scanning in the cold

We have a Trimble GX. The spec sheet says
Operating Temp: 0°C to 40°C
storage temp: -20°C to 50°C

First question: why the cold restriction? Laser? circuit board?

Second question: has anyone tried using somnething like heating pads around the scanner to keep it warm?

Mr. Hamilton,
                        At about 0 to 4 degress Celsius there is a possibility of " Atmospheric Ice Mist", which could confuse the data collection processor
                         I usually give up at -15 Celsius .
                         stan
                     

The laser tube inside the scanner needs to reach a predesignated temperature for proper operation. Using a heating blanket or heat lamp on the scanner may introduce refraction issues during operation.

Been there. Done that.

If you want cold-weather operation: buy a Riegl.
Their systems work in extreme cold and are reputed for their ruggedness and reliability

They're typically more expensive than the rest, but a few completed jobs (where others fail) will cover the cost.