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 channel, Camera 2, data products:
- Line of sight velocity, 45s cadence from Camera2 and 12m (720s) cadence from Camera1
- Synoptic Maps
- Continuum Intensity
- Line Depth
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 of the level1 series. In addition, this QUALITY keyword is copied to the QUALITY keyword of the observable series (e.g., there is a QUALITY keyword in hmi.M_720s). The bits that compose the quality flag are documented [Lev1qualBits here].
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