National Astronomical Observatory of Japan

The International Space Station Transiting across the Sun


The International Space Station Transiting across the Sun

We succeeded in capturing the moment that the International Space Station (ISS) transited across the face of the Sun! It transited during the less than a second between the first exposure and the last, appearing as a dotted line from upper right to lower left along the edge near the north pole of the Sun. The background image of the Sun was observed using light known as the Hα line. A little to the left of the center of the Solar Disk, you can see a sun spot and a bright plage. At this time, Japanese astronaut Kimiya Yui has been onboard the ISS since July 23, 2015.

Successful Photography Using the Solar Flare Telescope

This picture was taken on November 3, 2015 using the Hα Full-disk Imager on the NAOJ Solar Observatory’s Solar Flare Telescope. This is the first time the Solar Flare Telescope has photographed the ISS. Although there are times when the ISS passes through the space above Japan on a daily basis, it is rare to get a chance to see it not only traveling through the space above Mitaka City, but also passing in front of the Sun. What’s more, since the transit took less than 1 second, we had to snap these photos at exactly the right moment. The Solar Flare Telescope usually takes images in the wavelengths around the Hα line every two-and-a-half minutes. For this chance we wrote a special program to take pictures at 30 frames per second and set a timer for the instant that the ISS started to transit the solar disk. Fortunately, November 3 was blessed with blue skies and we succeeded in collecting 22 images. In the upper left of this image you can see a close-up of the ISS. Atmospheric turbulence was strong when this picture was taken, blurring the image, but if you look closely you can kind of make out the ISS’s solar panels.

Text by: Kentaro Yaji (Solar Observatory)
Translation by: Ramsey Lundock (NAOJ)