Produce simulated time series data from a SCUBA-2 map UNMAKEMAP
The output time series bolometer samples are created by interpolating the supplied input sky image at the position of the reference time series sample centre. Various interpolation methods can be used (see parameter INTERP). Gaussian noise and pointing errors may also be added (see parameters SIGMA and PERROR).
The output time series cubes inherit all meta-data from the corresponding input reference time series.
The only thing modified is the values in the NDF "
Data"
array.
"
QIN"
and "
UIN"
). This parameter is only used if HARMONIC is set
to its default value of 4 (a value of zero is assumed otherwise). It gives the amplitude of
the 2 Hz signal as a fraction of the total intensity. See also "
PHASE2"
. [0.0] "
QIN"
and "
UIN"
). This parameter is only used if
HARMONIC is set to its default value of 4 (a value of zero is assumed otherwise). It gives
the amplitude of the 4 Hz signal as a fraction of the total intensity. See also "
PHASE4"
. [0.0] "
QIN"
and "
UIN"
). This
parameter is only used if HARMONIC is set to its default value of 4 (a value of zero is
assumed otherwise). It gives the amplitude of the 16 Hz signal as a fraction of the total
intensity. See also "
PHASE16"
. [0.0] "
COM"
is set to null
(!). If two values are supplied, the first is taken to be the emission from the sky and the
second is taken to be an offset caused by the electronics. The total common-mode signal
is the sum of the two. If only one value is supplied, it is assumed that the second value
is zero (i.e. the entire common-mode is caused by sky signal). Note - when simulating
POL-2 data, Instrumental Polarisation is based on just the sky emission. Supplying zero
or null results in no common mode being included in the output time series data. [!] "
USER"
. The NDF should have
dimensions of (32,40). The total intensity falling on each bolometer is multiplied by the
corresponding value in this file, to get the instrumental Q value that is added onto the value read
from the QIN parameter. Bad values are treated as zero values. Note, currently there is no
facility to use different INSTQ values for different sub-arrays - all data supplied via IN
will use the same INSTQ values regardless of sub-array. To overcome this restriction, run
unmakemap separately for each sub-array supplying a different INSTQ each time. "
USER"
. The NDF should have dimensions of (32,40). The total intensity
falling on each bolometer is multiplied by the corresponding value in this file, to get the
instrumental U value that is added onto the value read from the UIN parameter. Bad values are
treated as zero values. Note, currently there is no facility to use different INSTU values for
different sub-arrays - all data supplied via IN will use the same INSTU values regardless of
sub-array. To overcome this restriction, run unmakemap separately for each sub-array
supplying a different INSTU each time. "
Linear"
– The output sample values are calculated by bi-linear interpolation among the four nearest
pixels values in the input sky cube. Produces smoother output NDFs than the nearest-neighbour
scheme, but is marginally slower.
"
Nearest"
– The output sample values are assigned the value of the single nearest input pixel. A very
fast method.
"
Sinc"
– Uses the sinc(pix)
kernel, where x is the pixel offset from the interpolation point and sinc(z)=sin(z)/z. Use of this scheme
is not recommended.
"
SincSinc"
– Uses the sinc(pix)sinc(kpix)
kernel. A valuable general-purpose scheme, intermediate in its visual effect on NDFs between the
bi-linear and nearest-neighbour schemes.
"
SincCos"
– Uses the sinc(pix)cos(kpix)
kernel. Gives similar results to the "
Sincsinc"
scheme.
"
SincGauss"
– Uses the sinc(pix)exp(-kxx)
kernel. Good results can be obtained by matching the FWHM of the envelope function to the
point-spread function of the input data (see parameter PARAMS).
"
Somb"
– Uses the somb(pix)
kernel, where x is the pixel offset from the interpolation point and
somb(z)=2J1(z)/z
(J1 is the first-order Bessel function of the first kind). This scheme is similar to the "
Sinc"
scheme.
"
SombCos"
– Uses the somb(pix)cos(kpix)
kernel. This scheme is similar to the "
SincCos"
scheme.
[current value]
"
JK"
: The Johnstone-Kennedy model based on analysis of skydip data.
"
PL1"
: A simpler model based on analysis of planetary data.
"
PL2"
: A simpler model based on analysis of planetary data.
"
PL3"
: A simpler model based on analysis of planetary data.
"
USER"
: IP is based on the values supplied for parameters INSTQ and INSTU.
"
NONE"
: No IP is added.
Note, if the PL1 or PL2 model is used, suitable values also need to be supplied for parameter PLDATA (the default values for PLDATA are appropriate for PL3).
Supplying a null value (!) value is equivalent to "
NONE"
. ["
PL3"
]
"
JK"
. [’
$STARLINK_DIR/share/smurf/ipdata.sdf’
] PARAMS( 1 ) is required by all the above schemes. It is used to specify how many pixels are to contribute to the interpolated result on either side of the interpolation point in each dimension. Typically, a value of 2 is appropriate and the minimum allowed value is 1 (i.e. one pixel on each side). A value of zero or fewer indicates that a suitable number of pixels should be calculated automatically. [0]
PARAMS( 2 ) is required only by the SombCos, SincSinc, SincCos, and SincGauss schemes. For the SombCos, SincSinc, and SincCos schemes, it specifies the number of pixels at which the envelope of the function goes to zero. The minimum value is 1.0, and the run-time default value is 2.0. For the SincGauss scheme, it specifies the full-width at half-maximum (FWHM) of the Gaussian envelope. The minimum value is 0.1, and the run-time default is 1.0. Good results are often obtained by approximately matching the FWHM of the envelope function, given by PARAMS(2), to the point-spread function of the input data. []
"
PL1"
, "
PL2"
or "
PL3"
. This should be a vector of three (PL1) or
four (PL2 and PL3) values, being the coefficients of a quadratic polynomial that gives the
fractional polarisation produced by instrumental polarisation, as a function of elevation (in
radians):
fractional IP = A Belev Celevelev
where the vector (A,B,C) are given by the first three elements of parameter PLDATA. The PL1 model assumes that the IP is parallel to the elevation axis at all elevations. The PL2 and PL3 require a fourth value to indicate the offset between the IP and the elevation axis.
The default values are appropriate for PL3. [2.624E-3,4.216E-2,-2.410E-2,-3.400E-2]
"
#"
in column one. These are comment lines, but if any comment line has the
form "
# SYSTEM=AZEL"
or "
# SYSTEM=TRACKING"
then it determines the system in which the
pointing correction are specified (SYSTEM defaults to AZEL). The last comment line should be a
space-separated list of column names, including "
TAI"
, "
DLON"
and "
DLAT"
. Each remaining line
should contain numerical values for each column, separated by white space. The TAI column
should contain the TAI time given as an MJD. The DLON and DLAT columns should give
arc-distance offsets parallel to the longitude and latitude axes, in arc-seconds. The TAI values
should be monotonic increasing with row number. The longitude and latitude axes are either
AXEL or TRACKING as determined by the SYSTEM value in the header comments. Blank
lines are ignored. The DLON and DLAT values are added onto the SMU jiggle positions
stored in the JCMTSTATE extension of the reference NDFs. DLON and DLAT values for
non-tabulated times are determined by interpolation. [!]