Instructions for ~rmaddale/bin/MappingCalculator.tclsh
Ronald J Maddalena
December 22, 2014
The script also has a web interface, though with fewer options and tailored just for the GBT.
MappingCalculator.tclsh -- Calculates the time needed to map an area based
on the integration time per beam area (e.g., the results from sensitivity
calculations, and the area to be mapped. Provides example ASTRID commands
as well as other mapping parameters. Supports the typical mapping commands
for OTF rectangular maps, OTF Daisy maps, and point rectangular maps. Does
not include the observing time or overhead if you use the Astrid observing
procedures of PointMapWithReference, RALongtMapWithReference, or
MappingCalculator.tclsh [-h | -help] [-freqGhz f] [-tPerBeam tsec]
[-xSizeDeg dx][-ySizeDeg dy] [-tMinSample tsec] [-fRowColPetal f]
[-fSample f] [-DishDiamMtr D] [-apEff a] [-slewMaxDegPerMin sr]
[-tOverheadPerRowCol tsec] [-tResolution tsec] [-useOmegaA]
Unlike the standard mapping calculator, which asks for integration time
per pixel, here one supplies the integration per beam area (i.e., the
results of any sensitivity calculation) without the need to calculate
pixels per beam area. In most cases, one need only supply values for
a few mandatory parameters to get reasonable results.
The algorithms makes sure that the calculated time per sample is an
integer multiple of the backends time resolution and has a value greater
than the backend's minimum sampling time. The calculated slew rate is kept
below the telescope's maximum. The time per row will always be an integer
multiple of the sample time. And, the number of rows or petals in the map
will be integer. The caculator always rounds up so that one will always
get at least the desired time per beam area.
Because of these restriction in possible sample and slew rates, the actual
time per beam area will be larger than that specified but that value will
always be as close as it possible to the user's input value. The user
should be aware that THERE ARE A LARGE NUMBER OF SITUATIONS WHEN THE
ACTUAL VALUE FOR TIME PER BEAM WILL BE MUCH LARGER THAN THE DESIRED VALUE.
In these cases, the only recourse is to find a backend that samples
faster or a telescope that slews faster.
Note: For mapType of OTFRect the calculator provides separate answers for
RALongMap and the DecLatMap as the overhead, row spacing, etc will be
different for the two styles of map.
-freqGhz f Observing frequency in GHz.
-tPerBeam Integration time per beam area, in seconds.
MANDATORY PARAMETERS DEPENDENT UPON -mapType
-xSizeDeg dx Map size in the RA/Long direction in degrees. Ignored
if -mapType is OTFDaisy.
-ySizeDeg dy Map size in the Dec/Lat direction in degrees. Ignored
if -mapType is OTFDaisy.
-mapRadiusDeg d Map radius in degrees. Only used if mapType is OTFDaisy.
The user can supply the following optional arguments:
-h or -help Brings up a help page. If specified, all other
options and operands are ignored
-mapType str The type of map. Either:
OTFRect -- on-the-fly rectangular area (default)
OTFDaisy -- on-the-fly daisy pattern, or
PointRect -- pointed map of a rectanguar region.
-DishDiamMtr D Dish diameter in meters. Default: 100.
-tMinSample t Backend's minimum sample time in seconds. Can be zero.
-tResolution t Backend's sampling time resolution in seconds. Can be
zero. Default: .1
-tOverheadPerRowCol t Overhead in move time between row/column in a map in
seconds. Default: 15, which is typical for a Point
or bidirectional OTF map. Unidirectional OTF maps
will havea higher overhead that is dependent upon the
map size. Ignored if mapType is OTFDaisy.
-slewMaxDegPerMin r Telescope's maximum slew rate in deg/min.
Default: 18. Ignored if mapType is PointRect
efficiency. If not supplied, the calculator will
use the theoretical value for a surface with an rms of 220
microns. Used in the antenna theorem to derive the area of
the telescope's beam when -useOmegaA is specified.
-fRowColPetal f For maptype of OTFRect, the amount of over sampling per row
(for RALongMap) or columns (for DecLatMap). For mapType of
PointRect the amount of over sampling per row and
per column. For mapType of OTFDaisy, the oversampling in
the pattern's petals. If > 1, you will be oversampling.
Default: 1 (i.e., critical sampling).
-fSample f The amount of over sampling in the direction of the OTF
slew. We usually recommend a value of 2, the default.
Ignored if mapType is PointRect.
-useOmegaA A flag, which is specified, tells the calulator to use
the beam solid angle (from the antenna theorem) instead of
the default of the main beam solid angle.
feed illumination taper in dB. Only used if -useOmegaA
is *not* specified. The default is 13 dB (the sign of
the input value is ignored). Accuracy will degrade if
> 40 dB.
The maximum number of accelerations per minute
above which a warning message will be generated. Warns
the user if they will be putting the telescope through
what would be considered excess fatique. Default = 2.
The calculator first displays all the user input values, followed by a table
of general results, then a table of results specific for the desired
mapType, and, finally, example ASTRID and Config Tool entries that would
execute the desired map.