The polar diagram shows the spacecraft corrected geomagnetic
co-ordinates: co-latitude - local time.
The geomagnetic co-latitude in the range (10°, 50°) is
shown with 10° step.
The geomagnetic local time meridians correspond to 6, 12 and 18 hours.
The different colours are used for each of the 4 spacecraft.
On the plot the SC names are shown by the corresponding colours.