|Operator||Japan Aerospace Exploration Agency (JAXA)|
|Orbital insertion date||2010-12-06 23:49:00 UTC (anticipated)|
|Launch date||2010-05-20 21:58:22 UTC|
|Carrier rocket||H-IIA 202|
|Launch site||Tanegashima Space Center |
|Mission duration||~2 years |
elapsed: 1 year, 3 months and 26 days
|Homepage||Venus Climate Orbiter|
|Mass||320 kg (710 lb)|
|Apoapsis||79,000 km (49,000 mi)|
|Periapsis||300 km (190 mi)|
|Orbital period||30 hours|
Akatsuki (あかつき, 暁, literally "dawn"), formerly known as the Venus Climate Orbiter (VCO) and Planet-C, is a Japanese unmanned spacecraft which was intended to explore Venus. It was launched aboard an H-IIA 202 rocket 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.
The mass of the spacecraft is 640 kg (1,400 lb), including 320 kg (710 lb) of propellants and 34 kg (75 lb) of scientific instruments.
The main bus 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 m (15 sq ft). 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 / 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.
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 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 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).
The budget for this mission is ¥13 billion (US$110 million) for the satellite and ¥12 billion (US$100 million) for the launch.
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 Hatsune Miku and her super deformed figure Hachune Miku were printed.
Akatsuki left the Sagamihara Campus on 17 March 2010, and arrived at the Tanegashima Space Center's Spacecraft Test and Assembly Building 2 on 19 March. On 4 May, Akatsuki was encapsulated inside the large payload fairing of the H-IIA rocket that launched the spacecraft, along with the IKAROS solar sail, 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) 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 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.
- JAXA Akatsuki Planet-C page
- JAXA Akatsuki Special Site
- Planet-C page (Solar Terrestrial Physics Group)
- JAXA/ISAS Planet-C site
- Presentation about Planet-C from the VEXAG meeting in November 2005 (PDF, 2.7 MB)
- Exploring the Venusian Atmosphere - Planet-C Venus Climate Orbiter
- Vieru, Tudor. "JAXA Gets Ready to Launch Venus Probe". Softpedia. http://news.softpedia.com/news/JAXA-Gets-Ready-to-Launch-Venus-Probe-137518.shtml. Retrieved 30 March 2010.
- Venus Climate Orbiter "AKATSUKI" (PDF, 1.72 Mb)
Retrieved from : http://en.wikipedia.org/wiki/Akatsuki_(spacecraft)