<p>Large space-based communication networks have been growing
in numbers of satellites, with plans to launch more than 10,000 satellites into
Low Earth Orbit (LEO). While these constellations offer many advantages over
ground-based communication systems, they pose a significant threat when they
fail and generate space debris. Given the reliability of current satellites,
engineers can use failure modeling to design satellite constellations that are
more resilient to satellite failures. Several authors have analyzed the
reliability of geostationary satellites, but few have expanded the work to
multiple-satellite systems. </p>
<p>To address this gap, we constructed a simulation model to
show the performance of satellite constellations with different satellite
reliability functions over time. The simulation model is broken down into four
key parts: a satellite constellation model, a network model, a failure model,
and a performance metric. We use a Walker star constellation, which is the most
common constellation for LEO broadband satellite constellations. The network
consists of satellite-to-satellite connections and satellite-to-groundstation
connections, which routes data using a shortest-path algorithm. The failure
model views satellites as either operational or failed (no partial failures)
and considers the groundstation operator’s knowledge or lack thereof of the satellites’
operational status and uses satellite reliability to estimate the expected data
throughput of the system. We also created a performance metric that measures
how well the entire network is operating and helps us compare candidate
constellations.</p>
<p>We used the model to estimate performance for a range of
satellite reliabilities, and for groundstations with different numbers of
communication dishes (effectively, satellite-ground links). Satellite reliability is a
significant contributing factor to the long-term constellation performance.
Using the reliability of small-LEO satellites, we found that a constellation of
1,200 small-LEO satellites completely fails after less than 30 days, given that
we do not consider partial failures. Satellite constellations with higher
satellite reliability, such as large geostationary satellites, last less than
50 days. We expect the constellations in our model to perform worse than real
satellite systems, since we are only modeling complete failures, however these
findings provide a useful worst-case baseline for designing sustainable satellite
constellations. We also found that the number of groundstation-to-satellite
communication links at each groundstation is not a significant factor for more
than five communication links, meaning that adding more communication antennas
to existing satellite groundstations would not improve constellation
performance significantly.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/12746648 |
| Date | 31 July 2020 |
| Creators | Islam Aly Sadek Nazmy (9192482) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/Reliability_Analysis_of_Low_Earth_Orbit_Broadband_Satellite_Communication_Constellations/12746648 |
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