This document discusses optimizing a ground station network for optical space-to-ground communication links. It aims to find a network of optical ground stations that maximizes the amount of data transmitted from low Earth orbit satellites while accounting for the impact of clouds on optical communications, unlike radio-frequency technologies. The document outlines advantages and disadvantages of optical communication compared to radio-frequency and discusses future work involving improving the ground station database and using longer timeframes of cloud data.

1. GROUNDED STATION
NETWORK OPTIMIZATION
FOR SPACE - TO -
GROUND OPTICAL
COMMUNICATION LINKS.

2. ABSTRACT :
Optical communication is becoming a mature
technology, but unlike current radio-frequency
technologies, they are strongly impacted by clouds. In
this paper, we aim to find a network of optical ground
stations maximizing the amount of data that can be
sent from a low-earth orbiting satellite to the Earth
during its mission and showing the difference between
Radio frequency and Optical communication.

3. Theme of the paper :
Free-Space-Optical (FSO) communications are seen as a key
technology to cope with the needs of higher data-rate
payloads for future low earth orbiting (LEO) observation
satellites in replacement to the current radio-frequency (RF)
technologies. Current RF technologies use X-Band for
download which can currently provide up to a few Gbps.
These are not impacted by weather or atmospheric
turbulences. Their main drawbacks are limited data-rates and
a need for frequency licensing which will become a major
issue in the upcoming years due to increases in the number
of operational satellites and constellations. FSO
communications offer data-rate order of magnitude higher
than current RF technologies: targeted data-rates go from

4. They do not require frequency licensing and are hard to
intercept by malicious observers. However, FSO
communications are strongly impacted by weather, cloud, and
atmospheric turbulences. To evaluate the impact of FSO
communications for spatial imagery systems, we aim to find a
subset of optical ground stations in order to maximize the
percentage of data downloaded from satellites taking cloud
information into account using archived data from previous
decades.
Theme of the paper :

5. Advantages :
1. High data rate.
2. Power consumption is less.
3. high bandwidth.
4. Coverage over a large geographical area can be cheaper over
a long distances.
5. Less bit error rates.
6. Ease of development.

6. Disadvantages :
1. Atmospheric adsorption ( rain, snow).
2. Fog (10 – 100 dB/km attenuation).
3. If the sun goes exactly behind the transmitter it can swamp
the signal.

7. Future developments :
Future work might involve the improvement of the OGS
database. For optical GEO feeder links, the connectivity to
optical fiber ground networks is essential. Reviewing the exact
capabilities of each ground station site in the data base and
adding further stations with good network connectivity will
enable more practical results. However, it is not expected that
the general trend in the evaluations would be different.
Furthermore, the analysis could benefit from a larger cloud
database, i.e., using 10 or 15 years of cloud data instead of five.

8. Conclusion :
In this paper, we briefly reviewed the calculation of correlated
and uncorrelated availability for OGS networks in the scenario
of space-to-ground optical communication links, with a focus
on links to GEO satellites.
In the near future, we hope to solve instances with bigger
networks and with more realistic costs by using custom
(possibly approximate) algorithms for the enumeration of
the networks.

9. Thank you