Colossus

A team of scientists is proposing to build a huge telescope-- twice as large as the current biggest on Earth-- to search for the heat signatures of advanced technological civilizations out to about 70 light years away.  They reasonn that such civilizations use huge amounts of energy and therefore generate prodigious quantities of waste heat.  That heat could be observed by a sufficiently telescope.  The team calls the telescope Colossus.

Estimated cost of Colossus is $1 billion, and it could be built in five years.