Krzysztof Kaminski, Astronomical Observatory of the Adam Mickiewicz University; Justyna Golembiewska, Astronomical Observatory of the Adam Mickiewicz University; Monika Kaminska, Astronomical Observatory of the Adam Mickiewicz University; Edwin Wnuk, Astronomical Observatory of the Adam Mickiewicz University; Michal Zolnowski, 6ROADS; Marcin Gendek, 6ROADS; Marek Polewski, Warsaw University of Technology
Keywords: re-entry, LEO optical observations
Abstract:
Observed in recent years, the increasing deployment of satellites in Earth’s orbits is leading to a vast increase in the number of artificial objects in the Earth’s vicinity. This makes the task of maintaining situational awareness and space traffic management an increasing challenge in the life cycle of these objects. This concerns the management of these objects’ end-of-life phase.
The foundation for effective implementation of this activity is awareness and the ability to accurately predict the behavior of an object just before and during its atmospheric re-entry. As such, it is possible to carry out the process of removing decommissioned objects in a planned manner without endangering any active ones in the vicinity and minimizing the likelihood of hazardous materials reaching the Earth’s surface. For uncontrolled atmospheric re-entry, the ability to accurately predict the trajectory and impact location is essential to implement timely evacuation measures and emergency response protocols, protecting both human life and property. Consequently, monitoring of satellite re-entry becomes an essential element to ensure the overall safety and well-being of the civilian population.
The improvement of accuracy in predicting re-entry moments and determining the geographical locations of satellite objects falling to Earth is becoming a crucial and urgent issue. This is due to the substantial increase in the number of objects being deployed in Earth’s orbits, especially those with large dimensions and high mass.
Contemporary methods for enhancing orbits and predicting re-entry moments primarily rely on radar observations conducted in the period preceding re-entry, often spanning 30 or 60 days before the given satellite object’s re-entry.
In the context of refining these processes, optical observations executed using a global network of wide-field telescopes seem to be a significant tool. Such observations can effectively contribute to enhancing the orbits of objects approaching re-entry.
The Astronomical Observatory of the Adam Mickiewicz University (AMU), Poznań, Poland in collaboration with the 6 Remote Observatories for Asteroid and Debris Searching (6ROADS) company, Krakow, Poland, possesses a network of several telescopes distributed across different continents. In this context, there are also telescope sets with a large field of view enabling optical observations of low Earth orbit (LEO) objects approaching re-entry.
Test observations carried out with PST3, a cluster of telescopes located in Chalin, Poland confirmed the effectiveness of such observations. Systematic observations covered approximately 10 objects approaching re-entry over a period of several days preceding the re-entry moment. The application of a global telescope network significantly increases the likelihood of visibility and the potential number of optical observations of a given LEO object in the period preceding re-entry.
Therefore, an experiment was conducted to demonstrate the usefulness of a global optical sensor network. The optical observations of LEO objects were made in collaboration between the AMU Astronomical Observatory and the 6ROADS company using two AMU telescopes (PST2 and PST3) and six 6ROADS telescopes (BEATA, ROLONIA, OBORNIKI, RANTIGA, ANJI-SAN, MOONBASE) located all over the globe (Europe, Africa, North and South America, and Asia). Each telescope is located on a fast mount capable of tracking objects in low Earth orbits (LEO) equipped with modern CMOS cameras. The observatories are fully robotic.
During the observation campaign, object observations were delivered to the AMU Observatory in Poznan within a few minutes, where orbits were determined on their basis. During the process, the physical parameters of the satellites—the ballistic coefficient (BC) — were also modeled.
Nevertheless, optical observations of very low LEO objects approaching re-entry pose a challenge, requiring the application of special strategies and consideration of difficulties associated with the high velocity of these objects.
Ephemeridal calculations for several objects approaching re-entry within the Polish telescope network indicate that most objects generate enough observable passes. However, some of these passes are relatively short in duration and occur low above the horizon. Therefore, they require short exposure times during observations and special astrometric processing of images.
Despite these challenges, results from sample observations and improved orbits demonstrate that difficulties associated with telescope observations of LEO objects can be overcome. The proposed work presents the results of observations, orbit improvements, re-entry moment predictions, and a comparison with predicted re-entry moments based on the analysis of historical Two-Line Element (TLE) data and other re-entry services, which are publicly available.
Date of Conference: September 17-20, 2024
Track: SDA Systems & Instrumentation