Data Receipt and Processing
Data Definitions
Most spacecraft mission data is typically divided into "levels" of processing and refinement.
- "Raw" data is the basic telemetry transferred from the spacecraft to the ground station, packaged as a file, with only basic r/f integrity checks run, and no processing done to it.
- Level Zero refers to the cleanest, time-ordered set of data for a given instrument or spacecraft. Telemetry Checking, APID Lookup, Housekeeping telemetry processing and Image Reconstruction are performed at this level. The only processing done is typically the removal of duplicate data points (due to multiple file sends or a solid state recorder overlap), the removal or minimal repair of bad r/f data, the sorting of the different APIDs, and the matching of the end of one packet to the beginning of the next. The images taken by an instrument are left "as is" - not manipulated, not flat-fielded nor otherwise calibrated. All of the Level Zero data is recorded in the JSOC DRMS (database).
- Level One data is "unpacked" Level Zero data, where images have been put together, bad pixels removed, and gains calibrated (i.e. flat-fielded). It is data in the cleanest state possible while remaining "pure" (no significant, irreversible data alteration). This data is time-sequenced, and quality-filtered. Expect to find Dopplergrams and Magnetograms here, along with single images.
- Level Two data has been irrevocably filtered, time-sequence-merged, Fourier-transformed or otherwise changed or cleaned up from Level 0ne in a way that is irreversible. Level Two data can be re-created from Level One data, but not one cannot create Level One data from Level Two data.
Telemetry access information
- DDS Data Capture (aka High Speed Bus)
- Offsite Data Archive (raw data)
- MOC Data Product Server Data Retrieval
[:MOCServer:Accessing the server] -- Information about accessing the MOC Product Server
Level 0 Processing
JSOC Level Zero Software Functional Specification. http://hmi.stanford.edu/development/JSOC_Documents/Level-0-Documents/JSOC-LEVEL0-PROCESSING-FS.pdf
- Level 0 Image Processing (HSB Telemetry)
BR -- Includes Time and Data Quality computations
- Level 0 Housekeeping Telemetry Processing
BR -- "Merged" Housekeeping DRMS record creation BR -- "Averaged" Housekeeping DRMS record creation
- Production Data Archive (raw and level0)
- Data Accounting
JSOC will also include sub-levels (e.g. Level 0.3, Level 1.5) to indicate various stages of processing. For example, Level 0.3 will represent less processing (and perhaps less information) than Level 0.5.
- [:Lev0.1Doc:Level 0.1 Data Processing]
- [:Lev0.3Doc:Level 0.3 Data Processing]
- [:Lev0.5Doc:Level 0.5 Data Processing ]
- Orbit information
- Pointing information
Level 1 Processing
- Level 1.0 Filtergram Calibration
Removal of overscan/underscan rows & columns
- Identification of corrupted pixels
- Application of offset and gain correction
- Calculation of image center and limb position
Data Clients
Typically, mission operations personnel and instrument operators want to see Level Zero data. It is available usually within minutes of receipt and persons very familiar with instrument/spacecraft engineering specs can make the best use of it. All kinds of raw image data and housekeeping data are present, including many useful temperatures, voltages and positions. Those requiring the most immediate spacecraft images are sometimes also Level Zero data users, such as CISM (Center for Integrated Space Weather Modeling).