Antenna Control Console The   most   obvious   feature   of   the   ARIA   is   the   radome   which   contains   the   83-inch   parabolic tracking    antenna.    The    acquisition    and    tracking    of    telemetry    signals    is    the    function    of    this subsystem,    which    is    controlled    by    the    antenna    control    assembly    (ACA),    and    the    antenna operator. Bendix   Corporation   designed   the   original   antenna   control,   Electrospace   Systems   designed   the replacement antenna control in 1978. The replacement control was microprocessor based. There    are    two    modes    of    antenna    tracking.    When    the    system    is    in    automatic    the    antenna positioning   is   controlled   by   the   antenna   control   assembly.   When   the   system   is   in   manual   the antenna   positioning   is   controlled   by   the   antenna   operator   by   the   use   of   the   hand   wheels   or joystick.   The   left   hand   wheel   control   adjusted   the   azimuth   of   the   dish   and   the   right   hand   wheel control allowed the operator to adjust the elevation of the dish. The   antenna   support   pedestal   attaches   the   antenna   yoke   assembly   to   the   aircraft   bulkhead. The pedestal   is   constructed   with   a   30   degree   downward   angle   to   allow   the   antenna   to   clear   the radome   when   operating.   Because   of   this   downward   angle   the   antenna   control   assembly   has   to perform   a   forward   and   backward   coordinate   conversion.   Unless   the   azimuth   of   the   dish   is centered both the yoke and dish will have to be positioned to achieved point to any give place Automatic   acquisition   mode   is   selected   by   the   antenna   operator.   Upon   acquisition   of   the   signal, the   antenna   system   electronically   simulates   a   conical   scan   of   3   dB   off   bore-sight   to   generate error   signals   that   indicate   in   which   direction   the   signal   is   off   bore-sight.   These   error   signals   are routed   to   the   telemetry/tracking   receivers   as   amplitude   modulation   on   the   sum   (data)   channel, demodulated   from   the   sum   channel,   and   sent   through   the   signal   interface   assembly   to   the tracking   combiner/converter   unit   (TCCU)   as   tracking   video.   The   TCCU   converts   the   tracking video   error   signals   to   DC   azimuth   and   elevation   error   voltages   which   are   then   routed   through   the antenna   control   assembly   (ACA)   to   the   servo   amplifier,   which   in   turn   controls   the   clutches   which engage drive motors to reposition the antenna. Trajectory Processor Unit The   antenna   may   also   be   automatically   controlled   by   the   trajectory   processing   unit   (TPU),   which computes   look   angles   (azimuth   and   elevation)   for   the   antenna   based   on   the   proposed   trajectory of   the   user's   vehicle   and   the   position   of   the ARIA.   The   versatility   of   the ACA   is   enhanced   by   the acceleration   memory   contained   within   the   TPU.   Should   the   vehicle's   trajectory   proceed   non- nominally,   the   antenna   will   continue   to   track   the   vehicle   and   store   the   error   buildup   between   the proposed   trajectory   and   the   actual   trajectory   in   the   acceleration   memory.   If   the   signal   is   then   lost, the   antenna   will   continue   tracking   along   the   original   look   angles,   biased   by   the   error   buildup, until the signal is reacquired. Rate Memory If   the   TPU   is   not   used   on   a   mission   and   the   antenna   has   been   automatically   tracking   for   at   least 10   seconds,   the   antenna   slew   (motion)   rate   will   be   stored   in   rate   memory.   If   the   signal   is   then lost,   the   antenna   will   continue   to   move   at   the   same   rate   as   it   did   before   loss   of   signal   (LOS)   for as   long   as   30   seconds,   at   which   time   the   antenna   will   stop   tracking   and   the   LOS   light   will illuminate. This is a valuable feature during momentary blackouts. Manual Tracking During   the   actual   data   gathering   interval   of   the   mission,   it   is   preferable   to   track   automatically;   but the    need    frequently    arises    to    control    the    antenna    manually,    such    as    during    pre-mission calibration   (PMC),   verification,   before   acquisition   of   signal   (AOS),   and   after   LOS.   After   placing the   antenna   system   in   manual   mode,   the   operator   has   two   ways   to   control   the   antenna   hand wheels and joystick. The   hand   wheels   are   located   on   the   front   panel   of   the   ACA,   one   for   azimuth   control   and   the other   for   elevation   control.   By   monitoring   the   signal   error   meter,   which   indicates   the   antenna pointing   error   when   a   signal   is   present,   the   operator   can   manually   correct   the   antenna   position using   the   hand   wheels. Typically,   prior   to AOS,   the   antenna   operator   will   drive   the   antenna   to   the initial   look   angles   and   press   ACQUISITION   ENABLE   (still   retaining   manual   control).   When   the signal   is   acquired,   the   system   will   automatically   switch   to   auto   track.   When   this   happens   the operator   will   lose   manual   control   of   the   antenna   and   must   press   ACQUISITION   DISABLE   to regain manual control. The   joystick   is   a   control   stick   which   can   individually   or   concurrently   control   the   yoke   and   dish, and is most commonly used to drive the antenna out of stow (described below). Stow Mode When   the   antenna   is   not   being   used,   it   is   stowed.   In   this   mode,   the   antenna   is   automatically locked   in   position   by   two   sliding   pins   (one   for   the   yoke   and   one   for   the   dish).   The   navigator's weather   radar,   which   is   located   just   aft   of   the   antenna   dish,   is   disabled   when   the   antenna   is   not in   the   stowed   position.   This   prevents   the   weather   radar   from   being   overloaded   and   damaged   by energy   being   reflected   off   the   rear   of   the   dish.   It   also   protects   the   flight   crew   from   radiation exposure. Antenna References The   antenna   system   requires   both   azimuth   and   elevation   references   in   order   to   compute   proper look   angles.   A   compass   card   located   in   the   ACA   is   slaved   to   the   aircraft's   Inertial   Navigation System   (INS)   heading,   and   is   used   as   the   reference   for   azimuth   (the   antenna   is   therefore referenced   to   true   heading).   The   INS   heading   simulator   can   be   used   to   test   the   ACA   in   case   of INS malfunctions and during pre-mission calibration. A   gyroscope   mounted   in   the   antenna   pedestal   is   used   as   the   elevation   reference. The   gyroscope requires   approximately   2   minutes   to   erect,   so   a   3-minute   delay   is   introduced   when   the   antenna system   is   powered   on.   The   gyro   is   used   to   compensate   for   aircraft   pitch   and   roll.   If   it   should   fail, the ACA has a zero pitch and roll simulator which can be actuated by the operator. These   two   references   are   used   to   keep   the   antenna   pointed   in   true   azimuth   and   elevation, regardless   of   the   aircraft's   heading,   pitch,   or   roll.   The   dials   at   the   antenna   operator's   position indicate   true   azimuth   and   elevation   (compared   to   the   mission   control   subsystem   dials,   which reflect yoke and dish position). The   antenna   position   is   limited   to   100   degrees   left   or   right   of   center   in   azimuth,   and   100   degrees up   to   30   degrees   down   in   elevation.   The   maximum   manual   slew   rate   is   45   degrees   per   second, and the maximum automatic slew is rate is 17 degrees per second. Memory Bypass A   memory   bypass   switch   is   provided   to   bypass   rate   and   acceleration   memory   to   enable   antenna positioning by either the manual tracking mode or the automatic tracking mode.
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Advanced Range Instrumentation Aircraft
     United States Air Force
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Antenna Control Console The   most   obvious   feature   of   the   ARIA   is   the   radome which   contains   the   83-inch   parabolic   tracking   antenna. The   acquisition   and   tracking   of   telemetry   signals   is   the function   of   this   subsystem,   which   is   controlled   by   the antenna    control    assembly    (ACA),    and    the    antenna operator. Bendix    Corporation    designed    the    original    antenna control,       Electrospace       Systems       designed       the replacement   antenna   control   in   1978.   The   replacement control was microprocessor based. There   are   two   modes   of   antenna   tracking.   When   the system    is    in    automatic    the    antenna    positioning    is controlled   by   the   antenna   control   assembly.   When   the system     is     in     manual     the     antenna     positioning     is controlled   by   the   antenna   operator   by   the   use   of   the hand   wheels   or   joystick.   The   left   hand   wheel   control adjusted   the   azimuth   of   the   dish   and   the   right   hand wheel    control    allowed    the    operator    to    adjust    the elevation of the dish. The   antenna   support   pedestal   attaches   the   antenna yoke   assembly   to   the   aircraft   bulkhead. The   pedestal   is constructed   with   a   30   degree   downward   angle   to   allow the    antenna    to    clear    the    radome    when    operating. Because   of   this   downward   angle   the   antenna   control assembly    has    to    perform    a    forward    and    backward coordinate   conversion.   Unless   the   azimuth   of   the   dish is   centered   both   the   yoke   and   dish   will   have   to   be positioned to achieved point to any give place Automatic   acquisition   mode   is   selected   by   the   antenna operator.   Upon   acquisition   of   the   signal,   the   antenna system   electronically   simulates   a   conical   scan   of   3   dB off   bore-sight   to   generate   error   signals   that   indicate   in which   direction   the   signal   is   off   bore-sight.   These   error signals   are   routed   to   the   telemetry/tracking   receivers as   amplitude   modulation   on   the   sum   (data)   channel, demodulated   from   the   sum   channel,   and   sent   through the      signal      interface      assembly      to      the      tracking combiner/converter   unit   (TCCU)   as   tracking   video.   The TCCU   converts   the   tracking   video   error   signals   to   DC azimuth   and   elevation   error   voltages   which   are   then routed   through   the   antenna   control   assembly   (ACA)   to the   servo   amplifier,   which   in   turn   controls   the   clutches which engage drive motors to reposition the antenna. Trajectory Processor Unit The   antenna   may   also   be   automatically   controlled   by the   trajectory   processing   unit   (TPU),   which   computes look   angles   (azimuth   and   elevation)   for   the   antenna based   on   the   proposed   trajectory   of   the   user's   vehicle and   the   position   of   the ARIA.   The   versatility   of   the ACA is    enhanced    by    the    acceleration    memory    contained within   the   TPU.   Should   the   vehicle's   trajectory   proceed non-nominally,   the   antenna   will   continue   to   track   the vehicle    and    store    the    error    buildup    between    the proposed    trajectory    and    the    actual    trajectory    in    the acceleration    memory.    If    the    signal    is    then    lost,    the antenna   will   continue   tracking   along   the   original   look angles,   biased   by   the   error   buildup,   until   the   signal   is reacquired. Rate Memory If   the   TPU   is   not   used   on   a   mission   and   the   antenna has     been     automatically     tracking     for     at     least     10 seconds,   the   antenna   slew   (motion)   rate   will   be   stored in   rate   memory.   If   the   signal   is   then   lost,   the   antenna will   continue   to   move   at   the   same   rate   as   it   did   before loss   of   signal   (LOS)   for   as   long   as   30   seconds,   at which   time   the   antenna   will   stop   tracking   and   the   LOS light   will   illuminate.   This   is   a   valuable   feature   during momentary blackouts. Manual Tracking During   the   actual   data   gathering   interval   of   the   mission, it    is    preferable    to    track    automatically;    but    the    need frequently   arises   to   control   the   antenna   manually,   such as   during   pre-mission   calibration   (PMC),   verification, before   acquisition   of   signal   (AOS),   and   after   LOS. After placing    the    antenna    system    in    manual    mode,    the operator   has   two   ways   to   control   the   antenna   hand wheels and joystick. The   hand   wheels   are   located   on   the   front   panel   of   the ACA,    one    for    azimuth    control    and    the    other    for elevation   control.   By   monitoring   the   signal   error   meter, which    indicates    the    antenna    pointing    error    when    a signal   is   present,   the   operator   can   manually   correct   the antenna   position   using   the   hand   wheels. Typically,   prior to   AOS,   the   antenna   operator   will   drive   the   antenna   to the     initial     look     angles     and     press     ACQUISITION ENABLE    (still    retaining    manual    control).    When    the signal   is   acquired,   the   system   will   automatically   switch to   auto   track.   When   this   happens   the   operator   will   lose manual     control     of     the     antenna     and     must     press ACQUISITION DISABLE to regain manual control. The   joystick   is   a   control   stick   which   can   individually   or concurrently   control   the   yoke   and   dish,   and   is   most commonly    used    to    drive    the    antenna    out    of    stow (described below). Stow Mode When   the   antenna   is   not   being   used,   it   is   stowed.   In this    mode,    the    antenna    is    automatically    locked    in position   by   two   sliding   pins   (one   for   the   yoke   and   one for   the   dish).   The   navigator's   weather   radar,   which   is located   just   aft   of   the   antenna   dish,   is   disabled   when the   antenna   is   not   in   the   stowed   position. This   prevents the   weather   radar   from   being   overloaded   and   damaged by   energy   being   reflected   off   the   rear   of   the   dish.   It   also protects the flight crew from radiation exposure. Antenna References The     antenna     system     requires     both     azimuth     and elevation   references   in   order   to   compute   proper   look angles. A   compass   card   located   in   the ACA   is   slaved   to the   aircraft's   Inertial   Navigation   System   (INS)   heading, and   is   used   as   the   reference   for   azimuth   (the   antenna is    therefore    referenced    to    true    heading).    The    INS heading   simulator   can   be   used   to   test   the   ACA   in   case of INS malfunctions and during pre-mission calibration. A   gyroscope   mounted   in   the   antenna   pedestal   is   used as    the    elevation    reference.    The    gyroscope    requires approximately   2   minutes   to   erect,   so   a   3-minute   delay is   introduced   when   the   antenna   system   is   powered   on. The   gyro   is   used   to   compensate   for   aircraft   pitch   and roll.   If   it   should   fail,   the   ACA   has   a   zero   pitch   and   roll simulator which can be actuated by the operator. These   two   references   are   used   to   keep   the   antenna pointed   in   true   azimuth   and   elevation,   regardless   of   the aircraft's    heading,    pitch,    or    roll.    The    dials    at    the antenna   operator's   position   indicate   true   azimuth   and elevation   (compared   to   the   mission   control   subsystem dials, which reflect yoke and dish position). The   antenna   position   is   limited   to   100   degrees   left   or right   of   center   in   azimuth,   and   100   degrees   up   to   30 degrees   down   in   elevation.   The   maximum   manual   slew rate    is    45    degrees    per    second,    and    the    maximum automatic slew is rate is 17 degrees per second. Memory Bypass A   memory   bypass   switch   is   provided   to   bypass   rate and      acceleration      memory      to      enable      antenna positioning   by   either   the   manual   tracking   mode   or   the automatic tracking mode.