Survey of the Current Activities in the Field of Modeling the Space Debris Environment at TU Braunschweig

The Institute of Space Systems at Technische Universität Braunschweig has long-term experience in the field of space debris modeling. This article reviews the current state of ongoing research in this area. Extensive activities are currently underway to update the European space debris model MASTER. In addition to updating the historical population, the future evolution of the space debris environment is also being investigated. The competencies developed within these activities are used to address current problems with regard to the possibility of an increasing number of catastrophic collisions. Related research areas include, for example, research in the field of orbit determination and the simulation of sensor systems for the acquisition and cataloging of orbital objects. In particular, the ability to provide simulated measurement data for object populations in almost all size ranges is an important prerequisite for these investigations. Some selected results on the distribution of space debris on Earth orbit are presented in terms of spatial density. Furthermore, specific fragmentation events will be discussed

Detectability of space debris objects in the infrared spectrum

While the quantity of space debris objects is steadily increasing, the necessity for space- or ground-based systems observing and cataloguing these objects grows as well. In principle, observations can be made by radar or optically by telescopes. Optical observations have various advantages over radar, such as low purchase and operating costs combined with high precision. A major disadvantage of optical observations in the visual spectrum, however, is their availability, as they depend on clear skies and can generally only be operated in the twilight phase, i.e. about four to 6 h per day. However, if the optical observations are shifted into the infrared range, it seems possible to observe objects in the Earth's shadow. Depending on material properties and trajectory, the object can also emit infrared radiation in the Earth's shadow, be it reflected thermal radiation from the Earth or its own thermal radiation due to the material temperature. Thus, it seems possible that the number of optical detections (space- or ground-based) could potentially increase by additional detections in the infrared range. Also, the sensitivity for some objects in the infrared range may be better than in the visual-optical range. In order to evaluate the general feasibility of such observations in the infrared range, a sensor model has been developed simulating the characteristics of real infrared sensors. This model was connected to the ESA software tool PROOF. Thereby, reference object populations and corresponding detections in the visible range were simulated and compared in succession with the implemented sensor model. Performing an exemplary simulation, it was indeed possible to achieve additional detections in the infrared spectrum that were not obtained in the visual spectrum. However, the observations were only simulated over a time span of 24 h. It is expected that the number of objects that are only detected in the infrared spectrum decreases significantly if a longer period would be simulated. Additionally, the sensor that allowed the best results represents one of the most advanced existing sensors for the infrared spectrum, developed for the James Webb Telescope. In comparison, a commercially available sensor showed clearly inferior results