Project activities in the latter half of 2008 concentrated on final design and construction of the MARS (Monterey Accelerated Research System) Extension Cable and the refurbished MOBB (Monterey Ocean Bottom Broadband) interface electronics. Early 2009 was dedicated to extensive testing of the completed system, followed by successful installation at sea and commencement of operation on February 25th and 26th, 2009. The system ran well for almost a year, but on February 11th, 2010 the Extension Cable was severed by commercial fishing operations and has ceased operations until a replacement cable can be installed.

The final design of the MOBB interface closely matches that described in the project proposal, and meets all of the original functional and design specifications. One of the greatest challenges was in sending the MARS 1 pulse-per-second timing signal over the 3.6 km Extension Cable to the MOBB electronics. The installed circuitry is performing well and providing accurate timing to both the Guralp CMG-1T Broadband Seismometer and the Quanterra Q330 digitizer. The power and data connections are working equally as well, providing much more capacity than required by MOBB as may be required by future applications.

The MOBB backup power system is different from that described in the original project proposal. Instead of single-use lithium batteries, the final design utilizes a large capacitor bank to provide power if power from the MARS cable is interrupted. The capacitors can maintain operation of the MOBB system for more than two hours, thus preventing any loss of data for short power outages. Unlike lithium batteries, the capacitors can recharge when power is restored and have an essentially unlimited lifetime.

The backup power system was tested when the MARS PMACS (Power Monitoring and Control System) indicated a fault in the Extension Cable on April 5th, 2009, five and a half weeks after the system was activated. PMACS was indicating a ground fault, i.e. an unintentional connection to seawater from the 375 VDC power carried by the Extension Cable. To isolate the fault, power to MOBB was interrupted twice and the system continued to operate as designed with no loss of data. The PMACS tests indicated possible damage to the cable, and visual inspection by the ROV Ventana on April 13th revealed that the Extension Cable was snagged by an unknown fishing vessel and was pulled tight near the MARS node. Three subsequent ROV dives were used to reposition the cable and relieve the tension. The MOBB system continued to operate even with the ground fault, but a supplementary funding request was submitted and granted in order to replace the damaged cable.

On September 28th, 2009 an ROV dive near the MARS node revealed that the MOBB Extension Cable had been trawled a second time. Once again, the system continued to operate despite additional damage to the cable. This second incident, however, indicated that trawling incidents are not rare occurrences despite the issuance of clear marine advisories warning fishermen to avoid the areas where research equipment is deployed. A decision was made to better protect the replacement cable by burying it 20 to 30 cm deep in the sediment. The Monterey Bay National Marine Sanctuary approved a request to perform the cable burial operations.

The design of an ROV cable-burial plow commenced in early 2010. Based on lessons learned from the first cable itself was redesigned with steel strength members