- Navigation satellite
- NORAD 27663
- 2003-005A
- Medium Earth orbit
Current orbit
View on live mapOrbit began over the People's Republic of China
Orbit ends over the United States of America
In view from you
Nobody watches NAVSTAR 51 (USA 166) go over, but a receiver still asks whether it is above the horizon. Say where you are and this card answers.
Your position is rounded to about a kilometre and sent only to the Orbinauts API, to find the pass.
No brightness has been published for NAVSTAR 51 (USA 166), so it is not a naked-eye satellite and no city page carries pass times for it. Nothing here estimates one.
Seeing it
There is nothing to go outside for: it is far too high and too faint for the naked eye. What you notice of it is a position fix, and the card above says whether it is above your horizon to give you one.
Timeline
Summary
Over the Caribbean Sea LIVE
Where is NAVSTAR 51 (USA 166)?
At 8:57:14 PM UTC NAVSTAR 51 (USA 166) was over the Caribbean Sea (18.9° N, 86.9° W), 19,837 km up, moving at 3.93 km/s and in sunlight.
What is NAVSTAR 51 (USA 166)?
A navigation satellite in medium Earth orbit, one of the 32 navigation satellites of the GPS constellation.
Can I see NAVSTAR 51 (USA 166)?
No, not with the naked eye: no brightness has been published for NAVSTAR 51 (USA 166), and nothing here estimates one; receivers on the ground use its signals instead, whenever it is above their horizon.
General
NAVSTAR 51 (USA 166) is one of the 32 navigation satellites of the GPS constellation. See every GPS satellite and how many are above you right now.
- Known to its operator as
- PRN 16
- Space vehicle number
- 56
- Clock in use
- Rubidium
- Generation
- GPS Block IIR
- Signals
- L1 C/A and P(Y) on L1 and L2
- Design life
- 7.5 years
- Built by
- Lockheed Martin
- Typical altitude
- 20,000 to 20,400 km
Latest orbital data
- Position received
- 8:57 PM UTC
- Station time (UTC)
- 8:57 PM UTC
- Latitude / longitude
- 18.9° N, 86.9° W
- Altitude
- 19,837 km
- Speed
- 3.93 km/s (14,130 km/h)
- Course
- north
- Light
- In sunlight
- Inclination
- 54.9°
- Orbital period
- 718 minutes
- Orbits per day
- 2.01
- This orbit
- 19,783 to 20,583 km
- In shadow
- None of this orbit
- In view from
- Within 7,360 km of the point below it
- Elements epoch
- Sep 17, 2026, 8:36 PM, 1 day old
- Source
- Position from Space-Track orbital elements of Sep 17, 2026, 8:36 PM, 1 day old.
No operator publishes an ephemeris for NAVSTAR 51 (USA 166), so every position here comes from its orbital elements.
In service
A receiver can count on it now.
- Usable now
- Yes: its operator has published no outage in force.
- Plane and slot
- Plane B, slot 1
- Last outage
- Sep 4, 2025, 9:29 PM to Sep 5, 2025, 3:15 AM, forecast Notice
From GPS’s own notices, as its operator published them on Sep 16, 2026, 1:55 AM.
In orbit
- Close approaches
- Close approaches to NAVSTAR 51 (USA 166) are not available right now. Try again in a few minutes.
Beside the others
| Constellation | Satellites | Typical altitude | Orbital period | Planes | Operator |
|---|---|---|---|---|---|
| GPS | 32 | 20,000 to 20,400 km | 718 minutes | 6 | The United States Space Force |
| Galileo | 27 | 23,100 to 23,300 km | 845 minutes | — | EUSPA, the European Union Agency for the Space Programme |
| BeiDou | 37 | 21,450 to 21,600 km | 773 minutes | — | The China Satellite Navigation Office |
| GLONASS | 22 | 19,050 to 19,200 km | 676 minutes | — | Roscosmos, the Russian State Space Corporation |
Data and API
The current elements from Space-Track as an OMM object, epoch Sep 17, 2026, 8:36 PM, 1 day old.
{
"OBJECT_NAME": "NAVSTAR 51 (USA 166)",
"OBJECT_ID": "2003-005A",
"EPOCH": "2026-09-17T20:36:16.192800",
"MEAN_MOTION": 2.00555608,
"ECCENTRICITY": 0.01505617,
"INCLINATION": 54.8679,
"RA_OF_ASC_NODE": 211.2898,
"ARG_OF_PERICENTER": 53.6734,
"MEAN_ANOMALY": 317.9316,
"EPHEMERIS_TYPE": 0,
"CLASSIFICATION_TYPE": "U",
"NORAD_CAT_ID": 27663,
"ELEMENT_SET_NO": 999,
"REV_AT_EPOCH": 17317,
"BSTAR": 0,
"MEAN_MOTION_DOT": 1.7e-7,
"MEAN_MOTION_DDOT": 0
}