Available Scientific Sampling Equipment
Scientific sampling with Alvin can range from relatively simple procedures like rock retrieval to more complex data collection using specialized sensors. The submersible’s capability to interface with instruments, and the reduction in size of many external sensors, has enabled acquisition of a wide range of data types and greatly improved the quality and quantity of the data collected.
Although many of the sampling techniques used during dives have been developed and refined through years of practice, Alvin Group engineers are available to assist with the development of mission-specific sampling concepts. This may include discussion of in-situ experimental methods and sampling techniques, design of custom sensors, joint operations with other vehicles (e.g., AUV Sentry), use of sampling elevators, etc.
The following are brief descriptions of the sampling gear routinely available for use by cruise participants. In most cases the samplers are resident on the support ship and available on short notice. In a few special cases there may be some lead time associated with preparation and availability of the equipment. In all cases the requirements to use Alvin-supplied sampling equipment must be made known to the Alvin Group as far in advance as possible during pre-cruise planning.
Biological Sample Collection Boxes (Bio Boxes)
Alvin’s standard biological sample boxes are constructed of 1" thick HDPE plastic and have a fully-hinged lid with a polyurethane tube seal. These boxes provide a reasonable measure of insulation and sample integrity. They are best used for robust samples as some mixing may occur during transit.
Standard - 12” x 12” x 12”, 2 available.
Large - 12” x 24” x 12”, 2 available (can be half-sectioned via a removable central divider)
Sensitive Sample Bio Box
Alvin’s sensitive sample bio box is constructed of 1" thick black HDPE plastic and has a fully-hinged latching lid and a highly effective watertight seal. This bio box is purpose-built for sensitive samples that require a high degree of insulation and sample integrity. This box is reserved for sensitive samples and is not intended for general use.
12” x 18” x 12”, 1 available
The SeaBird SBE49 profiling CTD measures conductivity, temperature, and depth (pressure) at 16 Hz (16 samples/second) as it travels through the water column. It features pumped and ducted constant flow for matched temperature and conductivity response, and measurements are made on the same sample of water with a predictable delay and predictable flow effects. CTD data can be used to calculate salinity, density, sound velocity, as well as other parameters of interest. The interface is RS-232.
Heat Flow Probes
Alvin has two heat flow probes available: a 1 meter long five-element temperature sensor and a 0.60 meter long four element temperature sensor.
Both sensors are used to measure temperature gradients when inserted into soft sediments. Measurable temperature range is 0 to 40 °C, with 0.2 degree accuracy and .001 degree resolution. Additionally, a temperature pulse can be generated and monitored to observe temperature decay in sediments. Data from the heat flow probe is normally displayed on the observer's internal video overlays and is additionally recorded in the submersible's computer data files. Only one probe may carried during a dive. Water weight is 4 lbs each. Basket space is required to carry the quiver.
The Sonardyne Homer Pro beacon system allows fast, efficient relocation of underwater targets such as sample elevators and deployed or in situ sampling equipment.
The system consists of an Alvin-mounted range and direction unit, control software and small, lightweight marker transponder beacons. Targets are equipped with a transponder before they are deployed. When the Pilot selects the target he wishes to 'home' to, the unit begins interrogating the designated transponder, determines its range and direction, and displays it for the Pilot, allowing the sub to be flown directly towards the target.Alvin has six beacons available, allowing multiple targets during a dive or series of dives, and a long battery life ensures the ability to retrieve them.
This 4-axis instrument is based on the IFG Four Component Vector Magnetometer. It consists of a 3-axis sensor with a redundant Z-axis sensor to provide gradient. It has a range of over ±100µT, with data resolution of 0.1nT. Absolute accuracy is expected near 1µT.
The instrument can be mounted in a variety of locations on the submersible. Most common is either in the submersible sail or the science basket. A total of two power conductors and one twisted/shielded wire pair are required to stream real time data into the submersible hull. Data from the magnetometer is normally displayed on the observer's internal video overlays and is additionally recorded in the submersible's computer data files. The magnetometer must be requested prior to the cruise. Instrument space requirement is dependent on location. If installed in the science basket, water weight is 16 pounds.
This is a 3-axis magnetometer based on the Honeywell HMR2300 sensor. It is capable of measuring up to ±2 Gauss with <70µGauss resolution, at about 10 samples per second. Absolute accuracy is expected near 5000 µGauss. This instrument is commonly mounted on the port aft end of the light bar.
Major Water Samplers
These 760 ml syringe-style instruments have inert titanium housings with an inductively-coupled link (ICL) for in situ temperature measurements, and are capable of handling water temperatures in excess of 400°C. They are configured in pairs on Alvin, but can be triggered individually. A total of six major pairs are available at any one time, and require a dedicated mounting frame on the science basket. Water weight is 22 lbs/pair with ICL. Post-dive care and maintenance of this equipment is the responsibility of the science party.
These instruments are commonly used to capture water column and hydrothermal vent plume water samples. They seal off the sample and allow it to be brought to the surface without mixing with water from different depths. The water collected by Niskin bottles is used for studying plankton or measuring many physical characteristics such as salinity, dissolved oxygen, nutrient concentrations (such as phosphate, nitrate and nitrite), and dissolved organic and inorganic carbon.One liter PVC bottles mounted in a 5-pack arrangement are standard, and can be triggered individually by the manipulator. The rack is easily removed post-dive for science processing. Water weight is 10 lbs. Overall basket space required is 12" x 18".
Push corers are soft sediment samplers deployed using a manipulator. They are 2.5" ID by 12" long, utilizing a removable, clear polycarbonate barrel. Commonly stowed in a 3 x 4 rack for a total of 12 corers, Alvin can carry two of these racks for a maximum of 24 corers per dive. Note that carrying this many corers will limit the basket space available for additional science equipment. A total of 48 push corers can be carried if investigators supply another 24 and there are no other basket space requirements. The racks are easily removable for post-dive processing.
There are a limited number of core barrels available during any particular leg. Investigators contemplating keeping samples in a collection barrel for post-cruise examination must make arrangements to replace all barrels used. PIs should also be prepared to supply watertight plastic endcaps for any samples taken. Procurement information for these two items can be furnished upon request. Water weight per 3 x 4 rack is 20 lbs; overall basket space required is 12" x 18" per rack.
Rock Collection Baskets
Alvin can be equipped with milk crates fastened to the science basket in order to transport rocks or other bulky items collected using a manipulator. If desired, the milk crates can be divided in order to help distinguish rocks taken from multiple sites.
- 12” x 12” x 12” milk crates
- 12” x 18” x 12” milk crates
- Dedicated 3’ x 4‘ wire basket with sections
A number of manipulator-deployed scoop sample nets are available in various shapes and sizes. Typically these are rigged with an open 1/4" mesh bag or canvas rock bag and placed in the science basket on a space available basis. Water weight is 2 lbs each.
The resistance temperature device (RTD) is capable of measuring water temperature up to 400°C, reporting about one sample per second. The instrument provides 0.01°C resolution and accuracy is 0.02°C. The case is 4” diameter by 6” long, with typical sensor tips ¾” diameter and 12” long. Sensors are manipulator deployable utilizing a T-handle. The instrument can be configured to report temperature from up to four sensors at once, though the time response is greatly decreased.
The inductively-coupled link (ICL) temperature probe is a wireless data transfer device most commonly used in conjunction with major water samplers to take real time temperature measurements during sampling. The ICL electronics can also be used for a variety of other data transfer and control functions. The sensor tip of the ICL probe is installed in the inner bore of the water sampler intake nozzle and senses the fluid temperatures as water flows past. The measurable temperature range of the probe is 0 to 450°C. Data from the probe is normally displayed on the observer's internal video overlays and is additionally recorded in the submersible's computer data files. Water weight (ICL probe only) is 1 lb.