ft2Util_2 testing

Here I collect the results of the testing I am performing, comparing the output generated by the old ft2Util code (written by Andrea Tramacere) with the output generated by my code (ft2Util_2).

Fake FT2

Testing procedure

I collected a bunch of Magic 7 files spanning ~55 days of in-orbit operation. These M7 files are the one produced by L1, in their latest versions. Thus, they should be complete (without gaps). This is, in other words, the "ideal" situation.

Then I run the executables to produce the fake FT2 files (i.e., without LIVETIME), and I compared the results. Specifically, for every quantity q (like LAT_GEO, LON_GEO, RA_SCX, DEC_SCX...) I computed (q_old-q_new)/q_old , that is, the "fractional difference". These are the two command lines I used:

• Old version: 

  makeFT2Entries.exe -M7File $magic7 \
                      -FT2_fits_File ${filenameroot}_andrea.fits \
                      --Gleam --test-quaternion \
                      -DigiTstart $start -DigiTstop $stop \
                      -new_tpl /afs/slac.stanford.edu/g/glast/ground/releases/volume02/ScienceToolsv9r18p5/fitsGen/v6r1p1/data/ft2.tpl 

• New version: 

  makeFT2.exe -m7file $magic7 \
              -ft2file ${filenameroot}_io.fits \
              -ft2start $start \
              -ft2stop $stop

The following plots show the results (mind the scales on the y axes, usually the differences are very small!):

As you can see, there are differences, but they are very small. There is only one case (QSJ_3) where the differences could be not negligible (~ 2%). QSJ_2 is the Y component of the vectorial part of the attitude quaternion. Usually the attitude quaternion is taken directly from the ATT message in the Magic 7 file. Those messages are issued by the spacecraft 5 times per second. Anyway, there are cases when there is no ATT message corresponding to a particular time interval, thus the codes have to interpolate (or extrapolate). This usually can happen at the very beginning of a run, or because of gaps in the Magic 7 file. The differences between the two codes arises mainly from two different strategies adopted for the interpolation/extrapolation: the old code uses only those ATT messages arriving in sync with an ORB message (that is, one time per second), discarding the others; the new code, instead, uses all the available ATT messages. Thus, the new code should provide better interpolation/extrapolation.