An archaeological perspective on orbital stratigraphy

One of the things I've been thinking about for a while is the the structure of the archaeological record of Earth orbit - all the spacecraft that have been launched over the last 60 years, and their decay products, fragments and molecules of Earth-manufactured materials. Something people ask me occasionally is how you can do archaeology when there is no stratigraphy. In terrestrial archaeology, everything eventually falls to the ground and becomes buried as winds, water and human activities erode higher places and move the sediment to lower places. Generally, the deeper you dig, the older the remains that you find.

This isn't how it works in Earth orbit. Everything's falling, for sure - but a large proportion of stuff never reaches the ground. It's all up there, the new mixed up with the old, the functioning with the defunct, the living with the dead. It's not a mirror of stratigraphy on Earth. The lower something is says nothing about how recent it is.

With one exception - everything in geostationary orbit is younger than 1963, when Syncom 3 became the first satellite to successfully reach this critical orbit, the importance of which for telecommunications had been predicted since the early 20th century. This is just seven years after the first satellite though - not very long. And there's only about 40 satellites left in orbit which date from this period.

Multigravity environments

It's more useful not to think of Earth as the standard, but as a special case in a solar system comprising many different levels of gravity and many different ways of experiencing it. For example, when we talk of microgravity in Earth orbit, it's not really that there is no gravity. The Earth is still there, pulling everything towards it as usual. It's the acceleration of falling towards it that creates the sensation of microgravity. You can experience the same thing in a droptower ride at an amusement part or the zero-gravity 'Vomit Comet'. You don't even have to leave Earth to have different gravity experiences!

The nature of the archaeological record varies according to the gravity you're in. In full Earth gravity, a powerful attractor, things fall. In Earth orbit, things float but can get pulled back to Earth by atmospheric drag. On the Moon, things fall, but more slowly, and less energy is needed to throw them up into orbit. At the five Lagrange points in the Earth-Moon-Sun system, things bounce around. (Indeed, just recently, they have been shown to be massive dust traps).

Lagrange points in the Earth-Moon-Sun system. Image credit: NASA

I prefer to conceptualise the way artefacts respond to variable gravity environments as a dynamical system. This is a visual, mathematical way of representing how objects move over time when certain boundary conditions are set. Objects are the recipients of energy through various sources, and gravity determines how much energy the objects need to move. The dynamical system is a map of places where objects end up as they lose energy - the process of entropy. Effectively, such a map is also an archaeological plan of a site or the surface of an excavation unit. (Now I wonder if we should be regarding our plans as frozen moments in a dynamical system, just one that is generally moving a lot more slowly than orbit. So the critical difference between the two regimes is not speed, but time).

These places are points of stable or unstable equilibrium. When an object falls to the ground, it's in a stable equilibrium place of low energy. To get off the ground, energy has to be added. The energy might come from someone kicking it, or a stream of water which moves it on. The Lagrange points include both stable (L4 and L5) and unstable equilibria (L1, L2 and L3). Unstable equilibrium is like balancing an egg on its pointy end: you can do it, but it's going to fall over pretty quickly. (Also, it helps if the egg is hard-boiled). Using this as a framework, Earth and Earth orbit are not completely different places with different rules, but places within the same system with different amounts of energy.

It also helps to visualise this as an Einsteinian gravity well. The bottoms of the wells are points of low energy and stable equilibrium.

A 2-D slice of a gravitational force vector field (left) is interchangeable with a 3-D gravity well (right), with the z-axis showing energy (potential). Image courtesy of Invent2HelpAll

How junk disperses, or a taphonomy of orbit

In fact, the stratigraphy of space junk does include a terrestrial component. The lowest point of energy in the orbital dynamical system is the surface of Earth: an orbit of zero apogee and perigee. The atmosphere is a barrier or boundary between different gravity regimes, as space objects can bounce off its upper surface, and those that get pulled into it tend to incinerate. However, some spacecraft parts are made of materials like stainless steel and titanium alloys, which have high melting temperatures. Other parts may have carbon-carbon insulation which provides some protection from temperature extremes. Sometimes these components scream at high speed into the atmosphere, with their flesh burning, and fall with a smoking thud to the surface. The so-called 'space balls', titanium pressure vessels, are one of the most common spacecraft parts to survive re-entry. These spheres are the best gravity travellers; they get to come back.

Of course little of the spacecraft is likely to remain in orbit after the main body has re-entered - perhaps some molecules or broken-off bits. When we find the space balls or other Earthbound space junk, it's most likely that this is all that remains of the spacecraft. They've fallen to the point of lowest energy. This includes the spacecraft graveyard at the bottom of the ocean. Earth orbit is bookended by graveyards, if you take into account the graveyard orbit a few hundred kilometres above the geostationary ring. This is where old GEO satellites go to rest in their undead way, as they can still drift down and across the orbits of living satellites.

In general the the structure of space junk is not vertical layers as we're accustomed to in archaeology. Instead, spacecraft decay fragments have an elliptical or cloud geometry. When a spacecraft is whole, all its components are on the one orbital trajectory. Now imagine a solar panel detaching from the main body. Initially, its speed and orbit will be pretty much the same as the main body. But as time passes, the orbits will diverge. If the panel is tracked by one of the Earth-based telescopes, then we will have all the data about it's orbit into the past and will be able to trace it back to the original spacecraft - as long as we keep tracking it.

If a spacecraft explodes, the debris initially forms a cloud around it. The cloud travels together for a little while and then the individual pieces, all with their own weight, size, shape and velocities, start to disperse. If you look at the orbital tracks of Fengyun 1C, the Chinese satellite which was the target of a test missile shot in 2007, the debris rapidly moves apart and starts to spread out as you see here:

Fengyun 1C debris evolution. Image by Karl Tate @space.com

Position in orbit is described using a set of six equations devised by Johannes Kepler. Usually what people use, however, is Two-Line Elements - a bit like Eastings and Northings. The position is simplified into two strings of numbers. But because of the non-linear unpredictability of orbits, the reliability of the TLEs diminishes pretty fast. After 30 days you can't be sure that the TLE will accurately predict where something is. What this means in practice is that objects have to be continually watched or tracked to know where they are. This is called persistent observation and it's not generally something archaeologists worry about on Earth. However, artefacts on the surface do move around, although very slowly. You can record a concentration of stone artefacts on the surface, but if you revisit the same site a year later, half of them might be missing. Some have worked their way underground; some are covered by vegetation; others have moved under the influence of wind, water, animal movement or land use and industrial activities. Ten years into the future, there may be nothing to see. So perhaps I should apply the principle of persistent observation to terrestrial archaeology after all...

Objects in space are, of course, moving at incredibly high speeds - an average of 7-8 km per second. It's not that objects within archaeological deposits don't move; soils can act as liquids over a long time period, with a gravity-driven convection that gradually makes artefacts rise higher in the profile. Sometimes objects rise to the surface like a fish and get stranded there. Others, like stone tools with narrow sharp edges, slip back in for re-circulation. This is something archaeologists are very interested in as it says something about the integrity of the site and the relationship between objects. We're looking to that relationship to try and work out the human behavioural correlates, so we need to understand how the relationships decay over time due to natural or cultural factors, such as water movement or scavenger activity.

It's the relationship that matters

Both inside Earth and in orbit, the way the relationships between objects within a space evolves over time is critical to working out the human behavioural component. Looking at how the space debris environment evolves, it seems that after a certain amount of time it would be impossible to reconstruct the orbital path and work out what spacecraft a piece of junk came from, if you did not already have tracking records. Let's imagine the scenario of a future human archaeologist after the records have vanished (we can't assume they will survive in their current form) or even an alien archaeologist looking at space debris to get a handle on Earth culture. They will initially use materials and style to identify which space objects belong in the same time frame or to the same culture. They'll also have to work out what differences are due to style, and which to function.

Effectively, orbital archaeologists of the future will be 'recapitulating' a period of terrestrial archaeology before there was absolute dating, when similarities in style were used to posit chronological and social relationships. This period of investigation is known as culture history, and it worked on a number of premises. The first was the definition of culture, which as V. Gordon Childe phrased it, was a consistently occurring suite of artefact types, features and structures that you could attribute to an ethnic group. The second was the assumption that things change over time, coming in and out of fashion. Graphs of the frequency of occurrence of different artefacts types or styles resembled battleship curves, as they were known. Something starts out at a low frequency, then its numbers increase as it becomes popular. Soon the next big thing starts to supersede it and the frequency declines until no-one makes or uses the object any more. This is pretty much what happens in the fashion industry. Using changing frequencies to date an object is called seriation.

Because atmospheric drag pulls objects out of Low Earth Orbit all the time, things that survive there will be those with the greatest numbers, eg rocket bodies. This makes it a matter of sampling. Future archaeologists may not find the rare satellites as easily as the common ones. It's like the famous section in Kent G. Flannery's The Early Mesoamerican Village, a classic of the 1960s-1970s movement known as the New Archeology. A Real Mesoamerican Archaeologist laughs about another's failure to find the city of Teotihuacan using a particular sampling strategy. The Skeptical Graduate Student explains that this is not the purpose of a sampling strategy - and that the sample should produce results in proportion to what exists in the entire population of artefacts.

In another post I'll consider whether we can apply absolute dating techniques to space junk in orbit.

Topological stratigraphy

Terrestrial stratigraphy is locally linear and Euclidean, but orbits are non-linear and non-Euclidean. At larger scales, space is better described as the topological object called a manifold. Stratigraphy might simply be the wrong concept to describe the structure of orbiting objects. What kind of word would we use instead? Perhaps gravigraphy - written in gravity? Or orbitography, which is 'the determination and positioning of satellite orbits by a form of geodesy'?

Visualisations of space junk show Earth surrounded by white dots, like a cloud of silent bees. If you took Earth out of the middle, you would have a donut shape or torus where geostationary satellites are concentrated, and perhaps a series of intersecting tori for low to medium Earth orbit satellites. This is in stark contrast to terrestrial stratigraphy, which is conceptualised in a box-shape (even though Earth is spherical). Objects in this gravitationally-constrained tori move on elliptical paths inside the shape.

Let's put Earth back in. If we sliced a wedge vertically through through this cloud or swam, and froze the objects within it, what would we see? At the outer edge, the graveyard orbit, there'd be a thin smattering of defunct satellites. They are all dead. Below it, in the GEO range, there is thick ring of living and dead satellites. The 'type fossil' of this layer is the winged bird.

Then there is a sparse background scatter of satellites and junk until we hit the navigation satellites in the Medium Earth Orbit range. The US GPS network orbit at around 20, 000 km.

In LEO, we get the highest density of rocket bodies as well as satellites. There is a more diverse size range, from ENVISAT, the International Space Station, to cubesats and nanosats. There is the sparsest smattering of organic material.

There's a dead zone from LEO to the height of the tallest building or structure on Earth. Birds and aeroplanes fly at different altitudes, but they don't stay there or live there. There are gases, clouds, dusts.

On the surface of Earth, the ancient is mixed up with the modern. I suppose it is more like orbit than we might think, the living and the dead jostling side by side. Organic material is dense. Movement is slow. The deeper you go under the surface, the older things become. In this subterranean sphere, everything human is dead.

In all of these layers, the past and the present are mixed up to different degrees. The closer to the present you get, the higher and deeper human culture goes. Mines and building foundations cut into the dead deep past and overlay it with modern material. This is the variable borderland between the Pleistocene, Holocene and Anthropocene, a diachronous boundary that archaeologist Matt Edgeworth and his co-authors (2015) have discussed in an insightful paper (see below).

What is a place in orbit?

I'm relatedly curious about the concepts of setting or site in the orbital environment. Here, a 'place' is really a set of equations that defines the way an object moves - not just now but in the past and into the future. Place is a prediction, effectively. Place is movement, not stasis.

Could an orbital pathway, in and of itself, have heritage significance? Could it be 'preserved', and what would be the relationship between a culturally significant trajectory and the equations that define it? Could those equations, in and of themselves, also be considered culturally or archaeologically significant?

Perhaps in the future, there will be markers along the orbits of significant spacecraft that are not longer there, alerting anyone/thing who approaches that they are at a heritage orbit. Perhaps certain orbits - like Vanguard 1's - could be registered as significant so that nobody can launch something into the same orbit. An orbit has economic significance - so why not heritage significance too?

I think I have a lot further to go in this line of thinking. But it's a start anyway.

References

Matt Edgeworth, Dan deB Richter, Colin Waters, Peter Haff, Cath Neal, and Simon James Price 2015 Diachronous beginnings of the Anthropocene: the lower bounding surface of anthropogenic deposits.  The Anthropocene Review 2(1):33-58

Flannery, Kent G. (ed) 1976 The Early Mesoamerican Village. Academic Press

Space Age Suds: women, washing machines and the astronautics of everyday life

'Space Age Suds' is a charming and slightly alarming little vignette which is about the seeping of the Space Age into domestic life, machines and technology and how they structure social relationships, and gender roles in the Space Age. It's meant to be humorous, of course, but there is so much going on here!

The author isn't just anyone - it's beloved South Australian writer and journalist Max Fatchen. I found the article on Trove and now can't relocate it, but it seems likely it was published in the Advertiser, Adelaide's daily broadsheet. The date is a bit uncertain but it's clearly Apollo era.

I like that the Space Age reverses gender roles and that by the analogy of the washing machine with the space capsule, the wife is accorded the power of technology. After some searching I was able to find her first name but not her original surname, so we will have to call her Jean Fatchen here.

Because the image is a little fuzzy, here is the text.

Space Age Suds: the script

So the Russians are developing a low-orbital bomb. Well, it's just one more complicated space-age development, like our washing machine.

Our washing machine has a shape like a capsule and it is computer programmed and uncanny.

I was never much of a one with technology, and as a member of the avant garde laundry set, I'm all washed up.

There's no longer the simple meshing of gears as with our old washing machine. The cheerful days when I got my tie caught in the wrangler are past.

Our washing machine is automated in a cold, impersonal way, and my wife now calls herself a laundry technician.

She subscribes to advanced scientific journals, keeps up with the Apollo space project and runs off at the mouth on everything from transistors to laser beams.

I have been given the title of junior wash and garment line adherer, which means I hang out the clothes. I suppose I should be grateful.

Yet I dread washing mornings. I belong to a generation of boiling coppers and copper sticks, the hot sudsy smell of saturated sheets, and of bars of yellowed soap.

Now there's an air of bristling technology in the laundry, with split-second timing and ruthless efficiency.

"Load", my wife rasps. I stuff the clothes into the washing machine.

She consults her watch. "Four minutes to wash off," she says.

She looks at the console. "Close hatch," she orders. I shut the washing machine. She begins the countdown, "Five.....four.....three..."

"Look, dear," I interrupt, "I've forgotten a couple of my shirts...."

"Clear the complex", she says icily. "Two.....one.....". She throws a switch.

I humbly take up my position.

"Motor running", I report.

Strange, uncanny sounds come from the interior of the machine.

'Hot water entering,' I chant, consulting my check sheet.

"All systems are go," says my wife.

I sit back and light a cigarette with clammy hands.

Time goes by. The washing machine murmurs, thumps, sighs and gurgles. Its programme goes its relentless way.

"Check machine and report," rasps my wife from the kitchen.

"Machine on course, entering spin-dry period," I say.

"Check systems," she says.

"Check, check, check," I cry. "Hoses running. Pump stops ... four...three...two ....one...NOW."

"Clothes touch down, five minutes," says my wife. "Stand by."

"Machine spinning," I cry.

"Fire retro-rockets," she says absentmindedly.

At last the machine is silent.

My wife climbs to her feet.

"Open hatch!" she orders. "Alert clothes waggon".

She begins unloading the washing machine.

She lets out a shriek. "These clothes still look dirty".

"You didn't," she says, "put in the washing powder, did you?".

"Well," I bluster, insubordinate and defiant to the last, "this machine is supposed to think of everything. If it hasn't enough brains to use washing powder....."

"That's all," she snaps. "We'll have to do another orbit. Get the powder".

No, I haven't been on the moon but there are times when it sounds attractive!

Exegesis

So much to say about this little piece! I'm only going to scratch the surface here.

There's the idea that the Space Age changes how we do small domestic things on Earth: more like machines than messy humans. Both the wife and the washing machine are now operating as Space Age robots (it's a little bit Stepford Wives-ish tbh). It shows how the public interpreted the machine-human interfaces of space technology, down to checklists just like those that the Apollo astronauts used. It's also very cybernetic, getting status updates and adjusting the conditions.

The washing machine drum is a little gravity machine in itself, spinning like a space station or a centrifuge such those astronauts train in. Front loading washing machines with a glass porthole resemble spaceships too. 

The countdown has permeated into the domestic level: precision timing is the key to Space Age efficiency. As a domestic astronaut in her small domain, Jean has assumed power: she commands and Max obeys. She is a robot herself, icy and distant, intolerant of human foibles like forgetting a few shirts - and also the washing powder. (Thanks a bunch, Max. I would have been far more annoyed were I Jean).

The irony is that the power of astronaut Jean is illusory. While Max is pretending to help, he's actually demonstrating a typical trope of the inept male. He boasts about hanging out the clothes, but in this scenario, he forgets the washing powder and sits about smoking a casual ciggie (as people did in those days) while Jean multitasks, back in the kitchen. He finishes with that golden oldie, the nagging wife. It's a perfect illustration of the separate gender spheres of the 1960s, when women were excluded from being astronauts in the US.

'Fire retro rockets,' Jean says, absentmindedly. Doesn't this seem at odds with the ruthless robot housewife, all hard, streamlined efficiency? It took me a few reads before I realised what the subtle Max was implying with this sentence. She is absent-minded and talking about retro-rockets - which the washing machine does not have - because she is dreaming. Standing in her apron at the kitchen sink washing the breakfast dishes, while Max lounges around in the laundry, she is an astronaut. She is in command of a space mission, brave and true. The washing machine is as close as she can come to realising this dream. It makes me feel a little sad.

Once upon a time in France (well probably about 2005), I saw a washing machine advertisement in which a rather attractive nude man crouched in front of the washing machine's porthole, presumably waiting for the spin cycle to finish. The caption read 'One small step for man, one giant leap for women' or something to that effect in French: the idea was that is was a bloody big leap to get a bloke to do any housework, so nude dude's efforts at laundry were going to emancipate women and allow them to leave the house, even go to space! In effect, the effort involved in getting a man to do the laundry was equivalent to landing on the moon!

Gallery of Space Age Suds

As it turns out, there are quite a few connections between washing machines and the Space Age. Here's a small sample.

A space-age shop front in Sheffield, UK. Used with permission, from
https://shopfrontsofsheffield.com/2013/09/30/apollo-appliances-ltd-12-meadowhead/

Look at those rocket portholes lined up outside this charming shop!

https://www.doorsteps.com/search/carson-city_nv?property_id=1004635807

A rental property in Carson City, NV, USA, was advertised with a Space Age Laundry!

From Freaking News,
http://www.freakingnews.com/Tom-Hanks-in-Washing-Machine-Spaceship-Pictures-110109.asp

This is a reference to the Apollo 13 mission.

Source: unknown

This advertisement from 1900 explicitly references the gravity of spinning.


















I'm sure I could find many more examples if I kept searching. Le me know if you find any!

And I'd like to finish by saluting astronaut Jean Fatchen. Here she is with Max in 2004.

Jean, with Max. Picture: Grant NowellSource:adelaidenow

Flying dreams and the human relationship to gravity

From time to time, I have flying dreams. Standing on my feet, just a tiny movement will launch me into the air, and I go soaring above the ground with my arms outstretched, as effortlessly as a bird, delighting in the freedom.

When I think about these dreams, they have certain elements in common. It's always sunny with a blue, blue sky - maybe a couple of white fluffy clouds. There is green, even grass below me. The ground is flat or gently undulating at most. There's always a house. Not a familiar house, more like a greeting-card house or a children's book illustration. There are no houses nearby, just the house on a wide green lawn. I fly above the house at a certain height. I can see trees and often there's a Hills Hoist clothesline in the garden. No fences, though. It's much lower than aeroplane height, and the view is always of the immediate environment of the house.

It's a domestic dream, and perhaps a child's dream, when your whole world revolves around the house and the extent of space is a concept you've yet to fully grasp.

When I wake up from a flying dream, I often still feel the lack of gravity. The sensation that I can just will myself into the air and fly stays with me until I put my feet on the ground and realise how heavy I am, and how adhesive gravity is. I feel intense sadness at this moment. Being heavy seems such a burden. After a few steps, the residues of the dream evaporate and I'm fully awake.

Thinking about these dreams has led me to a curious thought. What if they are part of a pre-adaptation to space?

Now it's true that the human body is not well adapted to microgravity, and we know a fair bit about this because of astronauts' experience in Earth-orbiting space stations. Blood pools in the upper body, muscles atrophy, bones lose their calcium and weaken. We probably don't really know enough yet about the long term health affects of living in space either - a year is a long, long time in space, and only a few people have spent that long up there.

Despite this, humans seem to have an urge to defy gravity, whether it's aeroplanes or rockets. This starts very early. Remember how you loved being thrown up in the air and caught when you were a little kid, and how it made you laugh? The thrilling sensation of a centrifuge, when an adult or older child held your hands and swung you around in a circle? And just how much fun swings in the local park were? Even little tiny babies love these things.

Swimming is fun because we can also defy gravity in water, moving in any direction we want with a twist and flap. In the water, our feet are not stuck to the clay of the Earth. There's nothing beneath them and our personal space expands to a sphere rather than a dome. It's just a shame that water exerts a drag that's absent in the air. Also, there are things that can bite you in water.

My desire to fly doesn't mean I'm drawn to sky-diving, or hang gliding, because that's not what this is about. It's about flight being in one's body, not a result of technology.

Having said that, I also have a slightly concerning desire to throw myself off heights just to experience the exhilaration of falling through the air. Maybe this is like Douglas Adams' 'learning to throw yourself at the ground and and miss'. I'm not afraid of heights, just afraid that if there isn't a barrier, the compulsion might become too great to resist. My lack of fear frightens me because I know logically that hitting the hard ground at acceleration is not going to have a good outcome.

I've learnt that this is called the High Place Phenomenon. One person described it thus: 'It was the opposite of vertigo. It was the urge to fly'.

I wonder how old this urge is, and if the much-vaunted 'urge to explore', when applied to space, is really just the echo of a flying dream.

Collage by Pilar Zeta.
http://www.emptykingdom.com/featured/pilar-zeta/

In Wild Air: Venus, Voyager, and more of my favourite obsessions

It's Monday <>, you are celestial. MOBILE VERSION — VISIT ARCHIVES Many thanks to the amazing Heath Killen for permission to republish this. You can find more of Heath's work here.  Alice Gorman is In Wild Air I’m an archaeologist who studies space exploration – the artefacts, the places, and the perspectives that lead to how we understand other worlds. Here I share some of my obsessions about space and time. PHOTO: ASHTON CLARIDGE / FLINDERS UNIVERSITY Help us spread the good word. TO FRIENDS TO STRANGERS TO LOVERS CULTURE The Venus of Willendorf The Venus of Willendorf, discovered in Austria in 1908, must be one of the most famous and least understood women in all of human history. She was made during the Ice Ages, between 30 000 and 28 000 years ago. The 11 cm high figurine is carved from limestone and was originally thickly coated in red ochre. Without facial features, or even feet, she’s all sexuality with great breasts and belly and a well-defined vulva. A multitude of theories have swirled around her: mother goddess religions, matriarchal cultures, Palaeolithic pornography, prehistoric selfies, the power of post-menopausal women, cross-cultural communication. But she’s also a massive Palaeolithic fuck-you to the ideas of female attractiveness that are often investigated by evolutionary psychologists. This branch of science often ends up justifying current human gender inequalities as some sort of evolutionary fitness. I think this is why I like her so much. She feels a bit like a revolutionary. She defies easy explanations. She is unique and herself. PEOPLE Woman with Microscope In 1977, two extraordinary spacecraft were launched on a mission to map the outer planets and then continue on to the space between the stars. Voyager 1 and 2 have become cultural icons, not only because they are the furthest extent of human culture and perhaps the most likely to make first contact with other sentient species, but also because of the Golden Records attached to them. The Records were the project of a team led by legendary science communicator Carl Sagan. They contain 90 minutes of music meant to represent the evolution of human culture, greetings spoken in many languages, and the natural sounds of life on Earth.  There’s also 116 images. One in particular captures my imagination. A black woman in a lab coat bends over a microscope, tiered earrings falling gracefully from her pierced ears. She is simply called “Woman with Microscope”. All I know about her is that the earrings were the subject of some debate: would an alien recognise the concept of “jewellery”, or think they were some sort of technology, or even a name tag?  She speaks to some very contemporary debates about women and other underrepresented minorities in science. Even today, little girls across the world are made to feel that they are not smart enough to be scientists, that space is the domain of men. The inclusion of a black female scientist on the Golden Records hence seems a bold statement about who gets to go to space. If only we knew her name. PLACES Voyage to Venus Venus has always been my favourite planet. As a child it was part of my atlas of the night sky and I was drawn to its association with creativity, passion, the arts of love, and mystery. And what lay beneath Venus’ impenetrable clouds was a mystery. It seemed a likely candidate for life, and many imagined a vibrant oceanic world populated with winged angelic beings who sang, telepathic frogs, or even dinosaurs. The USSR Venera landing missions of the 1960s and 1970s dashed hopes of a sister world with new solar system companions. Venus, under the clouds, was a pressure-cooker of dull brown rocks and slow soupy winds. Perhaps, most of all, my love for Venus was fostered by reading C.S. Lewis’ beautiful evocation of a new world, as a teenager in the 1970s. Published in 1943, Voyage to Venus (also known as Perelandra) describes a planet of floating islands and sensuous experiences of colour, taste, and touch that have philosophical dimensions. The reality of the Venusian surface did not deter me from falling in love with this vision. Every now and then I feel an urge to read Voyage to Venus again and relive the terror and desire of a world beyond human aesthetics. PRODUCTS Cable Ties I am obsessed with cable ties, as an artefact and a technology. There’s probably a stash of them in most households; and they’re used for everything from boning corsets to securing suitcases and backpacks. They seem so simple – a plastic strap that you thread and tighten to hold something together, cheap to buy and easy to throw away – yet they’re connected to larger currents of technology and politics that unite the worlds of aerospace and domestic space in the 20th century. Archaeologists are always looking at the ground. Once I would have sought the tell-tale angles of an Aboriginal stone tool; now I look for the characteristic t-shape of a severed cable tie lying in the streets. I’ve become shameless about picking them up from the ground and stashing them in corners of my bag, no matter who is looking askance at me. Cable ties were invented in 1958 in the US, for wiring aircraft. They migrated to Australia when NASA established a series of satellite tracking stations here in the 1960s. Antennas and computers needed a lot of cables. From there they insinuated themselves into everyday life, to the degree that most people don’t really even think about them. For me, they’re the quintessential space age artefact. And they are in space – inside the International Space Station, for example. Look more closely next time you watch a video of life on the ISS. Once you’ve seen them, they can’t be unseen – you’ll start to notice them everywhere. IDEAS Two Ways of Thinking About Space  1957-1958 was a significant year, or to be more precise, a significant 18 months. It was the International Geophysical Year, a massive effort of international scientific co-operation to understand the Earth and space. During the IGY, the first three satellites were launched – Sputnik 1 in 1957, and Explorer 1 and Vanguard 1 in 1958. And two books were published which explored the way we relate to space. Alexandre Koyré’s 1957 From Closed World to Infinite Universe is a work of jaw-dropping scholarship. It’s about the “replacement of the Aristotelian conception of space—a differentiated set of innerworldly places—by that of Euclidean geometry—an essentially infinite and homogenous extension—from now on considered as identical with the real space of the world”. Gaston Bachelard’s 1958 The Poetics of Space was rather a phenomenology of inner or experienced space, from corners, to attics, to the interior of shells. For him, the vehicle of space travel was the daydream: “One might say that immensity is a philosophical category of daydream. …And this contemplation produces an attitude that is so special, an inner state that is so unlike any other, that the daydream transports the dreamer outside the immediate world to a world that bears the mark of infinity”. The mark of infinity is the geometry of our senses, the mathematics of our dreaming. WILDISM Microgravity You don’t have to go into space to experience microgravity. All you have to do is seek out your nearest amusement park. There you’ll find rides which simulate higher gravity and free fall. Scientific drop towers are experimental facilities where scientists test materials and chemical processes in microgravity; it’s the same principle used in amusement parks. For high gravity, try a spinning rotor – this is like the centrifuge that astronauts use in training, but fortunately you won’t be required to perform mathematical calculations at the same time. I tried this at Vienna’s famous Prater park and I can’t say it was a pleasant experience, but those around me were clearly getting a kick out of it. Free fall, on the other hand, was exhilarating! Until zero-g parabolic flights and space tourism become affordable for regular Earth people, this may be the closest we can get to microgravity, even if only for a few seconds. Start your astronaut training now! ELSEWHERE The Archaeology of the International Space Station The Archaeology of the International Space Station is a new project that I’m working on with Dr Justin Walsh. We want to investigate how a distinct space culture is created. You can read more about this project and keep up to date with it on our blog. Alice Gorman is In Wild Air VOLUME III | EDITION XXXV In Wild Air is a project by Heath Killen Thank you for being here now COPYRIGHT © 2017 All rights reserved, all wrongs reversed

How geodesy created a vision of the Earth through the jewelled LAGEOS satellites

Image courtesy of NASA

Could this be the most beautiful satellite ever made? In fact it is one of twins, as there are two of these jewelled spheres in Earth orbit. They're the LAGEOS satellites, essentially inert reflectors to bounce lasers off. The jewels are fused silica, except for four made from germanium. The interior is not a void filled with instruments: it's a solid brass cylindrical core, covered in a thick aluminium shell, as you can see in the video below.

(Hang on, you say. Fused silica? Isn't that just glass? Well yes and no. It's amorphous silica, but without any of the other ingredients that make up the glass we use, like lime, soda and potash).

LAGEOS stands for  LAser GEOdynamic Satellite. The first was launched by the US on May 4 1976, and the second, made by the Italian Space Agency, was launched in 1992.  This means in 2017 the 60 cm sphere - harking back to the spherical satellites of the early space age, such as Sputnik, Vanguard and Echo, achieved 41 years in orbit. It's a veteran of space science.

And because they're completely passive, with no power, fuel, solar panels or instruments, their missions are not ending any time soon. They should be up there for about 8.4 million years according to the original prediction! They can just keep going until their reflectors are too weathered by exposure to the space environment to bounce a laser back to Earth. The glass eyes are meant to be dust and radiation-resistant, but, just like the famous space shuttle windows, they could be damaged by hypervelocity particle impact. Perhaps the quality of the return signal could even be a way of measuring deterioration in the surfaces since launch, and hence gauging something about taphonomy in space. I wonder if this is possible?

The two satellites orbit at around 6000 km in a circular polar orbit. The information they have provided has contributed to new perspectives of the Earth, as former LAGEOS project scientist David E. Smith explains: 

Today, we see Earth as one system, with the planet’s shape, rotation, atmosphere, gravitational field and the motions of the continents all connected. We take it for granted now, but LAGEOS helped us arrive at that view.

Even more importantly, the two LAGEOS define the centre point, based on the Earth's centre of mass, for the terrestrial reference system used in navigation.

One of the things they're used for is to measure the speed and direction of tectonic plate movement. Because of this, LAGEOS-1 was the recipient of one of Carl Sagan's time-travel interspecies communications.  He conceived a design - drawn by Jon Lomberg who also worked with him on the Voyager Golden Records - engraved on a thin steel plate that was wrapped around the brass cylinder core - depicting continental drift at three points in time: 268 million years ago, 1976, and in 8.4 million years. You'd have to crack the satellite open like an egg, though, to get at the message. It's precisely the sort of alien mystery object that science fiction writers imagine falling to a planet and catalysing personal and social revelations, even when the object is impenetrable. Who knows who or what might find it in 8.4 million years? Will it melt in re-entry, fall into the ocean unnoticed and unmourned, or slam into the Australian outback like Skylab, to lie under the stars for another few million years?

There's another little mystery too. LAGEOS 1 has the most precisely know orbit of any orbital object. In 1978, LAGEOS-1 began descending at a much greater rate than it should have. In 1983, as David E. Smith described in a Nature paper, the satellite rather unexpectedly began to ascend again. It's still losing altitude - 1.33 mm each day - but because it is mostly beyond the reach of the atmosphere which drags objects in lower orbits back in, the cause of the decay is still a matter of debate.

And here's another interesting fact. The Optus B series of GEO telecommunications satellites have laser retroreflectors mounted on them too. My colleague Owen Mace (one of the pioneering Australis Oscar V team) had the contract to make them. Optus B1 is in the GEO graveyard orbit; Optus B2 exploded on launch, and Optus B3 was replaced by Optus D1. This means it is still in GEO but technically classified as space junk. Is anyone ranging to the two reflectors? I don't know....


References
Dey, Uijal, Kar, Samanwita, and Amitabha Ghosh 2016 Possible effect of the Earth's intertial induction on the orbital decay of LAGEOS. Journal of Astrophysics and Astronomy 37(3):1-9

Fitzmaurice, M.W., Minott, P.O., Abshire, J.B. and H. E. Rowe 1977 Prelaunch testing of the Laser Geodynamic Satellite (LAGEOS). NASA report

Smith, David E. 1983 Celestial mechanics: Acceleration on LAGEOS spacecraft.  Nature Vol 304 p 15


Note: after I began writing this blog post, it morphed into an article for The Conversation.