“Space weather describes the changing environment throughout the Solar System, driven by the energetic and unpredictable nature of our Sun. Solar wind, solar flares and Coronal Mass Ejections can result in geomagetic storms on Earth, potentially damaging satellites in space and the technologies that rely on them, as well as infrastructure on the ground.
ESA’s future Lagrange mission will keep constant watch on the Sun. The satellite, located at the fifth Lagrange point, will send early warning of potentially harmful solar activity before it affects satellites in orbit or power grids on the ground, giving operators the time to act to protect vital infrastructure.”
“The Dawn mission was designed to study two large bodies in the asteroid belt in order to answer questions about the formation of the Solar System, as well as to test the performance of its ion drive in deep space. Ceres and Vesta were chosen as two contrasting protoplanets, the first one apparently “wet” (i.e. icy and cold) and the other “dry” (i.e. rocky), whose accretion was terminated by the formation of Jupiter. The two bodies provide a bridge in scientific understanding between the formation of rocky planets and the icy bodies of the Solar System, and under what conditions a rocky planet can hold water.
The International Astronomical Union (IAU) adopted a new definition of planet on August 24, 2006, which introduced the term “dwarf planet” for ellipsoidal worlds that were too small to qualify for planetary status by “clearing their orbital neighborhood” of other orbiting matter. Dawn is the first mission to study a dwarf planet, arriving at Ceres a few months before the arrival of the New Horizons probe at Pluto in July 2015.
Ceres comprises a third of the total mass of the asteroid belt. Its spectral characteristics suggest a composition similar to that of a water-rich carbonaceous chondrite. Vesta, a smaller, water-poor achondritic asteroid comprising a tenth of the mass of the asteroid belt, has experienced significant heating and differentiation. It shows signs of a metallic core, a Mars-like density and lunar-like basaltic flows.
Available evidence indicates that both bodies formed very early in the history of the Solar System, thereby retaining a record of events and processes from the time of the formation of the terrestrial planets. Radionuclide dating of pieces of meteorites thought to come from Vesta suggests that Vesta differentiated quickly, in three million years or less. Thermal evolution studies suggest that Ceres must have formed some time later, more than three million years after the formation of CAIs (the oldest known objects of Solar System origin).
Moreover, Vesta appears to be the source of many smaller objects in the Solar System. Most (but not all) V-type near-Earth asteroids, and some outer main-belt asteroids, have spectra similar to Vesta, and are thus known as vestoids. Five percent of the meteoritic samples found on Earth, the howardite–eucrite–diogenite (HED) meteorites, are thought to be the result of a collision or collisions with Vesta.
It is thought that Ceres may have a differentiated interior; its oblateness appears too small for an undifferentiated body, which indicates that it consists of a rocky core overlain with an icy mantle. There is a large collection of potential samples from Vesta accessible to scientists, in the form of over 1,400 HED meteorites, giving insight into Vesta geologic history and structure. Vesta is thought to consist of a metallic iron–nickel core, an overlying rocky olivine mantle and crust.”
“The stacked spacecraft will take seven years to position itself to enter Mercury orbit. During this time it will use solar-electric propulsion and nine gravity assists, flying past the Earth and Moon in April 2020, Venus in 2020 and 2021, and six Mercury flybys between 2021 and 2025.
The stacked spacecraft left Earth with an hyperbolic excess velocity of 3.475 km/s (2.159 mi/s). Initially the craft is placed in an orbit similar to that of the Earth. After both the spacecraft and the Earth completed one and a half orbits, it returns to Earth to perform a gravity-assist manoeuvre and is deflected towards Venus. Two consecutive Venus flybys reduce the perihelion nearly to Mercury distance with almost no need for thrust. A sequence of six Mercury flybys will lower the relative velocity to 1.76 km/s (1.09 mi/s). After the fourth Mercury flyby the craft will be in an orbit similar to that of Mercury and will remain in the general vicinity of Mercury. Four final thrust arcs reduce the relative velocity to the point where Mercury will “weakly” capture the spacecraft on 5 December 2025 into polar orbit. Only a small manoeuvre is needed to bring the craft into an orbit around Mercury with an apocentre of 178,000 km. The orbiters then separate and will adjust their orbits using chemical thrusters.”
“Rosetta launched in 2004 and travelled for ten years to its destination before deploying the lander Philae to the comet’s surface. Following the comet along its orbit around the Sun, Rosetta studied the comet’s surface changes, its dusty, gassy environment and its interaction with the solar wind. Even though scientific operations concluded in September 2016 with Rosetta’s own descent to the comet’s surface, analysis of the mission’s data will continue for decades.”
“The Transiting Exoplanet Survey Satellite (TESS) is a space telescope for NASA’s Explorers program, designed to search for exoplanets using the transit method in an area 400 times larger than that covered by the Kepler mission. It was launched on April 18, 2018 atop a Falcon 9 rocket. During its primary mission, it is expected to find more than 20,000 exoplanets compared to about 3,800 exoplanets known when it launched.
The primary mission objective for TESS is to survey the brightest stars near the Earth for transiting exoplanets over a two-year period. The TESS satellite uses an array of wide-field cameras to perform a survey of 85% of the sky. With TESS, it is possible to study the mass, size, density and orbit of a large cohort of small planets, including a sample of rocky planets in the habitable zones of their host stars. TESS will provide prime targets for further characterization by the James Webb Space Telescope, as well as other large ground-based and space-based telescopes of the future. While previous sky surveys with ground-based telescopes have mainly detected giant exoplanets, TESS will find a large number of small planets around the nearest stars in the sky. TESS records the nearest and brightest main sequence stars hosting transiting exoplanets, which are the most favorable targets for detailed investigations.
TESS uses a novel highly-elliptical orbit with an apogee approximately at the distance of the Moon and a perigee of 108,000 km, above the geosynchronous satellites. TESS orbits Earth twice during the time the Moon orbits once, a 2:1 resonance with the Moon. The orbit is expected to remain stable for a minimum of 10 years.”
“NASA’s Dawn spacecraft turned science fiction into science fact by using ion propulsion to explore the two largest bodies in the main asteroid belt, Vesta and Ceres. The mission will end this fall, when the spacecraft runs out of hydrazine, which keeps it oriented and in communication with Earth.”
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