The Akatsuki spacecraft, also known as the Venus Climate Orbiter (VCO) or Planet-C, is a Japanese space probe launched by the Japan Aerospace Exploration Agency (JAXA) to study Venus. It was part of Japan’s planetary exploration program and was designed to explore Venus’ atmosphere, weather patterns, and potential volcanic activity.
The Akatsuki Venus Orbiter marked Japan’s first successful planetary mission. Notably, after an initial failure to enter orbit around Venus, JAXA engineers successfully maneuvered the spacecraft into orbit in 2015 using its secondary thrusters—a remarkable achievement in spacecraft recovery.
Since then, Akatsuki has provided valuable insights into Venus’ climate, offering the most detailed look at the planet’s complex atmospheric phenomena. Its innovative suite of cameras and sensors has captured stunning images and data on cloud movement, thermal emissions, and possible volcanic activity. Akatsuki has become a symbol of resilience in space exploration, overcoming a major setback to continue contributing to scientific understanding.
Design and Construction
The design of the Akatsuki spacecraft incorporates a compact, efficient configuration that allows for maximum functionality with limited mass and volume.
The spacecraft is box-shaped, approximately 1.04 meters wide, 1.45 meters high, and 1.40 meters deep, and it weighs about 517 kilograms, including its fuel. One of the key design features is its use of solar panels to generate power, with two large, deployable wings that provide about 500 watts of power to operate its instruments and communication systems. Akatsuki’s body is constructed from lightweight aluminum alloys and carbon fiber-reinforced plastic, designed to endure the harsh conditions of space, including the intense heat and radiation near Venus.
A major engineering challenge during the development of Akatsuki was creating a propulsion system capable of inserting the spacecraft into Venus’ orbit, especially since the planet’s gravity and atmospheric conditions are extremely different from Earth’s.
The probe was equipped with a dual-mode chemical propulsion system designed to handle both large orbital insertion burns and fine adjustments. However, the failure of its main engine during the first orbit attempt necessitated innovative solutions. JAXA engineers creatively repurposed the attitude control thrusters to perform a second orbit insertion, showcasing Akatsuki’s resilient design. The spacecraft’s high-gain antenna ensures efficient data transmission, while its onboard thermal control systems regulate the temperature to protect its sensitive instruments from Venus’ extreme heat.
Mission Objectives
The primary mission objective of Akatsuki is to study the atmosphere of Venus in detail, particularly focusing on the phenomenon of super-rotation, where Venus’ upper atmosphere rotates much faster than the planet itself. The spacecraft seeks to understand how such fast-moving winds are generated and sustained, along with their implications for Venus’ climate. Another key goal is to map the cloud structure and investigate how the thick layers of sulfuric acid clouds behave, both on a small scale and over time.
Additionally, Akatsuki aims to explore thermal dynamics, observing heat distribution across the planet and determining how much heat is emitted from the surface. One of its significant secondary objectives is to search for evidence of volcanic activity on Venus, as the planet is thought to have active volcanoes under its dense atmosphere. Akatsuki also studies lightning and atmospheric phenomena, such as airglow, which can offer clues about the planet’s electrical environment and atmospheric composition. By providing continuous observations of Venus’ weather systems, Akatsuki helps scientists understand how Venus’ atmospheric conditions compare to Earth’s, giving crucial insights into planetary atmospheres in general.
Launch and Deployment
Akatsuki was launched aboard an H-IIA rocket on May 20, 2010, from the Tanegashima Space Center in Japan. The launch vehicle, a reliable workhorse of JAXA, delivered Akatsuki successfully into space for its journey to Venus. However, during the spacecraft’s initial orbital insertion attempt in December 2010, a critical malfunction occurred. Akatsuki’s main engine failed to fire as planned, causing it to miss the opportunity to enter Venus’ orbit. The spacecraft entered a heliocentric orbit instead, prompting JAXA engineers to initiate a recovery plan.
After careful analysis, the mission team discovered that Akatsuki’s attitude control thrusters could be used for a secondary attempt at orbital insertion. In a remarkable feat of engineering, JAXA successfully used these smaller thrusters to perform the delicate maneuvers required.
On December 7, 2015, five years after the original failure, Akatsuki was successfully inserted into an elliptical orbit around Venus. This was a major milestone, as it marked the first time a spacecraft had been recovered in such a manner. Since then, Akatsuki has made several key discoveries, including detecting large atmospheric gravity waves and capturing detailed thermal images of Venus’ thick cloud cover.
Technical Specifications
- Dimensions: 1.04 m x 1.45 m x 1.4 m (without solar panels)
- Weight: 517 kg (including fuel)
- Propulsion: Dual-mode chemical propulsion system with backup attitude control thrusters
- Power: Solar panels generating approximately 500 watts, supplemented by onboard lithium-ion batteries
- Instruments:
- Ultraviolet Imager (UVI): Observes ultraviolet wavelengths to study the cloud structure.
- 1 µm Camera (IR1): Focuses on near-infrared wavelengths for surface and lower atmosphere observations.
- 2 µm Camera (IR2): Studies the middle and upper atmosphere using infrared imaging.
- Longwave Infrared Camera (LIR): Measures thermal emissions to monitor Venus’ heat dynamics.
- Lightning and Airglow Camera (LAC): Detects lightning and faint airglow phenomena in Venus’ atmosphere.
Current Status
As of 2024, Akatsuki remains operational and continues to collect valuable data on Venus’ atmosphere and surface. It operates in a highly elliptical orbit, which allows it to observe the planet’s atmosphere from varying distances, providing a broad perspective on weather patterns and cloud movements.
Despite its initial challenges, Akatsuki has exceeded expectations by offering significant insights into the dynamics of Venus’ atmosphere, such as the discovery of stationary gravity waves and detailed thermal mapping.
Though Akatsuki’s mission was initially planned to last for a couple of years, the spacecraft is now in its extended mission phase. It remains in contact with Earth, relaying scientific data and images.
