U.S. Naval Observatory Master Clock
E181327
The U.S. Naval Observatory Master Clock is the primary time standard of the United States, providing ultra-precise reference time for military, governmental, and global positioning system (GPS) operations.
All labels observed (4)
| Label | Occurrences |
|---|---|
| U.S. Naval Observatory Master Clock canonical | 1 |
| USNO Master Clock | 1 |
| United States Naval Observatory Master Clock | 1 |
| United States Naval Observatory timekeeping system | 1 |
How this entity was disambiguated
This entity first appeared as the object of triple T1601913 — resolving that mention is where its identity was fixed. The disambiguator weighed these candidate entities and picked the highlighted one (or “None”, minting a new entity). This is how homonymy is resolved: the same surface form can point to different entities.
NED1
Entity disambiguation (via context triple)
gpt-5-mini-2025-08-07
Target entity: U.S. Naval Observatory Master Clock Context triple: [United States Naval Observatory, produces, U.S. Naval Observatory Master Clock]
-
A.
International Atomic Time
International Atomic Time is a high-precision time standard based on the combined output of atomic clocks worldwide, serving as the fundamental reference for modern civil and scientific timekeeping.
-
B.
cesium atomic clocks
Cesium atomic clocks are ultra-precise timekeeping devices that use the microwave frequency of cesium atoms’ electron transitions to define and maintain the international standard for the second.
-
C.
Astronomical Clock
The Astronomical Clock in Prague is a medieval timepiece and astronomical instrument famous for its intricate mechanical design and hourly animated figures, making it one of the city’s most iconic landmarks.
-
D.
Canberra Deep Space Communications Complex
The Canberra Deep Space Communications Complex is a NASA-affiliated ground station in Australia that tracks and communicates with interplanetary spacecraft as part of the Deep Space Network.
-
E.
Arecibo Observatory
Arecibo Observatory was a world-famous radio telescope facility in Puerto Rico known for its pioneering work in radio astronomy, atmospheric science, and the search for extraterrestrial intelligence.
- F. None of above. chosen
- G. Unsure - the case is ambiguous/there is not enough information to decide.
NED2
Entity disambiguation (via description)
gpt-5-mini-2025-08-07
Target entity: U.S. Naval Observatory Master Clock Target entity description: The U.S. Naval Observatory Master Clock is the primary time standard of the United States, providing ultra-precise reference time for military, governmental, and global positioning system (GPS) operations.
-
A.
International Atomic Time
International Atomic Time is a high-precision time standard based on the combined output of atomic clocks worldwide, serving as the fundamental reference for modern civil and scientific timekeeping.
-
B.
cesium atomic clocks
Cesium atomic clocks are ultra-precise timekeeping devices that use the microwave frequency of cesium atoms’ electron transitions to define and maintain the international standard for the second.
-
C.
Astronomical Clock
The Astronomical Clock in Prague is a medieval timepiece and astronomical instrument famous for its intricate mechanical design and hourly animated figures, making it one of the city’s most iconic landmarks.
-
D.
Canberra Deep Space Communications Complex
The Canberra Deep Space Communications Complex is a NASA-affiliated ground station in Australia that tracks and communicates with interplanetary spacecraft as part of the Deep Space Network.
-
E.
Arecibo Observatory
Arecibo Observatory was a world-famous radio telescope facility in Puerto Rico known for its pioneering work in radio astronomy, atmospheric science, and the search for extraterrestrial intelligence.
- F. None of above. chosen
Statements (45)
| Predicate | Object |
|---|---|
| instanceOf |
master clock
ⓘ
time standard ⓘ |
| alsoKnownAs |
U.S. Naval Observatory Master Clock
ⓘ
surface form:
USNO Master Clock
U.S. Naval Observatory Master Clock ⓘ
surface form:
United States Naval Observatory Master Clock
|
| basedOn |
atomic clocks
ⓘ
cesium atomic clocks ⓘ hydrogen maser clocks ⓘ |
| contributesTo |
International Atomic Time
ⓘ
TAI ⓘ |
| country |
United States of America
ⓘ
surface form:
United States
|
| governedBy | U.S. Department of Defense policies ⓘ |
| hasComponent |
ensemble of atomic clocks
ⓘ
time comparison systems ⓘ time distribution systems ⓘ |
| location | United States Naval Observatory, Washington, D.C. ⓘ |
| locationCountry |
United States of America
ⓘ
surface form:
United States
|
| maintainedBy |
United States Naval Observatory, Washington, D.C.
ⓘ
surface form:
USNO Time Service Department
|
| operator |
United States Navy
ⓘ
surface form:
U.S. Navy
United States Naval Observatory, Washington, D.C. ⓘ
surface form:
United States Naval Observatory
|
| partOf |
U.S. Naval Observatory Master Clock
self-linksurface differs
ⓘ
surface form:
United States Naval Observatory timekeeping system
|
| precision | ultra-precise reference time ⓘ |
| providesService |
time dissemination to GPS system
ⓘ
time dissemination to government users ⓘ time dissemination to military users ⓘ |
| relatedTo |
cesium atomic clocks
ⓘ
surface form:
NIST-F1
National Institute of Standards and Technology ⓘ precision navigation ⓘ satellite navigation ⓘ time synchronization ⓘ |
| significance |
official source of time for many U.S. government agencies
ⓘ
official source of time for the U.S. Department of Defense ⓘ primary timing reference for GPS control segment ⓘ |
| standardFor |
GPS system time alignment
ⓘ
U.S. government timing requirements ⓘ U.S. military timing requirements ⓘ |
| timeScale |
Coordinated Universal Time
ⓘ
Coordinated Universal Time ⓘ
surface form:
UTC(USNO)
|
| use |
primary time standard of the United States
ⓘ
reference time for GPS satellite constellation ⓘ reference time for Global Positioning System operations ⓘ reference time for U.S. government operations ⓘ reference time for U.S. military operations ⓘ reference time for navigation systems ⓘ reference time for scientific applications ⓘ reference time for telecommunications timing ⓘ |
How these facts were elicited
The pipeline generated the facts above by prompting gpt-5.1 with this entity's name + description and the instruction below.
Instruction
You are a knowledge base construction expert. Given a subject entity and a description of it, return factual statements that you know for the subject as a JSON list of dictionaries(triples), where keys must be "subject", "predicate" and "object". The number of facts may be very high, between 25 to 50 or more, for very popular subjects. For less popular subjects, the number of facts can be very low, like 5 or 10. # Requirements - If you don't know the subject at all, return an empty list. - If the subject is not a named entity, return an empty list. - Include at least one triple where predicate is "instanceOf". - Do not get too wordy. - Separate several objects into multiple triples with one object.
Input
Subject: U.S. Naval Observatory Master Clock Description of subject: The U.S. Naval Observatory Master Clock is the primary time standard of the United States, providing ultra-precise reference time for military, governmental, and global positioning system (GPS) operations.
Referenced by (4)
Full triples — surface form annotated when it differs from this entity's canonical label.
United States Naval Observatory, Washington, D.C.
→
produces
→
U.S. Naval Observatory Master Clock
ⓘ
subject surface form:
United States Naval Observatory
U.S. Naval Observatory Master Clock
→
partOf
→
U.S. Naval Observatory Master Clock
self-linksurface differs
ⓘ
this entity surface form:
United States Naval Observatory timekeeping system
this entity surface form:
USNO Master Clock
this entity surface form:
United States Naval Observatory Master Clock