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OKEANOS (Oversize Kite-craft for Exploration and Astronautics in the Outer Solar system) was a proposed mission concept to
Trojan asteroids, which share Jupiter's orbit, using a hybrid
solar sail
Solar sails (also known as light sails and photon sails) are a method of spacecraft propulsion using radiation pressure exerted by sunlight on large mirrors. A number of spaceflight missions to test solar propulsion and navigation have been p ...
for propulsion; the sail was planned to be covered with thin
solar panels
A solar cell panel, solar electric panel, photo-voltaic (PV) module, PV panel or solar panel is an assembly of photovoltaic solar cells mounted in a (usually rectangular) frame, and a neatly organised collection of PV panels is called a phot ...
to power an
ion engine
An ion thruster, ion drive, or ion engine is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating ions using electricity.
An ion thruster ionizes a neutral gas by extracting some electrons out of a ...
. ''
In situ
''In situ'' (; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in ...
'' analysis of the collected samples would have been performed by either direct contact or using a lander carrying a high-resolution mass spectrometer. A sample-return to
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
was an option under study.
[Sampling Scenario for the Trojan Asteroid Exploration Mission](_blank)
Jun Matsumoto, Jun Aoki, Yuske Oki, Hajime Yano; 2015
OKEANOS was a finalist for Japan's
Institute of Space and Astronautical Science
(ISAS) is a Japanese national research organization of astrophysics using rockets, astronomical satellites and interplanetary probes which played a major role in Japan's space development. Since 2003, it is a division of Japan Aerospace E ...
(ISAS) 2nd Large Mission Class to be launched in 2026,
[JAXA Sail to Jupiter's Trojan Asteroids]
Paul Gilster, ''Centauri Dreams'' 15 March 2017 and possibly return Trojan asteroid samples to Earth in the 2050s.
[ The winning mission was ]LiteBIRD
''LiteBIRD'' (''Lite (Light) satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection'') is a planned small space observatory that aims to detect the footprint of the primordial gravitational wave ...
.
Overview
The OKEANOS mission was a concept first proposed in 2010 to fly together with the Jupiter Magnetospheric Orbiter (JMO) as part of the cancelled Europa Jupiter System Mission – Laplace
The Europa Jupiter System Mission – Laplace (EJSM-Laplace) was a proposed joint NASA/ ESA uncrewed space mission slated to launch around 2020 for the in-depth exploration of Jupiter's moons with a focus on Europa, Ganymede and Jupiter's mag ...
.
In its latest formulation, the OKEANOS mission and LiteBIRD
''LiteBIRD'' (''Lite (Light) satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection'') is a planned small space observatory that aims to detect the footprint of the primordial gravitational wave ...
were the two finalists of Japan's Large Mission Class by the Ministry of Education, Culture, Sports, Science and Technology
The , also known as MEXT or Monka-shō, is one of the eleven Ministries of Japan that composes part of the executive branch of the Government of Japan. Its goal is to improve the development of Japan in relation with the international community ...
. LiteBIRD, a cosmic microwave background
In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all spac ...
astronomy telescope, was selected.s may help scientists understand how the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
was formed. It would also help determine which of the competing hypotheses is right:
remnant
planetesimal
Planetesimals are solid objects thought to exist in protoplanetary disks and debris disks. Per the Chamberlin–Moulton planetesimal hypothesis, they are believed to form out of cosmic dust grains. Believed to have formed in the Solar System a ...
s during the formation of Jupiter, or fossils of building blocks of Jupiter, or captured
trans-Neptunian object
A trans-Neptunian object (TNO), also written transneptunian object, is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune, which has a semi-major axis of 30.1 astronomical units (au).
Typically, ...
s by planetary migration. The latest proposal included a lander to perform ''in situ'' analyses.
[System Designing of Solar Power Sail-craft for Jupiter Trojan Asteroid Exploration]
Osamu MORI, Jun MATSUMOTO, Toshihiro CHUJO, Hideki KATO, Takanao SAIKI, Junichiro KAWAGUCHI, Shigeo KAWASAKI, Tatsuaki OKADA, Takahiro IWATA, Yuki TAKAO; ''J-Stage'' There were several options for this mission, and the most ambitious one proposed to retrieve and send samples to Earth for extensive investigations. Had it been selected in April 2019 for development, the spacecraft would have launched in 2026,
and may had offered some synergy with
''Lucy'' spacecraft that will flyby multiple Jupiter Trojans in 2027.
Spacecraft
The spacecraft was projected to have a mass of about including a possible lander
and would have been equipped with solar electric
ion engine
An ion thruster, ion drive, or ion engine is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating ions using electricity.
An ion thruster ionizes a neutral gas by extracting some electrons out of a ...
s.
The 1600 m
2 sail would have had a dual purpose of solar sail propulsion and solar panel for power generation. If a lander had been included, its mass would have been no greater than 100 kg. The lander would have collected and analyzed samples from the asteroid. A more complex suggested concept would have had the lander take off again, rendezvous with the mothership and transfer the samples for their transport to Earth.
Solar sail and solar panels
The unique proposed sail was a hybrid that would have provided both photon propulsion and electric power. JAXA referred to the system as a Solar Power Sail.
covered with 30,000 solar panels 25 μm thick, capable of generating up to 5 kW at the distance of
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, 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 ...
, 5.2
Astronomical Units
The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits t ...
from the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
.
The spacecraft would have used solar sail technology initially developed for the successful
IKAROS (Interplanetary Kite-craft Accelerated by Radiation of the Sun) that launched in 2010, whose solar sail was 14 m × 14 m in size.
As with the IKAROS, the solar angle of the sail would have been changed by dynamically controlling the reflectivity of
liquid crystal display
A liquid-crystal display (LCD) is a flat panel display, flat-panel display or other Electro-optic modulator, electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liqui ...
s (LCD) on the outer edge of the sail so that the sunlight pressure would produce torque to change its orientation.
Ion engine
The
ion engine
An ion thruster, ion drive, or ion engine is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating ions using electricity.
An ion thruster ionizes a neutral gas by extracting some electrons out of a ...
intended for the mission was called μ10 HIsp. It was planned to have a specific impulse of 10,000 seconds, power of 2.5 kW, and a maximum thrust magnitude of 27 mN for each of the four engines.
[Hayabusa
was a robotic spacecraft developed by the Japan Aerospace Exploration Agency (JAXA) to return a sample of material from a small near-Earth asteroid named 25143 Itokawa to Earth for further analysis.
''Hayabusa'', formerly known as MUSES-C ...]
'' mission, used for maneuvering, and especially for an optional sample-return trip to Earth.