NASA/JPL-Caltech rendering of the proposed Europa Clipper space probe.
|Mission type||Multiple flybys of Europa while in Jupiter orbit|
|Launch date||2025 (proposed)|
|Launch vehicle||Atlas V 551 or SLS|
|Mission duration||Cruise: 6.4 years
(Atlas V and VEEGA)
Cruise: 1.9 years
Science: 3.5 years
|Orbits||32  to 48 |
|Homepage||Europa Clipper - NASA Jet Propulsion Laboratory|
|Power||150W from MMRTG or Solar cells |
Immediately following the Galileo spacecraft's discoveries, JPL conducted preliminary mission studies that envisioned a capable spacecraft such as the Jupiter Icy Moons Orbiter (a $1.6B mission concept), the Jupiter Europa Orbiter (a $4.3B concept), an orbiter ($2B concept), and a multi-flyby spacecraft: Europa Clipper. The proposal and scope of the Europa Clipper mission are still in the conceptual stage, but the approximate cost is estimated at $2 billion. Meanwhile, the European Space Agency is already developing the Jupiter Icy Moon Explorer for a proposed launch in 2022.
In March 2013, $75 million USD were authorized to expand on the formulation of mission activities, mature the proposed science goals, and fund preliminary instrument development, as suggested in 2011 by the Planetary Science Decadal Survey. In May 2014, a House bill substantially increased Europa Clipper funding budget for the 2014 fiscal year from $15 million to $100 million. The funds would be applied to pre-formulation work.
The mission's science definition team is chaired by Louise Prockter from the Johns Hopkins University's the Applied Physics Laboratory (APL), and Barry Goldstein from the Jet Propulsion Laboratory (JPL), who presented an updated concept for Europa Clipper in July 2013.
The goals of the proposed Europa Clipper space probe are to explore Europa, investigate its habitability and aid in the selection of future landing sites. Specifically, the objectives are to study:
- Ice shell and ocean: Confirm the existence, and characterize the nature, of water within or beneath the ice, and processes of surface-ice-ocean exchange.
- Composition: Distribution and chemistry of key compounds and the links to ocean composition.
- Geology: Characteristics and formation of surface features, including sites of recent or current activity.
The Europa Clipper would not orbit Europa, but instead orbit Jupiter and conduct between 32 to 48 flybys of Europa at altitudes from 25 to 100 km each during its mission. Each flyby will cover a different sector of Europa in order to achieve a medium-quality global topographic survey, including ice thickness. The Europa Clipper could conceivably flyby at low altitude through the plumes of water vapor erupting from the moon's icy crust, thus sampling its subsurface ocean without having to land on the surface and drill though the ice. Europa's surface needs to be scouted out first; thus, the Clipper concept has as a secondary goal: to characterize scientifically compelling sites for a future lander mission to Europa.
Because Europa lies well within the harsh radiation fields surrounding Jupiter, even a radiation-hardened spacecraft in near orbit would be functional for just a few months. Another key limiting factor on science for a Europa orbiter is not the time the instruments can make observations. Rather, it is the time available to return data to Earth. Most instruments can gather data far faster than the communications system can transmit it to Earth, but there are a limited number of antennas available to receive the scientific data.
Studies by scientists from the Jet Propulsion Laboratory show that by performing several flybys with many months to return data, the Europa Clipper concept would enable a $2B mission to conduct the most crucial measurements of the cancelled $4.3B Jupiter Europa Orbiter concept. Between each of the flybys, the multi-flyby spacecraft would have seven to ten days to transmit data stored during each brief encounter. That would let the multi-flyby craft have up to a year of time to transmit its data compared to just 30 days for an orbiter. The result would be almost three times as much data returned to Earth, while reducing exposure to radiation.
- Shortwave Infrared Spectrometer (SWIRS) can identify materials exposed on Europa's surface and map their distribution, and eventually study it with a lander.
- Ice-penetrating radar (IPR) would determine the thickness of the ice, study whether bodies of water are trapped within the ice between the surface and the ocean below, study fracturing of the shell and help understand how material is transported between the ocean and the surface.
- Stereo Topographical Imager (TI) to map the surface.
- Neutral Mass Spectrometer (NMS) to elucidate the chemical structures of molecules on the surface, and to analyze the moon's trace atmosphere during flybys
- Magnetometer would characterize the magnetic field and gravity of Europa.
- Langmuir probes would measure the plasma field around Europa.
- Reconnaissance Camera (RC) to acquire surface images in the visible spectrum.
- Thermal Imager (ThI) to map temperature at the surface.
The scientists proposing this mission are also considering deploying from the spacecraft several miniaturized satellites of the CubeSat type, possibly driven by xenon thrusters, to sample and analyse Europa's plumes. Europa Clipper will relay signals from the satellites with its high gain antenna back to Earth. With propulsion, some nanosatellites will be capable of entering orbit around Europa. However, including additional mass would only be possible if the Europa Clipper is launched with the powerful Space Launch System (SLS) heavy lift launch vehicle.
Europa Clipper would inherit tested technology of the Galileo and Juno Jupiter orbiters with regards to radiation protection. Shielding will be provided by 150 kilograms of material. To maximize its effectiveness, the electronics will be nested in the core of the spacecraft for additional radiation protection.
In September 2013 it was decided that solar panels are the least expensive option to power the spacecraft. Early analysis suggest that each panel will have a surface area of 18m2 and produce 150 watts continuously when pointed towards the sun while at Jupiter. While in Europa's shadow, batteries will enable the spacecraft to continue gathering data. However, ionizing radiation can damage solar cells. The Europa Clipper's orbit causes the spacecraft pass through Jupiter's intense magnetosphere, which is expected to gradually degrade the solar cells as the mission progresses.
A more reliable alternative to solar panels is Multi-Mission Radioisotope Thermoelectric Generators, fueled with plutonium-238. The power source has already been demonstrated in the Mars Science Laboratory mission. Five units are currently available, with one reserved for the Mars 2020 rover mission and another as backup. If funding becomes available, a restart of plutonium production and replacement of the equipment needed to press it into pellets, it would be feasible to use MMRTGs on Europa Clipper.
A baseline profile for the mission would involve launch aboard an Atlas V 551. By using a Venus-Earth-Earth gravity assist trajectory the transit time to Jupiter would be about 6 years. Alternately, if the mission was launched by NASA's Space Launch System, it could arrive at Jupiter on a direct trajectory in less than 3 years.
- Europa Jupiter System Mission – Laplace
- Europa Lander by Russia
- Europa Orbiter
- Exploration of Jupiter
- Jupiter Icy Moon Explorer
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