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7B/TEMP/92-E

Radiocommunication Study Groups /
Source: Documents 7B/131, 177, 179 / Document 7B/TEMP/92-E
10 September 2009
English only
Working Party 7B
Liaison Statement to Working Party 4C
INFORMATION RELATED
TO WRC-12 AGENDA ITEM 1.25

Working Party 7B thanks Working Party 4C for the information provided in their liaison statements related to WRC-12 Agenda item 1.25 (Documents 7B/131 and 7B/177). Consideration was also given to 7B/179 referring to Annex 8 of Document 4C/338 regarding a working document towards a preliminary draft new Report ITU-R M.[MSS-SHARING].

For the bands listed below, WP 7B would like to provide answers to the specific questions raised by WP 4C, provide relevant additional information, characteristics of METSAT and SRS applications, as well as comments on current sharing studies performed in WP4C.

Band 7145-7190 MHz (deep space SRS links in the Earth-to-space direction):

Regarding the band 7 145-7 190 MHz, the criterion given in Recommendation ITU-R SA.1157 of 190 dBW/20 Hz at the spacecraft can be confirmed. Please note that the applicable distance is
d ≥ 2*106 km. Regarding antenna gain patterns for deep-space space research (SRS) systems, information can be found in Radio Regulations Appendix 8.

The transmitter power and antenna gains of these spacecraft, for use in interference analysis, are given in Recommendation ITU-R SA.1014. Although the assumption of deep space spacecraft distance from Earth being greater than 2*106 km is generally correct, there are many SRS missions that have regular Earth fly-bys, during which this distance is much less. Earth fly-bys are highly critical events, during which interference to a deep space spacecraft can jeopardise its health and safety and potentially result in losing control over the spacecraft. During these critical Earth fly-bys, the MSS downlinks may interfere with the reception of SRS uplinks at the spacecraft. Therefore WP 4C may wish to take this scenario into account.

In the Launch and Early Orbit Phase (LEOP), SRS systems operate with wide beam antennas and may well receive the full downlink signal from MSS during that critical phase where it cannot be excluded that control over the satellite could be lost. Furthermore, the maximum uplink power is generally not used but adjusted to the distance of the satellite from the Earth.

No distinction is made in the WP 4C studies between deep space and near-Earth systems. Furthermore, only near Earth protection levels are considered.

The studies only consider the potential interference from SRS systems to MSS systems. Separation distances between SRS earth stations and MES have not been addressed yet. For this, different station locations will have to be considered. Preliminary analysis in WP 7B indicates that under unfavourable conditions such distances could be in the range 500-600 km in view of the high EIRP levels towards the horizon. RR 21.10 allows for an EIRP density of 55 dBW/4 kHz towards the horizon.

In addition, it is likely that aeronautical MES will require very long separation distances.

Band 7190-7235 MHz (near Earth SRS links in the Earth-to-space direction)

The application of Recommendation ITU-R SA.609 can be confirmed. Satellite orbit heights can typically range from a few hundred kilometres to 1.5 million kilometres for Lagrange point mission. This is due to a number of different scientific objectives which require largely differing orbit heights.

SRS systems in LEOP and in nominal operating mode can be interfered with by MSS. In such situations, the maximum uplink power is generally not used but adjusted to the distance of the satellite from the Earth

This band is also allocated for the SRS space-VLBI. The description and protection criteria of the space-VLBI systems can be found in Recommendation ITU-R SA.1344 and in Reports ITU-R
SA.2065 and SA.2132.

Separation distances between SRS earth stations and MES have not been addressed yet. Preliminary analysis in WP 7B indicates that under unfavourable conditions such distances could be up to several hundred kilometres in view of the high EIRP levels towards the horizon. RR 21.8 allows for an EIRP density of 40 + 3* θ dBW/4kHz towards the horizon.

Furthermore it needs to be noted that this band is allocated for space operations of the Russian Federation (see RR 5.459).

7750-7900 MHz (non-geostationary meteorological satellite space-to-Earth links)

The MetSat systems characteristics contained in Draft New Report ITU-R [METSAT 7.9 GHz] (Document 7B/TEMP/91) can be confirmed including systems that might operate in the band 7 850-7 900 MHz, subject to the outcome of WRC-12 Agenda item 1.24. The use of cardioid antennas is expected to prevail for some time for transmissions to main stations and will generally be used for MetSat satellites operating in dissemination mode.

The number of current main stations is low and is expected to remain low. However, user stations are globally in operation in a number of countries in the 7750-7850 MHz band and it is expected that their number will increase with deployment of new MetSat systems.

Separation distances between MES and MetSat earth stations have not been addressed yet. Preliminary analysis in WP 7B indicates that such distances could be around 100km for radioclimatic zone A. Transmissions from maritime MES or land based MES near large bodies of water will require significantly larger distances. The distances would be even greater for aeronautical MES.

8400-8450 MHz (deep space SRS links in the space-to-Earth direction)

WP 7B emphasizes that a distinction will have to be made between the bands 8400-8450 MHz and 8450-8500 MHz in accordance with RR 5.465.

WP 7B confirms that, in the band 8400-8450 MHz, the protection criterion for the SRS deep space earth stations is given in the Recommendation ITU-R SA.1157 as –221 dB (W/Hz). The locations of SRS deep space earth stations can be found in the Recommendation ITU-R SA.1014, which also gives the transmitter power and antenna gain of a typical SRS deep space spacecraft. Regarding antenna patterns, information can be found in Radio Regulations Appendix 8.

Separation distances between MES and SRS earth stations have been addressed only for a single earth station in the centre of Spain showing separation distances up to around 200km but no information is available on the assumptions used for the terrain model. Recognizing that this analysis may not be representative for other earth stations locations, it will also be necessary to consider other earth stations using Recommendation ITU-R P.452 on a general basis. In addition, WP 7B also notes that the propagation studies used in current WP 4C study is based on a 0.1% percentage of the time whereas Recommendation ITU-R SA.1157 requires a 0.001% figure.

8450-8500 MHz (near Earth SRS links in the space-to-Earth direction)

WP 7B informs WP 4C that Recommendation ITU-R SA.609 should be used in sharing studies.

Separation distances between MES and SRS need to be addressed for representative earth stations.

Band 14.8-15.35 GHz:

With regard to the band 14.8-15.35 GHz, WP 7B confirms that Recommendation ITU-R SA.1414 may be used in sharing studies. However, WP 7B would like to inform WP 4C that this band is also used for the data downlinks of the SRS space-VLBI systems. Again, the information for the space-VLBI systems can be found in Recommendation ITU-R SA.1344 and in Reports ITU-R SA.2065 and SA.2132. In addition, reference is made to SA.1626.

Status: For action

Deadline: Next WP 7B meeting (June 2010)

Contact point: Philippe Tristant ()

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