Record Set for Space Laser Communication

Record Set for Space Laser Communication
By Ker Than, 05 January 2006

In late May of 2005, scientists used the spacecraft's Mercury Laser
Altimeter (MLA), an instrument designed to map Mercury's surface, to
exchange laser pulses with NASA's Goddard Geophysical and Astronomical
Observatory in Maryland. MESSENGER was approximately 15 million miles (25
million km) away at the time.

The experiment, reported today, marks the first successful back-and-forth
exchange of laser signals between Earth and space.

The record-setting effort is described in the Jan. 6 issue of the journal
Science.

Does anyone know what frequency light they used for this? Also how big is
the beam spot at earth? I am guessing much bigger than the whole earth?