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IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) is a Japan Aerospace Exploration Agency ( JAXA) experimental spacecraft. The spacecraft was launched on 20 May 2010, aboard an
H-IIA H-IIA (H-2A) is an active expendable launch system operated by Mitsubishi Heavy Industries (MHI) for the Japan Aerospace Exploration Agency. These liquid fuel rockets have been used to launch satellites into geostationary orbit; lunar o ...
rocket, together with the ''Akatsuki'' (Venus Climate Orbiter) probe and four other small spacecraft. IKAROS is the first spacecraft to successfully demonstrate solar sail technology in interplanetary space. On 8 December 2010, IKAROS flew by
Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...
at a distance of , successfully completing its planned mission, and entered its extended operation phase.


Purpose

The IKAROS probe is the world's first spacecraft to use solar sailing 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 Radiation pressure is the mechanical pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any wavelength that is a ...
on the solar sail #
Attitude control Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle ...
by varying the
reflectance The reflectance of the surface of a material is its effectiveness in reflecting radiant energy. It is the fraction of incident electromagnetic power that is reflected at the boundary. Reflectance is a component of the response of the electronic ...
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 In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic explosions that have been observed in distant galaxies. They are the most energetic and luminous electromagnetic events since the Big Bang. Bursts can last from ten millise ...
s,
solar wind The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sol ...
and
cosmic dust Cosmic dust, also called extraterrestrial dust, star dust or space dust, is dust which exists in outer space, or has fallen on Earth. Most cosmic dust particles measure between a few molecules and 0.1 mm (100 micrometers). Larger particles are c ...
. The probe's ALADDIN instrument (ALDN-S and ALDN-E) measured the variation in dust density while its Gamma-Ray Burst Polarimeter (GAP) measured the polarization of gamma-ray bursts during its six-month cruise. IKAROS is to be followed by a 40 × 40 m sail, the Jupiter Trojan Asteroid Explorer, intended to journey to
Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth t ...
and the Trojan asteroids, to be launched in the late 2020s, with a proposed goal of returning an asteroid sample to Earth in the 2050s. (the Venus Climate Orbiter) aboard an H-IIA rocket from the
Tanegashima Space Center The (TNSC) is the largest rocket-launch complex in Japan with a total area of about 9.7 square kilometers. It is located on the southeast coast of Tanegashima, an island approximately south of Kyushu. It was established in 1969 when the ...
on 21 May 2010. IKAROS spun at 20–25 revolutions per minute and finished unfurling its sail on 10 June 2010. The craft contains two tiny ejectable cameras, DCAM1 and DCAM2. DCAM2 was used to photograph the sail after deployment on 14 July 2010. Acceleration and
attitude control Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle ...
(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, 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. IKAROS continues to spin at approximately 2
rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...
, 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". On 30 November 2012, JAXA announced that IKAROS had been recognized by
Guinness World Records ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book published annually, listing world ...
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. 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 Usuda Deep Space Center is a facility of the Japan Aerospace Exploration Agency. It is a spacecraft tracking station in Saku, Nagano, opened in October, 1984. The main features of the station are two large beam waveguide antennas, an older 64 ...
antenna was limited, so data was gathered only intermittently to estimate the speed, trajectory and rotation of the satellite. As of August 2013, acceleration from the IKAROS sail had changed the craft's speed by approximately in total. 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. 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. 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 in May 2015 data the position of IKAROS at the time was about 110 million kilometers away from the Earth, and about 130 million kilometers from the Sun.


Scientific results

From the gamma-ray polarization data of GAP, Toma ''et al.'' put a stricter limit on CPT violation. It is an improvement of eight orders of magnitude over previous limits. JAXA scientists stated on 9 July 2010 that the measured thrust force by the solar radiation pressure on IKAROS' 196 m2 sail is 1.12 millinewtons.


See also

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Notes


References

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External links


Successful Image Shooting by the Second Separation Camera
– 28 June 2010 JAXA press release
Solar Sail Navigation Technology of IKAROS
{{DEFAULTSORT:Ikaros Japanese space probes Solar sail spacecraft Space probes launched in 2010 JAXA 2010 in Japan Spacecraft launched by H-II rockets