About

The ALOHA Cabled Observatory, or ACO, is a cabled observatory on the seafloor about 100 km north of the Hawaiian island of Oahu.  At almost 4,700 m below the sea surface, the ACO is the deepest cabled observatory on the planet.  A retired trans-Pacific telecommunication cable was donated to the University of Hawaii in early 2007.  Later, the US Navy cut the cable and dropped the end at Station ALOHA.  The other end of the cable is at a shore station on Oahu, and via this link Internet and power are supplied to the site.

The ACO thus provides infrastructure for continuous, interactive ocean sampling enabling new

measurements as well as a new mode of ocean observing that integrates shipboard, autonomous and cabled observations. The National Science Foundation (NSF) funded project began in 2002. In 2007, the retired AT&T HAW-4 submarine fiber optic cable was cut 100 km north of Oahu and a “proof module” (hydrophone and pressure sensor) attached. A general purpose “node” was connected in 2011 with instrumentation transmitting measurements of temperature, salinity, currents, acoustics and video. New projects facilitated by the ACO are

expected to span the water column addressing air-sea interaction, the carbon cycle, near surface plankton blooms, turbulence and mixing, abyssal ecosystems and more.

Different instruments have been deployed at ACO with varying degrees of success.  The extreme environment (mainly pressure) has proven a challenge for cable, connectors and housings.  At present the ACO provides:

• Salinity, temperature and pressure from two separate CTDs
• Acoustics from two separate hydrophones
• Currents from an ADCP

History

Instrument Layout

The ACO connects to the shore station via fibre optic cable.  This cable connects to the ACO via a junction box (JBox) that provides power and network addresses to the observatory.  The JBox connects to the main system (OBS).  The OBS has eight ports (E1 through E8) that connect to the various sensor packages.  These are configured as follows:

• E1:       Connects to Basic Sensor Package 4 (BSP4)
  • BSP4:   FLNTU, RBR, CTD2, umodem
• E2:       open/not used
• E3:       Connects to Basic Sensor Package 5 (BSP5)
  • BSP5:   CTD4
• E4:       Connects to Basic Sensor Package 3 (BSP3)
  • BSP3:   icListen
• E5:       Connects to hydrophones
  • HEM
• E6:       Connects to Basic Sensor Package ? (BSP?)
  • BSP?:   ADCP1, ADCP2, CTD1, 
• E7:       open/not used
• E8:       Connects to a secondary node (SN1)
  • SN1 connects via ports J1-J5
    • J1: Basic Sensor Package 2 (BSP2)
      • BSP2:   DQ, FLNTU, CTD3
    • J2: Camera 2 (CAM2)
    • J3: not used/open
    • J4: not used/open

Cruises

• ACO-1: October 2008, TAAM-1 deployed
• ACO-2: June 2011, OBS and TAAM-2, CAM, AAM deployed
• ACO-3: November 2014, BSP-1 and CAM deployed
• ACO-4: September 2015, BSP-2 deployed
• ACO-5: June 2017
• ACO-6: June 2018
• ACO-7: July 2019
• ACO-8: May 2021[JTP1] 
• ACO-9: August 2023

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