OKEANOS (Oversize Kite-craft for Exploration and Astronautics in the Outer Solar system) was a proposed mission concept to

Trojan asteroids In astronomy, a trojan is a small celestial body (mostly asteroids) that shares the orbit of a larger body, remaining in a stable orbit approximately 60° ahead of or behind the main body near one of its Lagrangian points and . Trojans can shar ...

, 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. '' In situ'' 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
Jun Matsumoto, Jun Aoki, Yuske Oki, Hajime Yano; 2015 OKEANOS was a finalist for Japan's Institute of Space and Astronautical Science (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.

Overview

The OKEANOS mission was a concept first proposed in 2010 to fly together with the

Jupiter Magnetospheric Orbiter The Jupiter Magnetospheric Orbiter (木星磁気圏オービター, JMO) is a cancelled space probe proposed by the Japanese Aerospace Exploration Agency (JAXA), to undertake detailed ''in situ'' studies of the magnetosphere of Jupiter as a templa ...

(JMO) as part of the cancelled Europa Jupiter System Mission – Laplace. In its latest formulation, the OKEANOS mission and LiteBIRD 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.

Spacecraft

and would have been equipped with solar electric ion engines. The 1600 m² 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 from the Sun. The spacecraft would have used solar sail technology initially developed for the successful

IKAROS 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 rocket, together with the ''Akatsuki'' (V ...

(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 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'' mission, used for maneuvering, and especially for an optional sample-return trip to Earth. A study indicated the need for 191 kg of

xenon Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...

propellant if it had been decided to bring a sample back to Earth.

Lander

The mission concept considered several scenarios, targets, and architectures. The most ambitious scenario contemplated ''in situ'' analysis and a sample-return using a lander. This lander concept was a collaboration among the German Aerospace Center (DLR) and Japan's

JAXA The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into orb ...

, starting in 2014. The spacecraft would have deployed a 100 kg lander on the surface of a 20–30 km Trojan asteroid to analyze its subsurface volatile constituents, such as water ice, using a 1-meter pneumatic drill powered by pressurized nitrogen gas. Some subsurface samples would have been transferred to the on board mass spectrometer for volatile analysis. The lander's scientific payload mass, including the sampling system, would not have exceeded 20 kg. The lander would have been powered by batteries and was planned to perform an autonomous descent, landing, sampling and analysis. Some samples were to be heated up to 1000 °C for pyrolysis for isotopic analysis. The conceptual payload for the lander would have included a panoramic camera (visible and infrared), an infrared microscope, a Raman spectrometer, a

magnetometer A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, o ...

, and a thermal radiometer. The lander would have operated for about 20 hours using battery power. * Mass spectrometer * Hyperspectral microscope * Hyperspectral panoramic imager * Optical navigation camera *

Laser rangefinder A laser rangefinder, also known as a laser telemeter, is a rangefinder that uses a laser beam to determine the distance to an object. The most common form of laser rangefinder operates on the time of flight principle by sending a laser pulse in ...

* Fluxgate 3-axis magnetometer * Alpha particle X-ray spectrometer (APXS) * Surface and subsurface sampler ;On the spacecraft: * Exo-Zodiacal

Infrared Telescope An infrared telescope is a telescope that uses infrared light to detect celestial bodies. Infrared light is one of several types of radiation present in the electromagnetic spectrum. All celestial objects with a temperature above absolute zero ...

(EXZIT) is a 10 cm-diameter telescope. * Gamma-ray burst polarimeter (GAP-2) * Monostatic radar to image the body's internal structures Jupiter Trojan's shallow subsurface: direct observations by radar on board OKEANOS mission
Alain Herique, Pierre Beck, Patrick Michel, Wlodek Kofman, Atsushi Kumamoto, Tatsuaki Okada, Dirk Plettemeier; EPSC Abstracts Vol. 12, EPSC2018-526, 2018 European Planetary Science Congress 2018 ;Attached to the sail: * Arrayed Large-area

Dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes ...

Detectors (ALDN-2) * Magnetic Field Experiment (MGF-2) is a fluxgate magnetometer GAP-2 and EXZIT were instruments for astronomical observations, and were not intended to be used for studying Trojan asteroids. The two would have conducted opportunistic surveys, taking advantage of the mission's trajectory. GAP-2 would have made it possible to locate the position of Gamma-ray bursts with high precision by pairing it with terrestrial observatories. EXZIT, as

zodiacal light The zodiacal light (also called false dawn when seen before sunrise) is a faint glow of diffuse sunlight scattered by interplanetary dust. Brighter around the Sun, it appears in a particularly dark night sky to extend from the Sun's direction in ...

gets significantly weak beyond the asteroid belt, would have enabled the telescope to observe the

cosmic infrared background Cosmic infrared background is infrared radiation caused by stellar dust. History Recognizing the cosmological importance of the darkness of the night sky (Olbers' paradox) and the first speculations on an extragalactic background light dates ...

. MGF-2 was a possible a successor of the MGF instrument on board the Arase satellite, and ALADDIN-2, GAP-2 were possible successors of the respective instruments onboard

References

{{Japanese space program Japanese space probes Jupiter trojans Missions to asteroids Missions to Jupiter Sample return missions Proposed space probes Solar sail spacecraft Solar sailing Japanese inventions