RESEARCH

Robust Space Mission Design under Uncertainty

Stochastic Optimal Control Approach to Robust Spacecraft Guidance & Control under Uncertainty
(CU Boulder, 2017-present)

 

Robust spacecraft guidance & control for precise science observation around asteroids. Left: without statistical TCM, right: chance-constrained statistical TCM (K. Oguri and J. McMahon, AIAA JGCD,  in press)
Stationkeeping on an unstable Halo orbit in the Earth-Moon system (K. Oguri, M. Ono, and J. McMahon, IEEE CDC, 2019)

Dynamical environments around small celestial bodies are complex and uncertain, leading to highly perturbed, uncertain orbital motions in their proximity. Under such complexity and uncertainty, mission designers need to plan robust guidance and control of the spacecraft orbit to meet some requirements derived from their mission objectives such as precise science observation campaigns. To develop a robust planner for spacecraft guidance under uncertainty, we develop a stochastic optimal control approach to optimize guidance policies that guarantee the requirement satisfaction with a user-defined confidence level (e.g., 99.9 % confidence).

The developed framework is applied to a small-body global-mapping scenario on a science orbit around asteroid Bennu, demonstrating the robustness of the optimized guidance policies: the stochastic orbital states are controlled to meet science requirements to 99.9% confidence over 31 days with minimum control cost.

The approach is also applied to a stationkeeping scenario on an unstable (quasi-periodic) halo orbits under uncertainty. The reference trajectory is one of the science orbit candidates of the EQUULEUS mission, which are designed in a full-ephemeris model (see below for more detail).  The stochastic state are successfully controlled close to the reference trajectory by the chance-constrained TCM controller.

Related Publications:

  • K. Oguri and J. W. McMahon. Robust Spacecraft Guidance around Small Bodies under Uncertainty: Stochastic Optimal Control Approach. Journal of Guidance, Control, and Dynamics, in press, 2020
  • K. Oguri, M. Ono, and J. W. McMahon. Convex Optimization over Sequential Linear Feedback Policies with Continuous-time Chance Constraints. In 2019 IEEE Conference on Decision and Control, Nice, France, 2019
  • K. Oguri and J. W. McMahon. Autonomous Guidance for Robust Achievement of Science Observations around Small Bodies. In AAS Guidance, Navigation, and Control, Breckenridge, Colorado, 2020

Robust Space Trajectory Design under Uncertainty
(CU Boulder, 2017-present)

Space trajectories are inherently subject to a considerable amount of uncertainties. Ideally, the space mission design process needs to optimize trajectories while dealing with possible uncertainties associated with the trajectories. However, most studies on trajectory optimization accumulated thus far primarily focus on deterministic trajectory optimization, i.e., optimization of the nominal trajectory only under deterministic dynamics, states, and controls. In reality, typical mission design processes mitigate potentially hazardous consequences due to uncertainties in rather heuristic manners, such as by adding extra deterministic margins to the original constraints, where the process of statistical TCM design is often separated from the reference trajectory optimization. This heuristic approach does not necessarily capture the actual realizations of the dynamical effects due to the uncertainties (i.e., it can be too conservative or can overlook critical realizations).

To fill the gap between the ideal goal and the current practices of the mission design, we are developing analytical and numerical methods for robust space trajectory design under uncertainty. We hope to publish some of the theoretical and numerical results on this topic sometime soon.

“Risk-aware” trajectory with impulsive maneuver around asteroid Bennu (K. Oguri and J. McMahon, AAS/AIAA ASC, 2019)

Related Publications:

  • K. Oguri and J. W. McMahon. Risk-aware Trajectory Design with Continuous Thrust: Primer Vector Theory Approach. In AAS/AIAA Astrodynamics Specialist Conference, Portland, ME, 2019
  • K. Oguri and J. W. McMahon. Risk-aware Trajectory Design with Impulsive Maneuvers: Convex Optimization Approach. In AAS/AIAA Astrodynamics Specialist Conference, Portland, ME, 2019

SRP-based Orbit Control

SRP-based Orbit Control around Small Bodies
(CU Boulder, 2017-present)

“With appropriate control algorithms, solar radiation pressure (SRP) can be effectively utilized for orbit control around small celestial bodies. In contrast to the historical treatment of SRP as a disturbance at the weak gravity environment, the present paper finds active control of spacecraft attitude promising for orbit control. We develop an optimal control law for the SRP-based orbit control, where a complex reflection model is considered to make the control law applicable to realistic surface reflection models.”
(K. Oguri and J. McMahon, JGCD, 2019)

Landing on asteroid Bennu via SRP-based orbit control (K. Oguri and J. McMahon, JGCD, 2019)

Related Publications:

  • K. Oguri and J. W. McMahon. Solar Radiation Pressure-Based Orbit Control with Application to Small-Body Landing. Journal of Guidance, Control, and Dynamics, 2019. doi: 10.2514/1.G004489
  • K. Oguri and J. W. McMahon. SRP-based Orbit Control with Application to Small Body Landing. In AAS/AIAA Astrodynamics Specialist Conference, Snowbird, UT, 2018
  • K. Oguri and J. W. McMahon. SRP-based Orbit Control for Asteroid Exploration. In 32nd International Symposium on Space Technology and Science, Fukui, Japan, 2019
  • K. Oguri and J. W. McMahon. SRP-based Orbit Control with Application to Orbit Stationkeeping at Small Bodies. Advances in the Astronautical Sciences, 2019

Solar Sailing Trajectory Optimization
(NASA/JPL-Caltech, Fall 2019-present)

 

NEA Scout mission (Link) ©︎NASA

Non-Keplerian Dynamics around Small Celestial Bodies

Science Orbit Design under Irregular Gravity Field Perturbations

 

Psyche mission (Link) ©︎SSL/ASU/P. Rubin/NASA/JPL-Caltech

Related Publications:

  • K. Oguri, G. Lantoine, W. Hart, and J. McMahon. Science orbit design with a quasi-frozen beta angle: effects of body obliquity on J2-perturbed dynamics. Celestial Mechanics and Dynamical Astronomy, 132(10):48, Oct. 2020. doi: 10.1007/s10569-020-09987-z (Link)

  • K. Oguri, G. Lantoine, W. Hart, and J. W. McMahon. Science Orbit Design with Frozen Beta angle: Theory and Application to Psyche mission. Advances in the Astronautical Sciences, 168(2):1971–1987, 2019

Space Mission Design

“Dismantling Rubble Pile Asteroids with AoES”
(CU Boulder, 2017-present) PI: Prof. Jay McMahon

Funded by NASA Innovative Advanced Concepts (NIAC) program.

I am currently working on mission design for the new concept of asteroid exploration, “Dismantling Rubble Pile Asteroids with AoES.” This mission concept is to explore and mine small asteroids using a light-weight soft robot. This spacecraft takes advantage of its high area-to-mass ratio to control the orbit around asteroids exploiting Solar Radiation Pressure (SRP), which is a dominant force around small bodies. My current work is to develop orbital control strategies and show the feasibility of the mission concept.

Related Publications:

  • K. Oguri and J. W. McMahon. Solar Radiation Pressure-Based Orbit Control with Application to Small-Body Landing. Journal of Guidance, Control, and Dynamics, 2019. doi: 10.2514/1.G004489
  • J. McMahon, S. K. Mitchell, K. Oguri, et. al. Area-of-Effect Softbots (AoES) for Asteroid Proximity Operations. In 2019 IEEE Aerospace Conference, Big Sky, Montana, 2019. doi: 10.1109/AERO.2019.8741680

 Mission Analysis for Cis-Lunar Exploration CubeSat EQUULEUS
(UTokyo & ISAS/JAXA, 2016-present)

Funded by ISAS/JAXA.

I worked on design of the science orbits for EQUilibriUm Lunar-Earth point 6U Spacecraft (EQUULEUS) mission, as a member of the Mission analysis team led by Dr. S. Campagnola (see here about EQUULEUS mission). Our work leverages the dynamical structure of the circular restricted three-body problem (CR3BP) and an ephemeris model to systematically and efficiently design low-energy transfers to an Earth-Moon libration point and quasi-halo orbits. Station-keeping analysis is performed each of the designed quasi-halo orbits. The systematic approach enabled us to design over 13,000 of quasi-halo orbits and perform Monte-Carlo station-keeping simulations for each, which contributed to the complex mission design in the multi-body regime with constrained launch conditions.

Quasi-halo orbits designed in the ephemeris model

Related Publications:

  • K. Oguri, K. Oshima, S. Campagnola, K. Kakihara, N. Ozaki, N. Baresi, Y. Kawakatsu, and R. Funase. EQUULEUS Trajectory Design. The Journal of the Astronautical Sciences, Jan. 2020. doi: 10.1007/s40295-019-00206-y
  • S. Campagnola, J. Hernando-Ayuso, K. Kakihara, Y. Kawabata, T. Chikazawa, R. Funase, N. Ozaki, N. Baresi, T. Hashimoto, Y. Kawakatsu, T. Ikenaga, K. Oguri, and K. Oshima. Mission Analysis for the EM-1 CubeSats EQUULEUS and OMOTENASHI. IEEE Aerospace and Electronic Systems Magazine, 2019. doi: 10.1109/MAES.2019.2916291
  • K. Oguri, K. Kakihara, S. Campagnola, N. Ozaki, K. Oshima, T. Yamaguchi, and R. Funase. EQUULEUS Mission Analysis: Design of the Science Orbit Phase. In International Symposium on Space Flight Dynamics, Ehime, Japan, 2017

Attitude-Orbit Coupled Dynamics & Control of Solar Sailing Spacecraft
(UTokyo, 2014-2017)

Funded by Grant-in-Aid for scientific research #17J09626 as a JSPS DC1 fellow (2017).

The first solar sail IKAROS. © JAXA

Related Publications:

  • K. Oguri, A. Ishikawa, S. Ikari, T. Kudo, and R. Funase. Precision Evaluation of Reduced Dynamics Model for Non-uniform Spinning Solar Sail Driven by Reflectivity Control. In 4th International Symposium on Solar Sailing, Kyoto, Japan, 2017
  • K. Oguri and R. Funase. Time-optimal Attitude Control Law with a Strategy of Applying to Orbital Control for Spinning Solar Sail Driven by Reflectivity Control. Advances in the Astronautical Sciences, 2016.
  • K. Oguri, T. Kudo, and R. Funase. Design Criteria of Reflectivity Control System Under Uncertainty in Sail Property for Maneuverability Requirement of Spinning Solar Sail. In AIAA/AAS Astrodynamics Specialist Conference, Long beach, CA, 2016

Small-Sat Development

 Cis-Lunar Exploration CubeSat EQUULEUS
(UTokyo & ISAS/JAXA, 2016-present) PI: Prof. T. Hashimoto & Prof. R. Funase

Funded by ISAS/JAXA.

For EQUULEUS mission, in addition to its mission analysis as a mission designer, I worked on the spacecraft system design as a systems engineer lead. EQUULEUS is a 6U CubeSat scheduled to be launched in 2021 by NASA’s Artemis I on-board Space Launch System (SLS) (visit here for more detail). The CubeSat aims to reach the 2nd Earth-Moon Lagrange point (EML2) by using a low-energy transfer, where the spacecraft will conduct three types of scientific observations. The mission objective is to demonstrate the low-energy orbit control technique via CubeSat. After the mission was officially selected by NASA in 2016 spring-summer, as a systems engineer lead, I led a small team consisting of master/undergrad students to conduct preliminary mission analysis to move the project forward. To achieve the mission objectives given the CubeSat’s limited capability, we explored an optimal solution to “what the spacecraft system should be like?”

Cis-lunar exploration CubeSat EQUULEUS. © UTokyo & JAXA

The First Deep-Space Micro Spacecraft PROCYON
(UTokyo & ISAS/JAXA, 2014-2017) PI: Prof. R. Funase & Prof. Y. Kawakatsu

Funded by ISAS/JAXA.

Group award:

  • Japanese government MEXT Commendation for Science and Technology “Prize for Science and Technology (Research Category)” (2017).
  • The University of Tokyo President’s Award for Students (2015).
First deep-space micro spacecraft PROCYON. © UTokyo & JAXA

-Acknowledgment-

Funding

2017-present

  • Graduate research assistantship, Department of Aerospace Engineering Sciences, CU Boulder
  • Masason foundation fellowship, from Masason foundation, Japan

2017-2019

  • Scholarship for study abroad, Nakajima Foundation, Japan

2017

  • Departmental fellowship, Department of Aerospace Engineering Sciences, CU Boulder
  • Tuition fee half exemption for outstanding students, the University of Tokyo, Japan
  • JSPS DC1 research fellowship for young scientists, Japan Society for the Promotion of Science (JSPS), Japan

2015-2016

  • Japanese Government MEXT Scholarship, the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan

2016

  • Support for international technological interaction, Tokyo Electric Power Company Holdings (TEPCO) Memorial Foundation, Japan
  • Grant for short overseas research, Murata Foundation, Japan
  • Short-term international travel support, Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan

If you can dream it, you can do it.
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