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XMM-Newton Science Analysis System Page: 1
chipcube
July 2, 2008
Abstract
chipcube is a library of routines for dealing with FITS storage of chip-coordinate
images.
1 Description
This library denes the chip cube, which is a way of storing CCD images in FITS les; the library also
provides some routines for manipulating these les. A CCD image in the XMM-Newton context is a
2-dimensional image which has the same dimensions as a CCD of one of the EPIC x-ray cameras, and
which usually records some quantity explicitly or implicitly related to the x-ray ux detected by the
CCD. Because all the CCDs from any given EPIC camera have the same dimensions, their images can
be stored as slices of a cube (3-dimensional array). This compact and convenient representation is the
format used by the present library. The chip cube is stored in the primary data array of the FITS le.
When I wrote this library, I chose the 1st index (of both the fortran and FITS array representations)
to be the CCD index, and the 2nd and 3rd as the CCD x and y coordinates respectively. Now it seems
obvious to me that a representation in which the CCD index was the 3rd index would be far more natural.
Since it seems unlikely that the present library will ever be widely used I feel reasonably sanguine about
changing this order at some future date.
For most quantities measured on EPIC CCDs, an association with a set of Good Time Intervals (GTIs)
is important. In the original x-ray event list created as part of the XMM product set, a separate series
of GTIs is provided per CCD. Thus in the FITS format for storing chip cubes, an series of binary table
extensions for storing GTIs, one per CCD, is an option.
Finally, for maximum generality, a key table is prescribed for the FITS le, for the purpose of relating
the CCD number to the relevant plane of the chip cube and also to the GTI extension name which should
apply to that CCD. This key table is a mandatory binary table extension with the name KEY2IMGS. The
table should have as many rows as there are CCD planes in the chip cube, and must have the following
columns:
1. CCDNR (8-bit integer)
2. NODE NR (8-bit integer)
3. GTI NAME (8-character string). If this is blank or empty, it is assumed that no GTI table is
attached for that CCD.
I may some time in the future add the following:
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1. a string-valued column SUBMODE to specify the data mode of the CCD.
2. WINDOWX0, WINDOWY0, WINDOWDX and WINDOWDY columns to delineate data windows on the
CCD.
There is a corresponding F90 data type dened:
type, public :: keyInfoType
integer(int8) :: ccdNum=0, nodeNum=0
character(8) :: gtiTableName=''
end type keyInfoType
Row i of the table refers to plane array(i,:,:) (assuming both series start at 0).
The dataset header should contain INSTRUME and DATE-OBS keywords.
2 Library routines
2.1 readCubeData
Reads the chip cube, key-table and GTI data from a FITS table obeying the chip cube format. Note that
the type gtiVecType is dened in ssclib, module intervals aux. It is just a 1-d array of pointers, each
of which is itself a 1-d array of intervals. If there are no GTIs for a given CCD, that intervals pointer is
dimensioned to size 0. None of the pointers are left unassociated.
subroutine readCubeDataSingle(cubeSetName, cube, keyInfo, gtiVec)
character(*), intent(in) :: cubeSetName
real(single), pointer :: cube(:,:,:)
type(keyInfoType), pointer :: keyInfo(:)
type(gtiVecType), optional, pointer :: gtiVec(:)
end subroutine
subroutine readCubeDataLogical(cubeSetName, cube, keyInfo, gtiVec)
character(*), intent(in) :: cubeSetName
logical, pointer :: cube(:,:,:)
type(keyInfoType), pointer :: keyInfo(:)
type(gtiVecType), optional, pointer :: gtiVec(:)
end subroutine
I'll overload this to more data types as I get time.
2.2 writeCubeData
All header keywords in the refSet are copied over to the new cubeSet.
subroutine writeCubeDataSingle(cubeSetName, refSetName, cube, keyInfo, gtiVec)
character(*), intent(in) :: cubeSetName, refSetName
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real(single), intent(in) :: cube(:,:,:)
type(keyInfoType), intent(in) :: keyInfo(size(cube, 1))
type(gtiVecType), intent(in), optional :: gtiVec(size(cube, 1))
end subroutine
subroutine writeCubeDataLogical(cubeSetName, refSetName, cube, keyInfo)
character(*), intent(in) :: cubeSetName, refSetName
logical, intent(in) :: cube(:,:,:)
type(keyInfoType), intent(in) :: keyInfo(size(cube, 1))
end subroutine
This second routine does not yet accept GTIs - it can be clearly seen that the library is relatively
immature.
2.3 readGtisFromCube
subroutine readGtisFromCube(chipCubeSetName, gtiVec)
character(*), intent(in) :: chipCubeSetName
type(gtiVecType), pointer :: gtiVec(:)
end subroutine
2.4 writeGtisToCube
subroutine writeGtisToCube(chipCubeSetName, gtiVec)
character(*), intent(in) :: chipCubeSetName
type(gtiVecType), intent(in) :: gtiVec(:)
end subroutine
2.5 readKeyTable
subroutine readKeyTable(set, keyInfo)
type(DataSetT), intent(in) :: set
type(keyInfoType), pointer :: keyInfo(:)
end subroutine
2.6 numberOfImagesInCube
integer function numberOfImagesInCube(chipCubeSetName)
character(*), intent(in) :: chipCubeSetName
end function
References
xmmsas 20080701 1801-8.0.0