randlemcmurphy
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G484 January 2013 Q2)b)ii)
(Paper: http://www.ocr.org.uk/Images/144792-...nian-world.pdf
Markscheme: http://www.ocr.org.uk/Images/142403-...ld-january.pdf)

Here is the question:
"The cameras on board the satellite continually photograph a strip of the Earth’s surface, of width 3000 km, directly below the satellite. Determine, with an appropriate calculation, whether the satellite can photograph the whole of the Earth’s surface in 24 hours. Stateyour conclusion."

I understand the mark scheme up until: "(But each orbit crosses the equator twice hence)". I cannot at this point understand this, maybe it is because I can't visualize it...

Could anybody give me guidance on how to think about this question. The understanding of it is more important to me than the calculation method.

Thanks
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Stonebridge
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(Original post by randlemcmurphy)
G484 January 2013 Q2)b)ii)
(Paper: http://www.ocr.org.uk/Images/144792-...nian-world.pdf
Markscheme: http://www.ocr.org.uk/Images/142403-...ld-january.pdf)

Here is the question:
"The cameras on board the satellite continually photograph a strip of the Earth’s surface, of width 3000 km, directly below the satellite. Determine, with an appropriate calculation, whether the satellite can photograph the whole of the Earth’s surface in 24 hours. State your conclusion."

I understand the mark scheme up until: "(But each orbit crosses the equator twice hence)". I cannot at this point understand this, maybe it is because I can't visualize it...

Could anybody give me guidance on how to think about this question. The understanding of it is more important to me than the calculation method.

Thanks
The point is that the satellite is orbiting the poles, as stated in the question. So imagine it starting at the N pole and going down over the equator to the S pole, then back up to the N pole.It crosses the equator twice. Once from N to S and once from S to N. So in each orbit it can photograph 2 strips of land stretching from N to S. So if, say, it needed to photograph 20 strips to map the whole earth, it would only need to orbit 10 times, as it gets 2 strips each orbit.
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randlemcmurphy
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(Original post by Stonebridge)
The point is that the satellite is orbiting the poles, as stated in the question. So imagine it starting at the N pole and going down over the equator to the S pole, then back up to the N pole.It crosses the equator twice. Once from N to S and once from S to N. So in each orbit it can photograph 2 strips of land stretching from N to S. So if, say, it needed to photograph 20 strips to map the whole earth, it would only need to orbit 10 times, as it gets 2 strips each orbit.
It all makes sense now. Thanks Stonebridge!
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