ANGROT = _REAL (Read)
The anti-clockwise
angle from the first (X) pixel axis of each image to the polarimeter reference direction,
in degrees. The supplied value is not stored explicitly within the POLPACK extension.
Instead, it is used to create a new Frame within the WCS component of the NDF. This
Frame is given the Domain name POLANAL and its first axis corresponds to the reference
direction. If a null (!) value is supplied for this parameter, any image which already has a
POLANAL Frame retains the existing Frame. Otherwise a POLANAL Frame is created using an
ANGROT value of zero (
i.e. it is assumed that the reference direction corresponds to the X pixel
axis).
The reference direction depends on the type of polarimeter; in a rotating half-wave plate polarimeter,
it should correspond to the direction of the fixed analyser; in polarimeters with multiple fixed
analysers or a single rotating analyser, it should correspond to the direction specified by a zero value
of ANLANG. [!]
ANLANG = _REAL (Read)
Specifies the anti-clockwise angle in degrees from
the reference direction (established using the ANGROT parameter) to the analyser. This
parameter should only be used with polarimeters which have either a rotating analyser or a set
of fixed analysers. If your polarimetry has a rotating half-wave plate instead, then you
should use WPLATE instead. The given value is stored in all supplied data files. If a null (!)
value is supplied, any image which already has an ANLANG value retains its existing
value, and any other images are left with an undefined ANLANG value. [!]
EPS = _REAL
(Read)
The analyser efficiency. This gives the efficiency with which the analyser rejects light
polarised across its axis. A perfect polariser has a value of 1.0. A perfect piece of glass would
have a value of 0.0. The stored value is used only when processing single-beam data. The
given value is stored in all supplied data files. If a null (!) value is supplied, any image
which already has an EPS value retains its existing value, and any other images are left
with an undefined EPS value (this will cause a value of 1.0 to be used by
POLCAL). [!]
FILTER = LITERAL (Read)
The filter name. The value of extension item WPLATE or
ANLANG (whichever is available) is appended to the supplied filter value before being stored,
unless the filter value already contains the WPLATE or ANLANG value. If a null (!) value is
supplied, then any existing FILTER value in the POLPACK extension is retained. If there is
no value in the POLPACK extension, then any value in the CCDPACK extension is used
instead. If there is no value in the CCDPACK extension, then a default value equal to the
value of WPLATE or ANLANG is used. [!]
IMGID = LITERAL (Read)
A group of image
identifier strings. These are arbitrary strings used to identify each original intensity frame.
They are used when processing dual-beam data to associate O and E ray images. They
are ignored when processing single-beam data. The supplied group may take the form
of a comma separated list of identifiers, or any of the other forms described in the help
on "Group Expressions". A separate, non-blank identifier should be supplied for each
data file specified by parameter IN, in the same order as the data files. If a null (!) value is
supplied, then any existing IMGID values in the POLPACK extensions are retained. Default
values equal to the name of the data file are used if there is no existing value. [!]
IN =
LITERAL (Read)
A group of data files. This may take the form of a comma separated list of
file names, or any of the other forms described in the help on "Group Expressions".
NAMELIST = LITERAL (Read)
The name of a file to create containing a list of the successfully
processed data files. This file can be used when specifying the input data files for subsequent
applications. No file is created if a null (!) value is given. [!]
QUIET = _LOGICAL (Read)
If
FALSE, then the contents of the POLPACK extension in each data file are listed before
being modified. Otherwise, nothing is written to the screen. [FALSE]
RAY = LITERAL
(Read)
You should use this parameter only if the images contain either O or E ray images
obtained by a dual-beam polarimeter. You should not use this parameter if your data is from a
single-beam polarimeter, or if the O and E ray images have not yet been extracted into separate
images. If used, the supplied value must be either "O" or "E". The same value is stored
in all supplied data files. If a null (!) value is supplied, any existing RAY values are left
unchanged, but no new ones are added. [!]
STOKES = LITERAL (Read)
You should use this
parameter only if the supplied data files are 3D cubes containing Stokes vectors. It should be a
string in which each character indicates the quantity stored in the corresponding plane of
the cube (I, Q, U or V). The length of the string should equal the number of planes in the
cube. If a null (!) value is supplied, any existing STOKES values are left unchanged, but no
new ones are added. [!]
T = _REAL (Read)
The analyser transmission. This gives the
transparency of the analyser to unpolarised light. A perfect polariser has a value of 1.0.
A perfect piece of glass would have a value of 2.0. The stored value is only used when
processing single-beam data. The given value is stored in all supplied data files. If a null
(!) value is supplied, any image which already has a T value retains its existing value,
and any other images are left with an undefined T value (this will cause a value of 1.0 to
be used by
POLCAL). [!]
VANGROT = _REAL (Write)
The ANGROT value stored in
the last data file on exit will be written to this output parameter.
VANLANG = _REAL
(Write)
The ANLANG value stored in the last data file on exit will be written to this output
parameter.
VEPS = _REAL (Write)
The EPS value stored in the last data file on exit will be
written to this output parameter.
VFILTER = LITERAL (Write)
The FILTER value stored in
the last data file on exit will be written to this output parameter.
VIMGID = LITERAL
(Write)
The IMGID value stored in the last data file on exit will be written to this output
parameter.
VRAY = LITERAL (Write)
The RAY value stored in the last data file on exit
will be written to this output parameter.
VSTOKES = LITERAL (Write)
The STOKES
value stored in the last data file on exit will be written to this output parameter.
VT =
_REAL (Write)
The T value stored in the last data file on exit will be written to this output
parameter.
VWPLATE = _REAL (Write)
The WPLATE value stored in the last data file
on exit will be written to this output parameter.
VVERSION = LITERAL (Write)
The
POLPACK version number which created the last data file will be written to this output
parameter.
WPLATE = _REAL (Read)
The half-wave plate position, in degrees. Use
parameter ANLANG if your polarimeter does not have a half-wave plate. The given value is
stored in all supplied data files. If a null (!) value is supplied, any image which already
has an WPLATE value retains its existing value, and any other images are left with an
undefined WPLATE value. Note, when using dual-beam data, Stokes vectors can only be
calculated for WPLATE values of 0.0, 22.5, 45.0 and 67.5. The
POLCAL application will fail if
any other values are supplied. There are no such restrictions on the value of WPLATE
when using single-beam data. [!]