Deriving the satellite signal path length equation

[rihanna]

The signal length from the satellite to the Earth station can be found as2(hs-he)/[{sin^2(theta)+(2(hs-he)/Re)}^1/2+sin(theta)] if theta < 5 degrees Due to the Earth projection

where "hs" is satellite height and "he" is the Earth station height and Re is the Earth radius=3700 Km

My question is Can you help me to derive this equation? how they have obtained it?

Regards

 

[tiny-tim]

welcome to pf!

hi rihanna! welcome to pf!

first, draw a clearly marked diagram

(including the centre of the earth)