Research

The reconstruction and mapping of small bodies by means of Lidar data requires proper handling of the underlying uncertainties in the reconstructed map, as well as a guaranteed robustness to the lack of a-priori information in the targeted small body’s shape and dynamical environment. This research aims at providing such a robust framework allowing successive observation, shape reconstruction and navigation of an unknown asteroid or comet.

Mark studies how the gasses streaming off active comets perturb the motion of spacecraft or natural objects orbiting the comet. He is interested in how these natural forces can be leveraged for spacecraft operations, improving science return, and for studying natural processes at comets.

(Left) Shows a ballistic trajectory propagated around Bennu with full dynamics over a period of 15 Earth days. At close distances, the gravity field of Bennu plays an import role in the evolution of orbits. (Right) Shows the results of a low-thrust orbital maneuver with uncorrected error components. As the figure shows, without active guidance the resulting trajectories vary substantially. 

(Left) Shows an orbital maneuver accomplished using a bi-linear tangent guidance algorithm. This maneuver, which is aggressive in both changing the shape and plane of the original orbit, was accomplished for only a few grams of fuel. (Right) Shows a family of Lambert guidance solutions when time-of-flight is varied. 

Solar Radiation Pressure (SRP) is a ubiquitous force that acts on any objects in space. We can exploit the force to control spacecraft orbits without consuming fuel. We analytically derived an optimal orbit control law for the "SRP-based orbit control" and demonstrated it with some small body exploration scenarios, including asteroid landing (left) and science orbit transfer (right) scenarios.

Recent asteroid missions have shown that asteroid surfaces are endure different processes that shape and reshape the asteroid both globally and locally. Daniel's research seeks to describe the relationship between an asteroid's rotation and the processes on its surface. Using the Surface phenomena Effect on Asteroid Rotational And Translational State (SEA-RATS) tool developed at ORCCA Daniel investigates the conditions for surface activity such as boulder motion and quantifies their effect on asteroid rotation.

A polyhedral model approach is used for the cometary gas model incorporating diurnal effects for 67P. The density distribution (sun-direction in black) and non-radial component of the velocity field for the coma are provided. Making use of this coma model and including the main dynamical perturbations (SRP, non-spherical gravity, drag, and third body perturbations), an estimate of the potential mass that can be obtained by orbiting an active comet is given. In this case, different inclinations are tested to determine a preferred region to maximize the capture.

Entry, Descent, and Landing on Mars requires the synchronization of a large number of subsystems, making lighter, nimbler systems valuable for automated entry processes. By testing novel methods for prediction of the atmosphere and targeting of mid-altitude coordinates, on-board systems can become more robust to handle a variety of mission profiles for the future.

Around asteroids, mission designers need to plan robust guidance and control of spacecraft orbits to meet operational requirements (e.g., science requirements) under complex, uncertain dynamical environments. We develop a robust guidance planner that minimizes the control effort while ensuring the requirement satisfaction with a user-defined confidence level.

Drag-modulation offers a straightforward solution to aerocapture (top left) guidance, leveraging vehicle geometric properties for trajectory control. (bottom left & top right) Jettisoning a rigid drag-skirt during the trajectory enables the guidance system to target a desired exit state. Investigations into multiple jettison events (bottom right) show promising improvements in aerocapture robustness and accuracy.

This research focuses on the development of an autonomous spacecraft guidance system to enable to use of low-thrust propulsion around small bodies. The ALT-G architecture is able to autonomously plan and execute finite, continuous low-thrust maneuvers between two orbits using a parametric bilinear tangent (BLT) guidance law and a predictor-corrector guidance scheme. The figures the slide show examples of the planning and guidance capabilities of low-thrust BLT using ALT-G.

On the left, this research investigates using methods from simultaneous localization and mapping for terrain relative navigation at small bodies and moons. On the right, we have a description of our quadrotor based testbed for navigation algorithms around small bodies, which we run in ASPEN Flight Lab in the Aerospace Engineering building at CU. 

Low-resolution mapping methods aid in the onboard processing of shape models for the purpose of proximity navigation when encountering and exploring small bodies. Our approach focuses on the optical data sources, taking limb and terminator information into account while building a visual hull. The aim of this work is to use computer vision approaches to enable shape modeling for SIMPLEx-level missions. 

Spacecraft formation flying is inherently very risky as multiple spacecraft need to operate in proximity with each other. There is an immense need for fast and efficient algorithms to compute safe, and collision-free relative trajectories for multi-spacecraft systems. At ORCCA, we leverage ideas from sampling-based motion planning in field of robotics and develop motion planning algorithms to achieve fuel-efficient, collision-free, and near-optimal trajectories for spacecraft reconfiguration in cluttered environments.