Europa Clipper
Europa Clipper (previously known as Europa Multiple Flyby Mission) is an interplanetary mission in development by NASA comprising an orbiter. Planned for launch in October 2024, the spacecraft is being developed to study the Galilean moon Europa through a series of flybys while in orbit around Jupiter. This mission is a scheduled flight of the Planetary Science Division, designated a Large Strategic Science Mission, and funded under the Planetary Missions Program Office's Solar System Exploration program as its second flight. It is also supported by the new Ocean Worlds Exploration Program. "Europa Clipper" will perform follow-up  studies to those made by the "Galileo" spacecraft during its eight years in Jupiter orbit, which indicated the existence of a subsurface ocean underneath Europa's ice crust. Plans to send a spacecraft to Europa were initially conceived with projects such as "Europa Orbiter" and "Jupiter Icy Moons Orbiter", in which a spacecraft would be injected into orbit around Europa. However, due to the adverse effects of radiation from Jupiter's magnetosphere in Europa orbit, it was decided that it would be safer to inject a spacecraft into an elliptical orbit around Jupiter and make 44 close flybys of the  moon instead. The mission began as a joint investigation between the Jet Propulsion Laboratory (JPL) and the Applied Physics Laboratory (APL), and will be built with a scientific payload of nine instruments contributed by JPL, APL, Southwest Research Institute, University of Texas at Austin, Arizona State University and University of Colorado Boulder. The mission will complement ESA's Jupiter Icy Moons Explorer launching in 2023, which will fly-by Europa twice and Callisto multiple times before moving into orbit around Ganymede. The mission is scheduled to launch in October 2024 aboard a Falcon Heavy, during a 21-day launch window . The spacecraft will use gravity assists from Mars in February 2025 and Earth in December 2026, before arriving at Europa in April 2030. History. In 1997, a "Europa Orbiter" mission was proposed by a team for NASA's Discovery program but was not selected. NASA's JPL announced one month after the selection of Discovery proposals that a NASA Europa orbiter mission would be conducted. JPL then invited the Discovery proposal team to be the Mission Review Committee (MRC). At the same time as the proposal of the Discovery-class "Europa Orbiter" the robotic "Galileo" spacecraft was already orbiting Jupiter . From 8 December 1995 to 7 December 1997 "Galileo" conducted the primary mission after entering the orbit of Jupiter. On that final date the Galileo orbiter commenced an extended mission known as the "Galileo" Europa Mission (GEM), which ran until 31 December 1999. This was a low-cost mission, with a budget of only US$30 million. The smaller team of about 40-50 people (one-fifth the size of the primary mission's 200-person team from 1995-1997) did not have the resources to deal with problems, but when they arose it was able to temporarily recall former  team members (called "tiger teams") for intensive efforts to solve them. The spacecraft made several flybys of Europa (8), Callisto (4) and Io (2). On each flyby of the three moons it encountered, the spacecraft collected only two days' worth of data instead of the seven it had collected during the primary mission. This "Galileo" Europa Mission was similar to a small-scale version of what the "Europa Clipper" is planning to accomplish. GEM included eight flybys of Europa, ranging from to , in two years. Europa has been identified as one of the locations in the Solar System that could  possibly harbor microbial extraterrestrial life. Immediately following the "Galileo" spacecraft's discoveries and the independent Discovery program proposal for a Europa orbiter, JPL conducted preliminary mission studies that envisioned a capable spacecraft such as the Jupiter Icy Moons Orbiter (a US$16 billion mission concept), the Jupiter Europa Orbiter (a US$4.3 billion concept), an orbiter (US$2 billion concept), and a multi-flyby spacecraft: "Europa Clipper". "Europa Clipper" is still in its planning phase and early development, but the approximate cost estimate rose from US$2 billion in 2013, to US$4.25 billion in 2020. The mission is a  joint project between the Johns Hopkins University's Applied Physics Laboratory (APL), and the Jet Propulsion Laboratory (JPL). The mission's name is a reference to the lightweight clipper ships of the 19th century that routinely plied trade routes around the world. The moniker was chosen because the spacecraft will "sail" past Europa, as frequently as every two weeks. In March 2013, US$75 million 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 the "Europa Clipper" (referred to as "Europa Multiple Flyby Mission") funding budget for the 2014 fiscal year from US$15 million to US$100 million to be applied to pre-formulation work. Following the 2014 election cycle, bipartisan support was pledged to continue funding for the "Europa Multiple Flyby Mission" project. The executive branch has also granted US$30 million for preliminary studies. In April 2015, NASA offered to the European Space Agency to submit concepts for an additional probe to fly together with the "Europa Clipper" spacecraft, with a mass limit of 250 kg maximum. It  could be a simple probe, an impactor, or a lander. An internal assessment at European Space Agency (ESA) is underway to see if there is interest and funds available, opening a collaboration scheme similar to the very successful "Cassini-Huygens" approach. In May 2015, NASA chose nine instruments that would fly on board the orbiter. They will cost about US$110 million over the next three years. In June 2015, NASA announced its approval of the mission concept, allowing the orbiter to move to its formulation stage, and in January 2016 it approved a lander as well. In May 2016 , the Ocean Worlds Exploration Program was approved, of which the Europa mission is part. In February 2017, the mission moved from Phase A to Phase B (the preliminary design phase). On 18 July 2017, the House Space Subcommittee held hearings on the "Europa Clipper" as a scheduled Large Strategic Science Missions class, and to discuss a possible follow up mission simply known as the Europa Lander. Phase B continued into 2019. In addition, subsystem vendors were selected, as well as prototype hardware elements for the science instruments. Spacecraft sub-assemblies will be built and tested as well. On 19 August  2019, the "Europa Clipper" was confirmed to move on to Phase C: final design and fabrication. On 3 March 2022, the spacecraft moved on to Phase D: assembly, testing, and launch. Objectives. The goals of "Europa Clipper" are to explore Europa, investigate its habitability and aid in the selection of a landing site for the future Europa Lander. This exploration is focused on understanding the three main requirements for life: liquid water, chemistry, and energy. Specifically, the objectives are to study: Strategy. 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. Most instruments can gather data far faster than the communications system can transmit it to Earth because there are a limited number of antennas available on Earth to receive the scientific data. Therefore, another key limiting factor on science for a Europa orbiter is the time available to return data to Earth. In contrast, the amount of time during which the instruments can make close-up observations is less important. Studies by scientists from the Jet Propulsion Laboratory show that by performing several flybys with many months to return data, the  Europa Clipper concept will enable a US$2 billion mission to conduct the most crucial measurements of the cancelled US$4.3 billion Jupiter Europa Orbiter concept. Between each of the flybys, the spacecraft will have seven to ten days to transmit data stored during each brief encounter. That will let the spacecraft have up to a year of time to transmit its data compared to just 30 days for an orbiter. The result will be almost three times as much data returned to Earth, while reducing exposure to radiation. The "Europa Clipper" will not orbit Europa, but instead orbit Jupiter  and conduct 44 flybys of Europa at altitudes from each during its 3.5-year mission. A key feature of the mission concept is that the "Clipper" would use gravity assists from Europa, Ganymede and Callisto to change its trajectory, allowing the spacecraft to return to a different close approach point with each flyby. Each flyby would 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 ice crust, thus sampling its  subsurface ocean without having to land on the surface and drill through the ice. The "Europa Clipper" will inherit tested technology of the "Galileo" and "Juno" Jupiter orbiters with regards to radiation protection. Shielding will be provided by 150 kilograms of titanium. To maximize its effectiveness, the electronics will be nested in the core of the spacecraft for additional radiation protection. Design and construction. Power. Both radioisotope thermoelectric generator (RTG) and photovoltaic power sources were assessed to power the orbiter. Although solar power is only 4% as intense at Jupiter as it is in Earth's orbit, powering a Jupiter  orbital spacecraft by solar panels was demonstrated by the "Juno" mission. The alternative to solar panels was a multi-mission radioisotope thermoelectric generator (MMRTG), fueled with plutonium-238. The power source has already been demonstrated in the Mars Science Laboratory (MSL) mission. Five units were available, with one reserved for the Mars 2020 rover mission and another as backup. In September 2013, it was decided that the solar array was the less expensive option to power the spacecraft, and on 3 October 2014, it was announced that solar panels were chosen to power "Europa Clipper". The mission's designers determined that  solar was both cheaper than plutonium and practical to use on the spacecraft. Despite the increased weight of solar panels compared to plutonium-powered generators, the vehicle's mass had been projected to still be within acceptable launch limits. Initial analysis suggest that each panel will have a surface area of and produce 150 watts continuously when pointed towards the Sun while orbiting Jupiter. While in Europa's shadow, batteries will enable the spacecraft to continue gathering data. However, ionizing radiation can damage solar panels. The "Europa Clipper" orbit will pass through Jupiter's intense magnetosphere, which is expected to  gradually degrade the solar panels as the mission progresses. The solar panels will be provided by Airbus Defence and Space, Netherlands. Scientific payload. The "Europa Clipper" mission is equipped with a sophisticated suite of 9 instruments to study Europa's interior and ocean, geology, chemistry, and habitability. The electronic components will be protected from the intense radiation by a 150-kilogram titanium and aluminum shield. The spacecraft payload and trajectory are subject to change as the mission design matures. The nine science instruments for the orbiter, announced in May 2015, have an estimated total mass of and are listed below : Europa Thermal Emission Imaging System (E-THEMIS). The Europa Thermal Emission Imaging System will provide high spatial resolution as well as multi-spectral imaging of the surface of Europa in the mid to far infrared bands to help detect geologically active sites and areas, such as potential vents erupting plumes of water into space. This instrument is derived from the Thermal Emission Imaging System (THEMIS) on the "2001 Mars Odyssey" orbiter, also developed by Philip Christensen. Mapping Imaging Spectrometer for Europa (MISE). The Mapping Imaging Spectrometer for Europa is an imaging near infrared spectrometer to probe the surface composition of  Europa, identifying and mapping the distributions of organics (including amino acids and tholins), salts, acid hydrates, water ice phases, and other materials. From these measurements, scientists expect to be able to relate the moon's surface composition to the habitability of its ocean. MISE is built in collaboration with the Johns Hopkins University Applied Physics Laboratory (APL). Europa Imaging System (EIS). The Europa Imaging System is a visible spectrum wide and narrow angle camera instrument that will map most of Europa at resolution, and will provide images of selected surface areas at up to 0.5 m resolution. Europa Ultraviolet Spectrograph  (Europa-UVS). The Europa Ultraviolet Spectrograph instrument will be able to detect small plumes and will provide valuable data about the composition and dynamics of the moon's exosphere. The principal investigator Kurt Retherford was part of a group that discovered plumes erupting from Europa while using the Hubble Space Telescope in the UV spectrum. Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The (REASON) is a dual-frequency ice penetrating radar instrument that is designed to characterize and sound Europa's ice crust from the near-surface to the ocean, revealing the hidden structure of Europa 's ice shell and potential water pockets within. This instrument will be built by Jet Propulsion Laboratory. Interior Characterization of Europa using Magnetometry (ICEMAG). The Interior Characterization of Europa using Magnetometry (ICEMAG) was cancelled due to cost overruns. ICEMAG will be replaced by a simpler magnetometer. Plasma Instrument for Magnetic Sounding (PIMS). The Plasma Instrument for Magnetic Sounding (PIMS) measures the plasma surrounding Europa to characterise the magnetic fields generated by plasma currents. These plasma currents mask the magnetic induction response of Europa's subsurface ocean. In conjunction with a magnetometer, it is key to determining Europa's ice shell  thickness, ocean depth, and salinity. PIMS will also probe the mechanisms responsible for weathering and releasing material from Europa's surface into the atmosphere and ionosphere and understanding how Europa influences its local space environment and Jupiter's magnetosphere. Mass Spectrometer for Planetary Exploration (MASPEX). The Mass Spectrometer for Planetary Exploration (MASPEX) will determine the composition of the surface and subsurface ocean by measuring Europa's extremely tenuous atmosphere and any surface materials ejected into space. Jack Waite, who led development of MASPEX, was also Science Team Lead of the Ion and Neutral Mass Spectrometer (INMS) on the "Cassini" spacecraft . Surface Dust Analyzer (SUDA). The SUrface Dust Analyzer (SUDA) is a mass spectrometer that will measure the composition of small solid particles ejected from Europa, providing the opportunity to directly sample the surface and potential plumes on low-altitude flybys. The instrument is capable of identifying traces of organic and inorganic compounds in the ice of ejecta. Possible secondary elements. The "Europa Clipper" mission considered an extra mass of about 250 kg to carry an additional flight element. About a dozen proposals have been suggested but none went beyond the concept study phase and none are planned for the Europa  Clipper mission. A few of which are described next: Since the "Europa Clipper" mission may not be able to easily modify its orbital trajectory or altitude to fly through the episodic water plumes, scientists and engineers working on the mission have investigated deploying from the spacecraft several miniaturized satellites of the CubeSat format, possibly driven by ion thrusters, to fly through the plumes and assess the habitability of Europa's internal ocean. Some early proposals include "Mini-MAGGIE", "DARCSIDE", "Sylph" and CSALT. These concepts were funded for preliminary studies but none were considered for hardware development or flight. The "Europa  Clipper" would have relayed signals from the nanosatellites back to Earth. With propulsion, some nanosatellites could also be capable of entering orbit around Europa. The "Europa Life Signature Assayer" (ELSA) concept by the University of Colorado consisted of a probe that could have been flown as a secondary payload. ELSA would have used a small impactor to create a plume of subsurface particles and catapulted them to altitudes where it would have been able to pass through to collect samples and analyze them on board. A variation of this concept is the 1996 "Ice Clipper", which involves a 10 kg  impactor that would be jettisoned from the main spacecraft to impact Europa, thereby creating a debris cloud in nearby space about 100 km altitude, subsequently sampled by a small spacecraft on a close flyby and use Europa's gravitational force for a free return trajectory. The collection mechanism is tentatively considered to be aerogel (similar to "Stardust" mission). Add-on lander history. An early "Europa Clipper" concept called for including a stationary lander about 1 meter in diameter, perhaps about with a maximum of for instruments plus propellant. Suggested instruments were a mass spectrometer and a Raman spectrometer to determine  the chemistry of the surface. The lander was proposed to be delivered to Europa by the main spacecraft and possibly require the sky crane system for a high precision, soft landing near an active crevasse. The lander would have operated about 10 days on the surface using battery power. The "Europa Clipper" would take about three years to image 95% of the surface of Europa at about 50 meters per pixel. With this data, scientists could then find a suitable landing site. By one estimate, including a lander could add as much as US$1 billion to the mission's  cost. It was determined in February 2017 that designing a system capable of landing on a surface about which very little is known is too much risk, and that the "Europa Clipper" will lay the foundation for a future landing mission by performing detailed reconnaissance first. This led to a stand-alone mission proposal in 2017: the Europa Lander. The NASA Europa Lander, if funded, would be launched separately in 2025 to complement the studies by the "Europa Clipper" mission. If funded, approximately 10 proposals may be selected to proceed into a competitive process with a US$1.5 million budget  per investigation. The President's 2018 and 2019 federal budget proposals do not fund the Europa Lander, but it did assign US$195 million for concept studies. The 2022 omnibus spending bill allocates $14.2 million for Icy Satellites Surface Technology for a future Ocean Worlds lander mission (Nasa had requested $5 million for the Europa Lander). Launch and trajectory. Congress had originally mandated that "Europa Clipper" be launched on NASA's Space Launch System (SLS) super heavy-lift launch vehicle, but NASA had requested that other vehicles be allowed to launch the spacecraft due to a foreseen lack  of available SLS vehicles. The United States Congress's 2021 omnibus spending bill directed the NASA Administrator to conduct a full and open competition to select a commercial launch vehicle if the conditions to launch the probe on a SLS rocket cannot be met. A launch on a Delta IV Heavy with a gravity assist at Venus was considered. On 25 January 2021, NASA's Planetary Missions Program Office formally directed the mission team to "immediately cease efforts to maintain SLS compatibility" and move forward with a commercial launch vehicle. On 10 February 2021, it was announced that the  mission would use a 5.5-year trajectory to the Jovian system, with gravity-assist maneuvers involving Mars (February 2025) and Earth (December 2026). Launch is targeted for a 21-day period between 10 and 30 October 2024, giving an arrival date in April 2030, and backup launch dates were identified in 2025 and 2026. The SLS option would have entailed a direct trajectory to Jupiter taking less than three years. One alternative to the direct trajectory was identified as using a commercial rocket such as a Falcon Heavy, with a longer 6-year cruise time involving gravity assist maneuvers at  Venus, Earth and/or Mars. Another option was to launch on a Falcon Heavy and perform a 700–800 m/s dV deep-space maneuver at insertion orbit aphelion. This launch window is open once a year and would have required only one gravity assist, with Earth, and would shorten the travel time to 4.5 years, while only needing a C3 of 25–28 km^2/s^2. The trajectory with the Mars assist was likely chosen so there would not need to be a deep-space maneuver at the spacecraft's aphelion, therefore decreasing spacecraft delta-V requirements. In July 2021 Falcon Heavy was  chosen to launch the spacecraft. Three reasons were given: launch cost, SLS availability, and "shaking". The move to Falcon Heavy saved an estimated US$2 Billion in launch costs alone. NASA was not sure an SLS would be available since the Artemis program would use the entire SLS production, and the SLS's use of solid rocket boosters (SRB)s intrinsically creates more vibrations in the payload than does a launcher that does not use SRBs. The cost to redesign Europa Clipper for the SLS vibratory environment was estimated at US$1 billion.