ITU-R REPORT SA.2192

Abstract

<strong>Introduction</strong> <br>This Report addresses compatibility between space research service mission and inter-satellite service links of HIBLEO-2-type satellite systems. It is envisioned that primarily three types of space missions would be supported by SRS earth station transmissions in the 22.55-23.15 GHz band: <br>1. low-Earth orbiting scientific satellites; <br>2. manned and unmanned Lunar exploration missions; <br>3. scientific missions using satellites located in the vicinity of the Sun-Earth L1 and L2 Lagrangian points. <br>Data transmissions in the space-to-Earth direction for these types of missions are either currently operational or are planned to be operational in the 25.25-27.5 GHz band &#8211; a band allocated for both space-to-Earth and space-to-space transmissions to data relay satellites. Data relay satellites, which are operated by several administrations (Recs ITU-R SA.1018 and ITU-R SA.1414), use the 22.55-23.55 GHz band for forward inter-orbit links and the 25.25-27.5 GHz band for return inter-orbit links to near-earth orbiting user satellites. <br>The purpose of WRC-12 Agenda item 1.11 is to add an Earth-to-space allocation in the 22.55- 23.15 GHz band segment to complement the existing space-to-space and space-to-Earth allocations. The Earth-to-space allocation will add the capability to support near-Earth missions using similar, if not identical technology, onboard the user satellite. The 22.55-23.15 GHz band will be used for both command and control of the user satellite and, in addition, for manned missions voice/video communication with the Earth. <br>The number of SRS earth stations transmitting in the 22.55-23.15 GHz band will be small. Rather than building new SRS earth stations, upgrading selected existing SRS earth stations will predominate. Selecting which SRS earth stations to upgrade will be based on a number of factors, including the type of mission to be supported. The maximum number of SRS earth stations capable of supporting Lunar and/or L2 missions is not expected to exceed eight or nine on a global basis. A similar number of SRS earth stations may support LEO missions, also on a global basis. These earth stations are typically located in rural, isolated areas at mid-latitudes. <br>Analyses have been performed to determine the criteria for transmitting earth stations in the space research service (SRS) to share with stations in the inter-satellite (non-GSO-to-non-GSO) service in the 22.55-23.55 GHz band. Analysed is the compatibility of SRS earth stations supporting typical types of space research missions in the Earth-to-space direction in the 23 GHz band. These uplinks are to an SRS satellite in low-Earth orbit; in an orbit around the Moon or on the surface of the Moon; and, in a halo orbit around the L2 Lagrange point. Only the Lunar case is analyzed below because this interference case was shown to be the most severe among the three SRS mission types. <br>These analyses are presented in the following sections.