======================================================================
Data Set Overview:
======================================================================

The data from the Rosetta Navigation Camera (NavCam) was extracted by
Bernhard Geiger; the data set was constructed and submitted by Maud
Barthelemy on behalf of the Planetary Science Archives (PSA).

The data have been observed and measured from 21st Nov 2014 to 19th
Dec 2014. The frequency of the navigation slots was of one 2x2 raster
every six hours, with interruption by manoeuvres. This gave 440
navigation images. In addition, 239 context images and 2 calibration
images have been taken.
This makes a total of 681 images.

Two originally planned navigation rasters were replaced by OSIRIS-NAC
rasters for lander search (2014-12-12T17:25:00, 2014-12-13T05:25:00)

There was no navigation image with lost rows but 40 context images
were tanken with lost rows (anomaly in the transfer to the spacecraft
memory only occurring for context images, for one image due to bad
weather or ground station problems). There was no completely lost
context images.

The spacecraft was first in 30km orbits and in terminator plane. Then,
it passes to 20km orbits.

All images in this data set are raw and uncalibrated data taken using
the imaging mode. The data set contains images resolved using both
NavCams onboard the Rosetta S/C and the DATA directory is organised
to reflect this with two sub directories:
 - CAM1
 - CAM2
For each image, the user can also find the FITS format of the
observation.


======================================================================
Filename Convention:
======================================================================

The filenaming convention for all data levels is given by:

           __.
              ROS     CAM1    YYYYMMDDThhmmss       IMG
                      CAM2                          LBL
                                                   (JPG)

Examples:
        ROS_CAM1_20140223T081016.IMG
        ROS_CAM1_20140223T081016.LBL
        ROS_CAM1_20140223T081016F.FIT
        ROS_CAM1_20140223T081016F.LBL
       (ROS_CAM1_20140223T081016.JPG)
        ROS_CAM2_20140223T094017.IMG
        ROS_CAM2_20140223T094017.LBL
        ROS_CAM2_20140223T094017F.FIT
        ROS_CAM2_20140223T094017F.LBL
       (ROS_CAM2_20140223T094017.JPG)

(In the case of the BROWSE directory)

======================================================================
Geometry Information - Coordinate System:
======================================================================

The label files include the following geometric variables:
- SC SUN POSITION VECTOR: The vector from the spacecraft to the Sun
  in equatorial J2000 inertial frame.
- SC TARGET POSITION VECTOR: The vector from the spacecraft to the
  centre of the comet nucleus in equatorial J2000 inertial frame.
- SC TARGET VELOCITY VECTOR: The spacecraft to comet nucleus velocity
  vector in in equatorial J2000 inertial frame.
- TARGET CENTER DISTANCE: The distance between the spacecraft and the
  comet nucleus centre. (Note that also for checkout and stellar
  calibration images the comet nucleus distance is given here.)
- SUB SPACECRAFT LATITUDE and SUB SPACECRAFT LONGITUDE: The latitude
and longitude of the sub-spacecraft point derived from the Flight
Dynamics body-fixed reference frame implicitly specified by the
information provided in the comet attitude file CATT.
- RIGHT ASCENSION and DECLINATION: Right Ascension and Declination of
the camera boresight direction in equatorial J2000 inertial frame.
- CELESTIAL NORTH CLOCK ANGLE: The direction of celestial north at the
  center of the image - measured from the upward direction,
  clockwise to the direction toward celestial north.
- SOLAR ELONGATION: The angle between the line of sight of observation
  and the direction of the Sun.
All geometric values are calculated for the time t = IMAGE TIME
(and not START TIME).

======================================================================

All data have been validated by
                ESA and found as expected. Any exceptions are noted by
                the DATA_QUALITY field in the label files.