Relevant Pipelines: APEX Multiframe; APEX User List Multiframe
Important Notes: Running this module will overwrite any pre-existing FIF.tbl file in the output directory. If you are working with MIPS images and plan to use the Mosaic PRFs then please see the Discussion below for important information.
If you are using the mosaic.fits file from a pre-pended Mosaic pipeline as input into APEX then you should omit this module.
PURPOSE
This module creates a unified grid coordinate system and defines the spatial boundaries that will include all BCD images. The output FIF table is required for later modules to run. It can be generated by this module, or set as an input using a pre-existing table. If you have appended your APEX pipeline to a Mosaic pipeline then you can omit this module; APEX will automatically use the Mosaic FIF table.
INPUT
Edge Padding: (int) This number specifies how much extra space (arcseconds) will be added to the four edges of the final mosaicked image.
Projection: This parameter specifies the projection type of the output mosaic. The TAN and SIN projections are implemented using the fast direct plane-to-plane coordinate transformation. The rest of the projections in the WCS library - LIN, AZP, STG, ARC, ZPN, ZEA, AIR, CYP, CAR, MER, CEA, COP, COD, COE, COO, BON, PCO, GLS, PAR, AIT, MOL, CSC, QSC, TSC, NCP, DSS, PLT, TNX - are implemented as a two step plane-sky-plane projection. The default projection is TAN.
Coordinate System: The coordinate system of the output mosaic. The choices are J2000 (Equatorial), Galactic, or Ecliptic. The default is J2000.
Use average input orientation: Defines the orientation of the output mosaic. Checking this box indicates that MOPEX should use the average of the input BCD orientations. This is the default setting. To specify an alternative orientation, see CROTA2.
CROTA2: (float) Defines the orientation (degrees East of North) of the output mosaic. CROTA2 = 0 indicates North up and East left. To use the average of the input BCD orientations (the default), check the Use average input orientation box.
COMMAND LINE INPUT
&FIDUCIALIMAGEFRAMEIN
Edge_Padding = 10,
Projection_Type = "TAN",
Coordinate_System = "J2000",
CROTA2 = A,
&END
In Global Parameters:
MARGIN = 0
MARGIN: (int; command line only) Specifies a margin in terms of the number of pixels around the Fiducial Image Frame. Normally this is set to zero or a (small) positive number, except when running the Mosaic flow, with the Mosaic Geometry module, when it should normally be set to a negative number to avoid including input images that have only marginal overlap with the FIF.
OUTPUT
Generated Headers List Table (header_list.tbl): This file lists the World Coordinate Systems (WCS) information from each of the BCD image headers. The information is used to make the Fiducial Image Frame table.
Generated FIF Table (FIF.tbl): This text file is used by later modules to specify the pixel size, orientation and final image size of the mosaic. The module overwrites any input FIF table specified in the Initial Setup. Note that the output mosaic will always use the set of keywords CDELT1, CDELT2 and CROTA2, even if the input images use the CD matrix convention.
The outputs of this module are written to the top output directory specified in the Initial Setup.
DISCUSSION
This module creates a table specifying a unified coordinate system and the spatial boundaries of the output mosaic. This table is required for any interpolation or mosaicking using MOPEX. If this module is not included, an existing FIF table has to be specified in the Initial Settings to enable later modules to run. Alternatively, this module can be omitted if the APEX pipeline is appended to a Mosaic pipeline; APEX will automatically pick up the Mosaic FIF table. After this module is run once, the output FIF table can be modified manually if desired, and used as input to subsequent runs (this is useful for e.g. mosaicking small sections of a large dataset - see §5.3 for more details).
Even if the input images use the CD matrix convention, the output mosaic images (and by extension the interpolated images) will use the set of keywords CDELT1, CDELT2 and CROTA2, since the mosaic image is undistorted.
If you plan to use the MIPS "mosaic" PRFs that are provided for PRF fitting on your mosaic, your mosaic must be built in the same way as the ones used to derive those PRFs, that is, from BCDs that have nearly the same orientation (close in time or taken at the same time of year) and with a CROTA2 angle that is properly aligned with the BCDs (Use average input orientation is recommended). All other cases would require you to make your own PRF from your mosaic.
