The Total Irradiance Monitor (TIM): Instrument Design

  • Greg Kopp
  • George Lawrence


The Total Irradiance Monitor (TIM) instrument is designed to measure total solar irradiance with an absolute accuracy of 100 parts per million. Four electrical substitution radiometers behind precision apertures measure input radiant power while providing redundancy. Duty cycling the use of the radiometers tracks degradation of the nickel-phosphorous absorptive black radiometer interiors caused by solar exposure. Phase sensitive detection at the shutter frequency reduces noise and simplifies the estimate of the radiometer’s equivalence ratio. An as-designed uncertainty budget estimates the instrument’s accuracy goal. The TIM measurement equation defines the conversion from measured signal to solar irradiance.


Equivalence Ratio Digital Signal Processor Total Solar Irradiance Combine Standard Uncertainty Phase Sensitive Detection 
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Copyright information

© Springer 2005

Authors and Affiliations

  • Greg Kopp
    • 1
  • George Lawrence
    • 1
  1. 1.Laboratory for Atmospheric and Space PhysicsUniversity of ColoradoBoulder

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