Transit to Dive Site
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18deg 38 53 N
Longitude: 104deg 24 42 W
Wind Direction: NW
Wind Speed: 14.5 Knots
Sea State 2
Height: 1 Foot
Sea Temperature: 83°F (28.6°C)
Barometric Pressure: 1014.3 MB
Visibility: 10 Nautical Miles
Chicken with rice soup
Grilled reuben sandwiches
Halibut with ginger sauce
London broil with onions and mushrooms
Half baked potato
Cauliflower with cheese sauce
Black and white cherries
January 28, 2000
By Dr. Dan Fornari
Daybreak saw the RV Atlantis steaming at
almost 13 knots through near glassy seas, scattering flying fish
by the dozens as it headed to the dive site on a course of 185°.
All the scientists on board are getting used to the routine of
life at sea, learning when meals are served, and getting acquainted
with the ships crew. Patrick Hennessy has the trolling
lines out but so far no fish has hit the lines, probably because
we are going so fast. Interestingly, weve heard that the
fishing out in this area of the Pacific has not been very good
the past few years because of El Nino. Well be able to
tell first hand when we get to the dive site and the fishermen
among us break out their rods and reels!
Today, graduate students, Greg Kurras, Jenny Engels
and Del Bohnenstiehl worked hard at preparing the Towed Camera
Sled for the night-time surveys it will do. This camera sled
is a much simpler version of the Argo towed mapping system operated
by the Woods Hole Oceanographic Institution for many scientists
[Click here to learn more about ARGO].
Argo is able to send up four video signals, sonar data, and loads
of other types of information to scientists on board a ship so
they can look at, and map the seafloor as they are driving over
it. It can even steer around a bit using its 2 thrusters.
The Towed Camera, on the other hand, has affectionately
been called a Dope on a Rope because it does not
have any of the smart features of the fiber optic
based Argo. The Towed Camera Sled does a good job though by collecting
photographs of the seafloor that scientists can use for their
research. It has a deep sea digital camera made by Benthos, Inc.
of North Falmouth, MA, a well known manufacturer of deep ocean
cameras and equipment. Dan Fornari has been working with Bill
Hersey , an engineer at Benthos to develop this camera over the
past few years. This camera takes 2300 black & white digital
pictures on each lowering to the seafloor and stores them on
a 4 Gigabyte (a Gigabyte is 4 billion bytes of information!)
hard drive in the computer that is built into the system.
The camera uses 2 high-power strobes (600 watt/sec)
for lighting. The sled is towed about 7 meters (23 feet) above
the seafloor and scientists onboard Atlantis are able
to tell how high it is above the rocky bottom by using a pinger.
The pinger makes a sound that is bounced off the seafloor and
also travels directly to the ship. The two sound pulses (the
direct one and the bounced one) are received by a hydrophone,
an underwater listening device on the hull of the ship, and fed
into an amplifier to make a record on a screen. The separation
between the two pulses tells us how far off the ocean floor the
camera is. Sometimes, if the seafloor is very rough it is hard
to keep from hitting. Thats why the Camera Sled is so
sturdy! After the tow, when the camera is back on board Atlantis,
the students will transfer the images from the camera to computer
disks and then analyze them. Well hear a lot more about
the discoveries that the Towed Camera Sled will make in the days
to come. We are hoping to do a first test lowering tomorrow night.
Briefing the scientists who will be diving on this
cruise continued today as the Alvin crew kept doing their
routine maintenance of the submarine as well as checking all
the wiring and operation of the gravimeter, magnetometer and
another Benthos digital camera (this one takes color photographs)
that will be used during the dives. One important task that the
crew has to do when a new science party comes on board and installs
new equipment is making sure that there are no grounds in the
electrical systems (Read more about the electrical
system in Alvin)
Because Alvin operates on batteries, and
because it dives in the ocean where the salt water easily conducts
electricity, they have to be very careful about how the electricity
flows in all the equipment that is operated in the sub. so that
it is safe and not wasted. It takes a lot of time, patience,
and knowledge to do this correctly. Tomorrow we plan to launch
transponders in the morning, and survey-in their positions so
that we have good navigation for Alvin when it dives on Sunday.
The Big O Out of Alvin
By BLee Williams
are often called electric boats because they
need lights and power to see and move, computers to log
data, and sensors to measure temperature and pressure.
Add to that the manipulation capabilities and the needs
of the scientific equipment that Alvin uses, and
you can see why Alvin needs electricity to operate.
Williams holding one of Alvin's penetrators. These
penetrators are located around the viewports and
are where wires from outside of Alvin's sphere
come inside the sub.
Understanding how electricity can be safely used in the Big O,
as submariners sometimes call the ocean, is one of the first and most important
lessons a new submariner learns. Seawater is able to conduct electricity
very easily. Very pure water will not conduct electricity, but if you add
salt to it, then electricity will pass through it because of the dissolved
salt. The electrical energy to run Alvin and all its tools is stored
in big batteries made up from lots of high-power golf cart batteries (see
the Interview with BLee Williams - Alvins chief electrician
and the person responsible for its batteries). It is very important
that the energy stored in these batteries is not allowed to leak out
of Alvin. Apart from wasting precious power and not being able to
complete all the science planned for a dive, leaking power causes damage
Electricians call leaking power a ground. When a piece of
equipment becomes grounded, the electricity no longer flows through it
correctly. Instead of staying in the wires, electricity gets out where
the equipment is plugged in or, in the case of equipment on Alvin,
into the pressure housing (the titanium metal case that protects the wires
and components from the pressure in the deep ocean). These grounds allow
the electrons holding together the atoms of metal in the electrical wires
to float away into the ocean. If the ground is bad enough,
or is left uncorrected, the metal actually begins to disappear as the bonds
holding the atoms together are removed. This is called corrosion.
Pretty soon, the wire disappears and electrons can no longer move along
it. This could lead to electrical connectors failing and could let seawater
into pressure housings or even the Alvin personnel sphere.
equipment does not work properly, so sensitive instruments
that rely on electricity from Alvins batteries
need that power to be good, or clean as electricians
call it. Alvins electrical team (ETeam) is
primarily responsible for the subs electrical systems
and testing for grounds on all its permanent equipment,
as well as additional equipment that different scientists
bring out to do their experiments. The ETeam inspects Alvins
electrical system for grounds before and after every dive.
During the dives, the pilots check for grounds frequently.
Equipment that becomes grounded is never operated. Even
a little ground on a piece of electronics
is not good enough; it is either not grounded
or it is not used.
close-up view of one of Alvin's penetrators.
I tell new members of the Alvin Group: Its nice to
love the sea, but a healthy respect for the awesome power of the water
is what will keep you alive. Keeping track of grounds and where
electricity is flowing in Alvin is important when working in the Big