calc_xysize,xpsize,ypsize,xsize,ysize ,nxchar=nxchar,nychar=nychar

            calculates xsize and ysize (in pixels or cm depending on device)
            to get correct aspect ratio given constant pixel size in x and y
            xpsize   xsize for data area only
            ypsize   ysize for data area only
            xsize    xsize including annotation areas
            ysize    ysize including annotation areas
            nxchar   number of characters in x, default total(xmargin)
            nychar   number of characters in y, default total(ymargin)

 NAME:
       CCSDS_HDR__DEFINE

 PURPOSE:
       CCSDS_HDR__DEFINE defines the class structure 'ccsds_hdr'. 
       An object of class 'ccsds_hdr' contains the parameters of 
       the 10 byte CCDSDS header, that comes with all SOLAR B data 
       packets (sent from the MDP to the ground). 

 CATEGORY:
       Hansteen/Wikstol Data analysis SW

 CALLING SEQUENCE:
       The CCSDS_HDR__DEFINE procedure is not called directly. An
       object of class CCSDS_HDR is created with the following
       statement: 
                   ccsds_hdr = obj_new('ccsds_hdr')
       To fill the object with information use the following statement:
                     ccsds_hdr-> read, lu

 INPUTS:

 KEYWORD PARAMETERS:

 OUTPUTS:
       Objects of type CCSDS_HDR

 CALLS: ***
	CCSDS_HDR::GETCCSDS_PKT_LEN, CCSDS_HDR::GETCCSDS_SEQ_COUNT
	CCSDS_HDR::GETCCSDS_SEQ_FLAG, CCSDS_HDR::GETCCSDS_TIME
	CCSDS_HDR::GETCCSDS_VER_NO, CCSDS_HDR::GET_APID
 CALLED BY:
	EIS_DATA__READ [1], EIS_DATA__READ [3], EIS_DATA__READCCSDS [1]
	EIS_DATA__READCCSDS [2]
 COMMON BLOCKS:
       

 PROCEDURE:
       The procedure opens an object of class CCSDS_HDR. The CCSDS_HDR
       class inherits the superclass HW_HDR, that defines the general
       structure of header classes used by the HW data analysis SW. 
       This procedure also includes various functions (methods of
       class  'ccsds_hdr') whose purpose is to get the different
       fields of the header. For example, if you want to know the
       version number:
               print, ccsds_hdr-> getccsds_ver_no()


 RESTRICTIONS:


 MODIFICATION HISTORY:
       21-Mar-2001: Oivind Wikstol.
       26-Sep-2001: Oivind Wikstol. Added documentation.

 NAME:
       CCSDS_HDR__READ

 PURPOSE:
       CCDSD_HDR__READ reads ccsds headers from SOLAR-B packet data
       and stores header info in the instance
       data of objects of class 'ccsds_hdr'


 CATEGORY:
       Hansteen/Wikstol Data analysis SW

 CALLING SEQUENCE:
       An object of class CCSDS_HDR is generated with this statement: 
                   ccsds_hdr = obj_new('ccsds_hdr')

       CCSDS_HDR__READ reads the CCSDS header, which is a part of all
       SOLAR B data packets. The ccsds header is read and stored in
       the object's instance data with this statement: 
                     ccsds_hdr-> read, lu  (logical unit of data file)

 INPUTS:
       lu:  Logical unit number of data file

 KEYWORD PARAMETERS:

 OUTPUTS:
       Reads CCSDS header data into the parameters of the CCSDS_HDR
       object.

 CALLS:
	MKU24LE, MKUINTLE, MKULONGLE
 CALLED BY:
	EIS_DATA__READ [1], EIS_DATA__READ [3], EIS_DATA__READCCSDS [1]
	EIS_DATA__READCCSDS [2]
 COMMON BLOCKS:
       

 PROCEDURE:
       The procedure reads CCSDS header data into the instance data
       of the CCSDS header object.
       The CCSDS header is 10 bytes long. It consists of the
       following parameters:
         Version number: (3 bit). Stored as IDL byte.
         Type: (1 bit). Stored as IDL byte
         Sequence header flag: (1 bit). Stored as IDL byte
         Apid: (11 bit). Stored as IDL unsigned integer.
         Sequence flag. (2 bit). Stored as IDL byte
         Sequence count: (14 bit). Stored as IDL unsigned integer
         Packet length: (16 bit). Stored as IDL unsigned integer
         Time: (32 bit). Stored as IDL unsigned long.
                
 RESTRICTIONS:


 MODIFICATION HISTORY:
       XX-Mar-2001: Oivind Wikstol.
       01-Oct-2001: Oivind Wikstol. Added documentation.
       03-Nov-2005: Oivind Wikstol - Added Swap keyword.