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Bin start and stop

START, STOP

There

are tiny differences, much smaller than the size of the bin immediately on the left of zero (they are of the order of 1E-9), nothing to worry about No differences. Actually, there will be differences, because of a different strategy of handling gaps between the new and the old code described in the "mother page". But for this comparison I have chosen only bins in common between the version from the reprocessing and the archived version.

Spacecraft position in ECI coordiantes (x,y,z)

SC_POSITION array

The differences in a very small number of bins are most probably due to Reason 1 above.

Ground point latitude and longitude

LAT_GEO, LON_GEO

Reason 1.

Spacecraft altitude

RAD_GEO

Reason 1.

Zenith direction

RA_ZENITH, DEC_ZENITH

McIlwain coordinates

L_MCILWAIN, B_MCILWAIN

Geomagnetic latitude

GEOMAG_LAT

16 percent of the time bins are in the underflow bin of the histogram. This is due to a known issue: on Feb. 2, 2010 we changed the quantity from unsigned to signed. Thus, all old FT2 files produced before that date have a always-positive GEOMAG_LAT, while the reprocessed ones have it signed from the beginning of the mission.

South Atlantic Anomaly flag

IN_SAA

Z-axis direction

RA_SCZ, DEC_SCZ

Reason 1.

X-axis direction

RA_SCX, DEC_SCX

Reason 1.

Orbital Pole direction

RA_NPOLE, DEC_NPOLE

Here there are considerable differences, because the new code compute the coordinates of the Orbital Pole in a different way respect to the old one. If v_i is the position vector for the i-th bin in the FT2 file, the old code computed the orbital pole vector for the i-th bin as the cross product between v_i-1 and v_i, while the new code uses the product v_i cross v_i+1. See next section for more information.

Rocking angle

ROCK_ANGLE

Reason 1.

LAT GNC mode

LAT_MODE

LAT Configuration

LAT_CONFIG

Data quality flag

DATA_QUAL

Need to check why there are these differences in a couple of runs. I suspect those are BAD runs, or runs with the new values for the DQM flag.

Attitude quaternion

QSJ_1,QSJ_2,QSJ_3,QSJ_4

Reason 1.

Live time

LIVETIME

Image Added

Differences are due to the bug already found in the old FT2 code. See below.