Observation Strategy to Cataloguing, Monitoring and Classifying Objects in Molniya Orbit through Optical Observations

The population of space debris in the Geostationary Earth Orbit (GEO) ring and in Low Earth Orbit (LEO) has been widely studied given the importance of these two regions, which are the most used and consequently the most saturated with debris. However, to achieve a comprehensive understanding of the space surrounding Earth, it is essential to acquire further knowledge about the population in other regions and orbital regimes. Within this complex framework, Molniya orbits represent an interesting orbital regime to be monitored. Acknowledging the operational objects and debris present in Molniya orbits is crucial because these orbits have their perigee in LEO and apogee in GEO, covering densely populated regions. In the past, objects in Molniya-like orbits were not frequently observed due to their high apogee altitude, which posed significant challenges for optical observations using the available instruments. Thanks to the latest generation of cameras and mounts, observing these orbits has now become more manageable. Researchers from the Sapienza Space System and Space Surveillance Laboratory (S5Lab), exploiting their extensive experience in Space Surveillance and Tracking (SST) along with a wide network of telescopes, performed an observation campaign to investigate the objects in these orbits to get a further knowledge of the trackable and the unknown populations. It is evident that a lack of precise information about Molniya debris elevates the risk of collisions. This paper describes the observation campaign designed to conduct an optical survey in Molniya-like orbital regimes, from formulating an optimal observation strategy to presenting the achieved results. Firstly, a region of interest (ROI) in terms of Right Ascension (RA) and Declination (Dec) was identified, considering all catalogued objects with values in inclination, eccentricity, and mean motion closely resembling those of a typical Molniya orbit. This ROI contains the highest density of observable objects from a telescope within the S5Lab network for each observation session. Once this region was identified, a strategy for scanning the ROI and conducting the survey using state-of-the-art cameras was implemented, optimising visibility conditions from the observation site. This paper provides a detailed description of the ROI's definition and the strategy, along with the presentation and explanation of the observation campaign's results.