Alexis Petit, Share My Space; Romain Lucken, Share My Space; Henri Tarrieu, Share My Space; Damien Giolito, Share My Space; Cyril Cavadore, Alcor System; Thierry Lépine, Institut dOptique Graduate School and Univ-Lyon, Laboratoire Hubert Curien
Keywords: Multi-telescope observation stations, global space surveillance, faint streak detection
Abstract:
Detecting and cataloging smaller objects in Earth orbits is a growing challenge for the space community as the traffic is increasing on Earth orbits. Better object mapping is key for the safety of future human spaceflights, as well as commercial and governmental satellites. Radar, optical, and laser solutions are now available to provide some overview of the space situation. While optical systems represent the standard way to perform observations, few studies asses their performance for object detection on all orbital regimes (and not only GEO).
In this paper, we present a new architecture of optical multi-telescope observation stations. When spread around the world, a few of these observation stations provide a global space coverage at relatively low cost.
The properties of the telescopes of the network as well as the layout and operating principle of the multi-telescope observation stations will be presented. Based on a population of objects generated artificially and representing the statistical distributions provided by the Master software (ESA), the number of objects that can be detected and cataloged over one month has been assessed. Each object is associated with a size according to the statistical distributions for altitudes between 200 km and 37500 km. The telescopes are set in a sidereal tracking such that all objects appear as streaks on the images. Whether or not an object is detected from one of the telescopes of the network depends on multiple parameters that include:
– The object has to be illuminated by the Sun and in the field of view of the telescope while the observation station is in the night. This can be particularly challenging for objects below 1000 km.
– The signal-to-noise ratio of the illuminated object has to be above 5. The background magnitude of the sky ranges from 18 (full Moon) to 22 (optimal observation conditions).
– The length of the streak has to be above 50 pixels.
A simplified analytical orbit propagator is used to propagate all the objects in parallel, and assess which of them are observed at each date. The rates of revisit of each of the objects can, hence, be determined. Reasonable assumptions are made regarding the light back-scattering on the objects, and the optical transmission through the atmosphere and through the ground station optics. These assumptions are verified using individual telescopes on ground with properties that are similar to those that are used in the multiple-telescope observation stations.
The study is performed with 1, 2, 4 and 6 observation stations around the world, and three designs of telescopes including two off-the-shelf technologies and one new telescope design that is under development, which is briefly described. The performances of multiple cameras are compared in this context, with detector pixels sizes between 4 and 10 micrometers. The field of view that is aimed for, for a single telescope, is 4 degrees. The observation strategy is optimized by controlling multiple parameters such as the time of exposure and the elevation of the telescopes of the stations, depending on the altitude of the targeted objects, and the time of the night.
Combined with the adequate computational facilities, this network can supply and maintain a catalog of objects well beyond 50,000 objects, and create a new way to manage traffic on Earth orbits.
Date of Conference: September 14-17, 2021
Track: Optical Systems & Instrumentation