Given: Mass of the astronaut Ma = 75 Kg
Radius of the earth re = 6.38 x 10⁶ m
Altitude of the astronaut h = 600 Km = 600,000 m
Total radius will be r = 6.38 x 10⁶ m + 600,000 r = 6.98 x 10⁶ m
G = 6.67 x 10⁻¹¹ N.m²/Kg²
Mass of Earth Me = 5.98 x 10²⁴ Kg
Formula: F = GmeMa/re²
F = (6.67 X 10⁻¹¹ N.m²/Kg²)(5.98 X 10²⁴ Kg)(75 Kg)/(6.98 x 10⁶ m)²
F = 2.99 x 10¹⁶ N.m²/4.87 x 10¹³ m²
F = 613.96 N or around 615 N