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SUBSCAN

    SUBSCAN xOffset    yOffset
    SUBSCAN xStart     yStart     xEnd       yEnd
    SUBSCAN xAmplitude yAmplitude frequencyX frequencyY xCenter yCenter phiX phi

    NB: this is a protected command (needs privilege).

    Add to user-defined list of subscans and segments for observing mode "DIY";
    compare command DIY. The subscan command has the 3 main variants above,
    depending on the number of parameters:

    2 --> Track subscan with fixed offsets
    4 --> Linear OTF segment (subscan)
    8 --> Lissajous OTF segment (subscan), IMPORTANT: SEE NOTE BELOW

    Option /TYPE allows to enforce that the command is interpreted for one
    the 3 different types, independant of the number of parameters.

    Option /TUNE allows to specify that a Track subscan will be used to "tune"
    an instrument, e.g., NIKA.

    Real :: xOffset     ! x offset fixed-position TRACK subscan
    Real :: yOffset     ! y offset fixed-position TRACK subscan

    Real :: xStart      ! x offset start  of linear OTF  segment
    Real :: yStart      ! y offset start  of linear OTF  segment
    Real :: xEnd        ! x offset end    of linear OTF  segment
    Real :: yEnd        ! y offset end    of linear OTF  segment

    Real :: xAmplitude  ! x amplitude              Lissajous OTF segment
    Real :: yAmplitude  ! y amplitude              Lissajous OTF segment
    Real :: frequencyX  ! frequency    [Hz]  for x Lissajous OTF segment
    Real :: frequencyY  ! frequency    [Hz]  for y Lissajous OTF segment
    Real :: xCenter     ! x center                 Lissajous OTF segment
    Real :: yCenter     ! y center                 Lissajous OTF segment
    Real :: phiX        ! phase offset [rad] for x Lissajous OTF segment
    Real :: phiY        ! phase offset [rad] for y Lissajous OTF segment

    If an asterisk * appears in place of any parameter, the value will
    remain unchanged from the last valid SUBSCAN command.

    NOTES: pako will make its best effort to "guess" the values for
    unspecified parameters based on the values of its internal variables
    after the previous valid SUBSCAN command.
    Each time a SUBSCAN is accepted without error message, a subscan is
    added to the list; even if the command is only "SUBSCAN" by itself!
    Be careful that a parameter in the command line can refer to different
    variables depending on the type of the segment/subscan, e.g., the 1st
    parameter can refer to xOffset, xStart, or xAmplitude.
    These features should be used with special care, e.g., to experiment
    with the DIYLIST and SUBSCAN commands.
    It is recommended to collect all SUBSCAN commands in a paKo script and
    explicitly specify all parameters for each subscan!

    Before START of a DIY subscanlist, you can enter DIYLIST to review
    pako's I-DIY messages listing the subscan currently defined (this
    requires SET LEVEL 2 or lower), e.g.:
    PAKO> set level 2
    PAKO> diy
    I-DIY,  segments #: 1 to 3
    I-DIY,  1 track on at -400.0 -300.0 arcsec projection 10.0 s
    I-DIY,  2 onTheFly -300.0 -200.0 to 330.0 220.0 arcsec projection 66.0 s
    I-DIY,  3 track on at 440.0 330.0 arcsec projection 10.0 s


    IMPORTANT: LISSAJOUS OTF

    During a Lissajous OTF segment, the position offsets
    x and y as a function of time t are:

    x = xCenter + xAmplitude * SIN(2 Pi frequencyX t + phiX)
    y = yCenter + yAmplitude * SIN(2 Pi frequencyY t + phiY)

    SIN is the usual sine function, Pi is the number Pi.

    xAmplitude yAmplitude xCenter yCenter are in angle units ([arc sec])
    frequencyX frequencyY                 are in [Hz]
    phiX       phiY                       are in [rad]

    Note that the possible frequencies are very low,
    typically 0.01 to 0.15 Hz.

    At the start of a Lissajous subscan, paKo will insert a "ramp" along a
    straight line, i.e., a linear OTF segment, increasing the count of
    segments by 2.  This ramp up starts with speed 0 relative to the
    source and joins smoothly with the start position and velocity of the
    Lissajous segment.  The purpose is to avoid a sudden aceleration at
    the start of the Lissajous segment.  Command DIY lists this inserted
    OTF segment as well as the Lisssajous segment.  The inserted ramp up
    segment and the Lissajous segment become part of the same subscan.

    Lissajous curves with large amplitudes or frequencies can reach the
    antenna's speed and acceleration limits for tracking.  Lissajous
    curves can be executed only for elevations less than a maximum, which
    depends on the Lissajous parameters.  For information, this elevation
    condition is shown by pako. Even below the limits, during very fast
    Lissajous curves the tracking errors will be higher, several arc sec,
    than during most other observations.

    DO NOT TRY TO OBSERVE LISSAJOUS ABOVE THIS MAXIMUM ELEVATION.


Subsections

Gildas manager 2023-06-01