A spacecraft is in a circular orbit around a distant neutron star. The spacecraf
ID: 1275485 • Letter: A
Question
A spacecraft is in a circular orbit around a distant neutron star. The spacecraft signals Earth when it is at position A. It is designed to operate at a frequency, of 109 MHz, but the signal is observed to reach Earth with a frequency of 141 MHz. (a) The rocket is going Counter-clockwise around the star. (b) What is the speed of the rocket? M/s c) What is the frequency observed at Earth when the rocket is at position C? MHz d) What is the frequency observed at Earth when the rocket is at position at B or D? MHz Comment: There are also effects from general relativity (gravity) in this problem, but we are ignoring these.Explanation / Answer
f = sqrt( (1 + beta)/(1 - beta)) f0
141 = sqrt( (1 + beta)/(1 - beta))109
beta = 0.252
so v = 0.252*3.0E8= 7.56E7 m/s
c)
now beta = -0.252
f = sqrt( (1-0.252)/(1 + 0.252))*109= 84.3 MHz
d) since motion is perp to earth direction f doesnt change
so 109 MHz
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