BackForwardInstrument:  STRATOS 

Instrument details
Acronym STRATOS
Full name STRATOS
Purpose Atmospheric temperature and humidity sounding, space-weather monitoring (TEC and scintillation), and Earth-surface sensing through GNSS reflectometry. GNSS-R applications include ocean winds, roughness, and soil moisture.
Short description

Multi-constellation GNSS receiver measuring direct signals, atmospheric phase delay and bending during radio occultations, and signals reflected from Earth’s surface.
Background

Consolidated technology flown operationally on Spire’s Lemur satellites since 2016. The radio-occultation payload was extended to perform dual-frequency grazing-angle GNSS-R measurements, and single-frequency near-nadir GNSS-R measurements.
Scanning Technique

Limb sounding of rising and setting GNSS signals from approximately 400 km altitude to near the surface, using fore- and aft-looking antennas. The same antennas receive grazing-angle surface reflections, typically at 5–30° elevation. Spire also supports near-nadir GNSS-R observations for ocean wind and soil moisture observation.
Resolution GNSS-RO: about 300km horizontal and 0.5km vertical.
Coverage / Cycle GNSS-RO: approximately 18,000 soundings per day from a diversity of orbits. Global coverage every 6 hours. GNSS-R: constellation and tasking-dependent; Spire processes 4 GNSS constellations.
Mass Power Data Rate

 

Providing Agency SPIRE
Instrument Maturity Flown on operational programme
Utilization Period: 2016 to 2040
Last update: 2026-09-14
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
  • Active and radio-occultation sensor
  • GNSS radio-occultation
WIGOS Subcomponents
  • Subcomponent 2
  • Magnetospheric energetic particles and magnetometers
  • Ionospheric total electron content sensor [at LEO and cross magnetosphere]
  • Ionospheric electron density sensor [in LEO and cross magnetosphere]
  • Subcomponent 4
  • GNSS radio occultation (commercial)
  • GNSS radio occultation constellation (commercial)
Mission objectives
Primary mission objectives
  • Atmospheric density
  • Atmospheric temperature
  • Electron Density
  • Height of the top of PBL
  • Height of the tropopause
  • Ionospheric Scintillation
  • Ionospheric Total Electron Content (TEC)
  • Specific humidity
  • Temperature of the tropopause
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
Atmospheric temperature*1 - primaryInaccurate in low troposphere.Flown in a satellite cluster. Two directional antennas, three GNSS systems tracked, about 1500 soundings/day per satellite
Geoid4 - fairHighly indirect.Radio-occultation processing implies precise orbitography. Geoid derived from multi-temporal analysis
Gravity field5 - marginalHighly indirect.Radio-occultation processing implies precise orbitography. Gravity field derived from multi-temporal analysis
Height of the top of PBL*1 - primaryNo specific limitation.Flown in a satellite cluster. Two directional antennas, three GNSS systems tracked, about 1500 soundings/day per satellite. PBL top measured as discontinuity of the refraction index
Height of the tropopause*1 - primaryNo specific limitation.Flown in a satellite cluster. Two directional antennas, three GNSS systems tracked, about 1500 soundings/day per satellite. Tropopause height measured as discontinuity of the refraction index
Specific humidity*2 - very highInaccurate in high troposphere.Flown in a satellite cluster. Two directional antennas, three GNSS systems tracked, about 1500 soundings/day per satellite
Temperature of the tropopause*1 - primaryNo specific limitation.Flown in a satellite cluster. Two directional antennas, three GNSS systems tracked, about 1500 soundings/day per satellite
Atmospheric density*1 - primaryNo specific limitation.Measuring atmospheric density
Electron Density*1 - primaryNo specific limitation.Flown in a satellite cluster. Two directional antennas, three GNSS systems tracked, about 1500 soundings/day per satellite
Ionospheric Total Electron Content (TEC)*2 - very highNo specific limitation.Flown in a satellite cluster. Two directional antennas, three GNSS systems tracked, about 1500 soundings/day per satellite
Ionospheric Scintillation*4 - fairNo specific limitation.Flown in a satellite cluster. Two directional antennas, three GNSS systems tracked, about 1500 soundings/day per satellite