ACCURATELY DETERMINING THE POSITION OF OBJECTS IN SPACE#
Freeways and highways in metropolitan areas are not the only places where traffic density is high. Low-earth space is also very busy and sometimes crowded: It is littered with active satellites as well as space debris, and their density is increasing rapidly. Similar to road traffic, this involves increasing dangers. After all, if collisions occur, satellites can be destroyed, affecting infrastructure that is vital to society (e.g. satellites used for navigation or communications). It is therefore essential to detect, monitor and track space objects: By keeping an eye on the objects circling around at all times, in the event of imminent danger, countermeasures, such as evasive maneuvers by satellites, can be initiated in good time. Therefore, Space Situational Awareness (SSA) is one research topic that is becoming increasingly important in both the European and international context. This area of research is also gaining in significance from a military viewpoint: Suspicious maneuvers in which spy satellites approach or even dock on other satellites are on the rise. New space powers such as India and China have tested anti-satellite missiles to showcase their capabilities. The U.S. recently established a space army due to the increasing threat in and from space. France has also announced a plan to develop laser weapons for defense reasons.
GESTRA and TIRA: Hand in hand
The radar systems researched and developed by Fraunhofer FHR's Business Unit Space are ideally suited to monitoring, observing and identifying objects in low-Earth space. In this context, the TIRA and GESTRA radar systems complement each other in an optimal way. The GESTRA radar system, which is being developed on behalf of DLR German Space Agency, allows continuous monitoring in wide-range space. It can be used to determine the orbital data of many objects simultaneously. Moreover, it has the capability to determine the altitude of the objects as well as their inclination – the degree between the Earth's equator and their orbit. Another special feature: GESTRA combines phased array antennas, mechanical mobility of the radar units in three axes, and mobility of the entire system. GESTRA can thus be deployed at any location, enabling a network of radar systems for space surveillance.
If, on the other hand, a specific satellite or other space object needs to be detected with more precision, the TIRA system already in use is the system of choice. It allows satellites to be detected and imaged much more precisely – and additionally enables statements to be made about the satellite itself. If a satellite is not working, for example, TIRA can be used to clarify whether this may be due to the solar panel not being deployed correctly. The ability to image space objects in high definition using TIRA is unique in Europe, which is why the system has already supported numerous missions.
To date, the Business Unit Space has been focusing on the aforementioned space situational awareness of space objects. Other areas of activity are to be added in the future. Firstly, there are plans to supplement Earth-based SSA sensors with space-based radar. In this case, the radar system that observes the space objects is no longer located on Earth, rather on a satellite in orbit. Secondly, the portfolio is to be expanded with the inclusion of other research topics. Examples include active antenna technologies for communications satellites, SAR (Synthetic Aperture Radar) technology for Earth observation satellites and satellite-based microwave radiometers for climate and environmental research. The Business Unit Space will therefore be even more broadly positioned in the future than it has been to date, allowing other space research fields to benefit from its major competencies also.
GESTRA and TIRA: Hand in Hand
The radar systems that Fraunhofer FHR's Business Unit Space researches and develops are ideal for the monitoring, observation, and identification of objects in near-Earth space. In this respect, the two radar systems TIRA and GESTRA complement each other perfectly. The radar system GESTRA currently being developed for the DLR Space Administration allows for the continuous monitoring of large areas of space – it is capable of simultaneously determining the orbital data of a large number of objects. For example, GESTRA also makes it possible to determine the height of the objects as well as their inclination – the degrees between the Earth's equator and the orbit. Another special feature: GESTRA combines phased array antennas, mechanical mobility of the radar units in three axes, and the mobility of the entire system. Thus, GESTRA can be deployed at any given site and allows for the creation of a radar system network for space surveillance.
If, however, one wants to capture a certain satellite or any other space object in more detail, the system of choice is TIRA. TIRA is already in use and provides a significantly more accurate capturing and imaging of satellites – even delivering information about the satellite itself. For example, if a satellite is not working, TIRA can help find out if this might be due to a solar panel that failed to unfold correctly. The possibility of obtaining extremely sharp images of space objects with TIRA is unique in all of Europa – the system has already supported a multitude of missions.
To date, the focus of the Business Unit Space was on the described surveillance and tracking of space objects. Additional fields of work are set to be added in the future. On one hand, the plan is to complement Earth-based SSA sensors with a space-based radar. The radar system observing the space objects will then not be located on Earth, but on a satellite in orbit. On the other hand, the portfolio is to be expanded to include other research topics. Examples are active array antenna technologies for communications satellites, SAR (synthetic aperture radar) technology for Earth observation satellites and satellite-based microwave radiometers for climate and environmental research. Thus, in the future, the Business Unit Space will be even more diversified than now – this wealth of expertise of Fraunhofer FHR will then benefit other fields of space research as well.