Comments on: Moving plane exchanges quantum keys with Earth

By: Editor

Editor — Mon, 17 Sep 2012 14:53:38 +0000

Right, a circle at fixed altitude and max distance would be optimal (only azimuth tracking, not Az-El).

By: Timothy

Timothy — Mon, 17 Sep 2012 14:40:03 +0000

Sorry, I guess I read the artlcle after the fix.

By: Timothy

Timothy — Mon, 17 Sep 2012 14:39:27 +0000

The article said the distance was 20km, not the altitude. Since the transmission lasted 10 minutes, the plane was probably flying a wide slow circle around the transmitter. At an altitude of 5 km (16,250 feet) a plane 19.3 km downrange would be 20 km away, and still well above the horizon.

By: Editor

Editor — Mon, 17 Sep 2012 14:24:36 +0000

Good catch! Fixed. A New Scientist error, but my bad for not reading carefully. The 20 km is obviously slant range, both because of the altitude envelope and to achieve reduced delta-f (doppler effects) and stationkeeping problems.

By: Gorden Russell

Gorden Russell — Mon, 17 Sep 2012 14:04:04 +0000

That altitude just didn’t look right so I clicked over to Wolfram Alpha and converted 20 kilometers into feet and got the answer of 65,617 feet. That plane has turboprops that can’t possibly get that high. This has got to be a misquote.