4.2.2 CONV_P2A and CONV_A2P

When converting between pixel value and angle the following steps are taken.

1. Determine the pixel address for the center of the sun. SXT_CEN is used to derive this value. It will read the ATT database by default, but can use the commanded value if the /CMD option is used on the call to CONV_P2A.
2. Determine the roll. SXT_CEN returns this value too.
3. Perform the simple math to convert from absolute pixels to an angle relative to the sun center.

  
Figure: Corrections Performed by CONV_P2A

Some sample calls are:
IDL> ang = conv_p2a(pix, date)
 
IDL> ang = conv_p2a(pix, date, /cmd)

IDL> pix = conv_a2p(ang, date, /cmd)
  The date is required in order to determine the location of the sun on the CCD and the roll angle. The S/C roll angle and S/C pointing is taken into consideration, but the solar B-angle is not taken into account.