The theory goes that the mirrors will help reflect the intense heat of the sun, with the mirrors remaining at a temperature of about 160C (320F), and the inner body of the craft holding the observation equipment being kept to below 60C (140F) – hopefully enabling the MMO to survive.
The craft will stand around 6ft high and will be powered in part by solar energy collected by panels wrapped around a main body that will constantly rotate to prevent any one side becoming too hot.
Mercury is the closest planet to the Sun although not the hottest. Because of its proximity to the sun it lacks an atmosphere as this was 'burned off' long ago, leaving an empty wasteland of rock with a similar surface to the Earth’s moon. There is nothing to hold in solar radiation and so it just flies out into space.
Next planet along Venus, however, is a different story altogether. The atmosphere there is mainly composed of carbon dioxide (the primary green house gas) which acts like a one-way door for the solar heat - solar heat enters, but cannot leave again and thus, an oven is created.