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ISS by Moonlight

ISS by Moonlight. Credit: CESAR Team

Is it a bird? Is it a plane? No it’s the ISS as it apparently flies across the surface of the Moon. This spectacular image was captured a dedicated team at ESAC on Saturday 14 January.

Taking advantage of the full Moon, the relative orbit of the International Space Station and the excellent night sky at ESA’s Iberian Establishment, this composite image clearly shows some of the main elements of the station’s structure. The image is a superposition of thirteen frames captured at 02:01:14 CEST. The phenomena is extremely fast: the ISS only took 0.56 seconds to cross the lunar disk. Because of this, careful planning was required to successfully record the event.
ISS-Moon crossings are common, but a crossing visible from a specific location on Earth is not. The observer, the ISS and the Moon must be precisely aligned. The geometry is so particular that the ground path where observers can see the event is only a few hundred meters wide. Therefore careful planning of the observation must be performed. With all this taken into account, and considering that the ISS flies at over 27,000km/h, the transit is over in the blink of an eye.

The ISS is the largest man-made object in orbit, spanning the size of a football pitch. Even so, its orbital distance of approximately 400 km it still appears tiny through a telescope. Depending on the ISS orbit altitude and the Moon elevation over the horizon, our natural satellite is at least 30-40 times bigger than the station.

The intrepid group (Michel Breitfellner, Manuel Castillo, Abel de Burgos and Miguel Perez Ayucar) braved freezing temperatures to set up two telescopes with Canon reflex cameras behind the A-building at ESAC. The ISS, being in Earth's shadow, cannot be spotted before the crossing, so the observation was carried out blind, using the predicted crossing time as the cue to record the event. Fortunately the orbital mechanics were perfect and the ISS was captured exactly as predicted.

Michel Breitfellner, Miguel Pérez Ayucar, Abel de Burgos and Manuel Castillo. Credit: CESAR Team

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