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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