Chasing Satellites With Jacques Cousteau
by Laura Rocchio, NASA Goddard Space Flight Center
July 23, 2020
Leaving from Nassau on a Tuesday night in August 1975, Jacques
Cousteau and his team set out on the Calypso for a three-week
expedition designed to help NASA determine if the young Landsat
satellite mission could measure the depth of shallow ocean waters.
Jacques Cousteau and his
team of expert divers were a key part of the success of the
1975 NASA-Cousteau Bathymetry Experiment. In this photo from
left to right: Bernard Delemotte, Chief Diver; Henri Garcia;
Jean-Jérome Carcopin, and Jacques Cousteau. (Courtesy photo by
The Cousteau Society)
For days, the Calypso played leapfrog with the Landsat 1 and 2
satellites in the waters between the Bahamas and Florida. Each
night, it sailed 90 nautical miles to be in position for the morning
overpass of the satellite.
Ultimately, research done on the
trip determined that in clear waters, with a bright seafloor, depths
up to 22 meters (72 feet) could be measured by Landsat.
The primary test site for the expedition was just west of the Berry Islands on the northern edge of the Great Bahama Bank. The location was chosen as the prime testing site because it gradually changed depth from one meter to deep ocean in a short north-south span (25 nautical miles). This natural-color Landsat 8 image acquired on March 23, 2019, shows where the northern Great Bahama Bank meets the deep ocean.
(Image by NASA/USGS Landsat)
This revelation gave birth to the field of satellite-derived
bathymetry and enabled charts in clear water areas around the world
to be revised, helping sailing vessels and deep-drafted supertankers
avoid running aground on hazardous shoals or seamounts.
“It was a tremendous example of how modern tools of scientists
can be put together to get a better understanding of this globe we
live on,” the Deputy NASA Administrator, George Low, said of the
joint Cousteau-NASA expedition in a 1976 interview.
But it couldn’t have happened without the world’s most famous
aquanaut, his team of expert divers, and the Calypso.
Astronauts and Aquanauts Together
The ocean’s vastness made Cousteau an early supporter of
satellite remote sensing.
Cousteau, by then a decades-long oceanographer, was keenly aware
that ocean monitoring from above would be necessary to understand
the ocean as part of the interconnected Earth system and to raise
the awareness requisite for protecting the sea. There was a growing
recognition in the 1970s that helping the planet required
understanding the planet.
“Everything that happens is demonstrating the need for space
technology applied to the ocean,” Cousteau said during a 1976
interview at NASA Headquarters.
George Low, the Deputy NASA Administrator, himself a recreational
diver, connected Jacques Cousteau with former Apollo 9 and Skylab
astronaut Russell Schweickart. Schweickart was heading up NASA’s
User Services division and both he and Cousteau were looking for
ways to advance Earth science.
At the time, it was theorized that the new Landsat satellites
might be useful for measuring shallow ocean waters. New deep-drafted
supertankers were carrying crude oil around the globe, and to avoid
environmental catastrophes it had become important to know where
waters in shipping lanes were less than 65 feet (20 meters).
For this experiment,
Landsat data was downlinked to NASA Goddard Space Flight
Center in Greenbelt, Maryland where it was processed into
depth contour data. This was uplinked to the Applications
Technology Satellite-3 (ATS-3) and then sent via Very High
Frequency (VHF) relay to a VHF receiver system that had been
installed on the Calypso for an earlier 1974 experiment in
the Gulf of Mexico. (Image credit: NA)
To establish if Landsat could accurately measure ocean depth from
space, simultaneous measurements from ships, divers and the
satellite were needed.
Schweickart knew a coordinated
bathymetry expedition was an essential step. He had honed his diving
expertise while training for his Skylab mission in NASA’s water
immersion facility and was enthusiastic about scuba work. Teaming
with Cousteau was a natural fit.
An elaborate experiment was designed to determine definitively if
multispectral data from the Landsat satellites could be used to
calculate water depth. The clear waters of the Bahamas and coastal
Florida were selected as the test site.
The experiment design
involved two research vessels, the Calypso and Johns Hopkins
University Applied Physics Lab’s Beadonyan, being in position, or
“on station,” when the Landsat 1 and 2 satellites went overhead on
eight different days (four consecutive days on each of two weeks).
The overall concept was simple: the research ships would use
their fathometers to measure water depth at the exact same time that
the satellite flew overhead and then those measurements would be
compared (the simultaneous measurements eliminated any environmental
or atmospheric differences that could have complicated comparisons).
But realizing that plan took extraordinary coordination.
A detail from the planning
map used for the 1975 NASA-Cousteau Bathymetry Experiment
showing the Berry Islands. The hatched lines show the
location of Landsat scene edges. (Image by NASA)
As the Landsat satellite flew overhead, Cousteau and his team of
divers made a series of carefully timed measurements of water
clarity, light transmission through the water column, and bottom
reflectivity. This was done both near the Calypso and at two sites
60 meters from the Calypso using small motorized Zodiac rigid
To make the light transmission
measurements, two teams of divers had to use a submarine photometer
to measure light at the water’s surface, one meter under the water
and in 5-meter increments to the bottom (down to 20 meters).
The divers had to hold the photometer in a fixed position looking up
and cycle through four different measurements. They also used
specially filtered underwater cameras to measure bottom reflectivity
(assisted by gray cards for reference). Everything was carefully
timed. Schweickart and President Gerald Ford’s son Jack helped with
these underwater measurements.
To make the precision
measurements, the skill of these divers – including Cousteau’s chief
diver, Bernard Delemotte – was essential.
“I was in charge of
the divers,” Delemotte explained in a recent interview. “We were
very convinced that we could do serious work together [with NASA].”
Before the satellite overpass, the Calypso and Beayondan were in
position, anchored side-by-side, and ready to make all specified
“Two small Zodiacs left from the Calypso just
before the satellite passage,” Delemotte recalls.
stationed themselves 200 feet (60 meters) from the Calypso, and at
the moment that the satellite was overhead someone on the Calypso
would call to the divers through the portable VHF radio: “Go now!”
The divers would then start the series of prescribed
Using these measurements, scientists developed
mathematical models describing the relationship between the
satellite data and water depth, accounting for how far the light
could travel through water, and how reflective the ocean floor was.
“Particular thanks” was given to Cousteau’s team of divers in
the experiment’s final report “for their dedication and expertise in
the underwater phases of the experiment, without which, measurements
of key experimental parameters could not have been made.”
diving prowess of Cousteau, Delemotte, and the Calypso crew added
inextricably to the realm of satellite-derived bathymetry. Because
of data collected during the NASA-Cousteau expedition, charts in
clear water areas around the world were updated, making sea
navigation safer. It was the precision measurements made by
Delemotte and Cousteau’s team of divers that made bathymetry
calculations for those chart updates possible.
National Aeronautics and Space Administration