Keiken Ninomiya

Optical guidance for autonomous landing of spacecraft

An autonomous rendezvous guidance scheme for spacecraft to descend to small celestial bodies by using optical information is presented. First, a new guidance, navigation, and control (GNC) method based on fixation-point (FP) inheritance is proposed. A spacecraft can safely descend toward the target point on the celestial body by tracking and autonomously renewing the FPs on the surface. Next, we deal with the method of extracting the FPs. A spatial band-pass filter (BPF) is applied to pictures taken to enhance features having comparable size with the tracking window. Local variance of the filtered image is used as a criterion of the extraction. Then, the relative information between the spacecraft and the celestial body (position, velocity, attitude, etc.) is calculated from the image coordinates and the range measurements of the FPs from the spacecraft. To suppress observation noise and improve navigation accuracy, an application of the extended Kalman filter is also presented. Finally, simulations are conducted to verify the guidance precision and the fuel consumption of the proposed guidance scheme.

Space Plasma Physics Space Experiments with Particle Accelerators

Electron and plasma beams and neutral gas plumes were injected into the space environment by instruments on Spacelab 1, and various diagnostic measurements including television camera observations were performed. The results yield information on vehicle charging and neutralization, beam-plasma interactions, and ionization enhancement by neutral beam injection.

An autonomous navigation and guidance system for MUSES-C asteroid landing

Abstract ISAS plans to launch an asteroid sample and return spacecraft MUSES-C in 2002 and the spacecraft arrives at near earth asteroid 1989ML in 2003. To approach, rendezvous with, and land on the asteroid safely, the spacecraft has an autonomous navigation, guidance, and control system. That is, it has some functions of station keeping at the distance of about 20 km , landing guidance using optical camera and laser altimeter, hovering at about 20 m above the surface to synchronize the rotation of the asteroid and adjust touchdown attitude, and final descent control including obstacle detection and touch down sensing for reliable and safe collection of asteroid samples. In this paper, at first, the navigation, guidance, and control system onboard MUSES-C is presented, and then, rendezvous and landing scenario are described. Performance and robustness of the system are verified by numerical simulations, GRAphical computer Simulator (GRAS), and hardware simulator called TRAnslational Motion simulator (TRAM). A example of numerical simulation results and brief description of GRAS and TRAM are also shown.

Magnetic Torquing Scheme for Attitude Control of a Wheel-Stabilized Astronomy Satellite

Abstract A new pointing control law by magnetic torquing is proposed for a wheelstabilized astronomy satellite. This law is based on a linear feed-back of attitude error and rate, and achieves both angular momentum control and nutation damping. Actuators are magnetic torquers along three axes plus one bias-momentum wheel. Sensors are rate-integrating-gyros and magnetometers. Stability analysis is carried out by root-locus method. A large angle maneuver scheme is also proposed, which utilizes the same pointing control law. The maneuver is carried out around the eigen axis of rotation, and the advantage is a small amount of processing required for the on-board computer. Computer simulation for the Case of ASTRO-C, a Japanese X-ray-observation satellite, shows that the proposed system works satisfactorily.

Systematic Approach to Achieve Fine Pointing Requirement of SOLAR-B

Abstract The systematic approach adopted in SOLAR-B in order to achieve its fine pointing requirement is presented. The approach consists of : (1)unique pointing requirement analysis in frequency domain that provides a framework of satellite system design, (2)pointing performance analysis including attitude control, telescope pointing control, spacecraft dynamics, structural dynamics and telescope optics, (3)careful disturbance management both in frequency and time domain based on specially devised control parameters, and (4)elaborate tests such as microvibration transmissibility test using the structural model of the spacecraft with real and simulated disturbance sources and very sensitive inertial sensors.

Design of H∞ Attitude Controllers for Spacecraft Using a Magnetically Suspended Momentum Wheel

This paper suggests a method to design a H ∞ attitude controller for a three-axis-stabilised satellite using a magnetic bearing momentum wheel (MBMW) with gimballing capability. According to our method, we can explicitly take into account non-linearity of the actuator and flexibility of appendages in order to design a high performance attitude control system. A double loops control scheme, consisting of the wheel control loop and the satellite control loop, is adopted as a method to solve problems on controllability and observability occurring in the system model. In the design of the wheel control loop, the magnetic bearing non-linearity is modelled by parameter variations and equivalent disturbances, and a structured model uncertainty matrix is used. In the satellite control loop, structural flexibility resulting from appendages attached to the satellites main body, such as solar paddles, is considered as a model uncertainty factor causing the satellites inertia tensor to vary in frequency domain, and an unstructured model uncertainty matrix is used. The effectiveness of the designed H ∞ controllers in improving the control performance is confirmed through computer simulations.

Autonomous imaging of Phobos and Deimos for the PLANET-B Mission

The Institute of Space and Astronautical Science is currently planning to launch the PLANET-B spacecraft toward Mars, carrying an optical imaging instrument Mars imaging camera, and close-up imaging of Martian satellites Phobos and Deimos is planned. This paper presents analysis of using the optical images as a source in an autonomous, real-time onboard navigation scenario. The results obtained here show that radio metric navigation using ephemerides of Martian satellites will not correctly orient the camera. This paper proposes a nonlinear observer as well as navigation schemes that provide orbital properties in real time such as ballistic parameters and the phase angle in the #-pIane (defined as the plane perpendicular to the relative velocity to the target.) Special attention is focused on how the camera angle is programmed in the case of spin-stabilized spacecraft like PLANET-B. Also provided is a new algebraically implemented tracking scheme that is independent of the /?-plane properties.

Simulation System for a Space Robot using 6 Axis SERVOS

Abstract We aim to develop the space robot with a manipulator which is operated to catch and handle a target, in zero gravity environment. In this case, the behavior of the robot main body caused by the reaction force exerted by the manipulator motion has to be taken into consideration, in order to control the manipulator correctly. To solve this problem, we have constructed the ground simulation system combining numerical simulation and servo mechanisms. On this system, dynamics of the space robot and the target is solved based on the momentum conservation law, and the relative motion between them is realized. Using this simulation system, we can develop space robots efficiently.

International edition of iaa multilingual dictionary coordinated through computer network

Abstract This paper proposes a procedure for editing the “IAA Multilingual Space Dictionary”. The dictionary is constructed through international cooperation. Therefore, assignment of the work to each country and international information exchange methods should be discussed. To ensure efficient editorial work, active use of a computer network is proposed. Some anticipated difficulties of editing based on a computer system are also described.

Terrain shape recognition for celestial landing/rover missions from shade information

Abstract This paper proposes a direct geographic recognition scheme from a gray-scale image without shape reconstruction. Several geographic categories are expressed in 3x3-arrays of normal-vector directions. Only by looking up a table, observed pixel-values (intensities) in a window are transformed into indeces of conformity whether the scene in the window is due to each geographic category or not. The recognition is accomplished by multi-resolution interpretation and fuzzy-logical operations. The results of recognition has shown the feasibility and robustness of the proposed method.