69
conditioning units and power supplies and can be equipped with satellite and/or
cellular communication antennae and global positioning system (GPS) antennae
for accurate timing.
In recent years, synchronized high frequency radar transmitter/receiver (Tx/Rx)
arrays have become useful for synoptic measurement of surface currents within about
200 km of the coast. Antennae and associated electronics are deployed on land as
close to shore as possible or on existing docks. Antennae are mast mounted and masts
in turn are mounted on fixed or swiveling bases on concrete pads when possible.
3.1.2 Ocean-Based Ocean Observing Platforms
Floating Bottom-Tethered Buoys
Payloads aboard fixed buoys are integrated into flotation structures of various
designs. Pan forms (Fig. 3.2) are common, but spheres, monohulls, catamarans,
vertical spars, and other designs attend to specialized applications. Buoyancy can be
provided by metal or fiberglass hulls or by different polymeric formulations such as
syntactic and ionomeric foams. Deep sea floatation units favor glass spheres encased
in hard polymer shells.
Mooring materials include chain link, wire rope, synthetic rope, and elastic components. A combination of link chain at the buoy and anchor ends and synthetic wire
rope in between minimizes tackle weight. Mooring anchors made up of sets of two
or three railroad wheels (weighing about one metric ton each) cojoined through the
axes provide a compact modular solution. Other anchor alternatives are scrap chain,
properly decontaminated junk motor blocks or purpose-built armored concrete
blocks (Fig. 3.3). In coastal shelf moorings, excess chain beyond the tidal datum
may be specified such that some chain remains on the bottom even under the highest
wave conditions. This slack chain configuration is effective in ensuring buoy integrity in heavy seas but results in bottom scouring around the mooring anchor as the
varying tides, winds, and currents drive the buoy. Deployment sites devoid of major
biota are consequently sought to minimize environmental damage. Loose gravel or
sand, subject to recurrent environmental bottom scouring, are preferred. A selfstanding frame with lead-filled legs can assist in ballasting the buoy at sea, and
facilitates maintenance on land. It can furthermore serve as a mounting surface for
instruments intended to monitor near-surface seawater properties. Additional oceanographic instrumentation may be deployed at various depths pertinent to local environmental variability. Such instrumentation is deployed within purpose-built
protective cages, integrated to the anchor line using specialized shackles and terminal couplings. Public or commercial satellite systems are used for data telemetry.
For nearshore applications, with appropriate antennae, redundant telemetry can be
achieved using commercial cellular networks or HF radio. Solar panels and wind
turbines can provide system power to the buoys. Power storage is economically
achieved using deep-discharge marine lead-acid batteries which double as additional ballast at the bottom of the buoy payload bay.
3.1 Fixed Ocean Observing Platforms
conditioning units and power supplies and can be equipped with satellite and/or
cellular communication antennae and global positioning system (GPS) antennae
for accurate timing.
In recent years, synchronized high frequency radar transmitter/receiver (Tx/Rx)
arrays have become useful for synoptic measurement of surface currents within about
200 km of the coast. Antennae and associated electronics are deployed on land as
close to shore as possible or on existing docks. Antennae are mast mounted and masts
in turn are mounted on fixed or swiveling bases on concrete pads when possible.
3.1.2 Ocean-Based Ocean Observing Platforms
Floating Bottom-Tethered Buoys
Payloads aboard fixed buoys are integrated into flotation structures of various
designs. Pan forms (Fig. 3.2) are common, but spheres, monohulls, catamarans,
vertical spars, and other designs attend to specialized applications. Buoyancy can be
provided by metal or fiberglass hulls or by different polymeric formulations such as
syntactic and ionomeric foams. Deep sea floatation units favor glass spheres encased
in hard polymer shells.
Mooring materials include chain link, wire rope, synthetic rope, and elastic components. A combination of link chain at the buoy and anchor ends and synthetic wire
rope in between minimizes tackle weight. Mooring anchors made up of sets of two
or three railroad wheels (weighing about one metric ton each) cojoined through the
axes provide a compact modular solution. Other anchor alternatives are scrap chain,
properly decontaminated junk motor blocks or purpose-built armored concrete
blocks (Fig. 3.3). In coastal shelf moorings, excess chain beyond the tidal datum
may be specified such that some chain remains on the bottom even under the highest
wave conditions. This slack chain configuration is effective in ensuring buoy integrity in heavy seas but results in bottom scouring around the mooring anchor as the
varying tides, winds, and currents drive the buoy. Deployment sites devoid of major
biota are consequently sought to minimize environmental damage. Loose gravel or
sand, subject to recurrent environmental bottom scouring, are preferred. A selfstanding frame with lead-filled legs can assist in ballasting the buoy at sea, and
facilitates maintenance on land. It can furthermore serve as a mounting surface for
instruments intended to monitor near-surface seawater properties. Additional oceanographic instrumentation may be deployed at various depths pertinent to local environmental variability. Such instrumentation is deployed within purpose-built
protective cages, integrated to the anchor line using specialized shackles and terminal couplings. Public or commercial satellite systems are used for data telemetry.
For nearshore applications, with appropriate antennae, redundant telemetry can be
achieved using commercial cellular networks or HF radio. Solar panels and wind
turbines can provide system power to the buoys. Power storage is economically
achieved using deep-discharge marine lead-acid batteries which double as additional ballast at the bottom of the buoy payload bay.
3.1 Fixed Ocean Observing Platforms