Nobutada Sako

Attitude control system for the nano‐astrometry satellite “Nano‐JASMINE”

Purpose – This paper aims to present an attitude determination and control system for a nano‐astrometry satellite which requires precise angular rate control. Focus of the research is methods to achieve the requirement.Design/methodology/approach – In order to obtain astrometry data, the satellite attitude should be controlled to an accuracy of 0.05°. Furthermore, attitude spin rate must be controlled to an accuracy of 4×10−7 rad/s during observation. In this paper the following unique ideas to achieve these requirements are introduced: magnetic disturbance compensation and rate estimation using star blurred images.Findings – This paper presents the feasibility of a high accurate attitude control system in nano‐ and micro‐satellite missions.Practical implications – This paper presents a possibility of the application of nano‐satellites to remote‐sensing and astronomy mission, which requires accurate attitude control.Originality/value – Originalities of the paper are the methods to achieve the high accurat...

Strategy of magnetometer calibration for nano-satellite missions and in-orbit performance

Magnetometers are lightweight, reliable, and low power consumption sensors, therefore most of nano and micro satellites in low-earth orbit have adopted magnetometers as an attitude sensor. These days, the nano and micro satellites, specifically for remote-sensing and astronomical missions, must meet strict attitude requirements for obtaining scientific data or images. These missions require precise geomagnetic field data for precise attitude control. In order to obtain precise geomagnetic field data, eects of noise which can be caused from temperature change, residual magnetic moment of a satellite, and magnetic anomaly should be canceled. This research proposes methods to estimate these eects and cancel in orbit for nano-satellites, and assesses the proposing methods using in-orbit performance and simulation results.

NANO-SATELLITE ATTITUDE STABILIZATION METHOD USING STAR IMAGES

Abstract Infrared astrometry nano-satellite Nano-JASMINE is now under development. It aims to achieve 1 arcsecond high attitude stability compared to traditional nano-satellite for its observation. In this case, standard methods and equipments are useless. Therefore a new method by using star images from mission telescope to measure its attitude stability and for control is proposed.

Nano-JASMINE: a 10-kilogram satellite for space astrometry

The current status of the nano-JASMINE project is presented. Nano-JASMINE - a very small satellite weighing less than 10 kg - aims to carry out astrometry measurements of nearby bright stars. This satellite adopts the same observation technique that was used by the HIPPARCOS satellite. In this technique, simultaneous measurements in two different fields of view separated by an angle that is greater than 90° are carried out; these measurements are performed in the course of continuous scanning observations of the entire sky. This technique enables us to distinguish between an irregularity in the spin velocity and the distribution of stellar positions. There is a major technical difference between the nano-JASMINE and the HIPPARCOS satellites-the utilization of a CCD sensor in nano-JASMINE that makes it possible to achieve an astrometry accuracy comparable to that achieved by HIPPARCOS by using an extremely small telescope. We developed a prototype of the observation system and evaluated its performance. The telescope (5cm) including a beam combiner composed entirely of aluminum. The telescope is based on the standard Ritchey- Chretien optical system and has a composite f-ratio of 33 that enables the matching of the Airy disk size to three times the CCD pixel size of 15μm. A full depletion CCD will be used in the time delay integration (TDI) mode in order to efficiently survey the whole sky in wavelengths including the near infrared. The nano-JASMINE satellite is being developed as a piggyback system and is hoped for launch in 2008. We expect the satellite to measure the position and proper motion of bright stars (mz < 8.3) with an accuracy of 1 mas, this is comparable to the accuracy achieved with the HIPPARCOS satellite.

Online Magnetometer Calibration in Consideration of Geomagnetic Anomalies Using Kalman Filters in Nanosatellites and Microsatellites

AbstractMagnetic sensors are reliable, lightweight, and low power consumption sensors that are utilized in almost all nanosatellites and microsatellites for a magnetic attitude control system using magnetic torquers (MTQs). In some nanosatellites and microsatellites, magnetic sensors are utilized for magnetic moment estimation to compensate for torques owing to magnetic dipole disturbances, which are the dominant disturbances in these small satellites. To estimate the magnetic moment accurately, the errors of the magnetic sensors caused by the magnetic anomaly and bias noise from electrical devices should be estimated and compensated precisely. Although several previous studies have focused on the estimation and compensation of the errors of the magnetic sensors, the magnetic anomaly of the geomagnetic field has not been considered, even though the anomaly introduces large estimation errors. This research proposes a method to estimate the time-variable errors arising from both magnetometer bias and the ma...

TARGET ATTITUDE MOTION ESTIMATION AND TRACKING EXPERIMENT ON MICRO-SATELLITE "MICRO-LABSAT"

On a NASDA’s microsatellite named “μ-LABSAT,” which was launched by H-IIA on December 14, 2002 (Fig.1), Communications Research Laboratory (CRL), National Aerospace Laboratory (NAL) and University of Tokyo (UT) have been jointly performing several orbital experiments as technology demonstration towards the future orbital servicing missions. In University of Tokyo’s experiment which was held on May 14, 2003, the micro-satellite released a small object named “target,” and its rotational motion was estimated by the images captured continually using a camera developed by CRL. Then satellite attitude control was performed by visual feedbacks of the target image position on the camera frame so that the target image may come to a certain point on the camera frame. This is a pre-experiment of so-called LOS (Line Of Sight) control, which will be indispensable during rendezvous and docking to the satellite to be serviced. In this paper, the objectives and procedure of these experiments, and the results will be described. 54th International Astronautical Congress of the International Astronautical Federation, the International Academy of Astronautics, and the International Institute of Space Law 29 September 3 October 2003, Bremen, Germany IAC-03-A.P.06 Copyright

Nano-JASMINE: current status and data output

The current status of the Nano-JASMINE project is reported. Nano-JASMINE is a very small-sized (50 cm cubic form) satellite that is expected to carry out astrometric observations of nearby bright stars. The satellite will determine distances of more than 8000 stars by performing annual parallax measurements, which is the only direct method to measure the distance of an astronomical object. The mission is required to continue for more than two years to obtain reliable annual parallax measurements. In addition, Nano-JASMINE will serve as a preliminary to the main JASMINE mission. We expect that Nano-JASMINE will be launched in August 2011 from the Alcantara Space Center in Brazil using the Cyclone-4 rocket.

Thermal Design and Testing of a Micro-satellite for Infrared Astrometry (Nano-JASMINE)

This paper discusses the thermal design and testing for Nano-JASMINE. NanoJASMINE is a micro-satellite for infrared astrometry. Due to its small size, there are several strict requirements that should be met for the mission to be accomplished. The design to meet the requirements by the efficient using of a thermal shield and the multi-layered thermal insulation and the efficient components configuration is shown in this paper, as well as the simulation and thermal vacuum tests we did to for assessment. Since some of the requirements are difficult to even measure because of the necessity of the measurement accuracy, we used some unique methods to divide the whole test into several phases. NanoJASMINE’s thermal design shows that even a small satellite can also achieve strict thermal requirements with only passive control. This will make various scientific advanced missions possible at a low cost and a short development period.

Attitude stabilization using blurred star images for a nano-astrometry satellite mission

This research presents a new method to stabilize a 30 kg satellite attitude to a high accuracy using star blurred images. The method is intended to use on the Nano-JASMINE (Nano-Japan Astrometry Satellite Mission for INfrared Exploration) satellite, which is developed at Intelligent Space System Laboratory (ISSL) University of Tokyo in cooperation with National Astronomical Observatory of Japan (NAOJ). The objective of the mission is to measure the three dimensional positions of stars to an accuracy of 1.8 milli-arcsecond (mas). In order to get accurate star position data, Nano-JASMINE should be stabilized to better than 740 mas / 8.8 s accuracy during observation. To achieve the requirement, the satellite must determine the angular velocity to an accuracy of 5 £ 10 i8 rad=s and control angular velocity to an accuracy of 4 £ 10 i7 rad=s. Currently there are not sensors available for a micro-satellite to get accurate attitude information as is required by the mission. To achieve the requirement, the satellite uses star images obtained by a mission telescope. The angular velocity is determined by assessing the quality of a star image based on how blurred it appears. Based on simulation results, the research concludes that the use of star blurred image data to determine and to stabilize attitude is a feasible method for the Nano-JASMINE mission.

Attitude determination and control system for the Nano-JASMINE mission

Abstract Nano-JASMINE (Nano-Japan Astrometry Satellite Mission for INfrared Exploration) is a nano astrometry satellite developed at the ISSL, University of Tokyo. The mission objective is to measure the positions of stars to accuracy of 1.8 milli-arcsecond (mas). In order to obtain accurate astrometry data, the satellite should be stabilized to better than 4 × 10 −7 rad/s, which is difficult to achieve using only conventional sensors. In Nano-JASMINE mission, the attitude will be determined by assessing the quality of the star image observed with the mission telescope. In this research, sequence of each attitude control mode and how to estimate angular velocity in observation phase is focused on. Based on simulation results, the research concludes that the use of star blurred image data to estimate attitude information is a feasible method for use on the Nano-JASMINE mission.