Satellite Systems
Venus Climate Orbiter "AKATSUKI" (PLANET-C)
The Venus Climate Orbiter AKATSUKI is the first Japanese orbiter to explore Venus and the world's first planetary meteorological satellite.
AKATSUKI's mission is to investigate the movements of the Venusian atmosphere and to establish Venusian meteorology and comparative planetary meteorology.
Under the direction of JAXA, NEC is participating in the total system development, manufacturing, and testing for AKATSUKI.
AKATSUKI's mission
Venus and Earth have roughly the same size and weight.
By gaining a thorough understanding of Venus, we can deepen our understanding of Earth.
There are still unanswered questions about how the atmospheric circulation of Venus works. The rotational speed of the Venusian atmosphere is 60 times that of Venus itself, a phenomenon called a super rotation. AKATSUKI's main mission is to investigate the mysterious Venusian atmosphere.
Characteristics of AKATSUKI's mission
By using cameras that use various wavelengths to simultaneously capture images of Venusian clouds at various altitudes, it is possible to gain an understanding of the 3D movement of the clouds.
AKATSUKI will travel along an elliptical orbit approximately over Venus's equator. At its closest, AKATSUKI will be approximately 300 km away from Venus, and, at its most distant, the orbiter will be approximately 80,000 km away.
- When AKATSUKI is at its most distant point from Venus, the orbiter will move in synchronization with the Venusian atmosphere to observe changes in the same cloud over a long period of time.
- When AKATSUKI is at its closest point to Venus, the orbiter will change its relative positional relationship with the Venusian atmosphere and move over different atmospheric locations.
96% of the Venusian atmosphere is carbon dioxide. Due to the greenhouse effect caused by this gas, the temperature of the surface is a scalding 460属C. By investigating the Venusian atmosphere, we might be able to determine how to effectively handle Earth's global warming if it becomes worse in the future. We hope AKATSUKI's observational data is also useful for understanding Earth's global warming process.
AKATSUKI's technology
As the AKATSUKI system integrator, NEC has played a major role in the AKATSUKI project, including system design, since the early planning stages.
In addition, during the manufacturing phase, NEC not only designed and manufactured the structural and temperature systems, but also designed and manufactured bus equipment including the power system, communication system, data processing system, and attitude orbit control system. Furthermore, NEC developed mission equipment including the ultraviolet imager (UVI) and long wave infrared camera (LIR).
Bus equipment characteristics
- Overall bus system
- By handling the three panels on which the main equipment is installed as one unit, NEC wired the electrical system instrumentation (cables) without relay connectors, thereby reducing the weight of the overall bus system.
- Structural system
- NEC used a thrust tube incorporating an aluminum honeycomb core and CFRP skin as the main load path (main structure) to reduce the weight of the system.
- SAP (Solar Array Paddle)
- NEC developed a solar array paddle that is resistant to high and low temperatures and can withstand twice the sunlight intensity of that on Earth.
- Temperature control system
- To supply the required electrical power by using the SAPs, which were reduced in size to lighten the orbiter, NEC used software capable of leveling out the heater power supply and preventing peak power output.
- Power system
- NEC used a series switching regulator that makes it possible to always output the peak power even if the distance to the sun and solar cell voltage change. In addition, NEC developed two secondary lithium ion batteries for the orbiter; each consists of 11 cells in series and has an electric charge of 23.5 Ah.
- Communication system
- NEC used a radial line slot antenna as the X-band high gain antenna to avoid light condensing and reduce the weight of the system. In addition, NEC used a small, lightweight 20 W traveling wave tube amplifier as the main power amplifier.
- Data processing system
- NEC used an on demand telemetry method that makes it possible to freely output desired telemetry data within the previously determined range. In particular, this makes it possible, by defining report packets, to output short packets indicating changes in the orbiter status in order to collect and check data at the start of communication. The AKATSUKI data processing can also be automated with a high degree of freedom.
- Attitude orbit control system
- NEC used a three-axis attitude control system that determines the attitude by using a combination of various attitude sensors (two star trackers, three inertial reference units, a fine sun sensor, and five coarse sun sensors) and controls the attitude by using four diagonally placed reaction wheels. This configuration is made highly reliable by its advanced failure detection, isolation, and recovery features.
- Mission system
- NEC developed DE (Digital Electronics) that control four cameras and perform image processing. Through integration with a DR (Data Recorder), high-speed image recording is also possible. NEC also utilized the design of its general use bolometer camera to develop the long wave infrared camera (LIR). NEC also developed an ultraviolet imager (UVI) with a filter wheel.
- Operation planning system
- This system provides a visual display of Venus and the direction to Earth as seen from the orbiter, prompts the user to specify the observation and communication details, and generates operation procedures, macro commands, and timelines (absolute time specified command lines) based on various constraints (including constraints on the power, communication link, and attitude).
Description of mission equipment
Long wave infrared camera (LIR)
This camera uses infrared rays that have a wavelength of 10µm to create an image of the cloud temperature, and to clarify undulations and convection currents in the upper cloud layer, as well as the wind speed distribution at the cloud-top altitude on the night side.
Earth taken by the LIR
Ultraviolet imager (UVI)
This imager determines the wind speed distribution at the cloud-top altitude based on both variations in the distribution of sulfur dioxide included in clouds and the distribution of unknown chemicals that have absorptive properties at ultraviolet wavelengths captured using ultraviolet rays.
Earth taken by the UVI (artificially colored)
AKATSUKI's status
AKATSUKI is currently well on its way to Venus. The orbiter should be closest to Venus and enter its orbit on December 7th.
Top of this page
