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Mission & Vision
Naval Oceanographic Office
Fleet Numerical Meteorology & Oceanography Center
United States Naval Observatory
News from the Naval Observatory
Earth Orientation Department
USNO Earth Orientation Products
Contents of Bulletin A
USNO GPS Products
GPS User Information
USNO VLBI-based Products
VLBI Correlator Data
VLBI-based Earth Orientation Parameters (EOP)
Earth Orientation Information Center
General Information about Earth Orientation
Frequently Asked Questions About Earth Orientation
What Is Earth Orientation?
What Is Polar Motion?
What does the Earth rotation coordinate measure?
What is the Celestial Pole Offset?
What is a Leap Second?
How do we measure Earth Orientation?
What causes variations in the Earth's orientation?
Who uses Earth orientation information?
Publications About Earth Orientation Products
Earth Orientation Software
Precise Time Department
The USNO Master Clock
The USNO Master Clock
Time Dissemination at the USNO
USNO Alternate Master Clock (AMC)
Cesium Atomic Clocks
Hydrogen Masers at the USNO
Rubidium Fountain Clocks
USNO Time Scales
International Time Scales and the BIPM
Definitions of Systems of Time
Global Positioning System
Global Positioning System Overview
USNO GPS Data Categories Explanation
CGGTTS Data Format
USNO GPS Time Transfer
GPS Information: SA, DGPS, Leap Seconds, etc.
GPS Week Number Rollover
GPS Timing Data and Information
USNO Format Explanation
USNO Computer Display Clocks
Two-Way Satellite Time Transfer (TWSTT)
Network Time Protocol (NTP)
US Eastern Time Zone NTP Servers
US Mountain Time Zone Servers
DoD Customer Servers
Astronomical Applications Department
Celestial Reference Frame Department
Senior Enlisted Advisor
Naval Oceanography Operations Command
Fleet Weather Center - Norfolk
Fleet Weather Center - San Diego
Joint Typhoon Warning Center
Public Use of Limitations
Naval Meteorology and Oceanography Command
Captain Hartwell F. “Rip” Coke
Superintendent, U.S. Naval Observatory
15 June 2022
Captain Coke is a 1995 graduate of the Virginia Polytechnic Institute and State University (VA Tech) where he earned a Bachelor of Science degree in Environmental Sciences with a focus in Aquatic Resources.
Coke received his commission in the United States Navy as a Surface Warfare Officer in 2000 from the Navy’s Officer Candidate School. His first assignment was as the Assault Officer attached to PCU IWO JIMA (LHD-7) located in Pascagoula, Mississippi. Upon ship’s commissioning, he earned his surface warfare pin, steam Engineering Officer Of the Watch and Command Duty Officer qualifications. Prior to leaving this assignment, Coke was accepted into the Navy’s Information Warfare Community as a Meteorology and Oceanography (OCEANO) Officer.
In September 2002 he reported to Yokosuka, Japan as the Gunnery Officer onboard USS VANDEGRIFT (FFG-48). During this tour, VANDEGRIFT was deployed to the Middle East for Operations Enduring Freedom and Iraqi Freedom. Coke served as a Visit, Boarding, Search, and Seizure officer and earned a Tactical Action Officer qualification.
In October 2003, Coke left Japan to attend Basic Oceanographic Accession Training. Coke then reported to Fleet Numerical Meteorology and Oceanography Center located in Monterey, CA. He served as the Expeditionary Warfare Division Officer leading focused support efforts for both Naval Special Warfare and United States Marine Corps units.
Coke departed Monterey in October 2005 to serve as staff OCEANO for COMCMDIV THREE ONE located in Bahrain. Coke returned to Monterey in March 2007 as a student at the Naval Postgraduate School. He graduated in September 2009 with a Master of Science degree in Meteorology and Physical Oceanography. He reported aboard Carrier Strike Group EIGHT embarked on USS EISENHOWER (CVN-69) as the Staff OCEANO and the strike group scheduling officer. The Group deployed in support of Operations Iraqi and Enduring Freedom in January 2010. While deployed, Coke earned qualifications as Force Tactical Action Officer and Battle Watch Captain.
In February 2012, Coke reported to the Naval Personnel Command in Millington, TN to serve as the Junior Oceanography Assignments and Placement Officer. Upon completion of his detailing tour in February 2014, Coke reported to the Naval War College in Newport, RI where he earned his Joint Professional Military Education and a Master of Arts degree in National Security and Strategic Studies.
In April 2015, Coke took command of the Naval Oceanography Special Warfare Center in Coronado, CA. After completing his command tour, he was assigned as deputy assistant chief of staff for Fleet Modernization and Facilities Management at Naval Information Forces, the Information Warfare TYCOM.
In May 2019, he transferred to US Fleet Forces Command and served as the Fleet Oceanographer. He assumed duty as the 58
Superintendent, U.S. Naval Observatory on 17 December, 2021.
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