ROOM
17
Special Report
behind them are in some cases new players to
spaceflight and space-based communication.
Space traffic debris
A significant disadvantage of the proposed concepts
is the high numbers of active satellites required to
operate within the constellation in order to provide
seamless coverage from low altitudes. Concepts
range from a few dozen satellites to several
thousand in the size class around 100kg dry mass.
The sheer number of satellites revolutionises
the way spaceflight is performed. On average, just
one such constellation will have more operational
satellites in space than all other spacefarers
together (currently around 1100). With the
operational lifetime of the satellites being limited
to a few years, the constellation will have to be
replenished regularly. This means that within a few
decades the number of constellations satellites
launched will be greater than the number of
satellites ever launched by other spacefarers in the
history of spaceflight (approximately 7,400).
Satellites will have to be manufactured using
mass production techniques common in the
automotive industry to achieve unit prices of well
Below: Evolution of the
number of objects
catalogued by the US
Space Surveillance
Network.
Left: Spacecraft
numbers launched into
LEO since 2000 per
satellite mass class (ESA
DISCOS database,
re-entry vehicles
excluded).
Providing global internet access from space
appears to be a logical alternative to costly
infrastructure on the ground. Today, internet
broadband services are rendered through
telecommunication providers using satellites
in geostationary orbit but their significant data
latency (the amount of time it takes to send
information from one point to the next), limited
bandwidth and channels and their requirement
for significant transmission power make them
unsuitable to serve a broader private community.
Several information technology and electronics
companies have announced plans to provide
such service via large constellations in low Earth
orbit (LEO) by 2018-2020. The proposed concepts
foresee spanning a global, leak-proof network of
inter-linked small satellites, accessible at any time
from a set of deployed ground terminals.
It is expected that this tailored solution
for wide-spread low-latency (less than 50
milliseconds) broadband (10 terabytes per second)
excess will challenge the classical space-based
and ground-based communication market. The
proposed concepts differ in their maturity levels
and constellation concepts and the companies
Within a few
decades the
number of
constellation
satellites
launched will
be greater
than the
number of
satellites ever
launched
Current mega-
constellation concepts for
global web-access.
Constellation
Satellites
Altitude
Sat. Mass
Constellation
720
1200 km
150kg
Constellation
4000+
1100 km
390kg
Constellation
4600
1400 km
< 200kg
Constellation
2960
1200 km
> 100kg
