ESA Document - Emits - ESA

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HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 315 of 422
The used frequencies (in Table 4-21) and data rate will be taken from the protocol. The
maximum data rate allowed, 2048 kbps, will be used. Figure 4-61 shows the frequency plan and
data rate for EVAs.
Due to the wavelength of the UHF signal (around 1.75 m), the effect of Martian dust on the
signal propagation is negligible.
The communications system in the space suit is similar to the one used in ISS. The radio has two
single UHF channel transmitters, three single channel receivers and a switching mechanism. The
low profile antenna is located in the (Portable Life Support System) PLSS.
Forward link (EVA->Base) Return link (Base->EVA)
Frequency See Table 4-21.
Data link layer protocol Proximity link
Data rate 2048 kbps 256 kbps
Coding Convolutional, rate ½, constraint length 7 Viterbi code.
Modulation scheme Bi-Phase-L modulated directly into the carrier
Modulation index 60º +/- 5%
Bit Error rate 10 -11 , obtained Eb/N0 = 8.4 dB
Doppler and Doppler rate Negligible
Table 4-20: Characteristics of the UHF link
UHF Forward Return
channel (MHz) (MHz)
1 435.6 404.4
2 437.1 401.6
3 439.2 397.5
4 444.6 393.9
5 449 390
Table 4-21: UHF proximity link protocol channels.
Figure 4-61: EVAs data rates and frequencies, respectively