H6564_0001_BL2.IMG

H - instrument HRSC

6564 - orbit name with first position as thousands

1-9, a=10, b=11, c=12, ...
last 3 positions are taken together as number to be added

e.g.

orbit name: 6564 -> orbit number: 6564,
orbit name: F234 -> orbit number: 15234,

0001 - number of the image in the orbit

BL - filter (and CCD line), with

ND - nadir
P1 - photometry 1
P2 - photometry 2
S1 - stereo 1
S2 - stereo 2
BL - blue
GR - green
RE - red
IR - infrared

2 - processing level