Space Situational Awareness Research
The University of Adelaide

People - Organisations - What is SSA? - Why is SSA important? - Our work on SSA - Demonstration - Publications


Dr Travis Bessell
Mr Samya Bagchi
Mr Daqi Liu



What is SSA?

Resident space objects (RSO) are man-made objects that orbit the Earth. These include satellites, spacecraft and other space installations. Another class of RSOs are junk objects or debris that form as byproduct of space launch, space flight, or spacecraft malfunction/destruction. Currently, there are more than 23,000 space debris of size as small as 5 cm. However, it is known that there are smaller objects that exist in even greater numbers. Space situational awareness (SSA) is the capability to detect, track, and predict the motion of all RSOs, including space debris.

Graphic from ESA plotting known RSOs as of 2013.

Why is SSA important?

Virtually all aspects of modern life depend on satellite technology, including communications, media, commerce, navigation, agriculture and meteorology. There are more than a thousand operating satellites in orbit, amounting to Trillions of dollars worth of investments, that underpin modern technology. Protecting these assets from interference and destruction is of utmost importance. Developing SSA is critically important to prevent the loss of space assets via unintended collisions.

The worsening pollution of space by junk and debris makes the prospect of widespread space asset destruction realistic. Regular collisions involving active satellites and space junk occur; in fact, one to two operating satellites are lost per year due to collisions. More recently, the increasing militarisation of space, which involves covertly placing weapons in orbit and the potential usage of space itself as a battlefield, makes it vitally important to monitor space utilisation.

Our work on SSA

In collaboration with Inovor Technologies and DST Group, we are developing a space-based space surveillance system to achieve SSA. The idea is to deploy a network of CubeSats that collectively observe and near-Earth orbit using optical sensors (cameras). The CubeSats will be placed in Low Earth Orbit (LEO) (altitudes of 500–700 km). Unlike most imaging satellites which fixate on the Earth’s surface, the SSA CubeSats will be pointing outwards. This allows the CubeSats to clearly observe up to the farthest orbital belts, in particular, the Geosynchronous Orbit (GEO) that contains the most critical space assets (satellites forcommunications, broadcasting, intelligence, etc.).

SSA CubeSat concept of operations (diagram not to scale).

The concept of operations involve each CubeSat orienting itself (by means of an attitude determination and control system or ADCS) to "lock on" a predefined region in GEO while in orbit. Any RSO that passes through the CubeSat field of view (FOV) can thus be detected. Fixating on a region in GEO while imaging causes stars to be imaged as streaks, and RSOs in the surveiled GEO region to be observed as dots.

Imaging model for RSO detection in GEO.
Based on the above setting, we are investigating the mathematical foundations of optical detection of RSO, and the application of computer vision and machine learning algorithms to perform the detection. In particular, we have developed several track-before-detect (TBD) algorithms that are specialised for optical detection of RSOs in GEO. We are also developing a multi-modality approach for SSA (e.g., combining radio and optical signals), and visual characterisation of space objects.

Demonstration - optical detection of GEO objects using our TBD algorithm

Relevant publications