and home and business intruder-detection systems.
    KEYWORDS:  Alternate Navigation, Celestial, Electronics, Cameras, 
    Surveillance, Detection, Infrared, Night-Vision, NAVWAR, GPS.
    -----Original Message-----
    From: Navigation Mailing List
    [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM]On Behalf Of Hal Mueller
    Sent: Monday, April 01, 2002 4:21 PM
    Subject: Re: Digital Sextant
    In the round of SBIR topics that closed back in January, US Navy's
    SPAWAR was looking for proposals for developing an automatic
    celestial navigation system that would be able to image stars in the
    daytime.  There was also some work by SPAWAR a few years back to
    adapt space/aviation star trackers to shipboard use.
    for the solicitation (topic N02-104).  Thought seriously about
    submitting a proposal, but in the end I did not.
    Hal Mueller                hal@mobilegeographics.com
    Mobile Geographics LLC     http://www.mobilegeographics.com/
    Seattle, Washington        (206) 297-9575
    MapTap public test now underway!

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