Dataset overview  :  Framing Camera 1 is one of two identical units flying on Dawn  spacecraft. This dataset includes the image files to be used in the  calibration of the raw data throughout the mission. These files  represent the behaviour of each individual pixel with respect to dark  current generation and pixel-to-pixel non-uniformity as a function of  the filter. As these are elaborated image products, not obtained from  a specific image acquisition, they do not have any ancillary data.   The data set contains two types of products. The pixel-to-pixel  non-uniformity (flat) images and the dark current generation maps.  The flat field images are nominally named FC1_Fx_FLAT_Vnn.IMG, where x  is a number between 1 and 8 for the appropriate filter number and they  represent perturbations in the illumination of the CCD due to the  filter (dust particles, blemishes, etc.), and they are expected to  stay fairly constant throughout the mission. Prior to the Vesta  encounter, there was the initial in-flight version of the flats for  each filter (*V02.IMG). The flats of the primary camera, FC2, evolved  over the mission as various improvements (stray light correction, etc.)  were added. For FC1 only an initial set of flats was created since there was no expectation that it would be used for science. Near the end of  the Ceres extended mission, the Dawn project decided to use both cameras simultaneously to protect against an FC2 reset during the Opposition  observation that would be a one-time event. This created a need for an  improved calibration, flats in particular, for FC1. This data set  includes both the new and the older version of the flats. The new  version should be used for any science calibration, the older version is retained for completeness.   The dark current maps are filter independent and are evolving in time  as the sensor is subject to a high-energy particle environment. They  are named yyyymmdd_FC1_pppxxxxx_Vnn.IMG, where yyyymmdd is the year,  month, and day when the file was created, ppp is the mission phase  identifier (e.g. CSH), xxxxxx is an observation identifier (e.g. CYCLE2) where applicable, and nn is the image version number. In general, the  highest version available for a given dark image should be used rather  than an earlier version. Darks are not available for every activity.  If there is no dark provided for a specific activity, then the highest  version of the preceding activity dark should be used for calibration.  For example, during the Ceres Survey observations, composite darks are  only available for the odd numbered cycles. To calibrate Ceres Survey  Cycle 2 images, users should select the dark images from Cycle 1 rather  than those from Cycle 3.   This dataset is the primary record of calibration data as it is  produced for the consumption of the bigger scientific community.   For more information on the contents and organization of the volume  set refer to the AAREADME.TXT file located in the root directory of  the data volumes.   Parameters  :   Filter number: Given that the imperfections vary from filter to filter,  one image is created per filter to account for these imperfection. This  map is not expected to vary along the mission, but should it be  necessary, a set of images per filter could be generated depending on  the time of the mission.   Mission phase: It is in the nature of the space missions that radiation  damage will evolve for worse during the lifetime of the instruments.  This makes necessary to keep track of the radiation damage for the  different phases of the mission. However, the time scale for significant variation of the radiation damage effects is in the order of several  weeks, so it might not be necessary to produce a new set of reference  flat fields with every operational slot of the cameras. Still, whenever  one of these files is used in the generation of level 1b data (RDR), the header of the RDR will clearly identfy which one of the images was used  for the calibration.   Processing  :  These calibration products have been produced from ground and flight  measurements and are intended for use in the calibration pipeline.   The data in one calibration file consists of one image frame, with the  accompanying header translated into text format in the label.  The dimensions and location (pixel coordinates) of each frame are  included for the co-location of the calibration and acquired images  during the processing. Each frame is formatted into one file (suffix  *.IMG), with an attached label.

Data Quality  :  Product Versions  :  This archive includes all versions of calibration images that have  been submitted for archive, including some that have been superseded  by newer versions. Data users should consider the latest version of  the file as the best available.   Version 1 of the archive volume included the calibration files through  Ceres Approach. Version 2 added new flats and composite darks for Ceres  XMO3 (CXG) and XMO4 (CXO).