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06-Nov-04 | Delta flight 308 – NAVSTAR IIR-13

In the early morning hours of Saturday, 6 November, Delta flight 308 successfully placed NAVSTAR IIR-13 into a perfect transfer orbit to replenish the U.S. Air Force’s Global Positioning System.

After several postponements due to the hurricane season, a launch date of 30 October was delayed to change out batteries on the Delta third stage. The existing batteries had “exceeded their qualification margin” for power capacity. (In other words, weeks of delays left them worn out.)

The first launch attempt was made in the early hours of 05 November. A problem with a ground transmitter at one of the range tracking stations led to an extension of the built-in hold at T-minus 4 minutes; the liftoff time was reset to the last moment of the launch window. Then with less than a minute left in the resumed count, an alarm was triggered by a database problem in the launch data system, and a hold was called. With no time left to recycle to the 4 minute mark, the launch was scrubbed for the night.

After a 24-hour turnaround, all systems were go for a second try. The weather was vaguely coorperative, with a couple of cloud layers that were thin and broken enough to fly through, and gusty ground winds that approached but never violated the 25-knot rule. An unspecified range issue cropped up but was quickly resolved, and otherwise the terminal count was quiet and delay-free.

At the very opening of its launch window, 05:39:00.384 UTC, the three-stage Delta 7925 left SLC-17B and arced out over the Atlantic Ocean. The smooth flight, with two second stage engine firings, ended 25 minutes, 35 seconds later with spacecraft separation from its third stage motor.

Within the next few days NAVSTAR (Navigation Signal Timing and Ranging) IIR-13, Space Vehicle Number 61, will fire its onboard apogee motor to enter a circular, 11,000 n.m. operational orbit, where it will take over Plane D, Slot 1 from 2A-11, which launched aboard Delta 206 on 04 July 1991. This is a significant fact, as the average age of the 24 satellites presently in the Global Positioning System constellation exceeds the design lifetime of the satellites. For this reason, 5 more NAVSTARs are scheduled to be launched during 2005. This latest satellite was the last of the standard IIR (replenishment) models, as the next GPS satellite will be a “modernized” IIR-M model with an additional civilian signal and two encrypted military signals with improved resistance to jamming.


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