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I noticed that in NASA world view web site it's take some time to get per day world wide coverage. enter image description here

I made some calculations:

  • The source is Aqua & Terra satellites
  • Both have orbital period roughly 100 min
  • NASA SW image processing delay is 3h
  • Capture possible only when it's day time on respective earth part

The only question is what is the scanning footprint? Usually it's almost "180 degrees". But maybe it's significant smaller due to requirements of high resolution imagery? Because if it's "regular" 180 degrees it should be faster.

  • Because the viewing platform is a finite number of satellites in orbit . . . – mdsumner Sep 12 '15 at 14:37
  • @mdsumner Can you explain? Still it's not clear for me. Thanks, – michael Sep 12 '15 at 14:40
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    Search for details on satellite remote sensing coverage. The Earth is rotating, and it's large. High resolution imagery requires that you be relatively close and for a satellite to be close it must be moving (there's only one orbit distance that is "geo stationary", and that's not "close"). There's only so much a satellite can "see", and there's only so many we can launch. It takes time to orbit the Earth. – mdsumner Sep 12 '15 at 14:45
  • The NASA FAQ states that the data is available within 3 hours of collection, and you're complaining that's not fast enough? – Vince Sep 12 '15 at 16:15
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    You provided links to a wiki that says the platforms are in low earth orbit (LEO). The FAQ reports the viewfield to be +/-55 degrees, with a swath width of 2330km. – Vince Sep 12 '15 at 19:10
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Together Terra and Aqua image the entire Earth every 1 to 2 days. The cross track swath is about 2330 km (about 3000 km is needed for "true" daily global coverage).

Compared to the geostationary satellites (35,786 km), sun synchronous satellites fly relatively low (600 to 850 km), their swath is thus smaller for a similar viewing angles.

The fact that sun synchronous satellites are moving relatively to the Earth surface is also a problem for the data transfer (data cannot be downloaded at any time). This has been improved, but "older" satellites had to be switched off because they didn't have enough bandwith to store all their images. Only recently do we have high resolution satellite with systematic acquisition (Landsat 8 and the Sentinels 1 & 2)

Note that a geostationary sensor only needs ~17.4 ° for an hemispherical coverage, so this is far from 180°.

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