Seeing Power Beaming

[stevebowers]

A really interesting article at Centauri Dreams
The Benfords are doing some really interesting stuff on boostbeaming.
http://www.centauri-dreams.org/?p=34133

Figure 1. Schematic of Mars cargo mission via microwave beaming, not to scale. The path of the sailship is the dashed arrow. The inset is the beam profile shown in green overlaying the sail of diameter Ds. The beam always overlaps the sail to some extent.

How to See Power Beams

At 100 parsecs (326 light years), beam intensity is estimated to be of order 1 Jansky, which is about 100 times the typical detectability of SETI radio searches. The sweeping action of the beam in Figure 2 has implications for observers. The receiving radio telescope will typically see a rising signal because the beam is beginning to sweep past, then a drop in signal as the sail’s shadow falls on the receiver, then a rise as the beam reappears, followed by a decline. In other words, the time varying history of intensity is a symmetric transient with two peaks with much less (or even nothing) in between. They estimate the timescale for the transit to be of order 10 seconds.