Engineering topics
Lo, Martin
Publications and source records attributed to Lo, Martin.
Interplanetary CubeSats: Radiation Considerations for Low-Cost Electronics beyond Low-Earth Orbit
No abstract available
Interplanetary CubeSats: Opening the Solar System to a Broad Community at Lower Cost
No abstract available
Dynamic Optimization of Multi-Spacecraft Relative Navigation Configurations in the Earth-Moon System
In this paper, the notion of relative navigation introduced by Hill, Lo and Born is analyzed for a large class of periodic orbits in the Earth-Moon three-body problem, due to its potential in supporting Moon exploration efforts. In particular, a navigation metric is introduced and used as a cost function to optimize over a class of periodic orbits. While the problem could be solve locally as an optimal control problem, a dynamical based approach that allows for a global/systematic view of the problem is proposed. First, the simpler problem of multiple spacecraft placement on a given periodic orbit is solved before the notion of continuation and bifurcation analysis is used to expand the range of solutions thus obtained.
Subregions of Motion and Elliptic Halo Orbits in the Elliptic Restricted Three-Body Problem
In this paper we present regions of motion and periodic orbits in the spatial elliptic restricted three body problem (ER3BP). Periodic orbits and regions of motion are fundamental keys to understand any dynamical system; for this reason the Hill's surfaces or the families of halo orbits have been extensively studied in the frame of the circular restricted three body problem. It is our opinion that their natural extensions to the ER3BP have not been studied enough. We divide the position space into forbidden subregions, subregions of motion and low-velocity subregions.We use these notions to define necessary condition for a transfer trajectory in the ER3BP. Also we compute branches of elliptic halo orbits bifurcating from halo orbits in the circular restricted three body problem. The new periodic orbits have principal periods and stability properties different from those of the originating halo orbit.
Trajectories leaving a sphere in the restricted 3-body problem
The set of trajectories leaving/impacting the surface of the Galilean satellites of Jupiter is analyzed from theoretical and computational veiwpoints in the ciruclular restricted three body problem in order to characterize the sensitive impact regions for spacecraft trajectory applications as well as the main dynmical structures influencing this set of trajecotries.
The TPF Mission at L2
The Terrestrial Planet Finder (TPF) is one of the center pieces of NASA's Origins Program. The goal of TPF is to identify terrestrial planets around stars nearby the Sun. For this purpose, a space-based interferometer with a baseline of approximately 100 m is required. To achieve such a large baseline, a distributed system of five spacecraft flying in formation is an efficient approach. Since the TPF instruments need a cold and stable environment, a halo orbit about 4 is ideal. First, we describe formation flight near the Lagrange point is feasible for the TPF mission. Second, we propose a novel approach for human servicing of Lagrange point missions by placing a Lunar service station in an Lunar L1 orbit. The TPF spacecraft can be transferred to a Lunar L1 orbit in a few days and requires relatively little delta-V. This efficient transfer results from the system of low energy pathways connecting the entire Solar System generated by the Lagrange points. The halo orbits are the portals of this Interplanetary . A Lunar Station at the L,portal, in addition to servicing missions from the Sun-Earth Lagrange points, may play an even more important role in the future development of space.
The Lunar L1 Gateway: Portal to the Stars and Beyond
Our Solar System is interconnected by a vast system of winding tunnels generated by the Lagrange Points of all the planets and their moons. These passageways are identified by portals around L1 and L2, the halo orbits. By passing through a halo orbit portal, one enters the ancient and colossal labyrinth of the Sun. This natural Interplanetary Supher highway System (IPS) provides ultra-low energy transport throughout the Earth's Neighborhood, the region between Earth's L1 and L2. This is enabled by an accident: the current energy levels of the Earth L1 and L2 Lagrange points differ from that of the Earth-Moon by only about 50 rn/s (as measured by AV). The significance of this happy coincidence to the development of space cannot be overstated. For example, this implies that Lunar L1 halo orbits are connected to halo orbits around Earth's L1 or L2 via low energy pathways...
On the Detection of Energetically Efficient Trajectories for Spacecraft
We propose a new method for the detection of energy-efficient trajectories for spacecraft. Via a so called target-shooting approach a pseudo-orbit between the relevant points in space is constructed in a simple model of the problem. This approximate trajectory is meant to serve as input for a more sophisticated direct method in order to compute a true trajectory in the full model. We demonstrate the applicability of the new method by considering the redesign of part of the trajectory of the NASA/JPL Genesis discovery mission.
Some Mathematical Problems of Satellite Networks
Economic forces and technology development have made low-earth-orbit satellite constellations extremely attractive to the emergent personal communications industry. These constellations range from 2 to nearly 1000 satellites. Even though none of the constellations are as yet completely deployed, design on second generation constellations have already begun. The satellite coverage and network links provide some interesting mathematical problems. We examine some of the geometric and combinatorial problems associated with these networks.
Sun-Earth Libration Point Trajectory Analysis
Due to the constant observation environment and low energy access of Sun-Earth libration point orbits, they have become extremely popular for many NASA science missions. The nonlinearity and instability of the orbits have made mission analysis more difficult as traditional approximations are no longer applicable. But the sensitivity of the orbits also provides greater flexibility in orbit design. Some typical mission trajectories are examined.
The NUONCE Engine for LEO Networks
Typical LEO networks use constellations which provide a uniform coverage. However, the
The application of lissajous orbits for the SIRTF mission
A lissajous orbit about L2 provides an ideal observation geometry for the SIRTF mission. To avoid contamination, the baseline SIRTF spacecraft uses a low thrust helium cold gas propulsion system. Three types of maneuvers are required for the L2 mission: trajectory correction maneuvers (TCM), lissajous orbit insertion maneuver (LOI), and orbit maintenance maneuvers (OMM). Analysis shows a total thrust level of 0.1 N is sufficient to achieve LOI and the smaller OMMs. Rough estimates indicate thrst level greater than 1N is needed to perform the TCMs. A hybrid hydrazine/cold gas propulsion system provides a possible solution.
Study of new systems concepts for a Titan atmospheric probe
Results of a systems concepts study for a Titan Probe were examined. The key tradeoffs performed are described in detail. Mass breakdown of each Probe subsystem or major element were given. The mission analysis performed to determine compliance with the high altitude sampling and descent time requirements are described. The baseline Descent Module design was derived. The element of the Probe System left on the Carrier after separation were described.