Jens Rodmann, German Aerospace Center (DLR); Wolfgang Riede, German Aerospace Center (DLR); Stefan Scharring, German Aerospace Center (DLR)
Keywords: Laser, space situational awareness, space debris, system study
Abstract:
With more than 13000 known resident space objects, most of which is space debris, the LEO space environment is nearing congestion. Several planned mega-constellations with hundreds or even thousands of small satellites, an expected increase in launch activities from spacefaring nations and the private sector, and inevitable fragmentation/collision events will likely lead to a significant growth in the population over the next decades.
A prerequisite of operating in a congested space environment is precise information on the objects orbits and their associated uncertainties. Many SSA use cases (e.g. catalog maintenance, conjunction assessment, collision avoidance, and re-entry analysis) need high precision orbits with small state vector covariances.
Laser ranging has demonstrated high accuracy for determining ranges to space objects to within a meter or better. Time-of-flight measurements from laser-ranging facilities of the ILRS network are regularly being used to determine precision orbits and ephemerides of ~80 satellites, mostly for geodesy, GNSS validation, and mission support. With better range accuracy and lower operational cost per station, laser ranging is a highly promising sensor technology for LEO space surveillance and can complement existing radar facilities.
However, as an optical ranging method, laser ranging requires clear skies with little cloud cover and good visibility. Furthermore, in most cases the space object needs to be illuminated by the sun and the station in umbra to allow passive-optical tracking in order to compensate for the typically low accuracy of TLE tracking predictions. These requirements and constraints drive the design of a laser-ranging network and have an impact on the orbit uncertainties that can be achieved for different LEO orbit types.
We present preliminary results from a large system study to investigate the performance of a global laser-ranging network. In order to determine when favorable weather and lighting conditions for laser ranging can be expected at any particular site of a network of globally-distributed stations, we compiled daily weather parameters for cloud, wind and visibility from publicly available long-term weather data. For these observing times, synthetic laser ranging measurements are simulated for various types of LEO orbits and subsequently used for precise orbit determination. We derive state vector uncertainties that can be achieved as well as predicted uncertainty when propagating the orbit for a couple of days without any new measurements.
Date of Conference: September 11-14, 2018
Track: Space Situational Awareness