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Akatsuki (spacecraft)

anime spacecraft, akatsuki spacecraft diagram of how it works
Akatsuki あかつき, 暁, "Dawn", also known as the Venus Climate Orbiter VCO and Planet-C, is a Japanese JAXA space probe tasked to study the atmosphere of Venus It was launched aboard an H-IIA 202 rocket on 20 May 2010,6 and failed to enter orbit around Venus on 6 December 2010 After the craft orbited the Sun for five years, engineers placed it into an alternative elliptical Venusian orbit on 7 December 2015 by firing its attitude control thrusters for 20 minutes4578 By using five different cameras, Akatsuki will study the stratification of the atmosphere, atmospheric dynamics, and cloud physics910 Astronomers working on the mission reported detecting a possible gravity wave that occurred on the planet Venus in December 201511

Contents

  • 1 Mission
    • 11 Spacecraft design
    • 12 Instruments
  • 2 Public relations
  • 3 Operations
    • 31 Launch
    • 32 Orbit insertion failure
    • 33 Recovery efforts
    • 34 Orbit insertion
    • 35 Status
    • 36 Science
  • 4 See also
  • 5 References
  • 6 External links

Missionedit

Akatsuki is a Japanese space mission to the planet Venus Planned observations include cloud and surface imaging from an orbit around the planet with an infrared camera, which are aimed at investigation of the complex Venusian meteorology Other experiments are designed to confirm the presence of lightning and to determine whether volcanism occurs currently on Venus12 In most planets, the atmosphere circulates much slower than the rotation speed of the planet However, on Venus, while the planet rotates at 6 km/h at the equator, the atmosphere spins around the planet at 300 km/h

Akatsuki is Japan's first planetary exploration mission since the failed Mars orbiter Nozomi probe which was launched in 1998 Akatsuki was originally intended to conduct scientific research for two or more years from an elliptical orbit around Venus ranging from 300 to 80,000 km 190 to 49,710 mi in altitude,1 but its alternate orbit, yet to be characterized, had to be highly elliptical The budget for this mission is ¥146 billion US$174 million for the satellite and ¥98 billion US$116 million for the launch13

Spacecraft designedit

The main bus is a 145 × 104 × 144 m 48 × 34 × 47 ft box with two solar arrays, each with an area of about 14 m2 15 sq ft The solar arrays provide over 700 W of power in Venus orbit The total mass of the spacecraft at launch was 5176 kg 1,141 lb1 The mass of the science payload is 34 kg 75 lb14

Propulsion is provided by a 500-newton 110 lbf bi-propellant, hydrazine-dinitrogen tetroxide orbital maneuvering engine and twelve mono-propellant hydrazine reaction control thrusters, eight with 23 N 52 lbf of thrust and four with 3 N 067 lbf It is the first spacecraft to use a ceramic silicon nitride retrofire thruster The total propellant mass at launch was 1963 kg 433 lb1

Communication is via an 8 GHz, 20-watt X-band transponder using the 16 m 5 ft 3 in high-gain antenna The high-gain antenna is flat to prevent heat from building up in it10 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 are used for housekeeping data downlink when the high-gain antenna is not facing Earth1

Instrumentsedit

The scientific payload consists of six instruments The five imaging cameras will explore Venus in wavelengths from ultraviolet to the mid-infrared:1516

  1. the Lightning and Airglow Camera LAC will look for lightning in the visible wavelengths of 552 to 777 nanometers
  2. the ultraviolet imager UVI will study the distribution of specific atmospheric gases such as sulfur dioxide in ultraviolet wavelengths 293–365 nm
  3. the longwave infrared camera LIR will study the structure of high-altitude clouds at a wavelength where they emit heat 10 μm
  4. the 1 μm camera IR1 will image heat radiation emitted from Venus's surface rocks 090–101 μm and will help researchers to spot active volcanoes, if they exist
  5. the 2 μm camera IR2 will detect heat radiation emitted from the lower reaches of the atmosphere 165–232 μm
  6. the Ultra-Stable Oscillator USO for high precision measurement of distance and communication

Public relationsedit

A public relations campaign was held between October 2009 and January 2010 by the Planetary Society and JAXA, to allow individuals to send their name and a message aboard Akatsuki1718 Names and messages were printed in fine letters on an aluminium plate and placed aboard Akatsuki17 260,214 people submitted names and messages for the mission19 Around 90 aluminium plates were created for the spacecraft,20 including three aluminium plates in which the images of the Vocaloid Hatsune Miku and her super deformed figure Hachune Miku were printed21

Operationsedit

Launchedit

The launch of Akatsuki

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 itself22

The spacecraft was launched on 20 May 2010 at 21:58:22 UTC from the Tanegashima Space Center,12 after being delayed because of weather from its initial 18 May scheduled target23

Orbit insertion failureedit

Akatsuki was planned to initiate orbit insertion operations by igniting the orbital maneuvering engine at 23:49:00 on 6 December 2010 UTC22 The burn was supposed to continue for twelve minutes, to an initial Venus orbit with an apoapsis of 180,000 to 200,000 km 110,000 to 120,000 mi, a periapsis of 550 km 340 mi, and a four-day orbital period24

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 ten minutes per rotation25 Due to the low communication speed through the low-gain antenna, it took a while to determine the state of the probe26 JAXA stated on 8 December that the probe's orbital insertion maneuver had failed2728 At a press conference on 10 December, officials reported that Akatsuki's engines fired for less than three minutes, far less than what was required to enter into Venus orbit29 Further research found that the likely reason for the probe malfunction was salt deposits jamming the valve between the helium pressurization tank and the fuel tank As a result, engine combustion became oxidizer-rich, with resulting high combustion temperatures damaging the combustion chamber throat and nozzle A similar vapor leakage problem destroyed the NASA Mars Observer probe in 199330

As a result, the probe was in a heliocentric orbit, rather than Venus orbit Since the resulting orbit had an orbital period of 203 days,31 shorter than Venus' orbital period of 225 days, the probe drifted around the sun compared to Venus

Recovery effortsedit

JAXA developed plans to attempt another orbital insertion burn when the probe returned to Venus in December 2015 This required placing the probe into "hibernation" or safe mode to prolong its life beyond the original 45-year design JAXA expressed some confidence in keeping the probe operational, pointing to reduced battery wear, since the probe was then orbiting the Sun instead of its intended Venusian orbit32

Telemetry data from the original failure suggested that the throat of its main engine, the orbit maneuver engine OME was still largely intact, and trial jet thrusts of the probe's onboard OME were performed twice, on 7 and 14 September 201122 However, the thrust was only about 40 newtons 90 lbf, which was 10% of expectations Following these tests, it was determined that insufficient specific impulse would be available for orbital maneuvering by the OME It was concluded that the remaining combustion chamber throat was completely destroyed by transient ignition of the engine As a result, the selected strategy was to use four hydrazine attitude control thrusters, also called reaction control system RCS, to drive the probe into orbit around Venus Because the RCS thrusters do not need oxidiser, the remaining 65 kg of oxidiser MON was vented overboard in October 2011 to lighten the spacecraft30

Three peri-Venus orbital maneuvers were executed on 1 November,12 10 and 21 November 2011 using the RCS thrusters A total delta-v of 2438 m/s was imparted to the spacecraft Because the RCS thrusters' specific impulse is low compared to the specific impulse of the OME, the previously planned insertion into low Venusian orbit became impossible Instead, the new plan was to place the probe in a highly elliptical orbit with an apoapsis of a hundred thousand kilometers and a periapsis of a few thousand kilometers from Venus Engineers planned for the alternate orbit to be prograde in the direction of the atmospheric super-rotation and lie in the orbital plane of Venus The method and orbit were announced by JAXA in February 2015, with an orbit insertion date of 7 December 201533 The probe reached its most distant point from Venus on 3 October 2013 and had been approaching the planet since then34

Orbit insertionedit

After performing the last of a series of four trajectory correction maneuvers between 17 July and 11 September 2015, the probe was established on a trajectory to fly past Venus on 7 December 2015, when Akatsuki would make a maneuver to enter Venus orbit after a 20-minute burn with four thrusters that were not rated for such a hefty propulsive maneuver4535 Instead of taking about 30 hours to complete an orbit around Venus—as was originally planned—the new orbit targeted would place Akatsuki in a nine-day orbit after an adjustment in March 20163

After JAXA engineers measured and calculated its orbit following the December 7 orbital insertion, JAXA announced on December 9 that Akatsuki had successfully entered the intended elliptical orbit, as far as 440,000 km 270,000 mi from Venus, and as close as 400 km 250 mi from Venus's surface with an orbital period of 13 days and 14 hours36

A follow-up thruster burn on 26 March 2016 lowered Akatsuki's apoapsis to about 330,000 km 210,000 mi and shortened its orbital period from 13 to 9 days3

Statusedit

The orbiter started its two-year period of "regular" science operations in mid-May 201637

Since 9 December 2016, two infrared cameras 1-μm and 2-μ are unavailable for observation due to electronic device failure38

Scienceedit

Soon after insertion in December 2015 and in "a few glimmers in April and May" 2016 the craft's instruments recorded a "bow-shape feature in the atmosphere stretching 6,000 miles, almost pole to pole — a sideways smile" Scientists on the project termed the feature a "gravity wave" in the planet's winds above Aphrodite Terra, "a highland region about the size of Africa that rises up to three miles from the surface"11

See alsoedit

  • Spaceflight portal
  • IKAROS, solar sail demonstrator, launched along with Akatsuki
  • List of missions to Venus
  • Nozomi Planet-B, 1998 Mars mission did not enter orbit
  • Sakigake, Japan's first interplanetary probe, 1985
  • Suisei Planet-A
  • Venus probes

Referencesedit

  1. ^ a b c d e f Takeshi, Oshima; Tokuhito, Sasaki "Development of the Venus Climate Orbiter PLANET-C AKATSUKI" NEC Technical Journal 6 1: 47–51 
  2. ^ Stephen Clark 20 May 2010 "H-2A Launch Report – Mission Status Center" Spaceflight Now Archived from the original on 20 May 2010 Retrieved 20 May 2010 
  3. ^ a b c "Japanese probe fires thrusters in second bid to enter Venus orbit" The Japan Times 7 December 2015 Retrieved 7 December 2015 
  4. ^ a b c Szondy, David "Akatsuki probe enters orbit around Venus" Retrieved 7 December 2015 
  5. ^ a b c Clark, Stephan "Japanese probe fires rockets to steer into orbit at Venus" Retrieved 7 December 2015 
  6. ^ Chris Bergin 20 May 2010 "AXA H-IIA carrying Akatsuki and IKAROS launches at second attempt" NASASpaceFlight Retrieved 19 November 2010 
  7. ^ Limaye, Sanjay "Live from Sagamihara: Akatsuki Orbit Insertion – Second Try" Retrieved 7 December 2015 
  8. ^ Wenz, John 21 September 2015 "Japan's Long Lost Venus Probe May Boom Back to Life" Popular Mechanics Retrieved 14 October 2015 
  9. ^ Nakamura, N; et al May 2011 "Overview of Venus orbiter, Akatsuki" Earth, Planets and Space 63 5: 443–457 ISSN 1880-5981 doi:105047/eps201102009 
  10. ^ a b "Exploring the Venusian Atmosphere – AKATSUKI/PLANET-C" Akatsuki Special Site Retrieved 5 December 2015 
  11. ^ a b Chang, Kenneth 16 January 2017 "Venus Smiled, With a Mysterious Wave Across Its Atmosphere" New York Times Retrieved 17 January 2017  Including link to Tetsuya Fukuhara et al, "Large stationary gravity wave in the atmosphere of Venus" preview/subscription, Nature Geoscience via NYTimes link, 16 January 2017
  12. ^ a b c "AKATSUKI orbit control at perihelion" JAXA 1 November 2011 Retrieved 3 December 2011 
  13. ^ Staff writers 8 December 2010 "Japan probe shoots past Venus, may meet again in six years" Spacedailycom Retrieved 3 December 2011 
  14. ^ "Mission overview" PLANET-C Team/JAXA Retrieved 3 December 2011 
  15. ^ "Akatsuki Venus Climate Orbiter / Planet-C" The Planetary Society Retrieved 19 November 2010 
  16. ^ Nakamura, Masato; Imamura, Takeshi; Ueno, Munetaka; et al "Planet-C: Venus Climate Orbiter mission of Japan" pdf Planetary and Space Science 55 12: 1831–1842 Bibcode:2007P&SS551831N doi:101016/jpss200701009 
  17. ^ a b "Messages From Earth: Send your Message to Venus on Akatsuki" The Planetary Society 2010 Archived from the original on 7 April 2010 Retrieved 2 April 2010 
  18. ^ "We will deliver your message to the bright star Venus – Akatsuki Message Campaign" JAXA Retrieved 19 November 2010 
  19. ^ "AKATSUKI Message Campaign" JAXA 2010 Retrieved 2 April 2010 
  20. ^ 金星へ届け! 県民が寄せ書き Hoping that It Will Reach Venus! Residents of The Prefecture Write Something Together in Japanese Oita Godo Shimbum 17 May 2010 Retrieved 20 July 2010 
  21. ^ "打ち上げを目前に控えた「あかつき」と「IKAROS」の機体が公開" The Airframes of "Akatsuki" And "IKAROS" just before Those Launch Are Opened Mycom Journal in Japanese Mainichi Communications 12 March 2010 Retrieved 20 July 2010 
  22. ^ a b c "Venus Climate Orbiter "AKATSUKI" PLANET_C: Topics" JAXA 1 November 2011 Retrieved 3 December 2011 
  23. ^ "Launch of Venus probe Akatsuki postponed due to bad weather" Japan Today 18 May 2010 Retrieved 19 November 2010 
  24. ^ 来月7日に金星周回軌道へ=あかつき、エンジン噴射−7年前は火星で失敗・宇宙機構 Jijicom in Japanese Jiji Press 18 November 2010 Retrieved 5 December 2010 
  25. ^ 金星探査機「あかつき」の状況について About the State of Venus Probe Akatsuki PDF in Japanese 7 December 2010 Retrieved 7 December 2010 
  26. ^ JAXA's press briefing, 22:00, 7 December 2010 JST
  27. ^ "Japan's Venus Probe Fails to Enter Orbit" ABC News Retrieved 8 December 2010 
  28. ^ "Akatsuki Mission statement" The Planetary Society Retrieved 8 December 2010 
  29. ^ David Cyranoski 14 December 2010 "Venus miss is a setback for Japanese programme" Nature Retrieved 21 December 2010 
  30. ^ a b Nakamura, M; Kawakatsu, Y; Hirose, C; Imamura, T; Ishii, N; Abe, T; Yamazaki, A; Yamada, M; Ogohara, K; Uemizu, K; Fukuhara, T; Ohtsuki, S; Satoh, T; Suzuki, M; Ueno, M; Nakatsuka, J; Iwagami, N; Taguchi, M; Watanabe, S; Takahashi, Y; Hashimoto, G L; Yamamoto, H 2014 "Return to Venus of the Japanese Venus Climate Orbiter AKATSUKI" Acta Astronautica 93: 384–389 Bibcode:2014AcAau93384N doi:101016/jactaastro201307027 
  31. ^ http://ccarcoloradoedu/ASEN5050/projects/projects_2016/Branham_Breana/voihtml retrieved 13 June 2017
  32. ^ "Japanese Venus Probe Misses Orbit" Aviation Week & Space Technology 
  33. ^ "Japanese craft to get second chance after missing Venus in 2010" 
  34. ^ 「あかつき」の旅 2013年特別公開向け資料 PDF in Japanese PLANET-C Team/JAXA 26 August 2013 Retrieved 8 June 2014 
  35. ^ "AKATSUKI: Orbit successfully controlled" PLANET-C Team/JAXA 5 August 2015 Retrieved 10 September 2015 
  36. ^ "Venus Climate Orbiter "AKATSUKI" Inserted Into Venus' Orbit" JAXA December 9, 2015 
  37. ^ Clark, Steven 17 May 2016 "Japanese orbiter officially begins science mission at Venus" Spaceflight Now 
  38. ^ "Two cameras on Akatsuki pause observations" JAXA 3 March 2017 Retrieved 6 May 2017 

External linksedit

  • JAXA Akatsuki Planet-C page
  • JAXA Akatsuki Special Site
  • Akatsuki on Twitter
  • Exploring the Venusian Atmosphere – AKATSUKI/PLANET-C – Video
  • Launch Report of the H-IIA Launch Vehicle No 17 with the Venus Climate Orbiter Akatsuki Planet-C – Video
  • Planet-C page Solar Terrestrial Physics Group
  • Detailed Space Review article about Akatsuki and its recovery
  • Presentation about Planet-C from the VEXAG meeting in November 2005 PDF, 27 MB
  • Vieru, Tudor "JAXA Gets Ready to Launch Venus Probe" Softpedia Archived from the original on 23 March 2010 Retrieved 30 March 2010 
  • Venus Climate Orbiter Akatsuki PDF, 172 Mb

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