As you enter a Space sector, like Space/M01, only one small 3x3 field at the center of the map is visible. To detect the contents of another 3x3 field, select a field next to an already visible field and click "Detect". You start your exploration with 10 detection energy (Proper name ?) and you recover 1 energy every 5 minutes.
Each field is numbered from 1 to 81 counting left to right and top to bottom. So that the top left field is 1, the top right field is 9, the bottom left field is 73 and the bottom right field is 81.