How many of them are there?
One. It makes life exciting to only have one- there are several back-up release mechanisms built into the hardware and software based on mechanics, chemistry, acoustics and computers, but everytime it gets deployed there is a slight chance that it won'tcome back.Has it ever hit the bottom?
Unfortunately, yes it has. We often attempt to profile to within 10-15 meters of the bottom. Since it will drift sideways as it falls through the water, there is no way to know exactly where it will encounter the bottom. So we turn the altimeter on well above the expected bottom depth. If the altimeter cannot sense the bottom, and the pressure for release is deeper than the actual bottom, it will crash. We have gotten it back every time, though, usually with minimal damage to the sensors.How many profiles has it done?
Over 880! The HRP has proven to be a very reliable instrument for making these kinds of measurements.Which end is up?
When the HRP is deployed, it falls with its long axis vertical. The sensors are at the bottom, so they acquire the data before the HRP mixes things up by going through the water. The lifting bail, strobe light and radio beacon are on the top. The HRP rides on its side while on deck for ease of handling.Why does the HRP have whiskers?
The whiskers are on the profiler to create turbulent flow around the top and to make it rotate along its axis as it descends. By adjusting the angle of the wiseacres you can increase or decrease the fall speed and change the direction and rate of rotation.Why do you want it to rotate?
Because we need to have some known instrument movement in order to convert the velocity of the water measured relative to the HRP to actual east and north. The internal compass and accelerometer pairs on the top and bottom of the instrument measure the instrument's movement- during the data processing, a model of this movement is used to convert the raw velocity measurements to geographic coordinatesHow long do you spend at sea?
Our cruises with the HRP are typically about a month long. We often work far from shore, and the transit to the site can be three days or more, so the cruises tend to be fairly long.
Yes we can. Since most of the time the HRP
is in the water, it is way below the surface,
our main concern is that it doesn't get damaged
on deployment or recovery. We think about
shutting down operations when the wind is
above 30 kts and/or the waves are larger than
15 feet. The picture at the left shows scientists
preparing to recover the HRP in rough seas.
Do you work at night?
Yes, we work 24 hours a day. Normally we
take enough people to make either two 12
hour watches or three 8 hour watches.
We try to allocate the timing of the watches
so no group has to work completely in the dark.
It is much more challenging to recover the HRP
at night, because all you can see of it is its strobe
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