Level 1+ HMI Data Products
HMI "Level-1" products are simply the individual filtergrams from level-0 but with flat-field images applied and fits to the limb computed to find the disk centerposition. Also ancillary metadata in included, such as SDO velocity and location from the SDO Flight Dynamics Service.
Level 1.5 HMI Products are calibrated science measurements computed from level-1 HMI filtergrams. We call these products "Observables" since, for the science goals of HMI, these are the basic observed physical quantities needed as input to specialized science processing.
Level 1.5 Observables include
- Line of Sight products from both Camera1 (12m) and Camera2 (45s)
- Doppler velocity
- Continuum proxy
- Line width
- Line depth
- Synoptic Maps
Vector field products from Camera1 (720s = 12m)
- Stokes parameters I,Q,U,V at 6 wavelengths
- Vector field inversions based on the Milne-Eddington approximations
- Vector field, disambiguated
The pipeline to produce these products relies on modules described briefly at HMIModuleTable
Summary of Magnetic Pipeline Modules HMIModuleTableSummary
Processing Errors & Quality Bits
If an error occurs during the processing of level-0 data into level-1 data, a corresponding bit is set in the "Quality Flag". This flag is implemented as a bit field which is stored in the QUALITY keyword. Each processing level has its own QUALITY keyword and copies of the lower level QUALITY keywords where appropriate.
The bit assignments for QUALITY are found at:
Processing Version Information
A keyword for calibration version keywords are included in level-1 data (CALVER32) through higher level products (CALVER64) starting in August 2012. This keyword is, at the start, considered to be a set of fields consisting of single hexidecimal digits. See CalibrationVersions.
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