Shyam,
Most of the time, whether it's a point and shoot, cellphone, etc, people are used to working with cameras that take the entire frame at once, but the NAC is a linescan camera which makes it a bit counter-intuitive at first.
If we imagine LRO traveling from north to south, and pixel 1 is on the west side of LRO and pixel 5064 is on the east side, as LRO moves south, capturing 1 line at a time, we get an image with north at the top and sample 1 (left side of the image) is west. If LRO performs it's yaw maneuver to keep the solar panel in the sun and is again traveling from north to south, now pixel 1 is on the east side and pixel 5064 is on the west side. As LRO moves south, capturing 1 line at a time, the resulting image has north at the top due to the direction of travel and sample 1 is east due to the orientation, but sample 1 is still the left side of the image making it appear mirrored rather than rotated like a normal point-and-shoot style camera would be. Line 1 is always the first line captured, whether moving from north to south or south to north, and sample 1 always maps to the first pixel on the CCD line array.
The EDR and CDR products are all in camera space, so it's the camera's point of view without any adjustment based on flight direction. When projecting the image data using SPICE, the orientation kernels (CK) are aware of whether LRO is moving in the +X or -X direction relative to the spacecraft so the resulting map-projected products viewed with something like Quickmap or Lunaserv match the map coordinates (normally north up and west to the left, but can vary depending on the map projection and coordinate system used).
The ISIS software package from the USGS is distributed with the appropriate LRO SPK and CK kernels and can take the EDR and CDR products and output a variety of map projected products. Nearly all NACs are also available via WMS using our Lunaserv service, and can be used directly in GIS software such as QGIS, JMARS, or ArcMap without any downloading or processing steps required. As June mentioned, the corner coordinates in the label can be helpful in interpreting the data in camera space, but keep in mind that those coordinates are calculated on a sphere. The actual sample coordinates will vary based on terrain. ISIS can take care of that as well.
I hope that explanation helps.
Nick Estes, LROC SOC Manager
