Low-Altitude Satellite Constellations Backgrounder Released by CBO
The Congressional Budget Office has released a background report on low-altitude satellite constellations in LEO as an introduction to the topic for members of Congress.
In this report, the CBO provides an introduction to the advantages of and challenges for constellations of low-altitude satellite constellations. In particular, the report describes the effects that orbital altitude has on the design of satellites and constellations of those satellites, focusing on DoD’s Earth-observation and communications missions.
In recent years, commercial investment in space has greatly increased, with emphasis on low altitudes, roughly 190 miles to 1,240 miles above the Earth. Today, several companies either are building and launching, or plan to build and launch, very large constellations of satellites in orbits at those altitudes. Similarly, the Department of Defense (DoD) has begun to plan for new large low-altitude satellite constellations to make the performance of their satellite missions more resilient against interference and attack by adversaries.
The report covers satellite basics, including such topics as how a satellite is defined, some of the common missions of the spacecraft, how they stay in orbit. It also goes into detail about how the altitude of a satellite affects its field of view and orbital characteristics.
Pros and Cons of Low-Altitude Satellite Constellations
The report points out that satellites in LEO generally are smaller, cost less, and have shorter operational lifetimes than those at higher altitudes. More LEO satellites are generally needed to achieve coverage comparable to smaller constellations at higher altitudes, and the LEO satellites need to be replaced more often to maintain the constellation.
Operating in LEO potentially allows for more timely communications, higher resolution imagery, and, for large constellations, greater resilience against attack or interference because many satellites share the same mission. However, LEO satellites can view a given point on Earth for only about 10 minutes, making constellation management more complex if continuous communication or observation is required.
The costs of maintaining low-altitude satellite constellations for many years are potentially higher than MEO or GEO constellations with comparable coverage, but LEO costs could be reduced if mass production significantly decreased unit costs or if launch costs continued to decline.
(Source: Congressional Budget Office. Images provided)