Oceanus (Uranus Orbiter)

OCEANUS (Origins and Composition of the Exoplanet Analog Uranus System)

Uranus, an ice giant planet, was photographed in real color by Voyager 2 in January 1986
Mission type	Reconnaissance
Operator	NASA/JPL
Mission duration	≥1.5 years[1]
Spacecraft properties
Launch mass	≈3,939 kg
BOL mass	≈2,000 kg[1]
Dry mass	≈1,110 kg
Power	290 kW[1]
Start of mission
Launch date	2030 (suggested)
Rocket	Atlas V 511 or SLS
Uranus orbiter
Orbital insertion	2041
Orbits	≥14 (proposed)[1]

OCEANUS (Origins and Composition of the Exoplanet Analog Uranus System) is a mission concept conceived in 2016 and presented in 2017 as a potential future contestant as a New Frontiers program mission to the planet Uranus.^[2][1] The concept was developed by the Astronautical engineering students of Purdue University during the 2017 NASA/JPL Planetary Science Summer School. OCEANUS is an orbiter, which would enable a detailed study of the structure of the planet's magnetosphere and interior structure that would not be possible with a flyby mission.^[2]

Because of the required technology development and planetary orbital dynamics, the concept suggests a launch in August 2030 on an Atlas V 511 rocket and entering Uranus' orbit in 2041.^[1]

Ice giant sized planets are the most common type of planet according to Kepler data. The little data available on Uranus, an ice giant planet, come from ground-based observations and the single flyby of the Voyager 2 spacecraft, so its exact composition and structure are essentially unknown, as internal heat flux, and cause of its unique magnetic fields and extreme axial tilt or obliquity,^[1] making it a compelling target for exploration according to the Planetary Science Decadal Survey.^[2][3] The primary science objectives of OCEANUS are to study Uranus' interior structure, magnetosphere, and the Uranian atmosphere.^[1]

The required mission budget is estimated at $1.2 billion.^[1] The mission concept has not been formally proposed to NASA's New Frontiers program for assessment and funding. The mission is named after Oceanus, the Greek god of the ocean; he was son of the Greek god Uranus.^[4]

Since Uranus is extremely distant to the Sun (20 AU), relying in solar power is not possible past Jupiter, so the orbiter is proposed to be powered by three multi-mission radioisotope thermoelectric generators (MMRTG),^[2][1] a type of radioisotope thermoelectric generator. There is enough plutonium available to NASA to fuel only three more MMRTG like the one used by the Curiosity rover.^[5][6] One is already committed to the Mars 2020 rover.^[5] The other two have not been assigned to any specific mission or program, ^[6] and could be available by late 2021.^[5] The trajectory to Uranus would require a Jupiter gravity assist, but such alignments are calculated to be rare in the 2020s and 2030s, so the launch windows will be scant and narrow.^[2] If launching in 2030, reaching Uranus would occur 11 years later, in 2041,^[1] and it would use two bipropellant engines for orbital insertion.^[1] Alternatively, the SLS rocket could be used for a shorter cruise time,^[7] but it would result in a faster approach velocity, making orbit insertion more challenging, especially since the density of Uranus' atmosphere is unknown to plan for safe aerobraking.^[6]

The orbital configuration and distance would require two Venus gravity assists (in November 2032 and August 2034) and one Earth gravity assist (October 2034) along with the use of solar-electric propulsion within 1.5 AU.^[1] The science phase would take place from a highly elliptical orbit and perform a minimum of 14 orbits.^[1]

The 12.5 kg scientific payload would include instruments for a detailed study of the magnetic fields and to determine Uranus' global gravity field: ^[2][1]

• UMAG (Uranus Magnetometer) – is a magnetometer to study the magnetosphere and constrain models for dynamo generation.
• GAIA (Gravity and Atmospheric Instrument Antenna) - it would utilize the on-board communications antenna, transmitting in both X band and Ka band frequencies for radio science that would allow maping Uranus' global gravity field.
• UnoCam (Uranus' Juno Cam) – is a visible light, color camera to detect navigation hazards in Uranus' ring system and to provide context and panoramic images.
• URSULA (Understanding Real Structure of the Uranian Laboratory of Atmosphere) – an atmospheric probe that would be jettisoned into the atmosphere of Uranus just before orbit insertion. It would descend under a parachute and measure the noble gas abundances, isotopic ratios, temperature, pressure, vertical wind profiles, cloud composition and density,^[2] via a mass spectrometer, atmospheric structure instrument, nephelometer and ultra-stable oscillator. The total mass of the probe's instruments is about 127 kg.^[1]

• Exploration of Uranus
• Magnetosphere of Uranus

Uranus mission proposals

• MUSE
• ODINUS
• NASA Uranus orbiter and probe
• Uranus Pathfinder

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