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I saw the waning crescent moon, a small sliver of white rising above the Earth limb. It reminded me of a glowing fingernail clipping. Like a rainbow of only blue, the atmosphere on edge filled the gap between Earth and space—electrifying diaphanous beauty.

Venus was there, watching. Aldebaran in Taurus was an orange dot. The ghost of Full Moon Past, the complete lunar disk, was dimly lit by the bluish hue of earthshine. The time was 07:45 on June 18 (GMT).

June 18, 07:45

One orbit later, at 09:17, I saw a sliver of a sliver.

June 18, 9:17

Work beckoned me for the next three orbits (about four and a half hours) before I could observe another moonrise. At 13:56, there was only the smallest glint that we even had a Moon.

June 18, 13:56

The next orbit I was waiting at dawn, but saw no moon. Initially I was baffled. Then it occurred to me that I had been witness to the birth of a New Moon.

Here’s a low-res version of a movie I made on Space Station during this week’s Venus transit.  Right now we are in a phase of continuous twilight.

The sky is not the limit for producing artistic compositions. Put a camera on a tripod, point at a dark starry sky, and hold the shutter open for about 10 minutes, and the image will show stars as circular arcs. Normally, these star trails are created as the Earth rotates on its axis, with the center being close to either Polaris, the north star, or the Southern Cross, depending on which hemisphere you are in.

I got the idea to do the same thing from Space Station; however, the physics of orbit adds a special twist. As Space Station orbits, it keeps one side always facing the Earth (the nadir direction from the crew’s point of view). This requires the Station to complete one revolution about its axis each orbit, just like the Moon. ISS rotates about its center of mass, which happens to be in the Unity, or Node 1 module. So it rotates almost aligned with the Station’s long, backbone-like truss.

Space Station makes one revolution every 90 minutes (the Moon takes 28 days). As a result, long-exposure pictures taken from the Station show star trails as circular arcs, with the center of rotation being the poles of Space Station (perpendicular to our orbital plane.) Space Station is inclined 51.6° from Earth’s equator, so the “poles” are now at 38.4°.

This picture was taken pointing to port, so it shows the end of the port truss with solar panels. Click on the images to see them larger.

My star trail images are made by taking a time exposure of about 10 to 15 minutes. However, with modern digital cameras, 30 seconds is about the longest exposure possible, due to electronic detector noise effectively snowing out the image. To achieve the longer exposures I do what many amateur astronomers do. I take multiple 30-second exposures, then “stack” them using imaging software, thus producing the longer exposure.

Due to our altitude, it is possible to see both the north and south axis of our orbit at the same time. This makes possible star trail images with two circles defined by arcs with opposite inflections. This geometry is hard to arrange from only one window, so I used a fisheye lens with a full 180° image circle to create the composition above.

In addition to the star trails, many other phenomena of nature can be seen. But I’ll save that topic for another post.

The flash of an Iridium satellite slants across the star trails.

An Ariane 5 rocket carrying Europe's ATV cargo vehicle appears as a diagonal streak in this March 23 photo.

Star trails and satellite flashes above, lightning storms below.

Flashing space station with beams of light as it passes overhead had never been successfully done—until yesterday.

It sounds deceptively easy. In an earlier post I wrote about the technical requirements. But like so many other tasks, it becomes much more involved in the execution than in the planning.

Early Sunday morning, at 01:27 our time, the San Antonio Astronomical Association, an amateur astronomy group, succeeded in flashing the space station with a one-watt blue laser and a white spotlight as we passed overhead. This took a number of engineering calculations. Projected beam diameters (assuming the propagation of a Gaussian wave for the laser) and intensity at the target had to be calculated. Tracking space station’s path as it streaked across the sky was another challenge. I used email to communicate with Robert Reeves, one of the association’s members. Considering that it takes a day, maybe more, for a simple exchange of messages (on space station we receive email drops two to three times a day), the whole event took weeks to plan.

I was ready with cameras for the early morning San Antonio pass and can report that it was a flashing success. Here’s one of the pictures to prove it:

Light (top center) flashed from the Lozano Observatory, about 40 miles north of San Antonio, was easily visible from orbit. Click on the image to see it full-sized.

From my orbital perspective, I am sitting still and Earth is moving. I sit above the grandest of all globes spinning below my feet, and watch the world speed by at an amazing eight kilometers per second (288 miles per minute, or 17,300 miles per hour).

This makes Earth photography complicated.

Even with a shutter speed of 1/1000^th of a second, eight meters (26 feet) of motion occurs during the exposure. Our 400-millimeter telephoto lens has a resolution of less than three meters on the ground. Simply pointing at a target and squeezing the shutter always yields a less-than-perfect image, and precise manual tracking must be done to capture truly sharp pictures. It usually takes a new space station crewmember a month of on-orbit practice to use the full capability of this telephoto lens.

That's Canada's Manicouagan Crater near the center. Click on the photo to see it full-size.

Another surprisingly difficult aspect of Earth photography is capturing a specific target. If I want to take a picture of Silverton, Oregon, my hometown, I have about 10 to 15 seconds of prime nadir (the point directly below us) viewing time to take the picture. If the image is taken off the nadir, a distorted, squashed projection is obtained. If I float up to the window and see my target, it’s too late to take a picture. If the camera has the wrong lens, the memory card is full, the battery depleted, or the camera is on some non-standard setting enabled by its myriad buttons and knobs, the opportunity will be over by the time the situation is corrected. And some targets like my hometown, sitting in the middle of farmland, are low-contrast and difficult to find. If more than a few seconds are needed to spot the target, again the moment is lost. All of us have missed the chance to take that “good one.” Fortunately, when in orbit, what goes around comes around, and in a few days there will be another chance.

It takes 90 minutes to circle the Earth, with about 60 minutes in daylight and 30 minutes in darkness. The globe is equally divided into day and night by the shadow line, but being 400 kilometers up, we travel a significant distance over the nighttime earth while the station remains in full sunlight. During those times, as viewed from Earth, we are brightly lit against a dark sky. This is a special period that makes it possible for people on the ground to observe space station pass overhead as a large, bright, moving point of light. This condition lasts for only about seven minutes; after that we are still overhead, but are unlit and so cannot be readily observed.

Ironically, when earthlings can see us, we cannot see them. The glare from the full sun effectively turns our windows into mirrors that return our own ghostly reflection. This often plays out when friends want to flash space station from the ground as it travels overhead. They shine green lasers, xenon strobes, and halogen spotlights at us as we sprint across the sky. These well-wishers don’t know that we cannot see a thing during this time. The best time to try this is during a dark pass when orbital calculations show that we are passing overhead. This becomes complicated when highly collimated light from lasers are used, since the beam diameter at our orbital distance is about one kilometer, and this spot has to be tracking us while in the dark. And of course we have to be looking. As often happens, technical details complicate what seems like a simple observation. So far, all attempts at flashing the space station have failed.

Looking through the cupola windows on Space Station, it’s only natural to reflect upon who we are and where we fit into the world below. Like something out of Alice in Wonderland, this orbital looking glass can be both a window through which to observe the jeweled sphere of Earth and a mirror that (sometimes, depending on your viewing angle) shows you a translucent reflection of yourself superimposed on the planet.

City lights over Belgium and the Netherlands

From orbit, the more you know about our planet, the more you can see. You see all the geological features described in textbooks. You see fault zones, moraines, basins, ranges, impact craters, dikes, sills, braided channels, the strike and dip of layered rocks, folding, meanders, oxbow lakes, slumps, slides, mud flows, deltas, alluvial fans, glaciers, karst topography, cirques, tectonic plates, rifts zones, cinder cones, crater lakes, fossil sea shores, lava flows, volcanic plumes, fissures, eruptions, dry lakes, inverted topography, latteric soils, and many more.

You see clouds of every description and combination: nimbus, cumulus, stratus, nimbo-cumulus, nimbo-stratus, cirrus, thunderheads, and typhoons, sometimes with clockwise rotation, sometimes with counter-clockwise. You notice patterns: clouds over cold oceans look different than clouds over warm oceans. Sometimes the continents are all cloud-covered, so you have no recognizable landmass to help you gauge where you are. If you see a crisscross of jet contrails glistening in the sun above the clouds, you know you are over the United States.

Lightning storms flash like gigantic fireflies looking for mates half a continent away. You see patterns on the ocean surface, swirls and vortices on large scales, wave diffraction patterns around capes, solitary waves forming long lines out in the middle of nowhere, and rivers that look like they are spilling milk chocolate into turquoise oceans.

You see light-scattering phenomena of all kinds—at sunrise, at sunset, across the terminator, 16 times a day. You see crepuscular rays, forward reddened lobes, off-axis blue lobes, and corona halos. With binoculars you can count six distinct layers in the atmosphere, with the outer one seemingly fading into fuzzy blackness.

The aurora is nothing short of occipital ecstasy. It is always moving, always changing, and like snowflakes, no two displays are the same. The glowing red and green forms meander like celestial amoebas crawling across some great petri dish. One time our orbit took us through the center of an auroral display. It was as if we were in a glowing fog of red and green. Had we been shrunk down and inserted into the tube of a neon sign? It looked like it was just on the other side of the windowpane. I wanted to reach out and touch, but of course I couldn’t. Afterwards, I had to clean nose prints off of the window.

André looking out the Cupola windows

You catch an occasional meteor while looking down at Earth. You see stars and planets in oblique views, next to Earth’s limb. And they do not twinkle. Perchance you might spot a ragged shadow from a total solar eclipse projected onto Earth. Amazing, it looks just like it does in the textbooks! You have a godlike view of the finer details of shadowy projections onto spherical bodies. You see space junk orbiting nearby. Sometimes it flickers due to an irregularity, catching light as it rotates. An overboard water dump produces a virtual blizzard in the surrounding vacuum. Like strangers passing in the night, you see other satellites flash brilliantly for a few seconds, then fade into oblivion.

Jungles are the darkest land features you can observe in full sunlight. They are so dark that you need to open your camera lens to obtain a proper exposure. If there are clouds partly shrouding your view, you can be fooled into thinking you are over the ocean. Only when you notice rivers with braided channels and meandering loops of chocolate brown do you realize that it is jungle and not water. Farmland, rich with vibrant crops, is different. Farmland is bright, much brighter than the jungles. Here nature is giving us a clue as to the efficiency of light capture by plants.

The impact of humanity on Earth is humbling from orbit. Our greatest cities appear to the bare eye as minor gray smudges on the edges of continents—they could be the fingerprints of Atlas, from the last time he handled the globe. They are hardly distinguishable from volcanic ash flow or other geologic features. If you didn’t know it was a city, it would be difficult to conclude it was the result of human design. Under the scrutiny of the telephoto lens, things appear different. Like ants moving crumbs of dirt, we are slowly changing our world. You realize that Earth will do just fine, with or without us. We are wedded to this planet, for better or for worse, until mass extinction do us part.

Cities at night are different from their drab daytime counterparts. They present a most spectacular display that rivals a Broadway marquee. And cities around the world are different. Some show blue-green, while others show yellow-orange. Some have rectangular grids, while others look like a fractal-snapshot from Mandelbrot space.

Patterns in the countryside are different in Europe, North America, and South America. In space, you can see political boundaries that show up only at night. As if a beacon for humanity, Las Vegas is truly the brightest spot on Earth. Cities at night may very well be the most beautiful unintentional consequence of human activity.

This looking glass incites your mind to ponder the abstract. Through the window, you explore the world. In the mirror, you reflect upon your place within it and the reasons we explore. Is it fundamentally about finding new places to live and new resources to use? Or is it about expanding our knowledge of the universe? Either way, exploration seems fundamental to our survival as a species. After all, if the dinosaurs had explored space and colonized other planets, they would still be alive today.

Twice a year, near the winter and summer solstices, the orbit of space station nearly parallels the terminator—the fuzzy line separating day from night on the surface below. For a period of about a week, we live in what seems like perpetual twilight, being in neither full daylight nor full night. Our orbit follows the terminator, so that space station is constantly sunlit. From this vantage I can see both day and night simply by swiveling my head from left to right. But the night is not really dark, and the day is lit by low-angle rays from the Sun.

Geographic relief casts long shadows, and imparts stark contrast to features that are typically overlooked. Small ripples in sand dunes make high contrast striations across the bright desert landscape that look like Nature’s way of drawing with pen and ink. Geographic relief plays tricks on you. First you see the Grand Canyon as this deep scar. Blink your eyes and it is now a rippling bump. Thunderstorms cast shadows that look like they come from some new type of ray beam weapon. Airliners, their path defined by contrails, leave glimmering lines like snail trails in the morning dew. The gardens of Earth appear to have quite an infestation of snails.

The Moon sets in a counterintuitive way. From this vantage it moves nearly parallel to the horizon. Once I saw it slowly set, only to reappear in a few minutes. The Moon was visible for nearly the whole orbit.

The night side is equally fascinating. The atmosphere on edge glows with a vibrant electric blue. Did van Gogh paint this scene? I can see at least five, maybe six distinct layers of blue—perhaps a visual display of the classic atmospheric strata. Just past the terminator, rays of sunlight can be seen projected above the darkened limb of the Earth.

The most striking aspect of our atmosphere is not the palette of electric blue colors but the thinness of it all. Our atmosphere is a diaphanous veil; thin, fragile, transparent, and the only thing that protects us from the harsh vacuum of space. Too much atmosphere, and the planet is choked and suffocated. Too little, and it is exposed to the harshness of cosmic space. My vantage on the station gives me a deep appreciation of this fact.