Friday, 13 November 2015

Discovery Friday (Discovery - 1962)

Discovery (1962)

The RRS Discovery that preceded our current home was built in 1962 and served British oceanography for 50 years. During that long time, this Discovery saw a huge change in how science was done at sea. A massive refit in 1992 saw her prepared for modern long oceanographic expeditions. 

Discovery as originally built in 1962

Sitting on probably the most modern research vessel in the world, it’s quite hard to imagine how science was done when the old Discovery was built in 1962. For a start, most of the data were gathered on paper. While now I can plug in a 1 TB disk to run from a USB port, the first hard drive fitted on Discovery in the late 1960’s stored up to a limit of 1 Mb (at least I think that’s how big it was—the only spec I could find stated it could hold 512 000 16-bit words, which I think is about 1 Mb). Navigation in those days was done by the stars. This was the world that Discovery began her life in but not how she would end it.

The change in the amount of data and how the data were gathered on research cruises has been immense. Our primary physical oceanography measurement from the ship is a CTD profile. This measures conductivity (from where we get salinity), temperature and depth. We lower the instrument over the side and, all being well, data flows direct to the control computer. In contrast to this, at the beginning of her life, the same measurements were made on Discovery by tying bottles to wires. When bottles were attached to the wire from the ship to seafloor, a messenger weight was sent down to close all the bottles where they sat. This delivered around 24 samples of the water column—a modern CTD makes 24 samples per second. The herald of the new age of continuous sampling came early in Discovery’s life. Cruise 25 saw what was then called a TSD (temperature-salinity-depth) probe. 

Revolutions were afoot in navigation also. Discovery’s first satellite aided navigation system was fitted in the late 1960s. The functionality of these early systems was varied. Even by the mid-1980s, the ship could spend over a month at sea with as little as 400 GPS fixes—the gaps were filled by dead reckoning. This was fine to know where you are going but not accurate enough for many scientific applications. GPS on the current Discovery are accurate now to a couple of centimeters and readings arrive every second.

Discovery (1962) really had two lives: in 1992, she was massively overhauled and ten metres added to her length. This extra space and capability would be needed as she embarked on longer and more remote global expeditions. A prime example is the World Ocean Circulation program that surveyed all the world’s oceans. Discovery played a full part in this experiment, contributing key hydrographic sections.

Discovery (1962) after major refit in 1992


Our project—RAPID—has a particular affinity with the old Discovery. She did more RAPID cruises than any other ship: nine in total. In 2004, Discovery was the ship that deployed the original RAPID moorings. It was fitting then that Discovery’s final scientific cruise in 2012 was a RAPID cruise. This was a special cruise for me as it was my first time being Principal Scientist. We didn’t give her an easy send off. We spent seven weeks working on all the moorings across the Atlantic, doing more than in any other single RAPID cruise. Discovery served us well, she was a great ship. 

Crew, technicians and scientists from Discovery’s last scientific cruise in 2012

Written by Gerard (posted by Darren)

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