T he light most recently crossed into New Haven sky on October 6 at 7:01 p.m. If you were outside, you could follow its trajectory, emerging from the last bit of twilight to the west and fading into the east after six solid minutes.
The International Space Station is on planetary business. It goes around the earth at a speed of 17,500 miles per hour, nearly 200 miles above the breathable atmosphere. A human event can’t be any less local, yet you can experience it from your own backyard.
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The station’s first occupants—one astronaut from the US, two from Russia—arrived in November 2000, establishing a routine of maintenance, expansion and scientific experimentation that has gone uninterrupted. According to NASA’s informative ISS website, the station has grown from a small cluster of three modules to “a sprawling research complex that today is as large as a five-bedroom home.” Much of its research is devoted to the effects of lengthy space habitation on the human body—the current crew, Expedition 63, is investigating the use of yeast in repairing space radiation damage to human DNA—and this renders crewmembers both experimenters and subjects. During six-month visits, they work several feet from where they sleep. They check in for regular physicals and try to stay active with two hours of daily exercise. They can gaze out the window at whole continents and oceans during their lunch break, getting a dramatic reminder of how much outdoor space they’re missing.
Even as confined as we have been during the pandemic, we can watch the space station travel hundreds of miles overhead and get a feeling of relief at not being quite so confined. The ISS crosses New Haven’s longitude every 92 minutes, and if it crosses that line far enough above the equator, it clears New Haven’s horizon. But if it does so during the day, the sky is too bright, and the station remains invisible beyond it. Too close to the middle of the night, and the station passes by in darkness, with no sunlight to reflect. Sighting opportunities are then limited to a couple hours after dusk or before dawn. When you factor in the 40 degrees by which it must clear the horizon in order to also clear trees and buildings, you may get a few opportunities to see it in a month, or sometimes none for several weeks.
An obvious question for anybody who’s seen the ISS more than once is: Why the inconsistency? Why does it pop up over the neighbor’s garage one night, over the silver maple the next, then not at all the night after that? The answer is offered by Dr. Elliott Horch, who teaches astronomy at Southern Connecticut State University. “The latitude of the earth over which [the ISS] is directly positioned is not always the same… And that’s because the orbit of the satellite is tilted with respect to our system of latitude and longitude.” With an audible shrug, Horch adds, “But that’s no different from the moon. Sometimes when you look at it in the sky, it’s higher up. And sometimes, it’s a little closer to the horizon.”
So when you look to the west, the ISS could be emerging on its orbital tilt away from the equator, in which case it will appear a little to the south of west, or it could be on its tilt toward the equator, in which case it will appear a little to the north of west. If its course is high and sustained, it may actually be flying directly over New Haven—or close to it—but this is rare. Station spotters are reliant on a delicate ballet between the satellite’s orbit and their own independently rotating position. “The spinning of the earth carries the observer away by a certain amount over the course of one orbital period,” Horch notes.
There have been 65 alerts emailed from Mission Control to New Haven-area “Spot The Station” subscribers so far this year. Some of them test your mettle with 3 to 4 a.m. start times. Of course, New Haven is not unique in its station-spotting opportunities. The ISS flies high enough to be seen by New Haveners and, say, Miamians at the same time. It’s also low and thus fast enough that New Haveners could see it in the course of one orbit and Chicagoans the next, before the sun comes up for either city.
The station’s visibility, when it is visible, is most directly a function of its high reflectivity. The power used by the ISS’s crew to heat their food packets and run their laboratories requires an array of solar panels large enough to balloon the station to “more than half the area of a football field,” according to the official website. It’s this mirror-like solar array, perpetually turning on gimbals to face the sun, that gives the station its bright, super-planetary aspect from below. According to NASA, 95% of the inhabited world can see the ISS at one time or another.
Still, New Haven has a unique place in the history of satellite-spotting. As reported by the Hartford Courant in 1957, it was on a rooftop on the campus of Southern Connecticut State University that Robert Brown, a professor of earth science, and James Plato, an amateur astronomer, became the first Americans to spot Sputnik.
This visual confirmation of the first man-made satellite would have been an occasion to pause in awe—and probably dread—of Soviet ingenuity. It was new, daring and secretive, only visible with a telescope after careful calculation. The ISS, on the other hand, comes with an invitation. Those “Spot The Station” alerts tell you when and where it will appear, how high it will get and how long it will be visible.
Part of the pleasure of accepting the invitation is in the clockability of the station’s course. It doesn’t streak like a meteor burning itself out in seconds, or push noisily against the prevailing winds like an overnight flight to Dubai. Instead, it draws a perfectly fluid, unstoppable and silent line across the sky, as it has over 100,000 times so far, no longer inspiring awe at how novel it is but rather at how reliable it is.
Written by David Zukowski. Image, featuring the ISS in 2010, courtesy of NASA.
