Experimental Study for Synthetic Aperture Telescope Using Formation Flying Micro-Satellites for High-Frequency and High-Resolution GEO Remote Sensing

Earth remote sensing from geostationary orbit (GEO) realizes high time resolution that is essential for disaster monitoring; however, the spatial resolution is commonly worse than observation from low Earth orbit. In order to achieve high-resolution and high-frequency GEO remote sensing, we have proposed a “Formation Flying Synthetic Aperture Telescope (FFSAT)” with multiple micro-satellites. The FFSAT can improve the spatial resolution by using the technique of a synthetic aperture, and therefore the relative positions and attitudes between the optical units of each satellite must be controlled with an accuracy better than 1/10 of the observation wavelength. In order to verify feasibility of such highly accurate control, the characteristics of sensors and actuators which are essential for an ultra-high-accuracy formation flying were numerically modeled. We consider control laws for keeping the relative position and attitude of the μm-class formation flying using the high-precision simulator built on the numerical models. In addition, the cooperative control of the piezo stages and the thrusters is studied to reduce the fuel consumption of the FFSAT system. The simulation results made the FFSAT mission more feasible

On-Orbit Operation Results of the World\u27s First CubeSat XI-IV – Lessons Learned from Its Successful 15-years Space Flight

In recent years, the size and cost of satellites have been reduced, and the frequent launch of satellites have been realized even by small private companies and universities. The first step of this big wave was the first successful launch of CubeSats, 1kg nano-satellites, in June 2003. One of the CubeSats was XI-IV, which was developed by Intelligent Space Systems Laboratory (ISSL) of the University of Tokyo. Its mission was the world’s first on-orbit demonstration of the CubeSat bus system. Due to the spatial, power and cost constraints, most of the bus system was composed of low-cost COTS parts, and a “cross-check” type fault redundancy system against the radiation effects was implemented to achieve as better reliability as possible within the resource constraints. Since the successful launch by the ROCKOT launch vehicle from Russia, the satellite has been in normal operation for over fifteen years since the launch (as of June 2019). The operation has been jointly conducted by the University of Tokyo and amateur radio operators in Japan. This paper reports its more-than-15-years world\u27s longest CubeSat operation results and the lessons learned from it

Satellite Software Development Framework With Rust That Improves Developer Enablement

Our challenge: developing various satellites with a small team in a short perio

Modeling of piezoelectric actuator's hysteresis and its effect on the control accuracy of a LEO-to-GEO laser-communication for a small satellite

Compared to conventional large satellites in the past, small satellite classes (less than 150 kg) show their advantages for mass production, such as short time and low cost for development and launch, to cope with the demand for emerging missions that require a sufficient number of satellites in orbit. However, the traditional communication method, in which a low earth orbit (LEO) small satellite sends data to a ground station using radio frequency, has several disadvantages. Firstly, the limitation of radio-frequency bandwidth leads to a low data rate and difficulty in getting a frequency license. Secondly, there is a significant delay during which data cannot be sent to the ground due to lacking a line of sight between the LEO satellite and the ground station. Additionally, the duration time for the small satellite to communicate with the ground station is just less than 10 minutes approximately. To resolve the above issues, we investigate the case that a less-than-150-kg satellite carries out a laser communication link from LEO to a satellite in geostationary orbit (GEO). Due to the constraints of size, weight, and power (SWaP), traditional bulky LEO-GEO relay systems cannot be applied for the small satellite. However, using the combination of the satellite body pointing and a piezo Fast-Steering Mirror (FSM), which reduces the SWaP considerably, makes it feasible that the LEO-to-GEO communication can be implemented in a small satellite for the first time. While utilizing laser communication can increase the data rate, the relay communication via the GEO satellite helps the small satellite to extend the communication duration significantly. Moreover, since there is a line of sight between the two terminals in any of about 15 orbits per day of the LEO satellite, data taken by the small satellite can be downloaded to the ground via the GEO one in almost real time. This research aims at investigating and proving the feasibility of a small satellite to transmit a laser communication link to its GEO counterpart. In this paper, we describe the LEO-to-GEO laser communication of the small satellite with a study of pointing-budget and link-budget analysis. Furthermore, a hardware-based simulation of the fine control mechanism is conducted. The hysteresis that affects severely to the piezo mechanism, and hence, the final control accuracy, is modeled accurately and its effect is shown