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ESA Document - Emits - ESA

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s<br />

Kind of<br />

antenna<br />

Telescope 1<br />

Dish<br />

antenna<br />

MGA<br />

Patch<br />

Dish<br />

antenna<br />

Patch<br />

antenna<br />

Wire<br />

antenna<br />

Quantity Band Gain<br />

1<br />

2<br />

1<br />

Optica<br />

l<br />

Ka-<br />

Band<br />

Xband <br />

Xband<br />

1 UHF<br />

3.3.7.6 Options<br />

4<br />

UHF/<br />

VHF<br />

3.3.7.6.1 Ka+ band<br />

Minimum<br />

required<br />

pointing<br />

precision<br />

59.1<br />

dBi<br />

0.01 deg<br />

18 dBi 20 deg<br />

30 dBi 2.25 deg<br />

6 dBi 40 deg<br />

-3 dBi Omnidirectio<br />

nal<br />

Size<br />

Radiated<br />

power<br />

Data rate<br />

Uplink<br />

Data rate<br />

Downlink<br />

2µrad 30.5 cm 5 W No uplink 10 Mbps<br />

3 m 65 W 1.8 Mbps 1.5 Mbps<br />

8.2 x 8.2 x 2<br />

cm<br />

65 W 22 Kbps 460 bps<br />

45 cm 65 W 30 Mbps 30 Mbps<br />

35 x 35 cm 10 W 128 Kbps 128 kbps<br />

20 x 10 x 10<br />

cm<br />

Table 3-47: TV antennas summary<br />

HMM<br />

Assessment Study<br />

Report: CDF-20(A)<br />

February 2004<br />

page 216 of 422<br />

Steering<br />

mechanism Commentaries<br />

180°<br />

hemispherical<br />

180°<br />

hemispherical<br />

180°<br />

hemispherical<br />

180°<br />

hemispherical<br />

180°<br />

hemispherical<br />

LASER link, only<br />

used for downlink<br />

Main link.<br />

Intelligence to<br />

point the Earth in<br />

a contingency<br />

case, even with<br />

loss of TV<br />

attitude<br />

Link with relay<br />

satellite<br />

UHF link with<br />

MAV/MEV<br />

5 W 2048 Kbps 2048 kbps None For TV EVAs<br />

Unit<br />

Number Unit massTotal<br />

MassPower<br />

of units (kg) (kg) (W)<br />

Optical transmitter 2 20.0 40 150.0<br />

Optical transmitter device (telescope)1 25.0 25<br />

UHF antenna system (EVA) 4 2.0 8<br />

Ka-band transponder 2 6.5 13 160.0<br />

Ka-band antenna (3m) 1 35.3 35.3<br />

X-band transponder 2 6.5 13 100.0<br />

MGA (X-band), patch 2 0.6 1.2<br />

UHF patch antenna 1 1.0 1<br />

UHF transceiver 2 2.5 5 16.5<br />

X-band dish antenna (0.45 m) 1 1.0 1<br />

Harness 21<br />

Total: 163.5 370<br />

Figure 3-64: TV communications budget summary<br />

One of the most straightforward ways of improving link capacity is moving to higher frequency<br />

bands. The 40 GHz up and 37 GHz down band (Ka+/Ka+) was allocated by ITU for the very<br />

purpose of human space exploration. Contrary to the 34 GHz up / 32 GHz down (Ka/Ka), the<br />

Ka+ band can be used for both deep-space (Mars) and near-Earth (Moon) missions, while Kaband<br />

can not be used from the Moon, but from Mars. To use the same frequencies for all human<br />

missions, Ka+ band is the best option. The problems of this band are firstly that Ka+ band is new<br />

to space activities and no technology development has been performed so far. Secondly,

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