GUARDIAN Near-Real-Time Ionospheric Total Electron Content product


Data Center Citation

Noll, Carey E., The Crustal Dynamics Data Information System: A resource to support scientific analysis using space geodesy, Advances in Space Research, Volume 45, Issue 12, 15 June 2010, Pages 1421-1440, ISSN 0273-1177,

Data Citation

NASA Jet Propulsion Laboratory, GUARDIAN Near-Real-Time Ionospheric Total Electron Content product, Greenbelt, MD, USA:NASA Crustal Dynamics Data Information System (CDDIS), Accessed [[enter user data access date]] at doi:10.5067/GNSS/guardian_ionotec_001.

Other standard citation formats may be used for this data set and can be found at the DOI Citation Formatter website.

More information about CDDIS data citations and acknowledgments is available.


Martire, L., Krishnamoorthy, S., Vergados, P. et al. The GUARDIAN system-a GNSS upper atmospheric real-time disaster information and alert network. GPS Solut 27, 32 (2023).


  • Name: GUARDIAN Near-Real-Time Ionospheric Total Electron Content product
  • Format: CSV
  • Spatial Coverage: 90.0 to -90.0, 180.0 to -180.0 (∼1200 km around monitored stations)
  • Temporal Coverage: 2022-09-15 to present
  • Temporal Resolution: 5 seconds
  • File Size: ∼ 20 MB/file
  • Platforms: Multiple GNSS


Developed at JPL, GUARDIAN is a near-real-time (NRT) ionospheric monitoring software (Martire et al.). Its main products are NRT total electronic content (TEC) time series, allowing users to explore ionospheric TEC perturbations due to natural and anthropogenic events on Earth. The NRT GUARDIAN time series are validated against well-established post-processing methods. Currently, time series are computed for more than 90 GNSS ground stations distributed around the Pacific Ring of Fire, which monitor the four main GNSS constellations (GPS, Galileo, BDS, and GLONASS).

Data Access

The GUARDIAN Near-Real-Time Ionospheric Total Electron Content products are online:

in subdirectories by year, and day of year as follows:


Code Meaning
YYYY 4-digit year
DDD 3-digit day of year
SITE four-letter code for a ground-based GNSS station/receiver
YY 2-digit year
MM 2-digit month
DD2-digit day
.CSV comma separated value file