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20-Dec-07 | Delta flight 331 – NAVSTAR IIR-18 (M5)

A Delta II 7925 today lofted another Global Positioning System replenishment satellite for the U.S. Air Force.

Liftoff was delayed by five minutes after the opening of the fourteen-minute launch window due to a collision avoidance period, or COLA, which is a common occurrence in launches since there are so many objects already in orbit. Despite the COLA, the countdown was without major issues, and the three-stage Delta II left the pad at Cape Canaveral’s SLC-17A with an official range liftoff time of 20:04:00.353 GMT.

Fifty-eight minutes later, the GPS satellite was released into its nominal transfer orbit, which is an elongated path of about 11,000 nautical miles in apogee. The satellite will fire its own onboard AKM within the next several days to circularise its orbit. It will enter Plane C, Slot 1, replacing IIA-24, which will move to Plane C, Slot 5 to replace IIA-20. (IIA-24 was launched aboard Delta 226 in 1994. IIA-20 was launched on Delta 220 in 1993, and has more than doubled its seven-year design lifetime. It is showing signs of its age and will be decommissioned.)

This was the 46th launch of a GPS satellite by Delta II, all but one of which have been successful. (A further 11 experimental GPS satellites were launched on Atlas vehicles between 1978 and 1985.) It was also the 79th consecutive successful launch for Delta II, a continuing world record.


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