NRL SSD has developed advanced operational software for the DMSP SSULI UV instruments, the SSULI GDAS, that uses state-of-the-art sensor and atmospheric algorithms to generate near-real-time ionospheric and thermospheric space weather data products for DoD.

The GDAS generates Sensor Data Records (SDRs) and Environmental Data Records (EDRs) from SSULI observational limb scan data. The GDAS products are used operationally at the Air Force Weather Agency (AFWA) for ingest into assimilative space weather models such as GAIM and as standalone space situational awareness (SSA) products.

SDRs: The first part of the software consists of data preprocessing/calibration algorithms applied to calibrate the SSULI engineering data in order to generate observed spectra. Multiple Linear Regression (MLR) and filters are subsequently applied which isolate specific emissions and flag observations that include stars, the South Atlantic Anomaly (SAA), and the auroral regions. Vertical intensity profiles of specific emission features are generated.

EDRs: The vertical intensity profiles are then fed to the three atmospheric inversion algorithms that use nonlinear Discrete Inverse Theory (DIT) to determine the Electron and Neutral Density composition of the upper atmosphere. Data products include O+, O, N2, O2 and temperature profiles, model parameters, and Total Electron Content (TEC).


  • The SSULI GDAS operational software suite has been in place at Schriever AFB and then AFWA since 1999. Once the SSULI sensor on DMSP F18 went operational in August 2012, GDAS began generating operational space weather data products for the USAF
  • The SSULI GDAS operational data products are used by the USAF for near-real-time ionospheric and thermospheric specification, ingest by GAIM model, and global space weather visualization in the USAF Space Weather Operations Center (Space WOC)