NASA 宇宙の記録
今日の天体写真 (APOD)= カレンダーから選ぶ「宇宙の神秘」=

Yes, but have you ever seen the space station do this? If you know when and where to look, watching the bright International Space Station (ISS) drift across your night sky is a fascinating sight -- but not very unusual. Images of the ISS crossing in front of the half-degree Moon or Sun do exist, but are somewhat rare as they take planning, timing, and patience to acquire. Catching the ISS crossing in front of minuscule Mars, though, is on another level. Using online software, the featured photographer learned that the unusual transit would be visible only momentarily along a very narrow stretch of nearby land spanning just 90 meters. Within this stretch, the equivalent ground velocity of the passing ISS image would be a quick 7.4 kilometers per second. However, with a standard camera, a small telescope, an exact location to set up his equipment, an exact direction to point the telescope, and sub-millisecond timing -- he created a video from which the featured 0.00035 second exposure was extracted. In the resulting image capture, details on both Mars and the ISS are visible simultaneously. The featured image was acquired last Monday at 05:15:47 local time from just northeast of San Diego, California, USA. Although typically much smaller, angularly, than the ISS, Mars is approaching its maximum angular size in the next few weeks, because the blue planet (Earth) is set to pass its closest to the red planet (Mars) in their respective orbits around the Sun. Portal Universe: Random APOD Generator