Space Situational Awareness – A Quick Overview


Space situational awareness (SSA) is the ability to accurately characterize the space environment and activities in space.

Civil SSA combines positional information on the trajectory of objects in orbit (mainly using optical telescopes and radars) with information on space weather. Military and national security SSA applications also include characterizing objects in space, their capabilities and limitations, and potential threats.

SSA is an inherently international and cooperative venture. It requires a network of globally distributed sensors as well as data sharing between satellite owner-operators and sensor networks. SSA also forms the foundation of space sustainability as it enables safe and efficient space operations and promotes stability by reducing mishaps, misperceptions, and mistrust.

Types of SSA Sensors

Ground-based radars have historically been the backbone of SSA. Radar consists of at least one transmitter and receiver. The transmitter emits radio waves at a specific frequency, some of which reflect off the target and are measured by the receiver, which can then calculate the location of the target in relation to the radar. The primary advantages of radars are that they can actively measure the distance to a target and some types of radars can accurately track many objects at once. Some radars can also detect the motion of an object and construct a representation of its shape. The main disadvantages of radars are their cost, size, and complexity.

Optical telescopes are also widely used for SSA. Telescopes collect light or other electromagnetic (EM) radiation emitted or reflected by an object and focused into an image using lenses, mirrors, or a combination of the two.

The main advantages of using optical telescopes for SSA is their ability to cover large areas quickly and, in particular, to track objects above 5,000 km altitude. Some telescopes can create high resolution images of space objects. The main disadvantage of optical telescopes is that they require specific lighting conditions and clear skies to see an object, although space-based optical telescopes eliminate some of these limitations.

Other types of sensors can be used for SSA, including sensors that detect radio frequency (RF) or other types of signals from satellites, lasers that measure the distance or range to a satellite very accurately, and infrared sensors that detect heat. Combining data from many different types of sensors, both ground- and space-based, that are also distributed around the globe provides a much more complete picture of the space environment and of activities in space.

Who does SSA?

Although historically done by the U.S. and Russian militaries, today there are a growing number of countries, academic and scientific institutions, commercial companies, satellite operators, and even private citizens who are providing various types of SSA data.

Over the last few years, there has been increased activity from the private sector on SSA. Multiple companies are now developing or providing data and analysis services to governments and satellites operators.

Examples of companies that offer SSA services include:

Why is SSA Important?

SSA is critical to the long-term sustainability of outer space. It provides knowledge that allows everyone who uses space to evaluate the impact of their activities and make informed decisions. SSA makes using space safer and more efficient and enables protection of valuable satellites and space-based services.

SSA also provides a level of transparency to reduce tensions, help verify agreements between countries, and prevent accidents or misperceptions from triggering or escalating conflict.

Source: Secure World Foundation