From schuehle@linmpi.mpg.de Tue Nov 18 16:45:49 2003
Date: Thu, 1 Jul 1999 16:13:00 +0200
From: schuehle@linmpi.mpg.de
Reply-To: sumer-soft@esa.nascom.nasa.gov
To: sumer-soft@esa.nascom.nasa.gov
Subject: SUMER-SOFT: Radiometric conservation of SUM_flatfield routine

A type conversion error has been found in the SUM_FLATFIELD.pro and
SUM_FFIELD.pro routines which persisted allthough it was thought to be
eliminated long before.
This error leads to rounding errors when the input variable is not a
float array. The rounding may lead to wrong counts depending on the
value of the pixel counts. Obviously, the error is small when the counts
are high. 
With some sample checks of single images I found discrepancies between
input total counts and output total counts ranging between 6% and 12%,
the output counts being too low. In images with low counts the error may
be much larger.
All image data that have been treated with the flat-field routines on
ground and were not converted to float arrays before, are in principle
effected.

The two routines will be corrected today.


Note that the data of Intercal_1 and the instrument radiometric
calibration data were not effected by this error.


Udo Schuehle, 1. July 1999