Michael Bilka, BAE Systems; Raymond Wright, BAE Systems, Space & Mission Systems; Joshua Wysack, BAE Systems
Keywords: Cislunar, SSA, SDA, STM, Lunar Missions
Abstract:
As human exploration returns to the Moon with the intent of establishing a permanent presence, infrastructure capabilities that are multi-service and scalable are required for a self-sustaining lunar economy. These activities will see growing lunar traffic to include landing, relaunches, and low-orbiting vehicles. Space Traffic Management and Domain Awareness in the near-Earth regimes (GEO and below) is a robust and growing capability space, but the ranges involved with monitoring activity in cislunar space add significant complexity on top of existing sensor technology. The expected increase in future lunar traffic requires coordination of trajectories and operations of spacecraft travelling to, from, and around the Moon as well as surface launches. A system is needed to monitor future lunar traffic, which will require a combined architecture of observers on the lunar surface and space-based observers. These two architecture components can perform complimentary roles in providing surveillance near the Moon. Space-based systems offer several advantages, including dynamic viewing geometries, ability to look up or down, and capability to cost advantage, but may suffer from stray light and surface clutter issues when viewing near the lunar surface. Ground-based sensors have the advantage of viewing along the lunar surface to detect landing or launch of objects but suffer from high deployment costs and the power challenges of the lunar night.
We will present in this paper the major architecture trades and estimated performance of a lunar STM architecture leveraging Lunar Surface Observatory (LSO) and Low Lunar Orbit (LLO) observers. These trades include number and location of observers, both ground and space, in this combined architecture. Our analysis will demonstrate coverage of lunar orbiters and sample descent trajectories based on historic missions. An exemplar of future missions is the recent Chandrayaan-3 lander that maintained a 100km circular orbit before maneuvering to a 35kmx100km elliptical orbit to set up landing. Portions of this trajectory are extremely challenging to observe for space-based observers given stray light effects of looking near the lunar surface. From observing orbits such as Earth-Moon Lagrange Point 1 or 2 (EML1 or EML2) or distant retrograde orbits (DRO), visibility within 1° of the lunar limb represents over 1000km of altitude; as these low transition orbits become more regularly used, near-persistent observations will be needed to maintain traffic management.
The Lunar Surface Observatory (LSO) described in this paper proposes a multi-platform lunar surface architecture to support lunar traffic management and communication. The LSO design features two key components, a wide field of view (WFOV) optical system and a radio antenna. The WFOV sensor allows the LSO to monitor the lunar sky, detecting objects in low lunar orbits directly from the Moon’s surface. This provides crucial information for managing and avoiding potential collisions. The radio antenna serves as a communication hub enabling data exchange within the mesh network of an LSO network, orbiting systems, and NASA’s LunaNet architecture, ensuring smooth communications for future lunar missions. The LSO integrates with this plan, adhering to draft interoperability specifications and paving the way for future expansions. The initial deployment of the LSO will be strategic, targeting key locations. However, the architecture is modular and scalable, allowing for expansion as lunar traffic increases.
Initially, it is expected the LSO provides coverage in strategic locations, such as the lunar south pole, and is scalable (as designed) to provide a communication mesh network on the lunar surface. The embedded communication system provides capability to hand-off tracking between elements. The growth of the LSO is dependent on the grid size, which is a function of desired coverage and gaps. We will present trades focused on optimization of the LSO architecture. For example, an LSO designed to provide full detection coverage up to 2000km altitude has large gaps at 100km, but requires less elements, and therefore cost, to provide the system. A system designed to provide full detection coverage at 100km requires more elements (smaller grid placement; higher cost) and results in redundant coverage at higher altitudes. Additionally, the impact of the communications grid for the mesh network and surface communication utility is to be considered.
The space-based component of this combined STM architecture will provide the capability to monitor traffic in lunar orbit and observe arrival and departure trajectories. We will demonstrate an LLO architecture that utilizes a hybrid visual sensor[1]. Communication with the LSO system will allow for a tip and cue system to allow handoff of the surveillance task as space traffic travels to and from the lunar surface. Communication between LSOs that do not share line-of-sight can be accomplished by using the satellites of the space-based architecture as communication relays. We will perform trades on the number of space observers and their orbits to optimize coverage of a lunar space volume.
Developing STM architectures for the lunar environment and surrounding space will be critical for the allowing the lunar economic zone to deliver on its full potential. Our work will present a thorough analysis of options and best choices in the development of this future STM architecture.
[1] A. M. Lawitzke, J. Van Cleve, J. Contreras et al., Hybrid Sensor for Joint Space Domain Awareness and Lunar Surface Intelligence, AMOS 2022
Date of Conference: September 17-20, 2024
Track: Cislunar SDA