BackForwardInstrument:  GERB 

Instrument details
Acronym GERB
Full name Geostationary Earth Radiation Budget
Purpose Frequent observation of Earth radiation budget
Short description Two broad-band channels, for solar reflected radiance and total reflected/emitted radiance [see detailed characteristics below]
Background New development
Scanning Technique Mechanical, spinning satellite, E-W continuous, S-N stepping
Resolution 42 km
Coverage / Cycle Full disk every 5 min.  Integration over three cycles (15 min) to comply with accuracy requirements
Mass 25 kg Power 35 W Data Rate 50.6 kbps


Providing Agency UKSA
Instrument Maturity Flown on operational programme
Utilization Period: 2004 to 2033
Last update: 2022-11-16
Detailed characteristics
Channel Spectral interval Noise Equivalent Radiance Absolute accuracy SNR
Short-wave 0.32 - 4.0 µm 0.8 W m-2 sr-1 2.4 W m-2 sr-1 1250
Total radiance 0.32 - 100 µm 0.15 W m-2 sr-1 0.4 W m-2 sr-1 400
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
  • Broadband Earth radiation radiometer
WIGOS Subcomponents
  • Subcomponent 1
  • Absolutely calibrated broadband radiometers, and TSI and SSI radiometers
  • Broadband radiometer (for ERB)
Mission objectives
Primary mission objectives
  • Upward long-wave irradiance at TOA
  • Upward 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
Upward short-wave irradiance at TOA*2 - very highInformation on BRDF needed.SW and Total (SW+LW) broadband channels. Frequent sampling (GEO) enable capturing diurnal variations, particularly due to clouds. Also, changing solar incidence angle helps with irradiance computation
Upward long-wave irradiance at TOA*2 - very highNo specific limitation.LW radiance achieved by difference between Total and SW. Frequent sampling (GEO) enable capturing diurnal variations due to clouds.and water vapour rapid evolution