BackForwardInstrument:  ACGS 

Instrument details
Acronym ACGS
Full name Atmospheric Carbon-dioxide Grating Spectrometer
Purpose Measurement of total-column CO2
Short description Three-band NIR/SWIR grating spectroradiometer, Band-1: O2 around 760 nm; Band-2: CO2 around 1610 nm (weak band); Band-3: CO2 around 2060 nm (strong band). 2000 channels total [see details in the table below]
Background Development after the Orbiting Carbon Observatory (OCO) flown on OCO-2
Scanning Technique Pushbroom, cross-track. Swath 18 km, 9 super-pixels per line. Three pointing modes: nadir, sun glint, and target within a solar zenith angle < 65 degree
Resolution 2 km (cross track) x 3 km (along track) at s.s.p.
Coverage / Cycle Global in 5 months; less by strategic pointing
Mass 180 kg Power 170 W Data Rate


Providing Agency MOST
Instrument Maturity Flown on an R&D satellite
Utilization Period: 2017 to 2022
Last update: 2021-06-16
Detailed characteristics

Spectral range

No. of channels

Spectral resolution

SNR @ specified input spectral radiance

758-776 nm


0.044 nm

360 @ 5.8 1019 photons s-1 m-2 sr-1 μm-1

1594-1624 nm


0.125 nm

250 @ 2.1 1019 photons s-1 m-2 sr-1 μm-1

2041-2081 nm


0.165 nm

180 @ 1.1 1019 photons s-1 m-2 sr-1 μm-1

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
  • Cross-nadir shortwave (UV/VIS) sounder
WIGOS Subcomponents
  • Subcomponent 1
  • UV/VIS/NIR sounders, nadir and limb
  • UV/VIS/NIR nadir sounder
Mission objectives
Primary mission objectives
  • CO2
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
CO2*1 - primaryCloud sensitive.. Daylight only.Very-high resolution SWIR spectrometry CO2 lines around 1.6 and 2.1 micrometers. Specifically designed for CO2.