Starlink-pyast

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- All FITS-CLASS headers are now created with a frequency axis. If the
FrameSet supplied to astWrite contains a velocity axis (or any other form
of spectral axis) it will be converted to an equivalent frequency axis
before being used to create the FITS-CLASS header.

- The value stored in the FITS-CLASS keyword "VELO-LSR" has been changed
from the velocity of the source to the velocity of the reference channel.

- Addition of a new method call astPurgeWCS (AST_PURGEWCS) to the FitsChan
class. This method removes all WCS-related header cards from a FitsChan.

- The astRebinSeq functions now have an extra parameter that is used to
record the total number of input data val;ues added into the output
array. This is necessary to correct a flaw in the calculation of output
variances based on the spread of input values. NOTE, THIS CHANGE WILL
REQUIRE EXISTING CODE THAT USES ASTREBINSEQ TO BE MODIFIED TO INCLUDE THE
NEW PARAMETER (CALLED "NUSED").
- The Plot class now honours the value of the LabelUp attribute even if
numerical labels are placed around the edge of the Plot. Previously
LabelUp was only used if the labels were drawn within the interior of
the plot. The LabelUp attribute controls whether numerical labels are
drawn horizontally or parallel to the axis they describe.
- The Plot class has a new attribute called GrfContext that can be used
to comminicate context information between an application and any
graphics functions registered with the Plot class via the astGrfSet
(AST_GRFSET) function.
- Functions registered with the Plot class using astGrfSet (AST_GRFSET)
now take a new additional integer parameter, "grfcon". The Plot class
sets this parameter to value of the Plot's GrfContext attribute before
calling the graphics function. NOTE, THIS CHANGE WILL REQUIRE EXISTING
CODE THAT USES astGrfSet (AST_GRFSET) TO BE MODIFIED TO INCLUDE THE
NEW PARAMETER.
- Support has been added for the FITS-WCS "HPX" projection (HEALPix).
- A new flag "AST__VARWGT" can be supplied to astRebinSeq. This causes
the input data values to be weighted using the reciprocals of the input
variances (if supplied).
- The Frame class has a new read-only attribute called NormUnit that
returns the normalised value of the Unit attribute for an axis. Here,
"normalisation" means cancelling redundant units, etc. So for instance, a
Unit value of "s*(m/s)" would result in a NormUnit value of "m".
- A new method astShowMesh has been added to the Region class. It
displays a mesh of points covering the surface of a Region by writing out
a table of axis values to standard output.
- A bug has been fixed that could segmentation violations when setting
attribute values.

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- The astFindFrame (AST_FINDFRAME) method can now be used to search a
CmpFrame for an instance of a more specialised class of Frame (SkyFrame,
TimeFrame, SpecFrame, DSBSpecFrame or FluxFrame). That is, if an instance
of one of these classes is used as the "template" when calling
astFindFrame, and the "target" being searched is a CmpFrame (or a
FrameSet in which the current Frame is a CmpFrame), then the component
Frames within the CmpFrame will be searched for an instance of the
supplied template Frame, and, if found, a suitable Mapping (which will
include a PermMap to select the required axes from the CmpFrame) will be
returned by astFindFrame. Note, for this to work, the MaxAxes and MinAxes
attributes of the template Frame must be set so that they cover a range
that includes the number of axes in the target CmpFrame.

- The DSBSpecFrame class has a new attribute called AlignSB that
specifies whether or not to take account of the SideBand attributes when
aligning two DSBSpecFrames using astConvert (AST_CONVERT).

- The Frame class has a new attribute called Dut1 that can be used to
store a value for the difference between the UT1 and UTC timescales at
the epoch referred to by the Frame.

- The number of digits used to format the Frame attributes ObsLat and
ObsLon has been increased.

- The use of the SkyFrame attribute AlignOffset has been changed. This
attribute is used to control how two SkyFrames are aligned by astConvert.
If the template and target SkyFrames both have a non-zero value for
AlignOffset, then alignment occurs within the offset coordinate systems
(that is, a UnitMap will always be used to align the two SkyFrames).

- The Plot class has a new attribute called ForceExterior that can be
used to force exterior (rather than interior) tick marks to be produced,
even if this would result in less than 3 tick marks being produced.

- The TimeFrame class now supports conversion between angle based
timescales such as UT1 and atomic based timescales such as UTC.

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- The SpecFrame class has a new attribute called SourceSys that specified
whether the SourceVel attribute (which specifies the rest frame of the
source) should be accessed as an apparent radial velocity or a redshift.
Note, any existing software that assumes that SourceVel always represents
a velocity in km/s should be changed to allow for the possibility of
SourceVel representing a redshift value.

- The astGetFitsS (AST_GETFITSS) function now strips trailing white space
from the returned string, if the original string contains 8 or fewer
characters.

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- The SideBand attribute of the DSBSpecFrame class can now take the
option "LO" in addition to "USB" and "LSB". The new option causes the
DSBSpecFrame to represent the offset from the local oscillator frequency,
rather than either of the two sidebands.

- The FitsChan class has been changed so that it writes out a VELOSYS
keyword when creating a FITS-WCS encoding (VELOSYS indicates the
topocentric apparent velocity of the standard of rest). FitsChan also
strips out VELOSYS keywords when reading a FrameSet from a FITS-WCS
encoding.

- The FitsChan class has a new method called astRetainFits (AST_RETAINFITS)
that indicates that the current card in the FitsChan should not be
stripped out of the FitsChan when an AST Object is read from the FitsChan.
Unless this method is used, all cards that were involved in the creation
of the AST Object will be stripped from the FitsChan afte a read operation.

- The ast_link_adam and ast_link scripts now ignore the -fsla and -csla
options, and always link against the minimal cut-down version of SLALIB
distributed as part of AST.

- A problem with unaligned memory access that could cause bus errors on
Solaris has been fixed.

- A new function called astTune (or AST_TUNE) has been added which can be
used to get and set global AST tuning parameters. At the moment there are
only two such parameter, both of which are concerned with memory management
within AST.

- A new method called astTranGrid (AST_TRANGRID in Fortran) has been
added to the Mapping class. This method creates a regular grid of points
covering a rectangular region within the input space of a Mapping, and
then transforms this set of points into the output space of the Mapping,
using a piecewise-continuous linear approximation to the Mapping if
appropriate in order to achive higher speed.

- A new subclass of Mapping has been added called SwitchMap. A
SwitchMap represents several alternate Mappings, each of which is used to
transforms input positions within a different region of the input
coordinate space.

- A new subclass of Mapping has been added called SelectorMap. A
SelectorMap tests each input position to see if it falls within one of
several Regions. If it does, the index of the Region containing the
input position is returned as the Mapping output.

- The behaviour of the astConvert (AST_CONVERT) method when trying to
align a CmpFrame with another Frame has been modified. If no conversion
between positions in the Frame and CmpFrame can be found, an attempt is
now made to find a conversion between the Frame and one of two component
Frames contained within the CmpFrame. Thus is should now be possible to
align a SkyFrame with a CmpFrame containing a SkyFrame and a SpecFrame
(for instance). The returned Mapping produces bad values for the extra
axes (i.e. for the SpecFrame axis in the above example).

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- A new control flag has been added to the AST_RESAMPLE<X>/astResample<X>
functions which produces approximate flux conservation.

- The SkyFrame class now supports a System value of "AZEL" corresponding
to horizon (azimuth/elevation) coordinates.

- The FitsChan class allows the non-standard strings "AZ--" and "EL--" to
be used as axis types in FITS-WCS CTYPE keyword values.

- The Frame class now has attributes ObsLon and ObsLat to specify
the geodetic longitude and latitude of the observer.

- The ClockLon and ClockLat attributes have been removed from the
TimeFrame class. Likewise, the GeoLon and GeoLat attributes have been
removed from the SpecFrame class. Both classes now use the ObsLon and
ObsLat attributes of the parent Frame class instead. However, the old
attribute names can be used as synonyms for ObsLat and ObsLon. Also,
dumps created using the old scheme can be read succesfully by AST V4.1
and converted to the new form.

- A new function astMapSplit has been added to the Mapping class. This
splits a Mapping into two component Mappings which, when combined in
parallel, are equivalent to the original Mapping.

- The default value for the SkyRefIs attribute has been changed from
"Origin" to "Ignored". This means that if you want to use a SkyFrame
to represent offsets from some origin position, you must now set the
SkyRefIs attribute explicitly to either "Pole" or "Origin", in addition
to assigning the required origin position to the SkyRef attribute.

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- Experimental support for reading IVOA Space-Time-Coordinates (STC)
descriptions using the XmlChan class has been added. Support is included
for a subset of V1.20 of the draft STC specification.

- A new set of methods (AST_REBIN<X>/astRebin<X>) has been added to
the Mapping class. These are accurately flux-conserving alternatives to the
existing AST_RESAMPLE<X>/astResample<X> methods.