Of Polar Bears and Thematic Mappers: The 40-Year Landsat Legacy

Landsat 7, the most recent arrival in a family which began as the Earth Resources Technology Satellite, has operated from near-polar orbit since April 1999. In February of next year, it and the aging Landsat 5 will be joined by the next-generation Landsat Data Continuity Mission (LDCM). Image Credit: NASA

Twelve miles off the north-east coast of Labrador lies a tiny island, named for one of the most successful satellite series of all time. ‘Landsat Island’ was discovered in 1976 during a Canadian survey which used data from Landsat 1 – a co-operative project between NASA and the Department of the Interior – to identify hitherto uncharted landmarks. Lowered by a helicopter harness, Dr Frank Hall of the Canadian Hydrographic Service narrowly missed being swiped by a polar bear and nearly became the first person to meet his maker on the island.

Today, the satellites which gave this frozen rock its name are celebrating 40 years of global coverage in support of agriculture and forestry, geology and mineralogy, hydrology and oceanography, geography and cartography, marine and meteorological science and environmental pollution and protection. “Landsat has given us a critical perspective on our planet over the long term and will continue to help us understand the big picture of Earth and its changes from space,” said NASA Administrator Charlie Bolden. “With this view, we are better prepared to take action on the ground and be better stewards of our home.”

In images which shocked the world, this view from Landsat 5 reveals the destructive extent of human activity on our planet: Saddam Hussein’s burning of Kuwaiti oilfields during the 1991 Gulf War. Image Credit: NASA/Department of the Interior/US Geological Survey

Originally conceived in the mid-1960s as the Earth Resources Technology Satellite, one of the first Landsat’s fundamental instruments – its multispectral scanner – was completed and tested a few months after Neil Armstrong and Buzz Aldrin landed on the Moon. In its early genesis, the project met with much opposition from the Bureau of the Budget, which argued that high-altitude aircraft provided a more practical means of conducting terrain mapping. There were other worries, too. The Department of Defense was fearful that a civilian effort of this nature might compromise its own national security missions, whilst on a political level there was uncertainty about the implications of imaging foreign countries without permission. However, the green light of approval finally came in 1970.

The satellite roared into near-polar orbit on 23 July 1972, aboard a Delta 900 rocket from Vandenberg Air Force Base in California. Three years later, the project name was changed to ‘Landsat’ and then-NASA Administrator James Fletcher predicted that it would one day revolutionise and save the world through its endeavours. Solar overheating caused Landsat 1 to be shut down in January 1978, but its mission was only the beginning of a remarkable journey. Landsats 2 and 3 continued to function well beyond their planned one-year operational life spans, but the arrival of Landsat 4 in July 1982 brought disappointment: shortly after launch, it lost half of its electrical power and its ability to transmit science data to Earth. To compensate for the loss, a backup spacecraft, Landsat 5, was hastily placed into orbit in March 1984.

At one stage, plans were advanced to launch a Shuttle mission from Vandenberg Air Force Base to retrieve, repair and refuel Landsat 4, but were shelved in the wake of the Challenger accident. With the arrival of NASA’s Tracking and Data Relay Satellite network, Landsat 4 rallied and even supported Landsat 5 for a time in 1987 when the latter experienced its own problems. Landsat 4 marked the first demonstration of the Thematic Mapper – a device capable of gathering seven spectral bands of data and achieving far higher resolution than its predecessors – and was decommissioned in December 1993.

The Operational Land Imager – one of the primary instruments aboard the Landsat Data Continuity Mission (LDCM), scheduled for launch in February 2013 – undergoes checkout. Photo Credit: Ball Aerospace

Both it and its successors far outlived their expected operational lifetimes. In fact, Landsat 5 continues to function to this day, although it has suffered serious problems in recent years: an anomaly with its backup solar array drive, difficulties with power and attitude control and, most recently, in November 2011, fluctuations in a critical data-transmission amplifier. The US Geological Survey declared the satellite to be approaching the end of its life after almost three decades – and more than 25 years longer than planned – of active science operations. Landsat 6 failed to reach orbit in October 1993 and the most recent arrival, Landsat 7, was successfully launched in April 1999. It continues to operate, despite having suffered a malfunction in its Enhanced Thematic Mapper a few years ago. The next spacecraft in the series, known as the Landsat Data Continuity Mission (LDCM), is presently scheduled for launch in February 2013.

“Over four decades, data from the Landsat series of satellites have become a vital reference worldwide for advancing our understanding of the science of the land,” said Interior Department Secretary Ken Salazar. “The 40-year Landsat archive forms an indelible and objective register of America’s natural heritage and has thus become part of this department’s legacy to the American people.” Anne Castle, the department’s assistant secretary for water and science, also stressed that in recent years Landsat data has been made increasingly available to a wider audience. “The Landsat archive serves as the world’s free press,” she said, “allowing any person, anywhere, to access vital information without charge.”

One Comment

  1. A few months before the ERTS-1 launch, an expert told me he could draw by hand the pictures we’d get from it. (I was on the test, launch, and initiol ops crews for ERTS-1 & 2.) I think he was proved wrong.

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