PLANET-C - AbsoluteAstronomy.com

, formerly known as the Venus Climate Orbiter (VCO) and Planet-C, is a Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

ese unmanned spacecraft

Unmanned spacecraft

Unmanned spacecraft are spacecraft without people on board, and probably includes unmanned resupply spacecraft, space probes, and most space observatories. A difference between robotic spacecraft and unmanned spacecraft, is that unmanned spacecraft is inclusive to non-robotic unmanned spacecraft,...

which was intended to explore Venus

Venus

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

. It was launched aboard an H-IIA 202 rocket

H-IIA

H-IIA is an active expendable launch system operated by Mitsubishi Heavy Industries for the Japan Aerospace Exploration Agency . The liquid-fueled H-IIA rockets have been used to launch satellites into geostationary orbit, to launch a lunar orbiting spacecraft, and to launch an interplanetary...

on 20 May 2010, after being delayed because of weather from its initial 18 May scheduled target. The total launch mass of the spacecraft including propellant was 480 kg, 34 kg out of this was scientific instruments. The mission reached Venus on 7 December 2010 (JST) but failed to enter orbit around the planet. It had been intended to conduct scientific research for two or more years from an elliptical orbit ranging from 300 km to 80,000 km from Venus.

Akatsuki is Japan's first planetary exploration mission since the Nozomi probe, which was launched in 1998 but failed to go into a Mars

Mars

Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

orbit in 2003 as planned.

Design

The main bus

Satellite bus

A satellite bus or spacecraft bus is the general model on which multiple-production satellite spacecraft are often based. The bus is the infrastructure of a spacecraft, usually providing locations for the payload .They are most commonly used for geosynchronous satellites, particularly...

is a 1.6 m x 1.6 m x 1.25 m box with two solar arrays, each with an area of 1.4 m² (1.7 sq yd). The solar array panels provide over 1,200 watts of power in Venus orbit.

Propulsion is provided by a 500 newton (N) bi-propellant, hydrazine

Hydrazine

Hydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...

/ nitrogen tetroxide orbital maneuvering engine and 12 mono-propellant hydrazine reaction control thrusters, eight with 23 N thrust and four with 3 N.

Communications is via a 8 GHz X-band 20 W transponder using the 1.6 m slot array high gain dish antenna used for most telemetry data. Akatsuki also has a pair of medium gain horn antennas mounted on turntables and two low gain antennas for command uplink. The medium gain horn antennas will be used for housekeeping data downlink when the high gain antenna is not facing Earth.

Instruments

The scientific payload consists of six instruments including a Lightning and airglow camera (LAC), an ultraviolet imager (UVI), a longwave infrared camera (LIR), a 1-μm

Micrometre

A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...

camera (IR1), a 2-μm camera (IR2), and the radio science (RS) experiment. The five cameras will explore Venus in wavelengths from ultraviolet to the mid-infrared.

The LAC will look for lightning in the visible wavelengths of 552 to 777 nanometers. The LIR will study the structure of high-altitude clouds at a wavelength where they emit heat (10 micrometres). The UVI will study the distribution of specific atmospheric gases such as sulfur dioxide

Sulfur dioxide

Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...

in ultraviolet wavelengths (293 to 365 nanometers). The IR1 will peer through semi-transparent windows in Venus' atmosphere to see heat radiation emitted from Venus' surface rocks (0.9 to 1.01 micrometres) and will help researchers to spot active volcanoes, if they exist. The IR2 will peer through semi-transparent windows in Venus' atmosphere to see heat radiation emitted from the lower reaches of the atmosphere (1.65 to 2.32 micrometres).

Mission

Planned investigations include surface imaging with an infrared camera and experiments designed to confirm the presence of lightning

Lightning

Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...

and to determine whether volcanism

Volcanism

Volcanism is the phenomenon connected with volcanoes and volcanic activity. It includes all phenomena resulting from and causing magma within the crust or mantle of a planet to rise through the crust and form volcanic rocks on the surface....

occurs on the surface.

The budget for this mission is ¥

Japanese yen

The is the official currency of Japan. It is the third most traded currency in the foreign exchange market after the United States dollar and the euro. It is also widely used as a reserve currency after the U.S. dollar, the euro and the pound sterling...

13 billion for the satellite and ¥12 billion (US$100 million) for the launch.

Public relations

There was a public relations campaign held between October 2009 and January 2010 by The Planetary Society and JAXA, to allow individuals to send their name and a message aboard Akatsuki. Names and messages were printed in fine letters on an aluminum plate and placed aboard Akatsuki. 260,214 people submitted names and messages for the mission. Around 90 aluminum plates were created for the spacecraft, including three aluminum plates in which the images of the Vocaloid

Vocaloid

is a singing synthesizer application, with its signal processing part developed through a joint research project between the Pompeu Fabra University in Spain and Japan's Yamaha Corporation, who backed the development financially—and later developed the software into the commercial product...

Hatsune Miku

is a singing synthesizer application with a female persona, developed by Crypton Future Media. It uses Yamaha Corporation's Vocaloid 2 synthesizing technology. The name of the character comes from a fusion of the Japanese for , and future , referring to her position as the first of Crypton's...

and her super deformed

Super deformed

Super deformed or SD is a specific style of Japanese caricature where characters are drawn in an exaggerated way, typically small and chubby, with stubby limbs and oversized heads, to make them resemble small children...

figure Hachune Miku were printed.

Launch

Akatsuki left the Sagamihara Campus on 17 March 2010, and arrived at the Tanegashima Space Center

Tanegashima Space Center

The is one of Japan's space development facilities. It is located on Tanegashima, an island located 115 km south of Kyūshū. It was established in 1969 when the National Space Development Agency of Japan was formed...

's Spacecraft Test and Assembly Building 2 on 19 March. On 4 May, Akatsuki was encapsulated inside the large payload fairing

Payload fairing

Payload fairing is one of the main components of a launch vehicle. The fairing protects the payload during the ascent against the impact of the atmosphere . More recently, an additional function is to maintain the cleanroom environment for precision instruments.Outside the atmosphere the fairing is...

of the H-IIA

H-IIA

rocket that launched the spacecraft, along with the IKAROS

IKAROS

IKAROS is a Japan Aerospace Exploration Agency experimental spacecraft. The spacecraft was launched on 21 May, 2010, aboard an H-IIA rocket, together with the Akatsuki probe and four other small spacecraft...

solar sail

Solar sail

Solar sails are a form of spacecraft propulsion using the radiation pressure of light from a star or laser to push enormous ultra-thin mirrors to high speeds....

, on a 6-month journey to Venus. On 9 May, the payload fairing was transported to the Tanegashima Space Center's Vehicle Assembly Building, where the fairing was mated to the H-IIA launch vehicle itself. The spacecraft was launched on May 20, 2010 at 21:58:22 (UTC

Coordinated Universal Time

Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...

) from the Tanegashima Space Center.

Orbit insertion failure

Akatsuki was planned to initiate orbit insertion operations by igniting the orbital maneuvering engine at 23:49:00 on 6 December UTC. The burn was supposed to continue for 12 minutes, to an initial orbit of 180,000 – 200,000 km apoapsis / 550 km periapsis / 4 days orbital period around Venus.

The orbit insertion maneuver was confirmed to have started on time. But after the expected blackout due to occultation

Occultation

An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy . It can also refer to any situation wherein an object in the foreground blocks from view an object in the background...

by Venus, the communication with the probe did not recover as planned. The probe was found to be in safe-hold mode, spin-stabilized state with 10 minutes per rotation. Due to the low communication speed through low-gain antenna, it took a while to determine the state of probe. JAXA stated on December 8, that the probe's orbital insertion maneuver has failed. At a press conference on 10 December, officials reported that Akatsuki's engines fired for less than 3 minutes, far short of what was required to enter into Venus orbit.

JAXA is developing plans to attempt another orbital insertion burn when the probe returns to Venus in 6 years. This requires placing the probe into a hibernation state to prolong its life beyond the original 4.5 year design. JAXA expressed some confidence in keeping the probe operational, pointing to reduced battery wear, since the probe is orbiting the Sun instead of its intended Venusian orbit.

The Venus Climate Orbiter “AKATSUKI” (PLANET-C) conducted a trial jet thrust of its onboard orbit maneuver engine (OME) twice on September 7 and 14 2011 , but acceleration by the thrust was only about one ninth of expectations, and the generated thrust was also only about 40 Newton. With these results, we found that we cannot gain enough specific impulse for orbit maneuvering by the OME. Also, we suspect that the OME may have gradually been damaged; therefore, we decided not to use the OME. We will carry out the orbit maneuver using the reaction control system (RCS) thruster to meet Venus in 2015. We plan to conduct a peri-Venus orbit maneuver in early November.

External links

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