iQPS use of DMU30 in satellites

Silicon Sensing’s DMU30 Inertial Measurement Unit (IMU) successfully monitoring iQPS’s Small SAR Satellite’s Control System in Low Orbit

Earlier this year, Silicon Sensing reported the selection and integration of its DMU30 inertial measurement unit (IMU) by the Institute for Q-shu Pioneers of space, Inc (iQPS) of Fukuoka, Japan. This was for the company’s first small synthetic aperture radar (SAR) satellite named Izanagi, which is preceding a full constellation of 36 satellites. After a successful launch and deployment in low orbit, Silicon Sensing’s DMU30 IMU is playing its critical role within the Satellite’s control system; monitoring its angular velocity and attitude angle in low orbit. Silicon Sensing took the time to speak with Masahiko Uetsuhara, Project Manager from iQPS, to learn a little bit more about their programme, and how the DMU30 fits in.

Silicon Sensing: Could you briefly explain the purpose and importance of your programme?

Masahiko Uetsuhara, Project Manager, iQPS: Currently, we are aiming for a near real-time data provision service using 36 QPS small SAR satellites. On 11th December 2019, the first QPS small SAR satellite ‘Izanagi’ was launched and started operation, and in 2020, the second unit ‘Izanami’ is planned to be launched. There are optical satellites that use cameras that use visible light, and SAR satellites that use radio waves as artificial satellites for acquiring images on the earth. It is difficult for optical satellites to observe the night-time and cloud areas that occupy about 75% of the earth, but SAR satellites are capable of observing even in bad weather – day or night. In general, SAR satellites require a large antenna and a large amount of power, so miniaturisation is difficult and enormous cost and resources are required to launch multiple satellites and observe the earth frequently. Under such circumstances, our company was able to develop a small SAR satellite of about 100 kg while having a high resolution of 1m by developing a large antenna that is highly packable and lightweight. Our satellite provides great wide-ranging potential for business use, including areas such as forest monitoring and infrastructure management.

Silicon Sensing: What made you choose the DMU30 for this application?

iQPS: Normally, an analogue gyro sensor causes errors due to the influence of temperature and continuous operation, but if you use the DMU30, you can perform calibration when converting from analogue to digital, so you can use it with confidence. That is a big reason. We know that your product has been used in satellite projects before, and we trust that it is reliable, and that the price was also attractive for this performance gyro sensor because, not having to calibrate it ourselves reduces man-hours, improves work efficiency and is really appreciated.

Silicon Sensing: What made you choose MEMS technology over Fibre Optic Gyro (FOG) or Ring Laser Gyro (RLG)?

iQPS: The additional cost to benefit ratio of those technologies (the angular velocity measurement accuracy obtained at the additional cost) is less than that of the DMU30.

Silicon Sensing: What is the exact function the DMU30 performs on the satellite?

iQPS: Satellite attitude angular velocity measurement and attitude angle estimation assistance. It provides an estimate of rocking when releasing a deployable structure (antenna, etc.)

Silicon Sensing: What key factors helped drive your selection of DMU30?

iQPS: Cost, and the fact that it is already calibrated and ITAR free were important elements.

Silicon Sensing: How do you predict that your requirements (and that of the wider space sector) for inertial sensing technology will change over this decade?

iQPS: Increasing demand for high-precision and high-frequency earth observation missions with fast attitude changes. For example, high-frequency earth observation while optical communication is performed between satellites and satellite ground.

Silicon Sensing: Did you encounter any technical challenges during the integration of the DMU30?

iQPS: There were no particular issues that we faced.

Silicon Sensing: What is the external environment and temperature when the DMU30 operates in low orbit?

iQPS: DMU30 is located in the satellite structure. There is no heating element surrounding it. The orbit around which the satellite orbits is a circular one with an altitude of 550 km and an orbital inclination of 37 degrees. The temperature the satellite is exposed to can be as low as -100°C.

Silicon Sensing: At what point during the launch, until reaching orbit, does DMU30 start to operate as part of your system?

iQPS: Soon after the satellite separation, the unit is powered on. The DMU30 was first used in the detumbling operation, this was in order to stabilise the satellite’s motion caused by the shock of the separation from the rocket. The DMU30 performed well in monitoring the satellite’s tumbling state throughout the whole activity. After commissioning the satellite operation, DMU30 is used in combination with actuators such as reaction wheel and magnetic torque along with external sensors for example star tracker, sun sensor, geomagnetic sensor, etc.

Silicon Sensing: Thank you for taking the time to answer our questions.

DMU11 enables Precision Agriculture

DMU11, the latest miniature Inertial Measurement Unit (IMU) from Silicon Sensing Systems Limited, is now in full production and has been selected by Agrifac Machinery BV for use in their latest cropsprayer, the MountainMasterPlus.

DMU11 is the latest in a family of high performance IMUs, offering market-leading inertial sensing capability in a cost-effective OEM package, and aimed at high volume industrial applications like Smart Agriculture. With each silicon MEMS sensor being made by Silicon Sensing in their foundry in Japan, the DMU11 combines three rotation rate sensors with six linear accelerometers. Sophisticated processing is included, allowing each unit to be individually calibrated to optimise its performance over a wide temperature range. Communication is via an industry standard RS422 link.

In Agrifac’s crop-sprayer application, their StabloPlus chassis controls the ride height of each wheel individually, enabling the cab to stay horizontal on steep slopes whilst the spraying boom maintains a fixed height over the crops. DMU11 plays a key role in these control loops, providing reliable real-time inertial data in a challenging real-world environment.

Key performance parameters of the DMU11 are:

  • Dynamic Range ±300°/s and ±10g
  • Bias Instability <10°/hr and 0.05mg
  • Random Walk <0.4°/rt hr and 0.05m/s

Silicon Sensing has a long heritage in the gyroscope marketplace; predecessor companies can be traced back to the first production of rotating gyroscopes for navigation – over 100 years ago. Recently, Silicon Sensing has been leveraging the inherent high performance capability of their particular MEMS sensors with a series of high-performance gyros and IMUs for a diverse range of applications, including autonomous self-driving vehicles.

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