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DAWN FC1 CALIBRATION IMAGES V1.0 (PDS)

NSSDCA ID: PSSB-00690

Availability: At NSSDC, Ready for Offline Distribution (or Staging if Digital)

Description

This description was generated automatically using input from the Planetary Data System.

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 identify 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.

These data are available on-line from the Planetary Data System (PDS) at:

https://sbnarchive.psi.edu/pds3/dawn/fc/DWNCALFC1/

Alternate Names

  • DAWN-CAL-FC1-2-EDR-CALIB-IMAGES-V1.0

Discipline

  • Planetary Science: Small Bodies

Additional Information

Spacecraft

Experiments

Questions and comments about this data collection can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Horst Uwe KellerData ProviderMax-Planck-Institut fur Aeronomiekeller@linmpi.mpg.de
Dr. Pablo Gutierrez-MarquesGeneral ContactMax-Planck-Institut fur Sonnensystemforschunggutierrez@mps.mpg.de
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