Archaeology from Space Read online

  Expanding interest such as this led to the first international colloquium on aerial photography in 1963,42 and he published a key tome, The Uses of Air Photography, in 1966.43 With the advent of new military rocket programs, archaeologists could set their sights higher, to spy, in every sense of the word, on the old and the new.

  The space race had unintended consequences for archaeologists today. Developed in the 1950s, CORONA, LANYARD, and ARGON were top-secret government spy satellite programs that mapped Russian activities during the Cold War. From 1960 to 1972, rockets launched camera systems into space, capturing large areas of the Earth’s surface and producing high-resolution black-and-white photos. A specially designed airplane collected the film capsules as they parachuted back to Earth. These photos had groundbreaking resolutions of up to 1.8 meters per pixel, and they helped to map developing countries prior to their major population growth in the 1960s and 1970s.44

  Since President Bill Clinton declassified these data sets in 1995,45 anyone can access them for a small fee, and it is my favorite data set to show remote-sensing students. While archivists in the US government have now fully digitized the imagery,46 in the early 2000s it arrived as black-and-white negative strips over a meter long and 10 centimeters wide. I love rolling them out and holding them up to my eyes like a spy in a 1950s movie, and the students do, too—most of what they do is on a computer screen, so hands-on adds to the fun. And if telling my students, “Why yes, I use spy imagery for my research,” makes them think I’m cooler, I’ll take all the help I can get.

  All joking aside, for Egyptologists and Near Eastern archaeology specialists, this data is a gold mine. In Egypt, the building of the Aswan High Dam in the 1960s allowed Egyptians to alter radically the Nile Valley and Delta landscapes, expanding towns into areas that had previously flooded. However, this meant leveling numerous archaeological sites. In Syria and Iraq, cultivated areas have also changed, obscuring well-traveled ancient paths called “hollow ways” and river courses that had still been visible only 50 years ago.47 These archaeological landscapes are now gone forever; without the CORONA data sets, the sites would have vanished without a trace.

  NASA’s Satellite Revolution

  The 1960s brought major upheaval in US history, with riots, protests, marches, the Vietnam War, the race to the moon, and bra burnings. These changes filtered out into the academic community. The United States had already experimented with weather satellites such as TIROS (Television Infrared Observation Satellite), which launched in 1960. The size of a small, very heavy television, tiny compared to satellites of today, and operational for only 78 days, TIROS showed scientists the potential of capturing Earth’s surface data.48 Emboldened by its success, NASA built more TIROS satellites: TIROS-7 lasted a remarkable 1,809 days, producing 30,000 cloud photographs before being deactivated in 1968.49

  Plans began in 1964 for an imaging system with the capability of mapping the entirety of Earth’s surface.50 Stewart Udall was Secretary of the Interior in the Kennedy and Johnson administrations, and a passionate early conservationist. He had seen power plant pollution in his home state of Arizona from an early space photograph and was appalled. Udall understood the potential power of a space image to share a story and contribute to science, and he took his vision for a global Earth observation system to the Johnson administration. This brought the Department of Interior and NASA together to develop what became the Earth Resources Technology Satellite 1 (ERTS-1).51 Modern enthusiasts know it as Landsat-1.52 This time, NASA invited the world to come together, too. Of the 300 researchers and scientists participating in the analysis of the ERTS-1 data, more than a third came from over 100 countries overseas.53

  It was an extraordinary shift in scientific thinking, especially during the Cold War. In fact, scientists discussing the initial results of ERTS-1 emphasized hopes of developing international, collaborative, remote-sensing programs for everyone to use for global benefit.54 This collaborative spirit had a profound effect on NASA’s more recent data-sharing policies. Amazingly, they have made their database of millions of satellite images free for use by the public.55 I must have used hundreds of thousands of dollars’ worth of their data to date. I could not do my research without it.

  With a multispectral scanner, ERTS-1 captured data in green, red, and two infrared bands in the electromagnetic spectrum, with an 80-meter resolution.56 Not only was 75 percent of the Earth’s surface mapped, but every 18 days, scientists could obtain an image of the exact same place to record changes. Such comparative data had immense implications for environmental mapping, disaster monitoring, and resource management.57

  The scientists behind the program called it the greatest contribution NASA had yet made to the world. In 1976, it even enabled the discovery of a “new” island 20 kilometers off Canada’s eastern coast.58 When Dr. Frank Hall of the Canadian Hydrographic Service explored the newly named Landsat Island, a polar bear took a swipe at him.59 Needless to say, he beat a quick retreat—from orbit to Ursus, indeed.

  NASA’s historians may argue that ERTS-1 had its birth in the Cold War, and from a technological perspective, I would agree. But before its decommissioning in 197860—coincidentally the year of my birth—you could say that we can trace its larger spiritual purpose in the rainbow headbands and peace symbols sported by today’s septuagenarians: for the first time, the world saw that its landmasses had no true borders.61

  Modern Space Archaeology

  Mary Marguerite Scalera, a NASA intern, receives credit as the first person to predict correctly the future of space archaeology. Writing about six then-current NASA projects in 1970,62 she gave an upbeat forecast for how NASA’s technologies could assist with future discovery efforts.63 NASA’s first historian, Eugene Emme, had supported her interest in researching this report, showing that great innovation in science starts with visionary mentoring.

  The 1980s saw the true birth of the field. Landsat data allowed the strategic planning of where to dig by subdividing land, especially in harder-to-survey zones. Unlike today, when a lottery ticket has more value for less effort, my colleagues have told me that then, archaeologists had a 25 percent chance of getting National Science Foundation project funding. But even so, efficiency in project planning made any available budget go further and achieve more. As early as 1981, R. E. Adams published an article in Science on using the new data sets to look for possible ancient landscape patterns across the Maya lowlands, a vast area no team could have covered on foot.64

  And then came “Spacecraft Detects Sahara’s Buried Past.” I’ll forgive you for mistaking it for the title of a Clive Cussler novel, but no, it’s the first global headline about a remote-sensing study, led by archaeologist William McHugh. In 1982, the New York Times 65 featured his team’s extraordinary discovery, first published in Science,66 showing that radar data collected by the space shuttle Columbia had penetrated 16 feet below the desert surface to reveal an entire river network in the eastern Sahara. It was a western equivalent of the Nile, dried up since time immemorial. Radar works best in dry environments like sand, so it shone in this sandy field.

  By following the river course on the ground, scientists collected a range of remains and stone tools from early hominids—Homo erectus, in this case—and the local people whose descendants moved east to kick-start ancient Egyptian civilization. Other finds showed that early sites in the desert had “deflated,” gradually becoming smaller, to finally leave nothing but the outlines of stone houses and stone-processing activity areas on the surface or visible just below it. McHugh, in an interview with the Washington Post, said: “We’ve got some sites where there are so many hand axes I stopped counting after I got to 200. It’s just incredible.”67

  The excited global reaction said it all: the study showed the tantalizing possibilities of these new technologies and what might be hidden beneath vast, seemingly empty landscapes. A new age was born.

  New Beginnings in Mississippi

  Meanwhile, the next leap forward c
ame from an unlikely place: Mississippi. A tall, mustachioed, energetic scientist by the name of Tom Sever (not to be confused with Tom Seaver, the former pitcher of the New York Mets) started working at NASA’s Stennis Space Center, where his tasks involved broadening the use of NASA space technologies across diverse fields. In a 1983 feasibility study, Sever proposed using a Thermal Infrared Multispectral Scanner and a Thematic Mapper Simulator to map Chaco Canyon, a major archaeological site in the American Southwest.68

  Since the 1960s, when the new theoretical movement of processual archaeology rattled the field to its core, archaeologists could no longer make grand sweeping statements about ancient cultures without much foundation in their findings. The movement pushed archaeology to become more scientific. Alongside the blossoming subfield of settlement archaeology, the processual wake-up call helped to form modern archaeological inquiry. It drove a change in focus, from concentrating on single sites to considering surrounding landscapes and understanding that the environment played a key role in how and why sites evolved. Advances in dating techniques, chemical residue analyses, and archaeological computing added momentum to archaeological science. These broader trends made archaeologists more open, if skeptical, to the application of space-based technologies suggested by Sever.

  Fortunately for my research and, frankly, for all of us in this field, NASA encouraged Sever to move ahead with his proposal and to host a conference that would become legendary.

  In 1984, he and his colleague, James Wiseman of Boston University, invited academics from across the United States to Mississippi to hear presentations on new Landsat and radar data sets. Specialists in the archaeology of the Paleolithic period, the Maya and Mexico, the Near East, and the southwestern United States gathered to form one of the most diverse and broad-minded assemblies of US scholars the field had ever seen.69

  Many of these scientists are luminaries in space archaeology today. Together, they developed guidelines for how researchers should approach remote-sensing data sets, which included using satellites not only to locate sites, but also to study past human–environment interactions; and they emphasized the importance of ground-truthing, or using ground surveys to test the satellite data.70 When he published the conference proceedings, Sever made it clear that archaeologists had to master the technology before the “pot hunters,” the looters, beat them to it. If only more people had heeded his prescient warning.

  The Mississippi conference delegates quickly put into practice what NASA scientists had preached. Tom Sever led the way with the detection of previously unknown ancient roadways at Chaco Canyon.71 Payson Sheets of the University of Colorado Boulder applied satellite imagery to his rainforest research area in Costa Rica, identifying old paths impossible to see with the naked eye.72 The data could be applied equally well to prehistoric sites: Pamela Showalter of Texas State University used Landsat data to detect previously unknown segments of a Hohokam canal system near Phoenix, Arizona, dating from around 1050 to 1450 AD.73

  With additional global satellites such as the French SPOT (Satellite Pour l’Observation de la Terre),74 archaeologists now had their pick of imagery data sets. Resolution improved drastically, moving from 80 meters to 10 meters in 14 years.

  But that still mattered little when most features measured a meter in width or less.

  A High-Resolution Solution

  In 1999, scientists hailed the newly launched IKONOS as the future of satellite technology. It had a resolution of 1 meter, and its ability to image the surface in the visual and infrared parts of the light spectrum meant archaeologists had their wishes answered, save one: cost.75

  A single IKONOS image could be many thousands of dollars. Now, we archaeologists may be responsible caretakers of priceless archaeological treasures, but our pockets are always empty. We had to be patient. Fortunately, patience is the one resource in which archaeologists are wealthy.

  We didn’t have to wait long. The field of space archaeology hit warp speed in the early 2000s. Early adopters had taken on a cohort of students, many of whom finished their PhDs during this time. Papers emerged not just on NASA’s satellite data sets, but also on the recently released CORONA spy imagery,76 and finally, here was imagery we could afford.

  With the first international conference on satellite archaeology, held in Beijing in the fall of 2004, the field was on the verge of becoming widely accepted. I mention that conference because I attended it as a PhD student, and it is still considered a key moment in the development of the field.

  The attendees at the Beijing conference represented the Satellite Archaeology Hall of Fame. Every big name I cited in my thesis was there: Guo Huadong, the director-general of China’s Institute of Remote Sensing and Digital Earth; Ron Blom, the legendary Jet Propulsion Laboratory scientist who worked on the discovery of the “lost” city of Ubar, in Saudi Arabia;77 Payson Sheets from Sever’s original conference,78 and so many others. I was starstruck by these academic superheroes, and our Chinese colleagues had gone all out to welcome us.

  With red crushed-velvet chairs lovingly tied with bows awaiting us in the auditorium, tea servers who rushed to refill our cups the moment we took a sip during talks, and extravagant dinners served in exquisite banquet halls, I thought I had hit the big time. Sign me up for this field! I volunteer as tribute! I only learned as the conference wound down that this represented the best conference any of my senior colleagues had attended in their 40-year careers. As a newbie, I was pretty much screwed because I would never have it this good again, ever.

  Nonetheless, my extraordinary colleagues at the conference had opened my eyes to a broader archaeological world—one of collaboration, encouragement, and cheering on, and they showed me that there’s a big planet to map and plenty of discoveries to go around.

  Space Archaeology Today

  Since that conference, the scale of discoveries made by my colleagues at sites and landscapes across the globe is simply mind-blowing. These findings have done nothing less than turn heads, make headlines, and help archaeologists to reinterpret several ancient cultures. And that’s before we even mention valuable work protecting heritage from looting. Space archaeology deserves its moment in the sun.

  In 2016, Greg and I took a bucket-list trip to Cambodia, where we spent a week in Siem Reap visiting the great temples of the Khmer Empire. I’m going to let you in on an archaeological trade secret: the absolute best part of being an archaeologist, bar none, is voyaging to the ancient parts of the world and getting behind-the-scenes tours from your expert colleagues. We had this glorious opportunity in Siem Reap via my friend Damian Evans, who also happens to be the world expert on LIDAR applications in Southeast Asia.79

  The tour is one thing. It is something else to sit with your colleague as he spreads out an enormous LIDAR 3-D map of the ancient site and shows you all its anomalies hidden beneath the dense rainforest. The ancient Khmer temples that Damian guided us around were strewn in heaps next to mostly intact walls, just awaiting conservation. I saw it as the block exhibit at our great local science center, where our son loves building structures out of soft blue oversized bricks. Just as excited as he gets, I wanted to start stacking the blocks and rebuilding immediately.

  Damian had worked in Siem Reap for over 15 years and used LIDAR—the same laser technology used by the Chases at Caracol—to rewrite our understanding of the Khmer Empire’s collapse.80 The lasers showed the bitter truth that the Khmer people relied far too heavily on unreliable yearly rainfall levels, trying in vain to divert water to their fields by altering landscapes on a large scale. In the face of environmental change, time can simply run out for sophisticated societies: no rainfall at all meant that all the moved land in the world would not save them. The rich culture still survives today in dance, music, and ritual, but the great temples and enclosures swarmed by tourists today saw wide-scale abandonment nearly 500 years ago.81

  These days, it seems there are headlines every other week regarding the use of high-resolution satellite imag
es to discover hidden archaeological treasures. In September 2017, archaeologists announced the discovery of the lost city of Qalatga Darband in Iraqi Kurdistan,82 a city that stood near where Alexander the Great fought the Persian emperor Darius III.

  Archaeologists first noted a potential site in the region using CORONA spy images. Additional on-site drone data showed the outlines of buildings and blocks. John MacGinnis of the British Museum specifically searched through imagery taken in spring, when differences in the wheat and barley growth formed promising crop marks.83

  As Qalatga Darband is located in a key area between Eastern and Western influences, archaeologists surveying and excavating there targeted their research to unearth evidence for a temple, wine presses, an inner fort, and a large wall fortifying the city. Work on the ground has only just begun, after years of conflict prevented archaeologists from returning to the site.

  Full Circle

  Space archaeology has come a long way from its very early days of tethered balloons. In many ways, we have come full circle: from airplanes to outer space, and now, closer to the earth again, with semiautonomous, miniature flying machines that give us far greater control over which areas we’re imaging. Drones are a new frontier for site mapping, but they cannot yet be used for mapping major landscapes, and in many parts of the world, they are banned outright.84 Though it may come sooner than we think, we can still only imagine the day when we will be able to map with a resolution of an inch, seeing individual potsherds on a site’s surface from 400 miles up in space. How much new information that process will divulge.