Observing Control

Mission Data Processor (MDP) of the Solar-B send commands to and handles data from three telescopes. As for the XRT, MDP controls it based on the XRT observation tables and parameters. They are normally uploaded during the contact with Uchinoura Space Center (USC) in Kagoshima, Japan. Besides pre-defined observation tables and parameters, MDP can perform on-board processing of the real-time data, which allows to determine appropriate exposure time and to detect flares immediately.

  • Normal observation based on pre-defined tables
    • MDP sets the XRT filter based on observation tables.
    • The shortest time cadence of the XRT is 2 sec.
    • MDP detects flares and switch to the flare observation table.
  • Automatic Exposure Control (AEC)
    • MDP decides an appropriate exposure time and the filter thickness
    • The AEC can be applied for images smaller than 256 k pixels (512×512 pixels)
  • Automatic Region Selector (ARS)
    • MDP selects region suitable for observation by onboard image analysis.
    • ARS have two modes.
      Global search
      Selecting the brightest region in the field of view
      Local search
      Tracking three specific regions
    • MDP uses ARS patrol images for the ARS function. The time resolution of ARS depends on time resolution of ARS patrol images. The baseline of ARS time resolution is 1.5 hour (one orbit).
  • Flare Detection (FLD)
    • MDP can detect the occurrence of a flare using flare patrol images
    • The criterion of the FLD is the intensity increase compared to the previous running-averaged patrol images.
    • In the event of flares, MDP can switch to XRT flare observation table and signal to SOT and EIS.
    • The function also detects radiation belts (South Atlantic Anomaly and High Latitude Zone).
  • Pre-flare buffer
    • Pre-flare buffer is allocated to store the pre-flare data of the XRT.
    • If MDP detects the occurrence of a flare and XRT is observing the flare site before the flare, MDP keeps the data in the pre-flare buffer until the following downlink. If MDP does not detect a flare, the oldest data in the pre-flare buffer is overwritten with the new data.
    • The size of the pre-flare buffer is 5.5 Mbytes in total.
  • Image compression
    • MDP can compress the observed data using lossy JPEG or loss-less DPCM method.

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