UVS Data Handling & Safety

  • Photons are recorded as (x,y,z) events in “pixel list mode” with time hacks every few ms; events & time hacks each use 24 bits; 11 bits spectral (i.e., 0-2047 values), 8 bits spatial (i.e., 0-255 values), and 5 bits for pulse amplitudes (i.e., 0-31 values)
  • Alternating “ping-pong” buffers allow continuous observations; 32K-event frames are sent to the S/C on the high-speed science line (2 Mbits/s; transfer time 0.39 s) as soon as they are filled with events & time hacks
  • A data quality (DQ) index, based on the expected count rate, is written to the header for each frame; this allows for the selection of the “best” 500 Mbits of data acquired during each orbit for transmission to the ground
  • In regions of high particle background, the count rate may exceed the maximum allowed count rate of ~106 counts/s; when this occurs the UVS high voltage is immediately (i.e., within 0.1 s) lowered for safety
  • After safing, UVS will attempt to autonomously ramp high voltage back up after a configurable delay (2-500 s)