Since the ISS is moving so fast, does NASA need to account for doppler shift in the radio signal? How do they account for this considering the ISS uses FM?

Question

Since the ISS is moving so fast, does NASA need to account for doppler shift in the radio signal? How do they account for this considering the ISS uses FM?

In: Engineering

Answer 1

out of interest i did the calculations.

The ISS broadcasts at 145.8MHz, and the maximum shifted frequency of the received waves on earth due to doppler shift would be 3.7kHz above the intended frequency.

Answer 2

NASA (and all communications with fast moving satellites) use Dynamic Doppler Compensation, where the frequency of the broadcasts are adjusted progressively through the broadcast to ensure that the receiver maintains a solid signal on the correct frequency.

Answer 3

The ISS is moving from side to side for most links, not the inward/outward path that would maximize Doppler shift. The dishes do move, to keep pointed at the ISS. The transmitters and receivers use phase locked loops to tune the carrier signal, so the shift is mostly tracked as it shifts.