4 ms·
Am I right, with ISS on the orbit it should happen several times every day. Not for 7 seconds, but..
by two_in_one 3y ago
Am I right, with ISS on the orbit it should happen several times every day. Not for 7 seconds, but..
- eesmith 3y agoNo. There ISS needs to be exactly in the shadow of the asteroid Leona. Both the Earth and Leona are going around the Sun, so the shadow sweeps across the surface of the Earth, taking about 18 minutes to go from Mexico to China, and effectively never coming back. Even if the ISS is in the shadow once - which would require amazing timing and last for fraction of a second - it is not fast enough to have a second interception.
- two_in_one 3y agoI meant different thing. ISS is big enough to cast a small shadow on Earth. It moves fast and covers a star for some fraction of second (roughly size/orbital velocity). Still every day several times.
- eesmith 3y agoIf I read https://www.aanda.org/articles/aa/full_html/2022/11/aa44496-22/aa44496-22.html https://www.aanda.org/articles/aa/full_html/2022/11/aa44496-... correctly, the occultation time for the ISS is under 20 ms (see figure 1, use a size of 100 m, and elevation of 400km). The paper says the current generation of CCD detectors aren't fast enough to detect that change in light flux with >1% accuracy, as they integrate the light collected over tens of seconds. The next generation of CMOS-based detectors might be fast enough. There are some issues to handle, like the complex light curve of the satellite itself affecting the detection, and the relatively low density of bright-enough stars along the path between telescope and ISS. The paper suggests using the tens-of-thousands of satellites in upcoming launches to improve the odds.