BackForwardInstrument:  DDMI 

Instrument details
Acronym DDMI
Full name Delay Doppler Mapping Instrument
Purpose To observe ocean surface roughness, from which wind speed is retrieved.
Short description System of GPS receivers embarked on a constellation of eight micro-satellites, to receive signals both directly from a GPS satellite by a zenith-pointing antenna, and after reflection from the sea surface by two nadir-pointing antennas.
Background New development
Scanning Technique Scanning provided by the changing relative position of the LEO and the GPS satellites.
Resolution N/A
Coverage / Cycle All-longitudes for latitudes < 35°
Mass Power Data Rate


Providing Agency NASA
Instrument Maturity Flown on an R&D satellite
Utilization Period: 2017 to 2026
Last update: 2021-06-17
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
  • Other payload component
  • Positioning system
WIGOS Subcomponents
  • Subcomponent 2
  • GNSS reflectometry (GNSS-R) missions, passive MW, SAR
  • Constellation of GNSS receivers [for reflectometry]
Mission objectives
Primary mission objectives
  • Wind speed (near surface)
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
Geoid4 - fairHighly indirect.Opportunity information from GNSS receiver used for precise orbit determination
Gravity field5 - marginalHighly indirect.Opportunity information from GNSS receiver used for precise orbit determination
Wind speed (near surface)*4 - fairOver sea only.GNSS receivers on a cluster of micro-satellites. Wind speed estimated from the intensity of signals from different incidence angles, reflected normally