View source for IKAROS

{{about|the spacecraft|the mythological figure|Icarus|genetics|Ikaros transcription factor|other uses|Icarus (disambiguation)}}
{{Use dmy dates|date=December 2016}}
{{Infobox spaceflight
| name                  = IKAROS<!--defaults to page title-->
| names_list            = <!--list of previous names if the spacecraft has been renamed.
Include the dates applicable if possible, and separate each name with a linebreak.
Omit if the spacecraft has only ever been known by one name.
Do not include Harvard, COSPAR/NSSDC or SATCAT/NORAD/NASA designations as alternative names-->

<!--image of the spacecraft/mission-->
| image                 = IKAROS IAC 2010.jpg<!--omit the "file" prefix-->
| image_caption         = A 1:64 scale model of the IKAROS spacecraft<!--image caption-->
| image_alt             = IKAROS model<!--image alt text-->
| image_size            = 300px<!--include px/em; defaults to 220px-->

<!--Basic details-->
| mission_type          = <!--eg. Technology, Reconnaissance, ISS assembly, etc-->
| operator              = [[JAXA]]<ref>Mori ''et al.'' (2009)</ref><ref>{{cite web |url=http://www.jaxa.jp/projects/sat/ikaros/index_e.html |title=Small Solar Power Sail Demonstrator "IKAROS" |publisher=JAXA |accessdate=1 October 2010}}</ref><ref name=spaceflightnow>{{cite news | author=Stephen Clark | title=H-2A Launch Report – Mission Status Center | url=http://www.spaceflightnow.com/h2a/akatsuki/status.html | work=Spaceflight Now | date=20 May 2010 | accessdate=21 May 2010}}</ref><ref>{{cite web | author=Samantha Harvey | title=Solar System Exploration: Missions: By Target: Venus: Future: Akatsuki | url=http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Akatsuki | publisher=NASA | date=20 May 2010  | accessdate=21 May 2010}}</ref><!--organisation(s) that operate(d) the spacecraft-->
| Harvard_designation   = <!--spacecraft launched 1962 and earlier only (eg. 1957 Alpha 2)-->
| COSPAR_ID             = 2010-020E<!--spacecraft launched since 1963 only (aka NSSDC ID; eg. 1998-067A)-->
| SATCAT                = 36577
| website               = {{url|http://global.jaxa.jp/projects/sat/ikaros|}}
| mission_duration      = ~0.5 years <br />elapsed: {{Age in years, months and days| year=2010 | month=05 | day=20}}<!--How long the mission lasted-->
| distance_travelled    = <!--How far the spacecraft travelled (if known)-->
| orbits_completed      = <!--number of times the spacecraft orbited the Earth - see below for spacecraft beyond Earth orbit-->
| suborbital_range      = <!--downrange distance reached if spacecraft did not enter orbit-->
| suborbital_apogee     = <!--altitude reached if spacecraft did not enter orbit-->

<!--Spacecraft properties-->
| spacecraft            = <!--Spacecraft name/serial number (eg. Space Shuttle ''Discovery'', Apollo CM-118), etc-->
| spacecraft_type       = <!--eg. GPS Block II, Kobalt-M, US-K, etc-->
| spacecraft_bus        = <!--eg. A2100M, Star-2, etc-->
| manufacturer          = <!--company or companies who built the satellite-->
| launch_mass           = {{convert|315|kg|lb|abbr=on}}<!--fuelled mass at launch, not including rocket or upper stage-->
| BOL_mass              = <!--spacecraft mass in orbit at beginning of operational life, after LEOP phase-->
| landing_mass          = <!--Mass after landing (recovered spacecraft only)-->
| dry_mass              = <!--spacecraft mass in orbit without fuel-->
| payload_mass          = <!--Mass of cargo carried by spacecraft (eg. for Space Shuttle), or total mass of instrumentation/equipment/experiments for mission-->
| dimensions            = Solar sail: {{convert|14|x|14|m|abbr=on}} (area: {{convert|196|m2|abbr=on}})<ref>{{cite web |url=http://www.isas.jaxa.jp/e/enterp/missions/ikaros/index.shtml |title=IKAROS: Solar Power Sail Demonstrator |work=ISAS |publisher=JAXA |accessdate=24 May 2015 }}</ref><!--body dimensions and solar array span-->
| power                 = <!--end-of-life power, in watts-->

<!--Launch details-->
| launch_date           = {{start date|df=yes|2010|05|20|21|58|22|TZ=Z}}<!--{{start date|df=yes|YYYY|MM|DD|hh|mm|ss|TZ=Z}}-->
| launch_rocket         = [[H-IIA|H-IIA 202]]<!--Rocket that launched the satellite, include upper stage if distinct from rocket* and if possible flight/tail/serial number-->
| launch_site           = [[Tanegashima Space Center|Tanegashima]], [[Yoshinobu Launch Complex|LA-Y]]<!--Where the rocket launched from, including complex and pad; do not include the full address or country-->
| launch_contractor     = <!--organisation(s) that conducted the launch (eg. United Launch Alliance, Arianespace, etc)-->
| deployment_from       = <!--place where deployed from-->
| deployment_date       = <!--date deployed-->
| entered_service       = <!--date on which the spacecraft entered service, if it did not do so immediately after launch-->
<!-- * - e.g. Proton-M/Briz-M not Proton-M, but Titan IV(401)A not Titan IV(401)A-Centaur-->

<!--end of mission-->
| disposal_type         = <!--Whether the spacecraft was deorbited, decommissioned, placed in a graveyard orbit, etc-->
| deactivated           = <!--when craft was decommissioned-->
| destroyed             = <!--when craft was destroyed (if other than by re-entry)-->
| last_contact          = <!--when last signal received if not decommissioned-->
| recovery_by           = <!--recovered by-->
| recovery_date         = <!--recovery date-->
| decay_date            = <!--when craft re-entered the atmosphere, not needed if it landed-->
| landing_date          = <!--when the spacecraft made a controlled landing, not needed if it did not return intact-->
| landing_site          = <!--where the craft landed; site/runway or coordinates-->
<!--
    The following template should be used for ONE of the three above fields "end_of_mission", "decay" or "landing" if the spacecraft is no longer operational.
    If it landed intact, use it for the landing time, otherwise for the date it ceased operations, or the decay date if it was still operational when it re-entered.
    {{end date|df=yes|YYYY|MM|DD|hh|mm|ss|TZ=Z}} (for Zulu/UTC) or {{end date|df=yes|YYYY|MM|DD}} (if time unknown)
-->

<!--orbit parameters-->
<!--as science-related articles, SI units should be the principal units of measurement, however we usually use {{convert}} to display imperial units in parentheses after the initial values-->
| orbit_reference       = [[Heliocentric orbit]]<!--geocentric, selenocentric, etc - please link (e.g. [[Geocentric orbit|Geocentric]])-->
| orbit_regime          = <!--high, low, medium, molniya, GSO - please link (e.g. [[Low Earth orbit|Low Earth]] - please don't use acronyms-->
| orbit_longitude       = <!--geosynchronous satellites only-->
| orbit_slot            = <!--Designation of orbital position or slot, if not longitude (e.g plane and position of a GPS satellite)-->
| orbit_semimajor       = <!--semimajor axis-->
| orbit_eccentricity    = <!--orbital eccentricity-->
| orbit_periapsis       = <!--periapsis altitude-->
| orbit_apoapsis        = <!--apoapsis altitude-->
| orbit_inclination     = <!--orbital inclination-->
| orbit_period          = <!--time taken to complete an orbit-->
| orbit_RAAN            = <!--right ascension of the ascending node-->
| orbit_arg_periapsis   = <!--argument of perigee/periapsis-->
| orbit_mean_anomaly    = <!--mean anomaly at epoch, only use in conjunction with an epoch value-->
| orbit_mean_motion     = <!--mean motion of the satellite, usually measured in orbits per day-->
| orbit_repeat          = <!--repeat interval/revisit time-->
| orbit_velocity        = <!--speed at which the spacecraft was travelling at epoch - only use for spacecraft with low orbital eccentricity-->
| orbit_epoch           = <!--the date at which the orbit parameters were correct-->
| orbit_rev_number      = <!--revolution number-->
| apsis                 = helion<!--planet specific apsis term (eg. gee/helion/selene/etc - defaults to generic "apsis")-->

|interplanetary         = <!--Infobox spaceflight/IP can be called multiple times for missions with multiple targets or combined orbiter/lander missions, etc-->
 {{Infobox spaceflight/IP
   |type                = flyby<!--delete as appropriate, MUST BE ONE OF THESE OPTIONS-->
   |object              = [[Venus]]<!--body visited - e.g. Jupiter, Venus, etc-->
   |orbits              = <!--number of orbits completed at target body (if applicable and known)-->
   |component           = <!--part of the spacecraft involved, if spacecraft split into multiple components-->
   |arrival_date        = 8 December 2010<!--Flybys: date/time of closest approach; Orbiters; orbital insertion date; Impactors/Landers/Rovers: impact/landing date/time; Atmospheric probes: atmospheric entry time-->
   |departure_date      = <!--Date of leaving orbit for orbiters, date of launch for landers which took off again-->
   |location            = <!--landing/impact site, including EOM impacts for atmospheric probes and lunar/asteroid orbiters-->
   |distance            = {{convert|80,800|km|mi|sp=us}}
   |sample_mass         = <!--mass of samples returned (sample return missions only)-->
   |surface_EVAs        = <!--number of EVAs on the surface-->
   |surface_EVA_time    = <!--time spent on surface EVAs-->

   <!--Orbit parameters, ONLY USE IF THE ABOVE ORBIT PARAMETERS SECTION DOESN'T APPLY TO THE TARGET-->
   |periapsis           = <!--periapsis altitude-->
   |apoapsis            = <!--apoapsis altitude-->
   |inclination         = <!--inclination to the object's equator-->
   |apsis               = <!--planet specific apsis term, as above-->
 }}

<!--transponder parameters-->
| trans_band            = <!--Transponder frequency bands-->
| trans_frequency       = <!--specific frequencies-->
| trans_bandwidth       = <!--bandwidth-->
| trans_capacity        = <!--capacity of the transponders-->
| trans_coverage        = <!--area covered-->
| trans_TWTA            = <!--TWTA output power-->
| trans_EIRP            = <!--equivalent isotropic power-->
| trans_HPBW            = <!--half-power beam width-->

<!--Only use where a spacecraft/mission is part of a clear programme of sequential missions.
If in doubt, leave it out-->
| programme             =
| previous_mission      =
| next_mission          =

<!--mission insignia or patch-->
| insignia              = <!--omit the "file" prefix-->
| insignia_caption      = <!--image caption-->
| insignia_alt          = <!--image alt text-->
| insignia_size         = <!--include px/em; defaults to 180px-->
}}

'''IKAROS''' ('''Interplanetary Kite-craft Accelerated by Radiation Of the Sun''') is a Japan Aerospace Exploration Agency ([[JAXA]]) experimental spacecraft. The spacecraft was launched on 21 May 2010, aboard an [[H-IIA]] rocket, together with the [[Akatsuki (spacecraft)|''Akatsuki'']] (Venus Climate Orbiter) probe and four other small spacecraft. IKAROS is the first spacecraft to successfully demonstrate [[solar sail]] technology in interplanetary space.<ref name=spaceflightnow/><ref>{{cite web | title=Launch Day of the H-IIA Launch Vehicle No. 17(H-IIA F17) | url=http://www.jaxa.jp/press/2010/03/20100303_h2af17_e.html | publisher=JAXA | date= 3 March 2010| accessdate=7 May 2010}}</ref>

On 8 December 2010, IKAROS passed by [[Venus]] at about {{convert|80800|km|abbr=on}} distance, completing the planned mission successfully, and entered its extended operation phase.<ref>{{cite web |url=http://www.isas.jaxa.jp/home/IKAROS-blog/?itemid=783 |title=今日の IKAROS(12/10)　– Daily Report – Dec 10, 2010 |language=Japanese |work=IKAROS Blog |publisher=JAXA |date=10 December 2010 |accessdate=22 January 2011}}</ref><ref>{{cite web |url=http://www.isas.jaxa.jp/home/IKAROS-blog/?itemid=796 |title=2010年の締めくくり(12/26)　– Daily Report – Dec 26, 2010 |language=Japanese |work=IKAROS Blog |publisher=JAXA |date=26 December 2010 |accessdate=22 January 2011}}</ref><ref>{{cite web |url=http://www.asahi.com/special/space/TKY201012100622.html |script-title=ja:宇宙帆船イカロス、お疲れさま…実験終え「人工惑星」に |language=Japanese |publisher=Asahi Shimbun |date=10 December 2010 |accessdate=22 January 2011}}{{dead link|date=December 2016}}</ref><ref name=jaxa20110126>{{cite web |url=http://www.jaxa.jp/press/2011/01/20110126_sac_ikaros.pdf |title=小型ソーラー電力セイル実証機（IKAROS）の定常運用終了報告 |first=Osamu |last=Mori |publisher=JAXA |language=Japanese |format=PDF |date=26 January 2011 |accessdate=2 February 2011}}</ref>

==Purpose==
The IKAROS probe is the world's first spacecraft to use [[solar sail]]ing as the main propulsion. It was designed to demonstrate four key technologies (comments in parentheses refer to figure):
# Deployment and control of a large, thin solar sail membrane (grey-blue areas numbered 3)
# Thin-film solar cells integrated into the sail to power the payload (black rectangles numbered 4)
# Measurement of acceleration due to [[radiation pressure]] on the solar sail
# [[Attitude control]] by varying the [[reflectance]] of 80 liquid crystal panels embedded in the sail (orange rectangles numbered 2)

The mission also includes investigations of aspects of interplanetary space, such as [[gamma-ray burst]]s, [[solar wind]] and [[cosmic dust]].<ref>{{cite web |url=http://www.jaxa.jp/press/2010/07/20100714_ikaros_j.html |title=小型ソーラー電力セイル実証機「IKAROS（イカロス）」のガンマ線バーストの観測成功について|language=Japanese |publisher=JAXA |date=14 July 2010 |accessdate=15 July 2010}}</ref>

The probe's ALADDIN instrument (ALDN-S and ALDN-E) measured the variation in dust density<ref>{{cite web|url=http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2647.pdf|title=COSMIC DUST DETECTION BY THE IKAROS-ARRAYED LARGE-AREA DUST DETECTORS IN INTERPLANETARY SPACE (ALADDIN) FROM THE EARTH TO VENUS|last=Yano|first=H.|work=42nd Lunar and Planetary Science Conference (2011)|accessdate=14 February 2011|display-authors=etal}}</ref> while its Gamma-Ray Burst Polarimeter (GAP) measured the [[Polarization (waves)|polarization]] of gamma-ray bursts during its six-month cruise.<ref>{{cite journal|arxiv=1010.5305|title=Gamma-Ray Burst Polarimeter – GAP – aboard the Small Solar Power Sail Demonstrator IKAROS|last=Yonetoku|first=D.|date=26 October 2010|class=astro-ph.IM|display-authors=etal|doi=10.1093/pasj/63.3.625|volume=63|issue=3|journal=Publications of the Astronomical Society of Japan|pages=625–638|bibcode = 2011PASJ...63..625Y }}</ref>

IKAROS is to be followed by a 50 × 50 m sail, the [[Jupiter Trojan Asteroid Explorer]], intended to journey to [[Jupiter]] and the [[Jupiter Trojan|Trojan asteroids]], launched in the late 2020s, with a proposed goal of returning an asteroid sample to Earth in the 2050s.<ref>{{cite web|url=http://www.jspec.jaxa.jp/e/activity/ikaros.html |archive-url=https://web.archive.org/web/20080922170700/http://www.jspec.jaxa.jp/e/activity/ikaros.html |dead-url=yes |archive-date=22 September 2008 |title=IKAROS Project |accessdate=12 July 2010 |year=2008 |publisher=JAXA |quote=The second mission will take place in the late 2010s. It will involve a medium-sized solar power sail with a diameter of 50m, and will have integrated ion-propulsion engines. The destinations of the spacecraft will be Jupiter and the Trojan asteroids. |df=dmy-all }}</ref>
<ref>
{{cite web
|url=http://www.space.com/8800-japan-solar-sail-toast-space-science.html
|title=Japan's Solar Sail Is the Toast of Space Science
|author=Jeremy Hsu
|publisher=space.com
|date=21 July 2010
|accessdate=8 December 2016
}}
</ref>
<ref>
{{cite web
|url=http://www.japantimes.co.jp/news/2016/07/21/national/science-health/huge-sail-will-power-jaxa-mission-trojan-asteroids-back/
|title=JAXA reveals asteroid probe solar panel
|author=Shusuke Murai
|publisher=The Japan Times
|date=21 July 2016
|accessdate=8 December 2016
}}
</ref>

==Design==
[[File:Ikaros solar sail key numbered bottom line.svg|thumb|250px|[[:File:Ikaros solar sail key numbered bottom line.svg|IKAROS sail schematic diagram]]:<div style="float:left;">1.(blue square on a line) Tip mass {{convert|0.5|kg|abbr=on}}, 1 of 4.<br />2. (orange rectangle) Liquid crystal device, 1 of 80.<br />3. (blue square) Membrane {{convert|7.5|μm|abbr=on}} thick, {{convert|20|m}} on the diagonal.<br />4. (black rectangle) Solar cells {{convert|25|μm|abbr=on}} thick.<br />5. (yellow and blue lines) Tethers.<br />6. (blue disc) Main body.<br />7. (yellow dots) Instruments.</div>]]
[[File:IKAROS solar sail.jpg|thumb|250px|IKAROS spaceprobe in flight (artist's depiction)]]

The square sail, deployed via a spinning motion using {{convert|0.5|kg|lb|adj=on}} tip masses (key item 1 in figure at right), is {{convert|20|m|abbr=on}} on the diagonal and is made of a {{convert|adj=on|7.5|μm}} thick sheet of [[polyimide]] (key item 3 in figure at right). The polyimide sheet had a mass of about 10 grams per square metre, resulting in a total sail mass of 2 kilograms, excluding tip masses, attached panels and tethers.<!-- calculated from polyimide density 1430 kg/m^3, sail area approx 200 m^2 --> A thin-film solar array is embedded in the sail (key item 4 in figure at right). [[PowerFilm, Inc.]] provided the thin-film solar array.<ref>{{cite web|author=Claire M. Umali |title=Japan tests power of solar sails in deep space |url=http://www.ecoseed.org/en/technology/emerging-renewables/article/28-emerging-renewables/7067-japan-tests-power-of-solar-sails-in-deep-space |archive-url=https://web.archive.org/web/20101202070314/http://ecoseed.org/en/technology/emerging-renewables/article/28-emerging-renewables/7067-japan-tests-power-of-solar-sails-in-deep-space |dead-url=yes |archive-date=2 December 2010 |work=EcoSeed |date=4 May 2010 |accessdate=25 January 2011 |df=dmy-all }}</ref> Eighty blocks of [[liquid-crystal display|LCD]] panels are embedded in the sail,<ref>{{cite web|url=http://www.jaxa.jp/press/2010/07/20100723_ikaros_e.html|title=Small Solar Power Sail Demonstrator 'IKAROS': Successful Attitude Control by Liquid Crystal Device |date=23 July 2010 <!-- (JST) --> |publisher=Japan Aerospace Exploration Agency (JAXA)}}</ref> whose reflectance can be adjusted for [[attitude control]] (key item 2 in figure at right). The sail also contains eight dust counters on the opposite face as part of the science payload.<ref name=jaxa20100311>{{cite web | title=Small Solar Power Sail Demonstrator | url=http://www.jaxa.jp/projects/sat/ikaros/index_e.html | publisher=JAXA | date=11 March 2010 | accessdate=7 May 2010}}</ref><ref>{{cite web|url=http://www.jspec.jaxa.jp/e/activity/ikaros.html |archive-url=https://web.archive.org/web/20080922170700/http://www.jspec.jaxa.jp/e/activity/ikaros.html |dead-url=yes |archive-date=22 September 2008 |title=IKAROS Project |year=2008 |publisher=JAXA |accessdate=30 March 2010 |df=dmy-all }}</ref>

==Mission progress==
IKAROS was successfully launched together with [[Akatsuki (probe)|''Akatsuki'']] (the Venus Climate Orbiter) aboard an H-IIA rocket from the [[Tanegashima Space Center]] on 21 May 2010.

IKAROS spun at 20–25&nbsp;revolutions per minute and finished unfurling its sail on 10 June 2010.<ref>{{cite news | last=Edwards | first=Lin | title=IKAROS unfurls first ever solar sail in space | publisher=PhysOrg | date=11 June 2010 | url=http://www.physorg.com/news195460006.html | accessdate=11 June 2010 }}</ref><ref>{{cite news | author=Staff writers| title=Japanese Spacecraft Deploys Solar Sail | work=Space.com | date=11 June 2010  | url=http://www.space.com/missionlaunches/japan-spacecraft-deploys-solar-sail-100611.html | accessdate=11 June 2010 }}</ref><ref name="Jonathan Amos">{{cite news | last=Amos| first=Jonathan | url=http://news.bbc.co.uk/2/hi/science_and_environment/10293284.stm| title=Japan unfurls Ikaros solar sail in space| work=BBC News | date=11 June 2010 | accessdate=25 January 2011}}</ref> The craft contains two tiny ejectable cameras, DCAM1 and DCAM2. DCAM2 was used to photograph the sail after deployment on 14 July 2010.<ref>{{cite news | author=Staff writers | title=Mini-camera pictures Japan's Ikaros solar sail | url=http://news.bbc.co.uk/1/hi/science_and_environment/10328584.stm  | work=BBC News | accessdate=17 June 2010 | date=16 June 2010}}</ref>

Acceleration and [[attitude control]] (orientation) were successfully tested during the remaining six-month voyage to Venus. On 9 July 2010, JAXA confirmed that IKAROS is being accelerated by its solar sail,<ref name="http://www.jaxa.jp/press/2010/07/20100709_ikaros_j.html">{{cite press release | title=About the confirmation of photon acceleration of "IKAROS" the small solar-sail demonstrating craft | work=JAXA website press release | publisher=Japan Aerospace Exploration Agency | date=9 July 2010  | url=http://www.jaxa.jp/press/2010/07/20100709_ikaros_j.html | accessdate=25 January 2011 |language=Japanese |quote=Graph suggests approx 1.1mN force}}</ref> and on 23 July announced successful attitude control.  Over a 23-hour period of time, the solar angle of the sail was changed by a half a degree, not by using thrusters, but by dynamically controlling the reflectivity of the 80 liquid crystal panels at the outer edge of the sail so that the sunlight pressure would produce torque.<ref>{{cite press release |url=http://www.jaxa.jp/press/2010/07/20100723_ikaros_e.html |title=Small Solar Power Sail Demonstrator 'IKAROS'Successful Attitude Control by Liquid Crystal Device| publisher=Japan Aerospace Exploration Agency (JAXA) |date=23 July 2010 | accessdate=25 January 2011}}</ref>
[[File:Venus_Image_Taken_by_IKAROS_Solar_Sail.jpg|thumb|This photo of Venus taken by the solar powered craft IKAROS has been released by JAXA, the Japan Aerospace Exploration Agency. The picture shows a crescent-shaped planet Venus, and the cords and solar sail of IKAROS in the foreground.]]

IKAROS continues to spin at approximately 2 [[Revolutions per minute|rpm]], requiring the LCD panels to be cycled at that rate for attitude control.

According to JAXA, IKAROS finished all planned experiments in Dec 2010, but the mission has continued beyond that date "in order to enhance the skill of controlling solar sail."<ref>{{cite news|url=http://www.jspec.jaxa.jp/e/activity/ikaros.html |archive-url=https://web.archive.org/web/20080922170700/http://www.jspec.jaxa.jp/e/activity/ikaros.html |dead-url=yes |archive-date=22 September 2008 |title=Solar Power Sail Demonstrator "IKAROS" |publisher=Japan Aerospace Exploration Agency (JAXA) |accessdate=30 December 2012 |df=dmy-all }}</ref>  On 30 November 2012, JAXA announced that IKAROS had been recognized by [[Guinness World Records]] as the world’s first solar sail spacecraft between planets, and that its two separated cameras, DCAM1 and DCAM2, had been recognized as the smallest size of a spacecraft flying between planets.<ref>{{cite news |url=http://www.jaxa.jp/projects/sat/ikaros/index_e.html |title=IKAROS world record certified!| publisher=Japan Aerospace Exploration Agency (JAXA) |date=30 November 2012 | accessdate=30 December 2012}}</ref><ref>{{cite news |url=http://ajw.asahi.com/article/behind_news/social_affairs/AJ201212300014 |title=JAXA’s solar spacecraft gets Guinness World Records entry| publisher=The Asahi Shimbun |date=30 December 2012 | accessdate=30 December 2012}}</ref>
As of 2012, the IKAROS continued to spin, but its attitude control had degraded. This resulted in unexpected sail motions and as a result, downlink through the medium-gain antenna was only intermittently available. The project team was dissolved on 28 March 2013, although a trial receipt of data was planned for a later date.

The project was reactivated on 20 June 2013 in the expectation that the satellite would wake up from a hibernation state as more power from the solar panels became available. The team was able to receive telemetry from the IKAROS between 20 June and 12 September 2013, after which contact was again lost. The loss of contact was around the predicted time of the spacecraft again entering a low-power hibernation mode as power from the solar panels decreased. Available communication time through the [[Usuda Deep Space Center]] antenna was limited, so data was gathered only intermittently to estimate the speed, trajectory and rotation of the satellite.<ref>{{cite web |url=http://www.isas.jaxa.jp/home/IKAROS-blog/?itemid=1011 |title=今日の IKAROS(2013/06/20)　– Daily Report – June 20, 2013| publisher=Japan Aerospace Exploration Agency (JAXA) |date=20 June 2013 | accessdate=8 June 2014 |language=Japanese}}</ref><ref>{{cite web |url=http://www.isas.jaxa.jp/home/IKAROS-blog/?itemid=1018 |title= 今日の IKAROS(12/7)　– Daily Report – Dec 7, 2013 | publisher=Japan Aerospace Exploration Agency (JAXA) |date=20 June 2013 | accessdate=8 June 2014 |language=Japanese}}</ref> As of August 2013, IKAROS was continuing to gain speed. At that time, it had gained approximately 400&nbsp;m/s of velocity from its solar sail.<ref>{{cite web |url=http://www.isas.jaxa.jp/home/IKAROS-blog/?itemid=1017|title=今日の IKAROS(8/29)　– Daily Report – Aug 29, 2013 | publisher=Japan Aerospace Exploration Agency (JAXA) |date=29 August 2013 | accessdate=8 June 2014 |language=Japanese}}</ref>

Transmissions were again received on 22 May 2014, the spacecraft flying at a distance of about 230 million kilometers from the Earth. By May 2014, IKAROS was on a ten-month orbit around the Sun, spending seven months of each orbit in hibernation mode due to insufficient power.<ref>{{cite news |url=http://www.isas.jaxa.jp/j/topics/topics/2014/0526.shtml |title= IKAROS：3回目の冬眠モード明けについて | publisher=Japan Aerospace Exploration Agency (JAXA) |date=26 May 2014 | accessdate=8 June 2014 |language=Japanese}}</ref> By 23 April 2015, the spacecraft woke up from hibernation mode for the 4th time and was flying at a distance of about 120 million kilometers from the Earth.<ref>{{cite news |url=http://global.jaxa.jp/projects/sat/ikaros/topics.html#topics4577 |title=IKAROS wakes up from hibernation mode for the 4th time |work=[[JAXA]] |date=30 April 2015 |accessdate=24 May 2015 }}</ref> On 21 May 2015, JAXA could not receive a signal from IKAROS and concluded that the spacecraft had shifted to the hibernation mode for the fifth time, as expected. Based on May 2015 data the position of the IKAROS at the time was about 110 million kilometers away from the Earth, and about 130 million kilometers from the sun. Data showed no anomaly in the IKAROS spacecraft.<ref>{{cite news |url=http://global.jaxa.jp/projects/sat/ikaros/topics.html |title=IKAROS enters hibernation mode for 5th time |work=[[JAXA]] |date=29 May 2015}}</ref>JAXA anticipated that it will come out from hibernation mode in the winter of 2015.<ref>{{cite web|title=IKAROS enters hibernation mode for 5th time|url=http://global.jaxa.jp/projects/sat/ikaros/topics.html#topics4743|website=JAXA|accessdate=5 May 2018}}</ref>{{update inline|date+March 2016|date=March 2016}}

==Science results==
From the gamma-ray polarization data of GAP, Toma ''et al.''<ref>{{cite journal |title=Strict Limit on CPT Violation from Polarization of γ-Ray Bursts |author=Kenji Toma |journal=Physical Review Letters |date=December 2012 |volume=109 |issue=24 |page=241104 |doi=10.1103/PhysRevLett.109.241104 |arxiv = 1208.5288 |bibcode = 2012PhRvL.109x1104T |display-authors=etal |pmid=23368301}}</ref> puts a stricter limit on [[CPT symmetry#CPT violation|CPT violation]].  It is an improvement of eight orders of magnitude over previous limits.<ref>{{cite web |url=http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.109.241104 |title=Synopsis: Distant Bursts Show no Signs of Predicted Light Rotation |author=Michael Schirber |publisher=American Physical Society |accessdate=16 December 2012}}</ref><ref>{{cite web |url=http://www.ipmu.jp/node/1458 |title=Strict Limit on CPT Violation from Gamma-Ray Bursts |publisher=Kavli Institute for the Physics and Mathematics of the Universe |date=7 December 2012 |accessdate=16 December 2012}}</ref>

JAXA scientists stated that the measured thrust force by the solar radiation pressure on IKAROS' 196 m<sup>2</sup> sail is 1.12 millinewtons.<ref>{{cite web|url=http://www.jspec.jaxa.jp/ikaros_channel/e/index.html |archive-url=https://web.archive.org/web/20100819085236/http://www.jspec.jaxa.jp/ikaros_channel/e/index.html |dead-url=yes |archive-date=19 August 2010 |title=IKAROS – All News Channel |work=JAXA |date=9 July 2010 |accessdate=24 May 2015 |df=dmy-all }}</ref>

==See also==
{{Portal|Spaceflight}}
* [[CubeSail]]
* [[CubeSail (UltraSail)]]
* [[LightSail 2]], a private solar sail project of the [[Planetary Society]]
* [[List of missions to Venus]]
* [[Near-Earth Asteroid Scout]], a [[CubeSat]] tasked with traveling to an [[asteroid]] ~1AU from Earth
* [[NanoSail-D2]], an American solar sail deployed in LEO in January 2011
* [[OKEANOS]], proposed successor to IKAROS targeting the [[Jupiter trojans]]
* [[Solar sail]]

==Notes==
{{Reflist|2}}

==References==
* {{cite web |url=https://archive.ists.or.jp/upload_pdf/2008-d-57.pdf |title=Development of Deployment System for Small Size Solar Sail Mission |author=Osamu Mori|work=26th International Symposium on Space Technology and Science |date=6 July 2008 |accessdate=9 May 2011|display-authors=etal}}
* {{cite web |url=https://archive.ists.or.jp/upload_pdf/2009-o-4-07v.pdf |title=First Solar Power Sail Demonstration by IKAROS |author=Osamu Mori|work=27th International Symposium on Space Technology and Science |date=9 July 2009 |accessdate=6 March 2010|display-authors=etal}}

==External links==
{{Commons category|IKAROS}}
* [http://www.jaxa.jp/press/2010/06/20100628_ikaros_e.html Successful Image Shooting by the Second Separation Camera] – 28 June 2010 JAXA press release
* [http://www.isas.jaxa.jp/e/forefront/2011/tsuda/index.shtml Solar Sail Navigation Technology of IKAROS]

{{Venus spacecraft}}
{{Japanese space program}}
{{Solar System probes}}
{{Orbital launches in 2010}}

{{DEFAULTSORT:Ikaros}}
[[Category:Japanese space probes]]
[[Category:Solar sail spacecraft]]
[[Category:Space probes launched in 2010]]
[[Category:Japanese space probes]]
[[Category:JAXA]]
[[Category:2010 in Japan]]