This weather site uses provides meteorological imaging from the Himawari-8 Earth observing satellite in GEO. https://www.cwb.gov.tw/eng/

The web site contains the following item:

2020-02-05: Around midnight during the spring and fall eclipse periods, sunlight can directly enter the satellite sensor. To avoid this, the part of the observation area can be skipped. The period of influence is from 19th February to 19th April.

Question: Why around midnight and during this particular period?

  • 2
    $\begingroup$ Because it's safest to look at the sun at night. $\endgroup$
    – Richard
    Feb 7, 2020 at 20:23

1 Answer 1


Why around midnight...

Because then the sun will be on the exact opposite site of the earth, from the satellites point-of-view.

A=Satellite, E=Earth, S=Sun (not to scale ;) )


As a geostationary satellite, Himawari 8 is always above the same area, roughly over Indonesia & Papua New Guinea.

NORAD 40267 Himawari-8 from n2yo.com from n2yo.com

...and during this particular period?

I guess it's because of the earth's axial tilt. Geostationary satellites are always right above the equator. If the earth's axial tilt is sufficient and the earth is tilted either towards or away from the sun, the angle changes, an exaggerated version looking like this:


The sun won't be obstructed by the earth and sunlight can enter the sensor directly.

Presumably the same thing will happen during the opposite months of the year as well.

  • 5
    $\begingroup$ No need to presume, the quote linked in the question says spring and fall eclipse so it confirms the same happens during the opposite months. $\endgroup$
    – gerrit
    Feb 7, 2020 at 9:14
  • 1
    $\begingroup$ Thanks for the extensive edits, was a bit lazy with the answer :) $\endgroup$
    – Infrisios
    Feb 7, 2020 at 10:23
  • $\begingroup$ The dates are a month about the March 19 equinox, so that makes sense. But why midnight? Those months are w he ends the sensor is eclipsed ie should be dark, no? $\endgroup$ Feb 7, 2020 at 19:18
  • 3
    $\begingroup$ The sensor is dark when the Sun is directly behind the Earth; but before and after that, the Sun is very near the Earth. (So it might be fine at exactly midnight but at risk from sun exposure at 11:55 and 12.:05.) $\endgroup$
    – Skyler
    Feb 7, 2020 at 20:15
  • 2
    $\begingroup$ +1 for ASCII diagrams alone $\endgroup$ Feb 7, 2020 at 20:59

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