BackForwardInstrument:  ALTIUS 

Instrument details
Acronym ALTIUS
Full name Atmospheric Limb Tracker for Investigation of the Upcoming Stratosphere
Purpose To measures high-vertical-resolution profiles of ozone and possibly other trace gases, and aerosol concentration, in the UT/LS.
Short description Limb sounding spectrometer. Three independent imaging spectrometers operating in UV, VIS and NIR respectively [see details below]. Acousto-optic tuneable filters for the visible and infrared channels and Fabry-Perot interferometer for the ultraviolet channel.
Background New development
Scanning Technique Limb sounding by bright limb, solar and star occultation. 25-40 stars/orbit, i.e. average 500 occultations/day, global. Few tens/day for solar occultation, limited to latitudes above ~70°.
Resolution 1 km vertical, 300 km horizontal (limb geometry)
Coverage / Cycle The orbit has a 3 day repeat. The spatial coverage is limited with a global coverage/day of one measurement every 1000 x 1000 km2 cell on average.
Mass Power 250 W Data Rate


Providing Agency ESA
Instrument Maturity Flown on an R&D satellite
Utilization Period: 2025 to 2028
Last update: 2023-02-27
Detailed characteristics

Spectral Range

Spectral resolution

SNR @ expected input radiance

250-355 nm

 2.5 nm


440-675 nm

10 nm


600-1020 nm

10 nm


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
  • Limb sounders
  • Limb sounder
WIGOS Subcomponents
  • Subcomponent 1
  • UV/VIS/NIR sounders, nadir and limb
  • UV/VIS/NIR occultation limb sounder
  • Subcomponent 2
  • UV/VIS/NIR/IR/MW limb sounders
  • UV/VIS/NIR/IR occultation limb sounder
Mission objectives
Primary mission objectives
  • O3
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
Aerosol mass mixing ratio5 - marginalLimited to high atmosphere.UV, VIS, NIR limb sounding by solar & stellar occultation. Self-calibrating
O3*5 - marginalLimited to high atmosphere.Ozone lines in the bands around 260 nm (Hartley) and/or 340 nm (Huggins) and 600 nm (Chappuis).
PSC occurrence5 - marginalLimited to high atmosphere.UV and VIS spectrometry.
Aerosol volcanic ash5 - marginalLimited to high atmosphere.UV, VIS and NIR spectrometry; limb sounding by solar & stellar occultation. Self-calibrating