Rec. ITUR S.1592
RECOMMENDATION ITUR S.1592
Methodology to assess compliance of nongeostationary fixedsatellite service
satellite systems in circular orbits with the additional operational limits on downlink equivalent power fluxdensity in Article 22 of
the Radio Regulations
(2002)
The ITU Radiocommunication Assembly,
considering
a) that the World Radiocommunication Conference (Istanbul, 2000) (WRC2000) adopted, in Article 22 of the Radio Regulations (RR), limits to the downlink equivalent power fluxdensity (epfd_{}) radiated by nongeostationary (GSO) fixedsatellite service (FSS) systems in certain frequency bands, to protect GSO FSS and broadcastingsatellite service (BSS) networks operating in the same frequency bands;
b) that RR Article 22 includes singleentry validation limits to the epfd_{} in RR Tables 221A to 22 1D, singleentry operational limits to the epfd_{} in RR Tables 224A, 224B and 224C, and single entry additional operational limits to the epfd_{} into antennas of certain sizes in RR Table 22 4A1, which apply to nonGSO FSS systems for the protection of GSO FSS networks;
c) that compliance of a proposed nonGSO FSS system with the singleentry validation limits will be evaluated by the Radiocommunication Bureau (BR), under RR Nos. 9.35 and 11.31, based on masks of pfd provided by the nonGSO FSS operator, using software defined in Recommendation ITUR S.1503;
d) that compliance of a proposed nonGSO FSS system with the singleentry operational limits to the epfd_{}_{ }and, for certain antenna sizes, singleentry additional operational limits to the epfd_{} is subject to verification by administrations;
e) that RR Appendix 4, as modified by WRC2000, requires an administration responsible for a non GSO FSS system to ensure that the singleentry additional operational limits to the epfd_{} are met,
recognizing
a) that administrations with assignments to GSO FSS networks in frequency bands where additional operational limits to the epfd_{} have been established require a reliable and independent means to determine whether a particular nonGSO FSS system is in compliance with the single entry additional operational limits to the epfd_{}, for their GSO FSS networks,
recommends
1 that the methodology defined in Annex 1 to this Recommendation, based on a full simulation of downlinks in a nonGSO FSS satellite system interfering into an operating GSO FSS earth station with a 3 m or 10 m antenna, be used to assess the levels of interference generated by the nonGSO FSS system, in order to verify compliance by the nonGSO FSS system with the additional operational limits to epfd_{} in RR Article 22;
2 that the methodology in Annex 1 to this Recommendation, based on full simulation of downlinks in a nonGSO FSS satellite system interfering into a GSO FSS network, be used by GSO operators as guidance to assess the levels of interference generated by nonGSO systems into any diameter antenna of planned or operational GSO FSS networks.
NOTE 1 Annex 2 discusses an approach that could be used to demonstrate that additional operational limits are met by an operational nonGSO system interfering into an operational GSO FSS earth station. In contrast with Annex 1, which is based on a full simulation approach, Annex 2 is based on the pfd mask approach adopted in Recommendation ITUR S.1503.
ANNEX 1
Methodology to assess compliance with additional operational limits of the interference generated by nonGSO FSS systems^{*} sharing
frequency bands with GSO FSS networks
1 Introduction
This methodology is based on modelling the satellite systems in their orbits and allows each space station and earth station to track their respective targets, while taking into account the Earth’s rotation. A simulation of this model is sampled over a period of time at a suitably fine sampling rate, and at each sample the range gain product is computed. This range gain product can be related directly to the level of interference, and the sampled data can be evaluated to determine the percentage of time that the range gain product for all interference paths exceeds a given level.
TABLE 1
Symbols and definitions used in this Annex
a

Angular velocity of satellite in Earthfixed coordinates

degrees/s

B_{t}

Transmit bandwidth

Hz

C_{traffic}

Traffic coefficient depending on local time


D

Antenna diameter

m

E

Argument of latitude

degrees

epfd_{}

Downlink equivalent power fluxdensity into earth station

dB(W/m^{2}) in reference bandwidth

g

Acceleration due to Earth’s gravity

M/s^{2}

G

Universal (Newtonian) gravitational constant

Nm^{2}/kg^{2}

G_{t}

Relative gain of transmit antenna


G_{r}

Relative gain of receive antenna


G_{rmax}

Maximum gain of GSO FSS earth station receiving antenna


G_{rw}

Maximum gain of wanted receive antenna


I

Inclination of satellite orbit

degrees

I_{0}

Interference power

W

J_{2}

Second harmonic Earth potential constant


k

Boltzmann’s constant

J/K

L_{p}

Polarization isolation factor


m_{s}

Mass of satellite

kg

M_{e}

Mass of the Earth

kg

N_{0}

Noise power

W

N_{a}

Number of transmitting nonGSO satellites visible from GSO FSS receiving earth station


N_{coarse}

Integer ratio of coarse time step size to fine step size to define dual time step simulations


N_{hits}

Number of mainbeamtomainbeam coupling events between nonGSO satellite antenna and GSO FSS earth station antenna


P_{t}

RF power at input to transmitting antenna

W

r

Orbital radius of satellite

km

r_{c}

Radius of nonGSO service area cell

km

r_{g}

Radius of GSO

km

r_{n}

Orbital radius of nonGSO satellite

km

R

Range between nonGSO satellite and GSO FSS earth station

m

R_{e}

Radius of perfectly spherical Earth

km

T

Receiver noise temperature

K

TABLE 1 (end)
T_{o}

Orbit period

s

T_{w}

Wanted receiver noise temperature

K

t

Simulation time increment

s


Earth station elevation angle

degrees


Topocentric angle defining exclusion zone for nonGSO satellite switching strategy

degrees

_{coarse}

Topocentric angle defining coarse step size in dual timestep simulation

degrees

_{FSR}_{1}

Topocentric angle defining fine step region (FSR)

degrees

_{FSR}_{2}

Topocentric angle defining boundary of exclusion zone

degrees


Antenna offboresight angle

degrees

_{3}

Antenna 3 dB beamwidth

degrees


Wavelength

m


Earth attraction constant

km^{3}/s^{2}

v

Constant velocity of satellite

degrees/s

v_{e}

Orbital velocity of the Earth

degrees/m

v_{r}

Orbital velocity of nonGSO satellite relative to the Earth’s surface

degrees/s

v_{n}

Orbital velocity of nonGSO satellite

degrees/s


Angular velocity of satellite

degrees/s


Right ascension of the ascending node (RAAN)

degrees

_{0}

RAAN at time t_{0}

degrees

_{e}

Rotational angular velocity of the Earth

degrees/s

_{r}

Orbital precession rate of satellite

degrees/s


GSO arc avoidance switching angle

degrees

_{d}

GSO arc avoidance switching angle desired at the edge of nonGSO service area cell

degrees

_{m}

GSO arc avoidance angle to be modelled to achieve desired switching angle at edge of cell

degrees

