In article , "Kevin Brooks"
wrote:

"D. Strang" wrote in message
news:1%obc.4658$zc1.3787@okepread03...
The F/A-22 also has an inherent air-to-surface
capability." It can already lug a couple of JDAM's. So how does that
even
*require* an optimized ground mapping radar to allow it to strike ground
targets with significant precision?

I'm not a bombardier, but I think the SAR radar is necessary for the INS
inputs. The INS being only updated by the GPS, and only if the GPS
isn't being jammed (which will be unlikely down the road). I think I read
where GPS only doubles the accuracy of the INS (50 feet versus 100 feet).

Without SAR, and GPS being jammed, you'll need a good pair of TACAN's,
which some enemies don't seem to provide :-)

I have yet to hear that a SAR update is required. Doing so would require the
preloaded data for the terrain (so that the SAR would have something to
relate its picture to). From what i understand, the weapon gets its update
from the aircraft (through its own INS), then after release it uses GPS to
improve the accuracy of its own INS. If SAR was required, then I guess the
A-10 would never be certified to carry JDAM...?

That's ridculous.

SAR updates to pre-programmed INS settings have been used since the
early 90's to improve the accuracy of GPS aided munitions.

You don't need the SAR update to launch a JDAM, but it dramatically
improves the CEP of the weapon and essentially means that you can use
a smaller weapon to take out a target.

--
Harry Andreas
Engineering raconteur