1.   A transponder allows Federal Aviation Administration radar to track aircraft in the skies.

2.   But some particles are too small to be tracked by radar.

3.   Conventional radar tracks storms by detecting microwave radiation reflected by precipitation.

4.   Military officials said Monday that an AWACS radar had tracked the jet to about one and a half miles from the point where the debris was spotted.

5.   Missile radars have tracked allied patrols and gunners have fired anti-aircraft artillery and surface-to-air missiles at them.

6.   Pentagon officials have also said they want to schedule tests in which ship-based radars track long-range missiles early next year.

7.   Radar tracks an average of three mortar shells a day.

8.   The radar tracked the plane until it flew too low to be picked up by that radar station, officials said.

9.   The receivers detect radar signals from enemy installations and warn pilots when a plane is being tracked by enemy radar.

10.   Until then, the Norwegian government had said the radar would track space debris, an assertion questioned by Postol.