ACP-WGF31/WP-25
International Civil Aviation Organization
WORKING PAPER
AERONAUTICAL COMMUNICATIONS PANEL (ACP)
31ST MEETING OF THE WORKING GROUP F
Seattle, Washington October 6-10, 2014
Agenda Item 7: Development of material for ITU-R meetings - other
SPECTRUM SUPPORTABILITY OF SPACE PLANES
(Presented by John Mettrop)
SUMMARY
This paper seeks support for an input paper to ITU-R Working Party 5B that
looks to establish a ITU-R Question on spectrum supportability of space
planes.
ACTION
The ACP WGF is invited to:



1.
Provide comments on the attached draft UK input to ITU-R
Working Party 5B
Support the submission of the paper to ITU-R Working Party
5B
Initiate work on planning criteria for aeronautical
communication and navigation systems that would
accommodate space plane operations in the interim.
INTRODUCTION
1.1
Commercial space flight is becoming a reality with a number of companies/consortia
promising the chance for those willing to pay the chance to experience weightlessness and a view that few
have experienced before. Their approaches vary between those using a single vehicle and those that use a
launch vehicle that carries the space craft up to an intermediary height before releasing the space craft to
accelerate away and into a sub-orbital space flight.
(11 pages)
ACP WG-F/31 WP-25
ACP WG-F/31 WP-25
-2-
1.2
Whilst these vehicles are in their infancy there is a clear indication that sub-orbital flight
will become a reality in the near future possibly leading to the final development of vehicles capable of
carrying passengers half way around the world in a few hours. The UK recognising this potential, have
commissioned the Civil Aviation Authority to investigate the various regulatory issues that will need to
be addressed to ensure the safety of such flights. One of those issues is radio systems that will be
required to support communication with, navigation and surveillance of these space planes and the
spectrum requirements to support those systems.
2.
DISCUSSION
2.1
Sub-orbital space planes present an interesting spectral challenge due to the altitude and
speed at which they fly. Current terrestrial aeronautical systems are designed, in general, to communicate
with aircraft that fly at sub-sonic speeds below 60,000 feet. Such systems will be suitable to meet the
requirements of the launch vehicle but not necessarily suitable for the actual space craft.
2.2
The remainder of the document therefore concentrates on understanding which radio
service, as defined by the Radio Regulations, the communication, navigation and surveillance systems
should operate, whether there is any suitable spectrum available and what can be done in the interim.
2.3
Appropriate Spectrum Allocation
2.3.1
The Radio Regulations define in Article 1 defines the terms and definitions used within
the Radio Regulations which include definitions of forty two different radio services relating to
radiocommunication1, a breakdown of which is given in Annex 1 (without definitions) and 2 (with
definitions). Radiocommunication is then further broken down into terrestrial radiocommunication2, space
radiocommunication3 and radio astronomy4.
2.3.2
Based on these definitions radiocommunication with a space plane does not fall under the
definition of radio astronomy and must either be a terrestrial or satellite service.
2.3.3
Given that these space planes are intended to reach altitudes of approximately 120 km
and therefore beyond the karman line5 they can be regarded as spacecraft6. As a result any station located
on-board that space plane should be regarded as a space station7 and therefore any radiocommunication
with that vehicle will be space radiocommunication.
2.3.4
The choice of suitable radiocommunication services is further restricted because these
space planes follow a ballistic trajectory and therefore do not meet the definition contained in the Radio
1 1.6 radiocommunication: Telecommunication by means of radio waves
2 1.7 terrestrial radiocommunication: Any radiocommunication other than space radiocommunication or radio
astronomy
3 1.8 space radiocommunication: Any radiocommunication involving the use of one or more space stations or the
use of one or more reflecting satellites or other objects in space
4 1.13 radio astronomy: Astronomy based on the reception or radio waves of cosmic origin
5 The karman line is an imaginary line that lies at an altitude of 100 kilometres above the Earth’s sea level and
commonly represents the boundary between the Earth’s atmosphere and space.
6 1.178 spacecraft: A man-made vehicle which is intended to go beyond the major portion of the Earth’s
atmosphere
7 1.64 space station: A station located on an object which is beyond, is intended to go beyond, or has been beyond,
the major portion of the Earth’s atmosphere.
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ACP WG-F/31 WP-25
Regulations for a satellite8. As a result this leaves 4 potential service as shown below with their associated
defintions:Safety service: Any radiocommunication service used permanently or temporarily for the
safeguarding of human life and property
Special service: A radiocommunication service, not otherwise defined in this Section,
carried on exclusively for specific needs of general utility, and not open to the public
correspondence
Space operation service: a radiocommunication service concerned exclusively with the
operation of spacecraft, in particular space tracking, space telemetry and space
telecommand. These functions will normally be provided within the service in which the
space station is operating.
Space research service: A radiocommunication service in which spacecraft or other objects
in space are used for scientific or technological research purposes
2.3.5
Currently there are no specific allocations to either a safety or special service in Article 5
of the Radio Regulations and the radiocommunication traffic that would be passed between the ground
and a space plane is not consistent with space research and hence this would leave the space operation
service. Within the Radio Regulations the following frequency bands are globally allocated on a primary
basis to the space operation service.
space to Earth
137-137.025 MHz
137.025- 137.175 MHz
137.175-137.825 MHz
137.825-138 MHz
148-149.9 MHz (by footnote)
272-273 MHz
401-402 MHz
Earth to space
1427-1429 MHz
1525-1530 MHz
1530-1535 MHz
2025-2110 MHz
2200-2290 MHz
2.3.6
In addition to these frequency bands those allocated to radionavigation satellite services
such as GPS, GLONASS and Galileo are available for the provision of navigation.
2.3.7
All of these frequency bands are shared and hence whether they would be suitable for an
aeronautical purpose, what additional regulatory measures are required and whether they would be
acceptable to incumbent users of those frequency bands needs to further investigated. However if the use
of sub-space orbits were to become more prevalent then it is likely that additional spectrum to that which
has already been allocated will be required especially given the number of services that are sharing the
currently allocated frequency bands.
2.3.8
It is therefore highly likely that Radio Regulatory action will be required and that at some
point in the future a World Radiocommunication Conference agenda item will have to be sought
2.4
Interim Measures
2.4.1
Whilst existing aeronautical spectrum may not be suitable for communications with space
planes it will be required for communication with any launch vehicle and could be used on a national
8 1.179 satellite: A body which revolves around another body of preponderant mass and which has a motion
primarily and permanently determined by the force of attraction of that other body.
ACP WG-F/31 WP-25
-4-
exemption basis to provide services. When considering whether existing aeronautical services the
following issues would have to be addressed:Doppler shift: The space planes are currently planned to fly at speeds in excess of Mach 4
which would result in a Doppler shift of approximately 650 Hz at VHF. Whilst such a
Doppler shift would be compatible 25 kHz standards it is not compatible with the frequency
stability requirements for either 25 kHz offset carrier or 8.33 kHz.
Received power: Current terrestrial aeronautical systems have been designed to operate with
aircraft that fly below 60,000 feet. Once a space plane exceeds this height then whether the
received power meets the minimum ICAO requirement would need to be checked however
the propagation model to use is not certain. The following advice was received from ITU
working parties 3l & 3M
From WP 3L: 120km is about the peak of the ionospheric E region so that the vehicle
will be immersed in a partly ionised medium, particularly during the daylight hours.
Most of the ionisation will be at greater heights, so it will not be relevant to use P.531.
The effects of going part way through the ionosphere have not been studied by ITU,
but Sputnik and many other LEOs have been at similar heights and there must be some
knowledge about. At VHF there will be some over the horizon ionospheric ducting.
There will also be some polarisation rotation. However I do claim any expertise in this
area.
From WP 3M: P.2041 is not entirely appropriate as it assumes that the airborne
platform is in the stratosphere (considering (b)) and 120 km is well into the
ionosphere. P.618 and P.681 would be generally relevant to estimate the effects of the
troposphere part of the path (treating the aircraft as a satellite), but in the frequency
range of interest, rain, cloud and gas attenuation (as in Rec P.618) are not
particularly significant effects although low elevation angle tropospheric scintillation
may be of concern (?). P.681 would be useful if there is an issue of shadowing (trees,
buildings) at the earth station end. If there are low-elevation angle paths with
diffraction or clutter, it becomes more complicated and I agree that P.528 (which only
goes to 20 km altitude) and P.682 (which is between an aircraft and a satellite) are
not particularly
Planning criteria: Current terrestrial aeronautical system planning criteria assume aircraft
heights of less than 45,000 feet. The introduction of space planes would potentially affect
the radio horizon distances and hence could impact on the planning criteria employed
2.4.2
Additionally current space operation service allocations might be available for use but
this would require the use of separate up and downlink frequency bands.
3.
CONCLUSION
3.1
Where a space plane uses a launch vehicle then the launch vehicle will be able to use
current terrestrial aeronautical systems although planning criteria may need to be modified to
accommodate such operations.
3.2
A space plane is, in ITU terms, a spacecraft which given it’s sub-orbital flight trajectory
should operate in the space operation service.
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ACP WG-F/31 WP-25
3.3
Whilst there are current allocations to the space operation service, it is questionable as to
whether those allocations would be suitable for use to support space plane operations
3.4
There is likely to be a requirement for a World Radiocommunication Conference agenda
item to address additional regulatory provision to ensure the safe operation of space planes however the
urgency of that need will depend on the changes that might be required and the rate at which space flights
expands.
3.5
Current aeronautical allocations may be able to support space flight communication,
navigation and surveillance requirements in the short term on an national agreement basis but there are
issues with respect to Doppler shift, transmit/receive power and planning criteria that will need to be
addressed.
4.
4.1
ACTION BY THE MEETING
The ACP WGF is invited to:

Provide comments on the attached draft UK input
to ITU-R Working Party 5B

Support the submission of the paper to ITU-R
Working Party 5B

Initiate work on planning criteria for aeronautical communication and navigation
systems that would accommodate space plane operations in the interim
ACP WG-F/31 WP-25
-6-
Attachment
DRAFT ITU PAPER
Radiocommunication Study Groups
-7-
Received:
ACP WG-F/31 WP-25
Document 5B/-E
XX October 2014
English only
United Kingdom of Great Britain and Northern Ireland
PROPOSED QUESTION ON SPECTRUM SUPPORTABILITY OF SPACE
PLANES
1
Introduction
Commercial space flight is becoming a reality with a number of companies/consortia promising the
chance for those willing to pay the chance to experience weightlessness and a view that few have
experienced before. Their approaches vary between those using a single vehicle and those that use a
launch vehicle that carries the space craft up to an intermediary height before releasing the space craft to
accelerate away and into a sub-orbital space flight.
Whilst these vehicles are in their infancy there is a clear indication that sub-orbital flight will become a
reality in the near future possibly leading to the development of vehicles capable of carrying passengers
half way around the world in a few hours. In order to ensure the seamless development and transition to
operational use of such vehicles all of the regulatory, including Radio Regulatory provisions need to be in
place that will ensure the safety of such flights.
Article I.
2
Discussion
2.1
Availability of suitable spectrum
Sub-orbital space planes present an interesting spectral challenge due to the altitude and speeds at which
they fly. Current terrestrial aeronautical systems are designed, in general, to communicate with aircraft
that fly at sub-sonic speeds below 60,000 feet. Such systems will be suitable to meet the requirements of
any launch vehicle but are not necessarily suitable for the actual space craft. If those systems are not
appropriate then what systems would be appropriate and in what spectrum should they operate.
The Radio Regulations define in Article 1 defines the terms and definitions used within the Radio
Regulations which include definitions of forty two different radio services relating to
radiocommunication9, a breakdown of which is given in Annex 1 (without definitions) and 2 (with
9 1.6 radiocommunication: Telecommunication by means of radio waves
ACP WG-F/31 WP-25
-8-
definitions). Radiocommunication is then further broken down into terrestrial radiocommunication10,
space radiocommunication11 and radio astronomy12.
Based on these definitions radiocommunication with a space plane does not fall under the definition of
radio astronomy and must therefore either be a terrestrial or satellite service.
Given that these space planes are intended to reach altitudes of approximately 120 km and therefore
beyond the Karman line13 they can be regarded as spacecraft14. As a result any station located on-board
that space plane should be regarded as a space station15 and therefore any radiocommunication with that
vehicle will be space radiocommunication.
The choice of suitable radiocommunication services is further restricted because these space planes
follow a ballistic trajectory and therefore do not meet the definition contained in the Radio Regulations
for a satellite16. As a result this leaves 4 potential service as shown below with their associated
defintions:Safety service: Any radiocommunication service used permanently or temporarily for the
safeguarding of human life and property
Special service: A radiocommunication service, not otherwise defined in this Section,
carried on exclusively for specific needs of general utility, and not open to the public
correspondence
Space operation service: a radiocommunication service concerned exclusively with the
operation of spacecraft, in particular space tracking, space telemetry and space
telecommand. These functions will normally be provided within the service in which the
space station is operating.
Space research service: A radiocommunication service in which spacecraft or other objects
in space are used for scientific or technological research purposes
Currently there are no specific allocations to either a safety or special service in Article 5 of the Radio
Regulations and the radiocommunication traffic that would be passed between the ground and a space
plane is not consistent with space research and hence this would leave the space operation service.
Within the Radio Regulations the following frequency bands are globally allocated on a primary basis to
the space operation service.
space to Earth
137-137.025 MHz
137.025- 137.175 MHz
137.175-137.825 MHz
137.825-138 MHz
148-149.9 MHz (by footnote)
272-273 MHz
401-402 MHz
Earth to space
1427-1429 MHz
1525-1530 MHz
1530-1535 MHz
2025-2110 MHz
2200-2290 MHz
10 1.7 terrestrial radiocommunication: Any radiocommunication other than space radiocommunication or radio astronomy
11 1.8 space radiocommunication: Any radiocommunication involving the use of one or more space stations or the use of one or
more reflecting satellites or other objects in space
12 1.13 radio astronomy: Astronomy based on the reception or radio waves of cosmic origin
13 The Karman line is an imaginary line that lies at an altitude of 100 kilometres above the Earth’s sea level and commonly
represents the boundary between the Earth’s atmosphere and space.
14 1.178 spacecraft: A man-made vehicle which is intended to go beyond the major portion of the Earth’s atmosphere
15 1.64 space station: A station located on an object which is beyond, is intended to go beyond, or has been beyond, the major
portion of the Earth’s atmosphere.
16 1.179 satellite: A body which revolves around another body of preponderant mass and which has a motion primarily and
permanently determined by the force of attraction of that other body.
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ACP WG-F/31 WP-25
All of these frequency bands are shared and hence whether they would be suitable for an aeronautical
purpose, what additional regulatory measures are required and whether they would be acceptable to
incumbent users of those frequency bands needs to further investigated. However if the use of sub-space
orbits were to become more prevalent then it is likely that additional spectrum to that which has already
been allocated will be required especially given the number of services that are sharing the currently
allocated frequency bands.
2.2
Interim Measures
Whilst existing aeronautical spectrum may not be suitable for communications to or navigation of space
planes it will be required for the launch vehicle and could be used on a national exemption basis to
provide an interim solution for the space plane. When considering whether existing aeronautical systems
are suitable the following issues would have to be addressed:Doppler shift: The space planes are currently planned to fly at speeds in excess of Mach 4
which would result in a Doppler shift of approximately 650 Hz at VHF. Whilst such a
Doppler shift would be compatible 25 kHz standards it is not compatible with the frequency
stability requirements for either 25 kHz offset carrier or 8.33 kHz.
Received power: Current terrestrial aeronautical systems have been designed to operate with
aircraft that fly below 60,000 feet. Once a space plane exceeds this height then whether the
received power meets the minimum ICAO requirement would need to be checked however
the propagation model to use is not certain. The following advice was received from ITU
working parties 3l & 3M
From WP 3L: 120km is about the peak of the ionospheric E region so that the vehicle
will be immersed in a partly ionised medium, particularly during the daylight hours.
Most of the ionisation will be at greater heights, so it will not be relevant to use P.531.
The effects of going part way through the ionosphere have not been studied by ITU,
but Sputnik and many other LEOs have been at similar heights and there must be some
knowledge about. At VHF there will be some over the horizon ionospheric ducting.
There will also be some polarisation rotation. However I do claim any expertise in this
area.
From WP 3M: P.2041 is not entirely appropriate as it assumes that the airborne
platform is in the stratosphere (considering (b)) and 120 km is well into the
ionosphere. P.618 and P.681 would be generally relevant to estimate the effects of the
troposphere part of the path (treating the aircraft as a satellite), but in the frequency
range of interest, rain, cloud and gas attenuation (as in Rec P.618) are not
particularly significant effects although low elevation angle tropospheric scintillation
may be of concern (?). P.681 would be useful if there is an issue of shadowing (trees,
buildings) at the earth station end. If there are low-elevation angle paths with
diffraction or clutter, it becomes more complicated and I agree that P.528 (which only
goes to 20 km altitude) and P.682 (which is between an aircraft and a satellite) are
not particularly
Planning criteria: Current terrestrial aeronautical system planning criteria assume aircraft
heights of less than 45,000 feet. The introduction of space planes would potentially affect
the radio horizon distances and hence could impact on the planning criteria employed
Additionally current space operation service allocations might be available for use but this would require
the use of separate up and downlink frequency bands.
3.
CONCLUSION
ACP WG-F/31 WP-25
- 10 -
Where a space plane uses a launch vehicle then the launch vehicle will be able to use current terrestrial
aeronautical systems however care will be needed in addressing the planning of those systems due to the
increased altitude.
A space plane is, in ITU terms, a spacecraft which given its sub-orbital flight trajectory would need to
operate in the space operation service.
Whilst there are current allocations to the space operation service, it is questionable as to whether those
allocations would be suitable for use to support space plane operations
There is likely to be a requirement for a World Radiocommunication Conference agenda item to address
the spectrum requirements and regulatory provision necessary to provide the radio environment that
would allow the safe operation of space planes to be ensured.
Current aeronautical allocations may be able to support space flight communication and navigation
requirements in the short term on an national agreement basis but there are issues with respect to Doppler
shift, transmit/receive power and planning criteria that will need to be addressed and such arrangements
would not be sustainable.
4.
ACTION BY THE MEETING
Working party 5B is invited to:


Forward the question as amended by the meeting to Study Group 5 for approval
Bring the question to the attention of Study Group 7
Use the information provided in the document as the basis for a report on spectrum supportability
of space planes
- 11 -
ACP WG-F/31 WP-25
ANNEX
QUESTION ITU-R XXX/5*
Spectrum Support for Space Planes
(2014)
The ITU Radiocommunication Assembly,
considering
a)
that the radio spectrum is a limited resource;
b)
that aircraft, commonly referred to as space planes, are being developed which can fly at altitudes
of up to 130 km;
c)
that the start of commercial operations are planned 2017/18;
d)
that the aircraft referred to in considering c) use ballistic trajectories;
e)
that there will be a need to provide air traffic control to aircraft referred to in considering c);
f)
that the Karman line located at 100km above the earth’s service is generally regarded as the
division between terrestrial and space services;
noting
a)
that existing terrestrial aeronautical services are designed to support aircraft flying at altitudes of
up to 21 km
b)
that air traffic control systems are considered as safety of life and hence require an allocation to
an appropriate aeronautical safety service,
decides that the following Questions should be studied
1
How much spectrum would be required to support space plane operations
2
Under which radiocommunication service as defined in Article 1 should the provision of air
traffic services for space planes be provided?
3
What would the radio regulatory implications be as a result of decides 1?
4
What interim measures might be required
further decides
1
2
that the results of the above studies should be included in Recommendations and/or Reports;
that the above studies should be completed by 2018.
Category: C2
* This Question should be brought to the attention of the International Civil Aviation Organization
(ICAO).