Space Raiders: Data at 27127

Alien row information. cx,cy of leftmost alien, then 704 bytes of alien graphic data. That's 11 UDGs, each being 2 bytes wide and 16 bytes high. That's 352 bytes, which is doubled because this actually stores the second set of UDG info for the row. i.e. when the aliens are looking right, and when the aliens are looking left. So this is 2 bytes, followed by 352 bytes, followed by another 352 bytes, which is 706 bytes in total for this structure. One for each row, so that's 3,530 bytes from here to 30856 inclusive.

Aliens are UDGs, 2 bytes per scan. They're 12 bits wide with a 4 bit gap on the right side, and 12 bits tall with a 4 bit gap at the bottom. Each graphic is 16x16 pixels, so 32 bytes per alien.
_RED_ALIEN_LOOK_LEFT	27127	DEFB 31,128,63,192,127,224,255,240,222,240,222,240,222,240,255,240
	27143	DEFB 63,128,48,192,96,96,192,48,0,0,0,0,0,0,0,0

_RED_ALIEN_LOOK_RIGHT	27159	DEFB 31,128,63,192,127,224,255,240,247,176,247,176,247,176,255,240
	27175	DEFB 31,128,25,128,25,128,25,128,0,0,0,0,0,0,0,0

_GREEN_ALIEN_LOOK_LEFT	27191	DEFB 192,48,192,48,255,240,134,16,231,144,134,16,255,240,47,64
	27207	DEFB 79,32,134,16,64,32,32,64,0,0,0,0,0,0,0,0

_GREEN_ALIEN_LOOK_RIGHT	27223	DEFB 192,48,192,48,255,240,134,16,158,112,134,16,255,240,47,64
	27239	DEFB 47,64,38,64,32,64,32,64,0,0,0,0,0,0,0,0

_YELLOW_ALIEN_LOOK_LEFT	27255	DEFB 48,192,48,192,9,0,15,0,31,128,63,192,127,224,176,208
	27271	DEFB 159,144,9,0,16,128,9,0,0,0,0,0,0,0,0,0

_YELLOW_ALIEN_LOOK_RIGHT	27287	DEFB 192,48,192,48,32,64,22,128,31,128,63,192,255,240,48,192
	27303	DEFB 31,128,9,0,16,128,32,64,0,0,0,0,0,0,0,0
_ALIEN_TYPE_TEMP	27319	DEFB 0,0
Yellow, green, green, red, red
_ALIEN_TYPES_PER_ROW	27321	DEFB 2,1,1,0,0
This is the screen row the aliens are drawn at. It's always _ALIENS_START_ROW plus 3. There's no obvious reason why it's held with the +3
_ALIEN_UDGS_START	27326	DEFB 0
Alien row information. cx,cy of leftmost alien, then 704 bytes of alien graphic data. That's 11 UDGs, each being 2 bytes wide and 16 bytes high. That's 352 bytes, which is doubled because this actually stores the second set of UDG info for the row. i.e. when the aliens are looking right, and when the aliens are looking left. So this is 2 bytes, followed by 352 bytes, followed by another 352 bytes, which is 706 bytes in total for this structure. One for each row, so that's 3,530 bytes from here to 30856 inclusive.
_ALIEN_ROWS_DATA	27327	DEFB 0,0,0,0,0,0,0,0