You are here: Home / Help
The USNO websites,,,,,, and are undergoing modernization efforts. The expected completion of the work and the estimated return of service is the first half of 2022, subject to change due to potential impacts of COVID-19.

Contact Information Regarding Products

Site Feedback  
Comments or questions regarding the portal.

Help with and information about our products is available for each of the topical areas served by this portal.  Please select the topical area to get to a information request form for that class of products.


Time Products

GPS timing, Loran-C, Two-Way Satellite Time Transfer (TWSTT), Network Time Protocol (NTP), and technical information about USNO timing products.

Earth Orientation Products

Polar motion, UT1-UTC, celestial pole offsets, long-term Delta T, 24-hour and 48-hour sets of GPS satellite orbits, satellite and receiver clock solutions, earth orientation parameters, and UTGPS (GPS-based UT1-like quantity).

Astronomy Products

Astronomical phenomena, astronomical data services, astronomical software products, almanacs, astrometric catalogs (NOMAD/UCAC/USNO-B1), imaging data (PMM/RRFID), double star catalogs (WDS), reference frames (CRF/TRF).

Meteorology Products

Meteorology product help.

Oceanography Products

Oceanography product help.

Ice Products

National Ice Center for links to product help.