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s HMM Assessment Study Report: CDF-20(A) February 2004 page 210 of 422 The TV communications direct link availabilities, considering just the direct visibility in the worst case, with the different mission elements are: • G/S: maximum blackout 41 min= 65 % availability. • MEV: average visibility 15 min = 12 % total time. • Relay: availability around 65 % of the time. From relay satellite to the G/S, the maximum blackout duration is 77.5 minutes, so 95% of total time, the relay will have contact with G/S. The exact figures will depend on the season. To increase the communications availability between MEV and TV, apart from a direct link, the solution is to use a relay satellite. With this solution, the availability will be around 65% of total time in the worst case. In LEO (400 km, 62 degrees), each of the three ground stations will have three or a maximum of five passes per day with a maximum duration of around 8 minutes. However, in LEO data relay satellites should be used. 3.3.7.5 Baseline design 3.3.7.5.1 Band and frequency design Laser communications has been used only for downlink while Ka-band has been used for uplink. The reason is a compromise between cost and data rate. In case of using laser communications for uplink as well, just the double of G/S would be needed in principle, so it is a too expensive option. Additionally, Ka-band data rates are higher for uplink than for downlink, mainly the higher transmitted power by the G/S. For contingencies, X-band has been used because it has less weather dependence than Ka-band, so in case of contingency the link availability will be higher. For the TV-relay satellite link, X-band has been choosen, since the pointing requirement is lower than Ka-band and with an small dish antenna diameter (40 cm) a high enough data rate, for the project needs, is achieved. For the TV-MEV/MAV/SHM link, UHF is used because its low propagation losses and very low pointing requirements, make it ideal for docking-undocking manoeuvres. The bands and frequencies used are consistent with the Space Frequency Coordination Group [RD48]. 3.3.7.5.2 Ground station assumptions Ground stations with Ka- and X-band capability and 70 m of diameter are used. See Table 3-40.

s 70-m antenna 70-m antenna 3.3.7.5.3 TV EVAs HMM Assessment Study Report: CDF-20(A) February 2004 page 211 of 422 Transmission Reception Frequency band EIRP Frequency band Effective 10º G/T, 89.31 dBW (1995W 7145 – 7190 MHz 8400 - 8450 MHz 42.52 dB/K 34200 –34700 MHz RF) 114.69 dBW (794W RF) 31800 – 32300 MHz Table 3-42: Assumed ground station characteristics 56.71 dB/K In assembly or contingency situations, EVAs could be necessary for TV. Two sets of external double (redundant) antennas have been used in TV design. The system will be able to transmit voice, biomedical data and receive voice data. The voice can come from TV or other astronaut. An ISS like antenna system has been used (see Table 3-47). 3.3.7.5.4 Links description TV will have five different communications links with the other mission elements: 1. Ka-band link with G/S, using a 3 m-dish HGA antenna. 2. X-band link with G/S using two MGA antennas, for contingencies 3. UHF link: for communications with SHM, DM and MAV. An UHF patch antenna is used. 4. X-band link with the relay satellite, for communications with SHM and with Earth. A 0.45m dish HGA antenna is used. 5. Laser link with G/S. Only used for downlink. Note that communications with the Earth will have a roundtrip delay of 40 minutes, in the worst case (distance TV-Mars of 2.7 AU). No real time communications are possible. Link Ka-band 1 X-band UHF 2 Laser X-band Uplink Downlink Uplink Downlink Uplink Downlink Uplink Downlink Frequency 34.5 GHz 32 GHz 7.15 GHz 8.42 GHz 437.1 MHz 401.6 MHz Wavelength =1064 nm 7.2 GHz 8.45 GHz Tx power 794 W 65 W 19953 W 65 W 5 W 5 W 5 W 65 W 65 W Modulation NRZ/PSK/PM GMSK. BTb=0.5 NRZ/PSK/PM GMSK BTb=0.5 PCM- NRZ/BPSK PCM- NRZ/BPSK 256-PPM QPSK QPSK Coding Concatenated: Concatenated: Turbo Coding Turbo Coding Convolutional Convolutional, Convolutio Convolutional + ¼ ¼ + rate ½ nal, rate ½ RS (255, 223) RS (255, 223) Reed Solomon (26143, 15685) 3 Concatenated, Concatenated, Interleaving= Interleaving=5 5 BER Negligible Negligible BER=10 -6 BER=10 -6 10 -6 10 -6 BER=10 -6 FER=10 -5 FER=10 -5 Bit rate (worst case) 1.76 Mbps 1.5 Mbps 22.6 kbps 460 bps 128 kbps 128 kbps 10 Mbps 20 Mbps 20 Mbps Table 3-43: Links description 1 Atmospheric attenuation of 4.34dB, it corresponds with a minimum elevation of 10deg and G/S availability of 90%. 2 Max distance 1070Km corresponding to a TV elevation of 10deg. 3 See [[RD52]]

s<br />

70-m<br />

antenna<br />

70-m<br />

antenna<br />

3.3.7.5.3 TV EVAs<br />

HMM<br />

Assessment Study<br />

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

February 2004<br />

page 211 of 422<br />

Transmission Reception<br />

Frequency band EIRP Frequency band Effective<br />

10º<br />

G/T,<br />

89.31 dBW (1995W<br />

7145 – 7190 MHz 8400 - 8450 MHz 42.52 dB/K<br />

34200 –34700<br />

MHz<br />

RF)<br />

114.69 dBW (794W<br />

RF)<br />

31800 – 32300<br />

MHz<br />

Table 3-42: Assumed ground station characteristics<br />

56.71 dB/K<br />

In assembly or contingency situations, EVAs could be necessary for TV. Two sets of external<br />

double (redundant) antennas have been used in TV design. The system will be able to transmit<br />

voice, biomedical data and receive voice data. The voice can come from TV or other astronaut.<br />

An ISS like antenna system has been used (see Table 3-47).<br />

3.3.7.5.4 Links description<br />

TV will have five different communications links with the other mission elements:<br />

1. Ka-band link with G/S, using a 3 m-dish HGA antenna.<br />

2. X-band link with G/S using two MGA antennas, for contingencies<br />

3. UHF link: for communications with SHM, DM and MAV. An UHF patch antenna is<br />

used.<br />

4. X-band link with the relay satellite, for communications with SHM and with Earth. A<br />

0.45m dish HGA antenna is used.<br />

5. Laser link with G/S. Only used for downlink.<br />

Note that communications with the Earth will have a roundtrip delay of 40 minutes, in the worst<br />

case (distance TV-Mars of 2.7 AU). No real time communications are possible.<br />

Link Ka-band 1 X-band UHF 2 Laser X-band<br />

Uplink Downlink Uplink Downlink Uplink Downlink Uplink Downlink<br />

Frequency 34.5 GHz 32 GHz 7.15 GHz 8.42 GHz 437.1 MHz 401.6 MHz Wavelength<br />

=1064 nm<br />

7.2 GHz 8.45 GHz<br />

Tx power 794 W 65 W 19953 W 65 W 5 W 5 W 5 W 65 W 65 W<br />

Modulation NRZ/PSK/PM<br />

GMSK.<br />

BTb=0.5<br />

NRZ/PSK/PM<br />

GMSK<br />

BTb=0.5<br />

PCM-<br />

NRZ/BPSK<br />

PCM-<br />

NRZ/BPSK<br />

256-PPM QPSK QPSK<br />

Coding<br />

Concatenated:<br />

Concatenated:<br />

Turbo Coding<br />

Turbo Coding Convolutional Convolutional, Convolutio<br />

Convolutional +<br />

¼<br />

¼<br />

+ rate ½ nal, rate ½<br />

RS (255, 223)<br />

RS (255, 223)<br />

Reed<br />

Solomon<br />

(26143,<br />

15685) 3<br />

Concatenated,<br />

Concatenated,<br />

Interleaving=<br />

Interleaving=5<br />

5<br />

BER Negligible Negligible BER=10 -6 BER=10 -6 10 -6 10 -6 BER=10 -6<br />

FER=10 -5 FER=10 -5<br />

Bit rate<br />

(worst case)<br />

1.76 Mbps 1.5 Mbps 22.6 kbps 460 bps 128 kbps 128 kbps 10 Mbps 20 Mbps 20 Mbps<br />

Table 3-43: Links description<br />

1<br />

Atmospheric attenuation of 4.34dB, it corresponds with a minimum elevation of 10deg and G/S availability of<br />

90%.<br />

2<br />

Max distance 1070Km corresponding to a TV elevation of 10deg.<br />

3<br />

See [[RD52]]

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