Sometimes people say that a problem with space archaeology is that we can't just pop into orbit or to the Moon for a season of fieldwork, and collect data in the usual way. How can you do archaeology without the quintessential archaeological activities of excavation and survey? Aren't we just the much-maligned 'armchair archaeologists'?
In answer to which I give you:
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| Cartoon by Robert Mankoff. Image courtesy of the New Yorker |
There's nothing wrong with a comfy armchair, if you ask me. They're good places for thinking. And cups of tea, with maybe cake too, or a fluffy lamington, or a delicious Iced VoVo, every space archaeologist's biscuit of choice.
The first archaeological surveys in orbit
However, surveys using remote sensing are now standard in archaeology. This involves both geophysical surveys - sending different signals into the ground to detect metal objects, cuts and cavities - and aerial or satellite surveys to locate and map sites, using optical or multispectral data collected from UAVs, aeroplanes or satellites in Earth orbit.
When considered from this perspective, it turns out that archaeological surveys of human material in Earth orbit have been conducted since the beginning of the space age, using antennas and optical telescopes of multitudinous configurations to locate and track spacecraft and space junk. (In orbital archaeology, tracking is the equivalent of mapping a site). Rather than turning a sensor towards the Earth, these eyes and ears look towards the heavens.
The first such survey had two artefacts as its target - Explorer 1 and Sputnik 1 in the International Geophysical Year of 1957-58. You could say that this was the turning point, when space ceased to be a purely 'natural' environment and became a cultural landscape. First it was just the one satellite, a small blip for three months. Sputnik 1 orbited from 4 October 1957 to 4 January 1958. Between 4 October and 3 November when Sputnik 2 was launched, Sputnik 1 was the only artefact of its kind in all the solar system - just think of that!
The survey team, if we can call it that, consisted of human and mechanical observers. The human observers were the volunteer brigades of Project Moonwatch. The brainchild of Professor Fred Whipple of the the Smithsonian Astrophysical Observatory, the Moonwatchers were teams established in 27 countries to look for and visually track the first satellites. Patrick McCray has written a wonderful book about them.
The mechanical observers were the antennas and cameras set up just to look for satellites. There were the Minitrack interferometers, of which there were 14 across the US, South America, South Africa and Australia. The Smithsonian Astrophysical Observatory set up a network of 12 Baker-Nunn cameras, not just for satellites but also natural objects in Earth orbit. The cameras were located in Argentina, Curacao, India, Iran, Japan, Peru, South Africa, Spain, US and Australia - where Woomera was one of the few locations to have both a Minitrack and a Baker-Nunn.
The USSR KIK network was developed from the ground tracking stations of the R-7 rocket, an intercontinental ballistic missile that was the launcher for Sputnik 1. There were 13 ground stations, all within the USSR. Now this is an interesting point, because the Vanguard satellite project was designed explicitly to disguise its military origins; hence their tracking network was not simply an adaptation of a defence one. The USSR was not so concerned about 'military taint'.
On 31st January 1958, Explorer 1 poked its head above the ionosphere and joined Sputnik 2. Just the two of them. Vanguard 1 was launched on St Patrick's Day on the 17 March, and then there were three. A bit less than a month later, Sputnik 2 re-entered on 14 April, and it was down to two satellites again. All that infrastructure for two little blips in the sky.
This is very like how observation of space junk from Earth happens. Most of the optical or radar tracking instruments can only 'see' pieces 10 cm or above. This is the top sieve. Others can 'see' smaller pieces - these tend to be lasers, or beam park instruments. This is the 2 mm sieve.
The analogy is even more apt when you consider that artefacts larger than 5 mm can slip through the top mesh, depending on their angle. Angle and cross-sectional area are also factors in how visible a bit of space junk is from the ground.
In archaeology the artefacts are often fragments, or by-products of manufacture. Sometimes we piece the bits back together to form a whole stone tool, or a ceramic vessel. Sometimes we use them to calculate the weight of a particular material in that excavation unit. For your edification, I can tell you that the weight of human material in Earth orbit is the equivalent of 10 million cane toads.
The mechanical observers were the antennas and cameras set up just to look for satellites. There were the Minitrack interferometers, of which there were 14 across the US, South America, South Africa and Australia. The Smithsonian Astrophysical Observatory set up a network of 12 Baker-Nunn cameras, not just for satellites but also natural objects in Earth orbit. The cameras were located in Argentina, Curacao, India, Iran, Japan, Peru, South Africa, Spain, US and Australia - where Woomera was one of the few locations to have both a Minitrack and a Baker-Nunn.
The USSR KIK network was developed from the ground tracking stations of the R-7 rocket, an intercontinental ballistic missile that was the launcher for Sputnik 1. There were 13 ground stations, all within the USSR. Now this is an interesting point, because the Vanguard satellite project was designed explicitly to disguise its military origins; hence their tracking network was not simply an adaptation of a defence one. The USSR was not so concerned about 'military taint'.
On 31st January 1958, Explorer 1 poked its head above the ionosphere and joined Sputnik 2. Just the two of them. Vanguard 1 was launched on St Patrick's Day on the 17 March, and then there were three. A bit less than a month later, Sputnik 2 re-entered on 14 April, and it was down to two satellites again. All that infrastructure for two little blips in the sky.
Sieving the sky
Since that time, the number of instruments surveying the sky for human artefacts has increased exponentially, as have their targets. It's not just whole satellites any more; it's also the fragments, of which there are millions. In fact, you could say that the tracking instruments are like the nested sieves archaeologists are accustomed to use in excavations. Usually, you screen the dirt through a top mesh which is 5 or 7 mm. This catches the larger artefacts. Beneath it is a smaller mesh, usually 2 mm. This catches the smaller pieces. Everything else falls through and becomes part of the spoil heap. If you use even smaller sieves, or flotation tanks, you can recover pollen and other microscopic objects.This is very like how observation of space junk from Earth happens. Most of the optical or radar tracking instruments can only 'see' pieces 10 cm or above. This is the top sieve. Others can 'see' smaller pieces - these tend to be lasers, or beam park instruments. This is the 2 mm sieve.
The analogy is even more apt when you consider that artefacts larger than 5 mm can slip through the top mesh, depending on their angle. Angle and cross-sectional area are also factors in how visible a bit of space junk is from the ground.
In archaeology the artefacts are often fragments, or by-products of manufacture. Sometimes we piece the bits back together to form a whole stone tool, or a ceramic vessel. Sometimes we use them to calculate the weight of a particular material in that excavation unit. For your edification, I can tell you that the weight of human material in Earth orbit is the equivalent of 10 million cane toads.
You could divide space objects into active and passive. The artefacts we excavate from the ground don't usually tell us where they are. If you're using a magnetometer, though, metal artefacts will reflect a signal back to your instrument above the ground. This is a passive signal. Functioning satellites are not your usual artefacts, in that they're often actively emitting signals that you can tune into.
Robot archaeologists
Terrestrial space object tracking could be recast as a kind of archaeological survey. But imagine an archaeological survey of orbital space done remotely using cameras mounted on other spacecraft. There are a few companies, such as HEO, who are imaging spacecraft on-orbit.
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| The International Space Station, taken from orbit. Image courtesy of HEO |
Does thus change our perception of what orbital debris is? Of course you would need a robust optical sample, and there are still many limitations of these camera surveys.
All of this is just to say the inability to do fieldwork in space does not invalidate us as archaeologists, and indeed gives the discipline a deeper lineage. Using remote sensing to collect archaeological data has a long history. So does using remote sensing from Earth-based instruments to survey the sky - including human artefacts.
References
Bonnal, Christophe 2025 The proliferation of space debris in Earth's orbit. Polytechnique Insights 12 FebruaryCentre for Invasive Species Solutions (2012) Overview of the cane toad. Factsheet. PestSmart website. https://pestsmart.org.au/toolkit-resource/overview-of-the-cane-toad accessed 06-09-2025
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