BackForwardInstrument:  TIM  

Instrument details
Acronym TIM
Full name Total Irradiance Monitoring
Purpose Total solar irradiance monitoring
Short description Assemblage of 4 active cavity radiometers.  Range: 0.2-10 µm. The Total Solar Irradiance (TSI) is measured with absolute accuracy of 350 ppm (0.035 %) and relative changes of less than 10 ppm/y (0.001 %/y)
Background TIM is built by the Laboratory for Atmospheric and Space Physics (LASP) of the University of Colorado, Boulder. The flight model flown on STPSat-3 implements the Total Solar Irradiance Calibration Transfer Experiment (TCTE), supported by NASA, NOAA and DoD
Scanning Technique Sun pointing during orbital movement, data sampled every 2 min
Resolution N/A (full solar disk)
Coverage / Cycle One measurement after integration on all data taken during the diurnal orbit arc; thus 100 min
Mass 7.9 kg Power 14 W Data Rate 539 bps


Providing Agency NASA
Instrument Maturity Flown on an R&D satellite
Utilization Period: 2003 to 2022
Last update: 2021-06-23
Detailed characteristics
Satellites this instrument is flying on

Note: a red tag indicates satellites no longer operational, a green tag indicates operational satellites, a blue tag indicates future satellites

Instrument classification
  • Earth observation instrument
  • Passive optical radiometer or spectrometer
  • Solar irradiance monitor
WIGOS Subcomponents
  • Subcomponent 1
  • Absolutely calibrated broadband radiometers, and TSI and SSI radiometers
  • TSI and SSI radiometers (for solar irradiance)
Mission objectives
Primary mission objectives
  • Downward short-wave irradiance at TOA
Evaluation of Measurements

The following list indicates which measurements can typically be retrieved from this category of instrument. To see a full Gap Analysis by Variable, click on the respective variable.

Note: table can be sorted by clicking on the column headers
Note: * Primary mission objective.
VariableRelevance for measuring this variableOperational limitationsExplanation
Downward short-wave irradiance at TOA*3 - highNo specific limitation.TSI over the range from UV to TIR