Before the advent of the polymetallic nodules programme, the National Institute of Oceanography had been conentrating on exploring and understanding the continental shelf of India.Polymetallic nodules occur at an average depth of 4500 m. Therefore a number of new equipment and techniques were required for the exploration at such great depths. In all, the vessels that were deployed for the project, a large number of new equipment were fitted and several new techniques were tried out frm time to time. For example, the Gaveshani had relied on shore based systems like Decca for fixing a few hundred kilometres. For deep sea work far removed from the land, the Omega system and a Satellite Navigation System were installed.(Fig 21). These systems were routinely used for fixing the position of the ship at sea. The position of the ship could now be plotted with an accuracy of better than 100 meters.

Pettersson grab which was used with great success on the continental shelf for obtaining sediment samples, failed to collect samples at greater depths. A new trigger mechanism was designed indigenously and the grab worked successfully thereafter. For obtaining nodule samples, it proved to be too tedious and time consuming as only one sample could be obtained every 4 hours. However the Petterson grab and the Van veen grab were used whenever sediment samples were required ( fig 22). Sediment samples were also obtained by using gravity corers.( fig 23).

Gravity corers are essentially long pipes to which lead weights of a few tonnes are attached at the top .They are lowered with the wire rope slowly to about 50 metres above the seafloor then allowed to fall freely on to the ocean bottom. The tube penetrates to a maximum of 12 metres into sediment and sediment is collected to decipher the past history of the ocean. More sophisticated corer like the spade corers were used to get shorter but virtually undisturbed sediment samples ( fig 24).These cores are being used for geotechnical studies and for oriented nodule samples.

Boomerang grabs or free fall grabs, a novel method of collecting nodule samples, had been just introduced into the world maret. The boomerang grab was the main equipment used to collect information on the abundance of nodules in an area. Since no winch wire was required for its deployment, several boomerang grabs could be deployed at a station to increase the reliability of data (fig 25). It has two bouyant glass spheres with grab attached to it. Two heavy ballast weights are attached to the grab and it was dropped into the sea. On reaching the seafloor the ballast weights fall off and the boyant glass spheres bring the grab to the surface collecting the bottom sample in the process. A camera attached to the grab can also take a photograph of the sea bottom if required (fig 26). This grab was first used on Gaveshani and is collected nodule samples successfully.

Power echosounders were installed to chart the bathymetry and topography of the area. Magnetometer, which measures the total magnetic intensity at a point was also installed and data were obtained throughout the duration of the cruise.

Deep sea cameras with stainless steel housing to withstand the tremendous pressure at depths of 4000 to 5000 metres were operated to get photographs of the sea floor (fig 29). The camera, battery pack and flashlight were mounted on a steel frame and lowered to about 5 meters above the sea floor. A heavy weight attached with a 5 meter rope acted as a trigger mechanism for the camera. By repeatedly raising and lowering the camera frame a number of snapshots of sea floor could be obtained. Later on, hydrodynamically designed frames with fins were fabricated with the help of IIT Madras so that the camera could be towed at slow speeds to have greater control over the area to be photographed.

An altimeter and pinger to help control the height of the camera above the seabed, a digital clodk and a transponder to locate the camera, were fixed to the frame. The camera could now take one photograph every 10-15 seconds in a straight line and at the same time the exact time and height above the seafloor could also be printed on the photographs.

To obtain the nodule sample in bulk for metallurgical studies, the sea floor was dredged using dredged using dredges ( fig 31 & 32). For using the big dredges an additional winch having a 10,000 metre long steel wire rope of 18 mm diameter had to be installed on all the ships.

Ocean exploration techniques have be progressing rapidly during the last few years and a number of even faster techniques are now available for exploring the mineral wealth of the seas. The "ORV Sagar Kanya" will shortly undergo major refitting of new equipment like finite amplitude depth sounder, seabeam and deep towed multi-sensor system to map the ocean floor at much higher speeds and with greater resolution.

LABORATORY EQUIPMENT

From the time a nodule is picked up from the ocean floor till it reaches the onshore laboratory for analyses, more than a month elapses during which time the quality of nodles that were recovered remains undertermined. The grade, if determined at the survey area itself would provide a "real time" picture of the area being surveyed. This information would help the planner onshore to arive at immediate estimates. In order to circumvent this time lag analytical equipment was set up onboard. A portable X-ray fluorenscene equipment was installed on "M V Skandi Surveyor" and an atomic absorption spectrophotometer ( fig 34) for chemical analysis of elements was installed on board " MV Farnella" and "MV G A Reay". "ORV Sagar Kanya" the most modern addition to the fleet of oceanographic ships in fully fitted with all the analytical and the necessary accessary facilities. The analytical data thus acquired was transmitted forthwith via radio telephone . The information thus provided regarding the grades and abundances of nodules in the survey area helped speedier planning of further work.

The existing research facilities in the Institute were augmented with sophisticated nalytical equipment to probe into several new aspects. A geochronological laboratory was set up ( fig 35) with radio active dating equipment to decipher the geologic past, the growth rates of nodules and crusts, and the rates at which sediments accumulate in different regions of the ocean. To study the small and minute details , and the oceanic microcosm a state of art scanning electron microscope( SEM) and an electrom microprobe was installed ( fig 36). This instrument has the capacity to mangnify the samples under study upto 2,40,000 times and the electron microprobe attached to it can chemically analyse a spot as 1 micrometer

The Department of Ocean Development had in the meantime sanctioned the requisite finance and a new building with a floor area of 740 sq. metres was constructed for the storage of the samples, the large amoung of underway data and the equipment ( fig 37, 38, 39 ).