Welcome back HA03 - Robinson Crusoe Island

The Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) has successfully finished its most complex station rebuilding effort ever. Hydroacoustic station HA03 at Robinson Crusoe Island, Chile, was destroyed by a tsunami in 2010 which had devastated the main settlement on the island. The repair effort lasted four years and involved a cost of over US$ 20 million.

The Juan Fernandez archipelago is situated around 670 kilometres west of the Chilean mainland.

This most complex reconstruction in the CTBTO’s history was made possible through the dedicated support of our Member States. I wish to thank, in particular, Ambassador Alfredo Labbé for Chile’s close cooperation, assistance and warm hospitality.

Hydroacoustic technology is used to measure changes in the water pressure caused by sound waves. Data obtained from hydroacoustic monitoring provide information on the location of a nuclear explosion that has been conducted underwater, near the ocean surface or near a coastline. With only 11 stations, the hydroacoustic network has the lowest density of any of the four International Monitoring System (IMS) networks. As sound propagates very efficiently through water, relatively few stations are sufficient to cover the world’s oceans. Due to the low number however, there is little redundancy.
Station HA03 is important for assuring coverage of large parts of the South Pacific Ocean. The reconstruction of HA03 means that the entire hydroacoustic network, except for station HA04 in the Crozet Islands in the southern Indian Ocean, is now operational - see interactive map.

Click to learn more about hydroacoustic technology

A hydrophone node being launched into the water

I am very proud of the team that conducted this project with excellence from A to Z. Seeing the data flow to the IDC is both a sigh of relief, a celebration and ultimate proof of the high quality project management.

The first data from HA03 reached the CTBTO’s International Data Centre (IDC) in Vienna, Austria, on 2 March 2014, immediately after the installation of the northern triplet of hydrophones. The signals pass through over 30 kilometres of underwater trunk cable to a shore station and from there via a satellite link to Vienna. CTBTO experts in Vienna were able to provide instant feedback to the installation team in Juan Fernandez on the quality of data from the hydrophones.

The data passes through 30 kilometres of underwater trunk cable to the shore station, is formatted and sent via a dedicated satellite link direct to the IDC in Vienna.

To meet the challenge of performing according to the specifications for many years at depths of up to 2 km, enormous effort has been put into the design, testing and quality assessment of all subsea equipment.

The installation successfully passed full System Acceptance Testing on 10 March when data were being received faultlessly at the IDC from both triplets. The system will now undergo a further period of testing prior to its final acceptance.
Detailed planning undertaken over the last few years with our contractors and the Chilean Authorities ensured the smooth installation of the HA03 underwater system. Calm weather conditions were, of course, a bonus.

Project Manager Jerry Stanley said: “Reports on the quality of the data being sent by HA03 were made available by colleagues at the IDC in Vienna to the installation team on-board the cable ship so we knew almost immediately that we had achieved a successful installation.” One of the first events recorded by the reinstated HA03 was the  sounds made by whales near the station.

Spectrogram of a recording of whales made by the station shortly after is started sending data again – click to hear sound (sped up by factor 16 for audibility).

Cross-divisional team work, planning and perseverance were critical success factors in this project. It is not that we did not face problems during the re-establishment of HA03, we just stayed long enough with them.

See station profile for more background on HA03. In cooperation with United Nations TV, the CTBTO is producing a video on the reconstruction project. HA03 is one of seven stations hosted by Chile, see country profile.