over 2,000 nuclear bombs were detonad in the last t half of the 20th century. [exxplosion] but in 1996, the global community said "enough" and signed the united nations comprehensive nuclear test ban treaty. today, 183 countries have voluntaririly agreed to stp nuclear testing. but while signed in good faith, the mission of the ctbto is to verify the treaty's compliance with hard data. stanley: we're moving towards the final stages now of installing the hao4 station, but we were working in the roaring forties, so the weather can be very unpredictable. mario zampolli: those places, the roaring forties, are legendary among sailors and people who work at sea as some as some of the most difficult oceans in the world. you have what is called an unlimited fetch, currents that are also merging, coming down from south africa, merging with certain polar currents, that go all around the world, really undisturbed. in these difficult conditions was really something that p put a lot of streress on everybody, on all the tteams. you know that you'u're t afafforded, you'u're n