My guess would be that the US is expecting to see more cruise missile threats, and this upgrade is about dealing with this.

Then again, it may be that the F-22 is too damn expensive to buy enough to use in a meaningful defense of the US, and the JSF is behind schedule.

US Air Force to expand Boeing F-15C active radar upgrade with Raytheon

By Stephen Trimble

Raytheon is reviving a programme to upgrade the US Air Force’s Boeing F-15C fighters with active electronically scanned array radars, expanding on an initial phase performed on a single squadron of 18 Alaska-based aircraft in the late 1990s.

The emergency supplemental funding bill for fiscal year 2007, signed by President George Bush in late May, contains about $62 million to upgrade a small number of active duty F-15Cs with an enhancement of the ‘brick’ array APG-63(V)2 radar previously integrated to now use a tile design, says Mike Henchey, Raytheon business development director. Raytheon has previously designated this as the APG-63(V)3, but it is likely to enter service under a new designation in the APG-series, he says. The (V)3 variant refers to the active array of transmitter/receiver modules, with this front-end to be mated with the APG-63(V)1 radar processor already installed on most of the USAF’s active duty F-15Cs.”

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