USA-251

A Block IIF GPS satellite
Mission type	Navigation
Operator	US Air Force
COSPAR ID	2014-026A[1]
SATCAT no.	39741[1]
Mission duration	12 years (planned)
Spacecraft properties
Spacecraft	GPS SVN-67 (IIF-6)
Spacecraft type	GPS Block IIF
Manufacturer	Boeing
Launch mass	1,630 kilograms (3,590 lb)[2]
Start of mission
Launch date	17 May 2014, 00:03 (2014-05-17UTC00:03Z) UTC
Rocket	Delta IV-M+(4,2), D365[3]
Launch site	Cape Canaveral SLC-37B[3]
Contractor	ULA
Orbital parameters
Reference system	Geocentric
Regime	Medium Earth (Semi-synchronous)
Perigee altitude	20,443 km (12,703 mi)[4]
Apogee altitude	20,474 km (12,722 mi)[4]
Inclination	55.04 degrees[4]
Period	729.22 minutes[4]
Epoch	17 May 2014

USA-251, also known as GPS IIF-6, GPS SVN-67 and NAVSTAR 70, is an American navigation satellite which forms part of the Global Positioning System. It was the sixth of twelve Block IIF satellites to be launched.^[2]

Launch

Built by Boeing and launched by United Launch Alliance, USA-251 was launched at 00:03 UTC on 17 May 2014, atop a Delta IV carrier rocket, flight number D366, flying in the Medium+(4,2) configuration.^[3] The launch took place from Space Launch Complex 37B at the Cape Canaveral Air Force Station,^[5] and placed USA-251 directly into medium Earth orbit.^[4]

Orbit

As of 17 May 2014, USA-251 was in an orbit with a perigee of 20,443 kilometers (12,703 mi), an apogee of 20,474 kilometers (12,722 mi), a period of 729.22 minutes, and 55.04 degrees of inclination to the equator.^[4] It is used to broadcast the PRN 06 signal, and operates in slot 6 of plane D of the GPS constellation. The satellite has a design life of 15 years and a mass of 1,630 kilograms (3,590 lb). ^[2] It is currently in service following commissioning on June 10, 2014.^[6]