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25-Jun-04 | Delta flight 305 – NAVSTAR IIR-12

On the evening of Wednesday, 23 June, the 305th Delta flight placed a NAVSTAR satellite into transfer orbit for the U.S. Air Force’s Global Positioning System.

The launch, previously slated for early June, slipped by nearly three weeks. At first a suspect hydraulic pump on the first stage of the Delta rocket was replaced, causing about a week of delay. This was followed by a wiring harness investigation, and then a faulty yaw actuator on one of the first stage vernier engines. A pad-clearing hazard alarm (which turned out to have been a false alarm) added a day to the pre-launch activities. And then Florida’s typical summer weather struck, and three straight attempts were scrubbed by fast-moving thunderstorms after tanking operations had completed.

Finally, though the launch weather officer was predicting a 70% chance of violating launch conditions at the start of the 150-minute Terminal Countdown, the Delta team tried again, and this time Mother Nature cooperated.

A smooth countdown procedure ended at exactly 18:54:00.693 EDT as the three-stage Delta 7925 lifted from Pad 17B. A quick, 25 minute 35 second flight followed, and NAVSTAR IIR-12 was released into a transfer orbit of 101.4 by 11,106 miles and 38.99 degrees of inclination.

The launch, the 58th consecutive success for Delta II, was dedicated to the memory of President Reagan. The latest addition to the GPS Space Segment, IIR-12 will soon boost itself into its operational orbit (Plane F, Slot 4), where it will replace the aging NAVSTAR IIA-16 spacecraft, which was launched aboard Delta 216 on 22 November 1992. IIA-16, having served long past its design lifetime, has begun to suffer from “degraded clock performance,” and will be retired into a nearby position in the same orbital plane to act as a backup satellite as needed.

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