APPENDIX 2a

Exclusive for space research.

PROPOSED NEW INTERNATIONAL SPACE RESEARCH BANDS

Two frequencies for earth-to-space
satellite command purposes. One should
be at 144 Mc/s and the other at 148 Mc/s,
each 20 kc/s bandwidth.

Two frequencies for earth-to-space
satellite command purposes. One should
be at 420 Mc/s and the other at 450 Mc/s.
The bandwidth should be 25 kc/s.

The band 1525-1540 Mc/s for space use,
for both telemetering and command purposes.

The band 2110-2120 Mc/s for deep space
command, footnote status.

A command band 7.12-7.13 Gc/s for command
of research satellites using the 8.4-8.5 Gc/s
space research band, footnote status.

Remarks:

The selection of these band-edge frequencies,
144 and 148 Mc/s, would produce the minimum
impact on existing services a "command" is
usually a single pulse of less than one second
duration adjacent services will not be

aware of its presence.

Suggested footnote:

The band 2110-2120 Mc/s
may be used for earth-to-space-probe command
purposes subject to agreement between adminis-
trations concerned and affected. This band
would be paired with the 2290-2300 Mc/s deep-
space research band for command purposes.

Suggested footnote: The band 7.12-7.13 Gc/s
may be used for command of spacecraft subject
to agreement between administrations concerned
and affected. This band is paired with the
8.4-8.5 Gc/s space research band for command,
interrogation and control purposes.

APPENDIX 3

TECHNICAL FACTORS INFLUENCING THE SELECTION
OF FREQUENCIES FOR SPACE COMMUNICATIONS

Adequate signal to noise ratio is a major factor in the satisfactory operation of any communication system. In this appendix available signal to noise ratio is assumed to be suitable criteria for selecting frequencies for space communication. Factors influencing the upper frequency limit in the range 1000 Mc/s to 40 Gc/s are emphasized. Transmissions are assumed to be from the satellite to the earth terminal. However, propagation may be assumed to be reciprocal and the available signals shown will apply to transmission in either direction.

Three major factors influence the available signal to noise ratio in a space communication: (1) The signal power available under free space propagation conditions (2) The absorption in the atmosphere and (3) The radio noise level.

Free Space Signals:

Figure 1 illustrates the frequency dependence of available power at the receiver when isotropic antennas are used at both the transmitting and receiving terminals. Note the available power decreases as frequency increases.

Figure 2 shows how antenna gain increases as either antenna physical size or operating frequency is increased. If a directive antenna is used at either the transmitting or receiving terminal or both, the gain from this chart may be combined with the values of Figure 1 to estimate available signal power when directive. antennas are used.

Figure 3 illustrates the decrease in antenna beamwidth as operating frequency or antenna size increase.

Figure 4 illustrates the lack of frequency dependence when a directive antenna is used at the earth terminal and an isotropic antenna in the satellite. Note that available power increases with antenna physical size but that the antenna's beamwidth becomes increasingly narrow.

Figure 5 is a portion of Figure 4 illustrating that available signal remains constant to the higher frequencies if ability to use narrow beamwidth improves. The chart assumes physical size of the antenna is limited.