ESA Document - Emits - ESA

s
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 314 of 422
See 3.3.7 TV communications report for a description of SHM/MAV with TV UHF link, and for
X-band communications with G/S in contingency situations.
RECEIVER CHARACTERISTICS ( X-BAND)
Noise Figure 1.6 dB
Ranging Bandwidth (double sided) 3 MHz
TC Modulation Scheme, Link with relay satellite: GMSK
Direct link with G/S in case of contingency: NRZ/PSK/PM
Coding (NRZ/PSK/PM) Turbo Code ¼ (*)
Concatenated:
Coding (GMSK)
Convolutional +
RS (255, 223)
TRANSMITTER CHARACTERISTICS
RF Transmit Power 65W (SSPA)
TM Modulation Scheme Baseline: GMSK (*)
(*) Availability of ground segment decoders-demodulators is supposed.
4.3.7.3.2 Relay satellite
Table 4-18: X-band transponder characteristics
The aerostationary satellite will relay SHM/MAV, TV and G/S and communications will be
possible between them. The link with SHM/MAV and TV will be in X-band, and will use Kaband
for the link with G/S. The time link availability relay-Earth (considering only the visibility)
will be, in the worst case, 95% because of the Earth eclipses.
As an aerostationary satellite, the position will be at height 17 030 km and over the equator. A
summary of the relay satellite antennas is shown in Table 4-19:
Band Antenna characteristics Transponder
Ka-band Dish 4 m. Two units, Transmitted power=65W
X-band Dish 0.53 m, steering mechanism. Two units, Transmitted power=30W
X-band Dish 0.53 m, steering mechanism. Two units, Transmitted power=30W
4.3.7.3.3 EVA
Table 4-19: Brief summary of the relay satellite antennas and transponders
Considering the drivers for EVAs described in Section 4.3.7.2.1, a summary for the designed
link is shown in Figure 4-61 and Figure 4-62 (in this case, a repeater is used).
Two omni-directional antennas are used, one in the emitter and another one in the receiver part.
The transmitted power is 500 mW. Proximity link [RD43] is the used protocol, in UHF. This
protocol is defined for short range, bi-directional, fixed or mobile radio links, characterized by
short time delays, moderate (not weak) signals, and short/independent sessions. The key
parameters in the physical link between the EVA or rover and the MEV are shown in Table 4-20.