GPSIII
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Mission Photos:
Mission Objective:
The Global Positioning System (GPS) is a satellite-based radionavigation system developed and operated by the U.S. Department of Defense. GPS permits land, sea, and airborne users to determine their three-dimensional position, velocity, and time 24 hours a day, in all weather, anywhere in the world with precision and accuracy.
GPS consists of three segments: space, control, and user. The Space Segment consists of a minimum of 24 operational satellites in six circular orbits 20,200 km above the earth at an inclination of 55° degrees with a period of 11 hrs 58 minutes. The Control Segment consists of a master control station in Colorado Springs, with five monitor stations and three ground antennas located throughout the world that track all GPS satellites and are used to produce the precise satellite orbits that are included in the GPS navigation messages. The User Segment consists of the receivers, processors, and antennas that allow land, sea, or airborne operators to receive the GPS satellite broadcasts and compute their precise position, velocity, and time.
Users determine their position on the Earth by measuring their distance from the GPS satellites in space, which act as precise reference points. Each GPS satellite transmits accurate position and time signals. The user's receiver measures the time delay for the signal to reach the receiver, which is the direct measure of the apparent range to the satellite. Measurements collected simultaneously from at least four satellites are processed to solve for the three dimensions of position, velocity and time.
The GPS III satellites developed by Lockheed Martin have 3X better accuracy than the previous generation of GPS satellites and a new L1C civil signal that is compatible with other global navigation satellite systems. GPS III Space Vehicles 9 and 10 also host NASA-provided laser retroreflector arrays (LRA’s) for improved precision orbit determination and improved realizations of the WGS84 and International Terrestrial Reference Frames.
Mission Parameters
| GPSIII-SV09 | GPSIII-SV10 | |
| Sponsor: | United States Space Force | United States Space Force |
| Expected Life: | 15 years | 15 years |
| Primary Application: | Positioning, Navigation, and Timing | Positioning, Navigation, and Timing |
| COSPAR ID: | 2026-017A (ILRS ID 2601701) | 2026-087A (ILRS ID 2608701) |
| SIC Code: | 5082 | 5083 |
| Satellite Catalog (NORAD) Number: | 67588 | 68791 |
| PRN | PRN20 (G20) | PRN13 (G13) |
| Launch Date: | 28-Jan-2026 | 21-Apr-2026 |
| RRA Size: | 16 inch diameter | 16 inch diameter |
| RRA Shape: | planar | planar |
| Reflectors: | 48 corner cubes | 48 corner cubes |
| Size of Reflector: | 1.6 inch diameter | 1.6 inch diameter |
| Orbit: | near-circular | near-circular |
| Orbital Period: | 718.0 minutes | 718.0 minutes |
| Inclination: | 55 degrees | 55 degrees |
| Perigee: | 20179.911 km | 20179 km |
| Eccentricity: | < 0.001 | < 0.001 |
Publications:
- Dilssner F., Springer T., Gini F., Schönemann E., Enderle W. (2023). "New type on the block: generating high-precision orbits for GPS III satellites", GPS World, May 15, 2023. (https://www.gpsworld.com/new-type-on-the-block-generating-high-precision-orbits-for-gps-iii-satellites/)
- Dilssner F., Springer T., Schönemann E., Enderle W. (2022). “GPS III Radiation force modelling”, IGS2022 Virtual Workshop, June 27 – July 1, 2022. (https://files.igs.org/pub/resource/pubs/workshop/2022/IGSWS2022_S07_03_Dilssner.pdf)
- Fischer A (2022). “GPS III Earth Coverage (EC) Antenna Patterns”, Lockheed Martin Space, https://www.navcen.uscg.gov/sites/default/files/pdf/gps/GPS_ZIP/GPS_III_EC_Antenna_Patterns_SVN_74_75_76_77_78.pdf
- Haddad, R., Kovach, K., Slattery, R., Gillis, J. (2020). "GPS Modernization and Beyond," 2020 IEEE/ION Position, Location and Navigation Symposium (PLANS), Portland, Oregon, April 2020, pp. 399-406, doi:10.1109/PLANS46316.2020.9110167.
- Kuang D., Bar-Sever Y.E. & Sibthorpe A.J. (2026). "In-orbit estimation of forces acting on GPS III spacecraft", J. Geodesy, 100 (26), doi:10.1007/s00190-026-02049-6.
- Merkowitz et al. (2018). “Thermal-Optical Performance of the GPS III Laser Retroreflector Array,” Presentation at 21st International Workshop on Laser Ranging, Canberra, Australia, November 5-9, 2018. https://ilrs.gsfc.nasa.gov/lw21/docs/2018/presentations/Session6_Merkowitz_presentation.pdf
- Marquis, W., Shaw, M. (2011). “Design of the GPS III Space Vehicle,” Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011), Portland, Oregon, September 2011, pp. 3067-3075.
- Montenbruck O., Duan B., Steigenberger P., Hugentobler U. (2026). “Improved attitude modeling for the GPS III satellites in eclipse season”, Adv. Space Res., 77(4), 4901-4908, doi:10.1016/j.asr.2025.12.111.
- Montenbruck O., Steigenberger P. & Mayer-Gürr T. (2024). "Manufacturer calibrations of GPS transmit antenna phase patterns: a critical review", J Geodesy, 98(2), doi:1007/s00190-023-01809-y.
- Steigenberger P., Thoelert S., Dach R., Montenbruck O. (2024). “Validation of GPS III transmit antenna calibrations”, Adv., Space Res., 73(5), 2488–2492, doi:10.1016/j.asr.2023.11.048.
- Thoelert S., Steigenberger P., Montenbruck O., et al. (2019). “Signal analysis of the first GPS III satellite“, GPS Solutions, 23, 92, doi:10.1007/s10291-019-0882-7.
Additional Information:
Mission Website:
- GPS.gov
- United States Coast Guard Navigation Center
- Lockheed Martin
- NASA Press Release (March 19, 2026): NASA Laser Reflecting Instrument Makes GPS Satellite More Accurate.
- GPS-SV10 launch
International GNSS Service
NANU Advisories (Notice of Advisory to NAVSTAR users)
