Sunday, November 19, 2017

Apollo 8: the shadow diaries

Mapping the shadows

Shadows on the Moon have many scientific implications, from temperature to the electrostatic properties of lunar dust. I'm more interested in the cultural and social aspects of lunar shadows, however, while noting that the lines are often blurred between these distinctions.

I've considered shadows as part of the fabric of the Apollo landing sites. In another post I looked at Apollo mission photographs in which the photographer is present only as a shadow. Here, I'm thinking about shadows cast by 'natural' features; light, perspective, and movement. 

This is a series of images taken by the Apollo 8 mission in 1968. (All these images are from the NASA archives). Apollo 8 was the first US human spaceflight mission to orbit the Moon. People usually remember this mission for the famous snap of Earthrise, claimed to be one of the most influential images of all time.

Over 20 hours, the Apollo 8 spacecraft with its three crew orbited the Moon 10 times. The aim was to map the lunar surface, supplementing data from the Lunar Orbiter in 1964. 

This wasn't all, though. The crew were scoping out possible future landing sites, and shadows were a factor. A little way into their sixth orbit, one of the astronauts says:
The sun angles that we see now from the first IP, second IP, and P 1 are just right, I think, for landing conditions. The shadows aren't too deep for you to get confused, but the land is - has texture to it, and there are enough shadows to make everything stand out.
Not too much shadow, but not too little either. So now let's look at the shadows as seen by Apollo 8.

A shadow sequence

I've chosen these images from different points in the magazine 17C roll to show how shadows change as the spacecraft flew over the surface from lunar day to lunar night. 

Figure 1: AS08-17-2813

The surface of the Moon is a bright mirror against the black of space (Figure 1).

Figure 2: AS08-17-2761

With a different camera angle, the brightness fills the entire screen. We can see even brighter white markings (Figure 2). If you didn't know this was the moon, it could almost be the surface of a stone tool under a Scanning Electron Microscope, the changes in colour representing incipient fractures too small for the naked eye to detect.

As the Apollo 8 spacecraft injected itself into lunar orbit and prepared to take the first photographs, the astronauts commented on the lack of shadows.

Figure 3: AS08-17-2704

The details start to be resolved. It's no longer a flat surface with markings or fissures; it's a raised surface where faint shadows give it depth and texture (Figure 3).

Here, we're moving away from the subsolar point where the sun is overhead. The angle of light does not produce shadows, much as on Earth.

Figure 4: AS08-17-2686

Now we see more detail, and gradations of shadows, as the Apollo craft heads towards the terminator. The craters look like footprints in deep sand interspersed with those of smaller animals and worms, such as you might see on the surface of a beach still wet from the retreating water of the tide. In fact, astronaut Jim Lovell compared the texture of the surface to greyish beach sand.

In each major depression there are two or three shades of shadow, with the deepest black on the left hand edge.

Figure 5: AS08-17-2674

The shadows are deeper and darker as Apollo 8 approaches the evening side of the Moon. They convey a sense of late afternoon with an oblique sun. At the base of the craters, the shadows are deep black and even a little sinister (Figure 5). There are surfaces on the Moon that are permanently shadowed, never exposed to sunlight.

Figure 6: AS08-17-2664

The proportion of light and dark is now starting to reverse. The shadows are taking over the craters, leaving a miniature new moon sliver of brightness on the right side (Figure 6). These are deep holes, perhaps the lair of a lunar worm waiting to propel itself towards the spacecraft with a snap and swallow it whole.

Figure 7: AS08-17-2660
It is night on the Moon and all lies in shadow. Only the rim of the craters catch residual sunlight - or is it Earthlight?

During the voyage, Bill Anders said 'There's not as much detail, of course, as in the sunlight, but you can see the - the large craters quite distinctly, and you can see the albedo contacts quite distinctly. And also, the - there's a good three-dimensional view of the rims of the large craters'.

In the debrief following their return Anders commented that 'night landing or landing on the moon in an earthshine condition would be acceptable from a visibility standpoint'.

Anders raised another interesting point in the official debrief:
I thought that the shadows were not nearly as black as there [sic] appeared to be in the simulations that I've seen on earth, particularly the Boeing simulation. We could even see the features that were on the shadowside of some rills and rims. So, although it's dark, it's not a complete black and white situation. 
Naturally I'm taken with the concept of the shadow simulation. These would have used images from the Lunar Orbiter, which was orbiting at a higher altitude. 

Shadow [moon] lander

So what's my point? These are so different to the shadows cast by the accoutrements of robotic and human landing missions on the Moon. All the ones I've shown here have a circular geometry, and they're mostly about 'bumps and holes', as one of the astronauts said (from the transcripts it's sometimes hard to tell who said what). There's a peculiar feature of these bumps and holes which is shared with microscope views: sometimes it's hard to tell which one it is. Depressions and hollows can look like hills and protruberances, and you have to 'get your eye in' to see them properly. It's a sort of optical illusion, I guess, but one in which the shadows are critical.

Most of the cultural shadows on the Moon are cast by objects resting on the surface rather than depressions into the surface (although there are some of those too). They're frequently angular or linear. More recently, the Lunar Reconnaissance Orbiter has used these shadows to identify features of the Apollo sites.

Shadows are a critical feature of the visual experience of the Moon, at least for the astronaut. I'm not sure whether we can see lunar shadows from the Earth with the naked eye, though. Light and dark areas are caused by the reflectance properties of different geologies (selenologies?), known as albedo features. I don't think we can see the movement of shadows as the light of the sun or the phases of the moon change. With a telescope, though, it's different. The elongation of shadows near the terminator can be seen and photographed. 

There's something about scale and distance here, and about technology and vision. I guess what I really want to say is that shadows aren't incidental to our experience of the Moon. They're signs that we can read, and translate into science, and into poetry too.


A patch of the Moon
flanked by shadows: trembling sense
we shouldn’t be here.

Image and poem by @tychogirl

Monday, October 16, 2017

A gallery of shadow astronauts Part 1

For the last few years, I have been playing with the idea of shadows as part of a site's fabric. It's not just about the hard materials. It's about the soft, the fleeting, the ephemeral, and the symbolic: about the interplay of darkness and light, presence and absence, loneliness and companionship.

Apollo 11. Shadow: Neil Armstrong. NASA

Apollo 12. Shadow unknown. NASA

Apollo 12. Shadow: Pete Conrad. NASA

Apollo 14. Body + shadow: Alan Shepard. Shadow: Edgar Mitchell. NASA

Apollo 14. Astronaut shadow unknown. NASA

Apollo 15. Shadows: Dave Scott and Jim Irwin. NASA
In these images, I'm interested in the astronaut who is not in the picture, whose presence is revealed by their shadow. It's also about the insubstantial shadow in relation to the hard and solid objects. In the image immediately above, it looks like the shadow of Jim Irwin is attempting to capture the solid stick-insect shape of the tripod with a shadow net. 

There's a pattern of elongated legs. The bodies are distorted, and also cyborg: in the shadow, flesh and camera meld into one amorphous shape.

The photos are silent, although we do have a beepy staticky soundtrack to them in our heads, implanted by the Apollo 11 television footage. Somehow the shadows accentuate the silence.

I particularly like Pete Conrad's shadow cast in the crater as he stands on the edge looking down. The angle of his body makes the shadow appear as if in profile, creeping silently along a shadow ridge to what end we cannot know. It has a dream-like quality.

We could say that of all the shadows, perhaps. Were they not caught in the photograph like a fly in amber, they would have vanished without trace in seconds, as evanescent as the dream on waking.

Wednesday, July 26, 2017

A different kind of 'Space Race': space-themed racehorses

I grew up around racehorses. One day, my father told me the story of how his application to call one of ours "Little Lemon", after Laika the space dog, was rejected by the Board. The reason was not that the name was unavailable; and one could speculate that there was some Cold War paranoia involved.

Here's another example of space-themed racehorses:

How about that? This is from Louise A. Ackerman's 1958 discussion about variants of the word Sputnik in American English.

According to Racing Australia, a horse cannot receive the same name as another horse until 17 years after the original horse has retired. So I am here to tell you that in Australia and New Zealand, the name Sputnik will become available again in 2026. Rocket becomes available in 2028. 

If your naming needs are more urgent, One Giant Leap is available in 2019, and Laika and Skylab are currently free! Perhaps Skylab isn't a great name for a horse, though. It does somewhat imply crashing and burning.

If you want to combine your racing and Star Trek passions, here is a list of racehorse names inspired by the cult classic.

And here is the cutest spacehorse ever, inspired by British astronaut Tim Peake.

Image courtesy of Attic Photographic

Ackerman, Louise A. 1958 Facetious variations on 'Sputnik'. American Speech 33(2): 154-156.

Friday, July 07, 2017

Autobiographical reminiscence: the phases of Venus

As a child, I loved stargazing, and this was a pretty easy thing to do growing up on a farm. We had constellation charts that were stored in the bottom shelf of the glass-fronted bookcase in the sitting room, and I learned to locate and name them. I think the charts may have come from Weekly Times special offers, which was how we acquired a Readers Digest atlas. (The Weekly Times was a newspaper devoted to rural issues).

The constellation of Andromeda
Of course the names were often figures from Greek and Roman mythology: Orion, Andromeda, Gemini, Perseus, etc. Among the books in the glass-fronted bookcase were volumes of classical mythology retold for popular consumption, which I devoured; and it only now occurs to me that the constellations united the stars and ancient civilisations in my mind. Perhaps it was not so illogical to love both astronomy and archaeology.

Venus was always my favourite planet. Not only was it the brightest thing in the firmament after the Moon, but Aphrodite seemed like a much more interesting goddess than any of the others - even Athene. I might have been a bookworm, but I wasn't giving up the allure of the flesh on that account. And of course, Venus is the only female planet to identify with.

My friend Ged remembers me pointing out Venus in the dawn sky when I was staying over on her parent's property, in primary school days. Something puzzled me, though. I had read of how the ancient Babylonian astronomers charted the phases of Venus (this may have been in one of my archaeology kid's books, or an encyclopedia). For the life of me, I couldn't see how this could be done. They didn't have telescopes, and I couldn't see any bloody phases. I never asked anyone about this; well, country NSW wasn't exactly crawling with astronomers, and there was no internet then.

In 6th grade, at the age of 10, it came to my mother's attention that I was short-sighted, and probably had been the whole time. I'd just developed strategies to make up for the fact that I couldn't read the blackboard at school, and it never occurred to me that everyone didn't experience the world like this. So I was duly taken away to get glasses. Suddenly, my father's hitherto mysterious ability to identify the species of a flying bird was revealed. I had thought him terribly clever because he clearly could distinguish between flying styles. Now I realised he could actually see them.

Ah, I thought. So this was how the Babylonian astronomers did it. They could see the phases of Venus without the benefit of modern telescopes.

It was now much easier to tell the difference between the stars and planets as the telltale twinkling was more obvious, and I could at last see the rabbit on the Moon.

However, this new sight was both a blessing and a curse. Glasses cemented a certain reputation captured by Dorothy Parker's famous aphorism: Men seldom make passes at girls who wear glasses. Being seen as smart was antithetical to being seen as desirable, the pinnacle of a woman's achievement. Athene was taking ascendency over Aphrodite as the contradictions and constraints of being a teenage girl were ushered in with high school life.

Another phase of Venus was about to begin.

Saturday, June 24, 2017

'Ah, that was a beautiful piece of engineering and archaeology!'. Cordwainer Smith's IOM rocket.

I'm always fascinated by how science fiction writers portray archaeology.  A couple of weeks ago, I was wandering through the Adelaide Central Markets on my way to work, and I spied a second-hand book sale. There was a box of old science fiction, and one leapt out at me: Cordwainer Smith's Space Lords, which I did not have.

To my delight, this volume of short stories contained one that I'd never read either. Drunkboat is the story of how the Lord Crudelta precipitated the discovery of Space3. I knew of the story as some critics have discussed it in reference to the evolution of the Vomact family. 

Leaving the plot aside, here is how Cordwainer Smith imagines a kind of space archaeology:
We had put him in a rocket of the most ancient style. We also wrote writing on the outside of it, just the way the Ancients did when they first ventured into space. Ah, that was a beautiful piece of engineering and archeology! We copied everything right down to the correct models of fifteen thousand years ago, when the Paroskii and Murkins were racing each other into space. The rocket was white, with a red and white gantry beside it. The letters IOM were on the rocket, not that the words mattered.

IOM, of course, stands for the Instrumentality of Mankind. The national symbols that adorned spacecraft in the 20th and 21st centuries are mystifying to the denizens of the future, but they copy them anyway.

Fifteen thousand years on from the Cold War space race - I assume the Paroskii and the Murkins are meant to represent the USSR and the USA - there's sufficient documentation and models of the early rockets to replicate them. The IOM rocket is thus a facsimile of old technology. If we think about what was happening 15 000 years ago for us, one of the principle technologies was the manufacture of stone tools. So perhaps this was like something archaeologists might do today in replicating a Magdalenian retouched point.

Magdalenian flaked stone artefacts, from Debout et al 2012
Such technology is often called 'primitive' in popular accounts, but it was very far from that, requiring a highly sophisticated knowledge of geology and engineering too - understanding the mechanical, chemical and fracture properties of stone are essential to making stone tools. Learning how to actually make and use ancient technologies is sometimes called ethnoarchaeology, and the idea is that you can learn something about how people lived in the past that simply analysing the artefact as an object cannot reveal.

Similarly, the facsimile of the rocket demands both engineering and archaeology to make it more than just another model. The rocket is launched from its red and white gantry - cheerful picnic colours - and if you want to know the rest, you will have to read the story.

Saturday, June 03, 2017

Cable ties in literature: from the boudoir to the post-apocalyptic

It's no secret that I have an obsession with cable ties. The nice thing is that when I explain their fascinating history to people, they often catch the bug as well, coming to appreciate the stunningly simple design of this monumentally successful piece of technology. If you want to know the full story, you can read my paper on cable ties here.

Anastasia Steel and Christian Grey in the cable tie section of the
hardware store. I mean seriously. What a depauperate population
of the popular plastic fastening device.
Sadly, cable ties have not yet set the world of literature alight, unless you count their famous appearance in Fifty Shades of Grey. I would say that E.L James paid insufficient attention to cable ties as critical material infrastructure in her novel; and the range of cable ties available in the hardware shop in the film version is frankly disappointing.

Hugh Howey's Wool is a different proposition. I was lent this book by a friend and was astonished that I hadn't heard of it before. It was immediately enthralling, and there really is nothing nicer than finding a new author whose work just makes you want to read more.

So you can perhaps imagine my breathless excitement when I started Chapter 21 of Wool to find a description of CABLE TIES OF THE FUTURE.

Oh yes.

So here, for your delectation, is the passage in question. I don't think there are any spoilers in it if you haven't read the book.

The next morning Juliette arrived early at her desk having stolen little more than four hours of sleep. Beside her computer, she saw a package waiting for her: a small bundle wrapped in recycled pulp paper and encircled with white electrical ties. She smiled at this last touch and reached into her overalls for her multi-tool. Pulling out the smallest pick from the tool, she stuck it into the clasp of one of the electrical ties and slowly pulled the ratcheting device apart, keeping it intact for future use. She remembered the trouble she'd gotten into as a mechanic's shadow the day she'd been caught cutting a plastic tie from an electrical board. Walker, already an old crank those decades ago, had yelled at her for the waste and then shown her how to tease the little clasp loose to preserve the tie for later use. 
Years had passed, and when she was much older, she had found herself passing this lesson on to another shadow named Scottie. He had been a young lad at the time, but she had had a go at him when he had made the same careless mistake she once had. ... 
She loosened the other tie crossing the package and knew the bundle was from him. Several years ago, Scottie had been recruited by IT and had moved up to the thirties. He had become 'too smart for Mechanical', as Knox had put it. Juliette set the two electrical straps aside and pictured the young man preparing this package for her. The request she'd wired down to Mechanical the night before must've bounced back up to him, and he had spent the night dutifully doing her this favour. 
She pried the paper apart carefully. Both it and the plastic ties would need to be returned; they were both too dear for her to keep and light enough to porter on the cheap. As the package came apart, she noticed that Scottie had crimped the edges and had folded these tabs under each other, a trick children learned so they could wrap notes without the expense of glue or tape.

Scottie leaves her a note: Keep the ties - I got plenty. 

Where do I start? There is so much going on here, and although I believe there are some technical unlikelihoods, on the whole Howey has paid the cable tie much greater respect as an artefact than E.L James.

At this point I must digress. I searched for a link to Wool to include and discovered something that astonished me. Another reviewer HAS ALREADY COMPARED WOOL TO FIFTY SHADES OF GREY.


Science fiction's answer to Fifty Shades of Grey, the review in the Guardian says. Perhaps I missed the BDSM scenes in Wool. I'm pretty sure I did. And I may be wrong, but I'm also pretty sure that few reviewers take the cable tie approach to literature. Well there's nothing for it but to read this other review.

Ah, now I read that the comparison is made on the basis that both works were initially self-published. There is no mention of cable ties. So I shall continue.

Juliette's cable ties are described as "white electrical". This is the industrial context in which cable ties were first invented, when Maurus C. Logan visited the Boeing factory in 1956 and watched the workers tying up the electrical wiring in an aircraft. He was employed by US electrical outfitters Thomas and Betts. Since their first manufacture, cable ties migrated into everyday life and a myriad of uses securing every kind of thing. Here, in the isolated culture of the silo, sealed off against the toxic world outside, cable ties have retreated to their original use.

Colour is significant in cable tie manufacture. Black cable ties are generally intended for outdoor use; their carbon content makes them UV resistant. In the silo, the cable ties are white. They will never be used outside, as no-one can survive outside in the poisoned atmosphere. They're like little pale fishes trapped in an underground pool.

There are two types of cable ties, those which have to be cut off and can't be re-used, and re-usable ones, which need to be undone with a special tool. It's not entirely clear from Howey's account which is intended here. If you loosen the ratchet head, will it really be useable again as it won't engage with the ridged tail? Juliette doesn't seem to be using a specialised tool, just the smallest one from her panoply.

This is a minor point against the real implications of the passage however: that in the closed world of the silo, an artefact that was once mass-produced and discarded without thought is now precious and valuable.

The cable ties are symbolic here as well: Scottie is using them as a material allusion to the history that he and Juliette share, knowing that they will make her recall the past. They symbolise the passing on of knowledge: the creation of new bonds - as well as their dissolution. They are used to secure the parcel, but they are part of the gift as well.

Fastening is an art when materials to secure objects are in short supply. The parcel is a contradiction of meanings. Scottie has used the valuable cable ties to hold it all together, but in the first layer he has employed the technique learned from childhood to fold the paper together. Here we see a discipline of alternatives in an alternative world.

I particularly appreciate the thought that has gone into this passage, projecting a social and technological context for an artefact of the present into the future. It's what science fiction does best.

So my Cable Ties in Literature Award today goes to Hugh Howey for Wool. It is perhaps not quite on the level of other literary awards, given the small pool of nominees. Nevertheless, I regard it as an achievement. Congratulations, Hugh.

Thursday, May 11, 2017

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....

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 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.