Performance index of a network of ground-based optical sensors for space objects observation and measurements

Abstract

The total number of space objects in Earth orbits is estimated to be over 600 thousands over 1 cm, while the current number of those that are constantly tracked and cataloged is around 25 thousands. In our era, where the space traffic is increasing every year, and so the risk of possible collisions, there is a global need to take control of the near Earth space environment, in particular the low Earth orbit. This is a common problem for every country and it can be solved with a global collaboration between nations. In addition, the uncertainty associated with the measured position of orbiting objects is one of the main factors impacting performance, accuracy and timeliness. For this reason, aiming for the coordination of a multitude of sensors is one of the most important aspects targeted in the domain. This paper proposes an algorithm to estimate the performance of a globally-distributed network of optical assets, equipped with off-the-shelf components, deployed in multiple sites distributed across different locations. The quantitative performance measure is calculated as the portion of total cataloged debris that is visible by the network in a 24 h time window, considering space objects of size down to 3 cm. The proposed algorithm takes as input all objects of the NORAD catalog, the whole set of objects’ physical data provided by the DISCOS and SATCAT catalogs, and optical and atmospheric data. It then propagates the space object population to obtain their position in the selected time window, filters out all the objects that are not in the ground station network line-of-sight for a sufficient amount of time to guarantee a feasible orbit determination, and on the remaining ones it estimates the signal-to-noise Ratio achievable by the assets, leveraging an advanced algorithm that models their optical performance. These values are directly translated into a probability of detection, thus providing a performance index for the given ground sensor network configuration that can be used as an objective function to be optimized when evaluating different architectures.