Question about the F-22 and it's radar.

"Kevin Brooks" wrote

"D. Strang" wrote

The way I picture it, and I admit I may be completely bogus on this, but
I
picture the navigator finding a reference point (coordinates), and then
using
the SAR to find the point in weather, and then updating the INS from
this
point. You wouldn't need SAR if the point was available by other means,
or the target could tolerate greater than 100 foot error. For example,
if
a 2k/lb jobber hit 500 foot from my house, I'd still be dead, and the
house
would be destroyed :-)

I am guessing that the primary means of updating the aircraft INS is via
GPS; maybe BUFFDRVR or one of the folks who has a clue can answer that
question. Otherwise you'd have a wee bit of a problem if your target was a
coastal one and your ingress was from over the water, or if you were
dropping it over a nice, relatively flat desert plain where you could not
get much in the line of significant terrain features from which to perform
your update, etc.

On-board SAR's main purpose in fighters is autonomous targeting. As far as I
know, no fighter is planned to have GMTI functions but SAR imaging has been
a standard function for a long time. Other targeting options of course
include off-board sensors and Guys On the Ground. GPS is unlikely to be
jammed for aircraft since any ground based jammer is going to be 'way out of
the main lobe of an AJ GPS antenna. JDAM and SDB are going to get AJ
antennas as well.

There is an issue with geolocation. From what I've read in AvWeek,
geolocation errors are the dominant error term in the JSTARS to JDAM loop.
B2s (again according to AW) are the most accurate platform for RADAR imaging
and targeting, which is surprising.