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Solar Missions

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Parker Solar Probe

Parker Solar Probe was launched on 12 August 2018 to study the Sun.
It will assess the structure and dynamics of the Sun's coronal plasma and magnetic field, the energy flow that heats the solar corona and impels the solar wind, and the mechanisms that accelerate energetic particles.

Solar Orbiter is a satellite mission of ESA (in the footsteps of Helios, Ulysses, SOHO and the Cluster missions) to explore the inner regions of the sun and the heliosphere from a near-sun orbit. Solar Orbiter is part of the ESA's Science Program Cosmic Vision 2015-2025. The Solar Orbiter project was initially selected by ESA's Science Program Committee in Oct. 2000 and re-confirmed as part of the ESA program in 2003. The Solar Orbiter mission of ESA and the SPP (Solar Probe Plus) mission of NASA (launch scheduled for 2018)  are part of the common GHO (Great Heliophysics Observatory) program.

In 2011, the Solar Orbiter mission has undergone extensive study over a period of more than 10 years, both internally in ESA and in industry. This has resulted in a mature, detailed design that satisfies the requirements placed on the mission by the science objectives and addresses the key risk areas. - ESA's Science Program Committee selected the Solar Orbiter mission for implementation on October 4, 2011 with a launch scheduled for 2017. 1) 2) 3) 4)

ESA-NASA collaboration: NASA and ESA have a mutual interest in exploring the near-Sun environment to improve the understanding of how the Sun determines the environment of the inner solar system and, more broadly, generates the heliosphere itself, and how fundamental plasma physical processes operate near the Sun. A NASA-ESA MOU (Memorandum of Understanding) for a Solar Orbiter mission cooperation was signed in March 2012. 5)

For Solar Orbiter, also referred to as SolO in the literature, ESA is providing the spacecraft bus, integration of the instruments onto the bus, mission operations, and overall science operations. NASA is providing an EELV (Evolved Expendable Launch Vehicle) that will place the Solar Orbiter spacecraft into an inner heliospheric orbit with perihelia ranging from 0.28 to 0.38 AU and aphelia from 0.73 to 0.92 AU. The SolO nominal science mission will begin with a series of perihelion passes where the spacecraft is nearly co-rotating with the Sun. It will then use multiple Venus gravity assist maneuvers to move its orbital inclination to progressively higher helio latitudes, reaching 25° by the end of the nominal prime mission phase and around 34° by the end of the extended mission.

The overall objective is to provide close-up views of the sun's high latitude regions - to study fundamental physical processes common to solar, astrophysical and laboratory plasmas. The Solar Orbiter will, through a novel orbital design and its state-of-the-art instruments, provide exactly the observations required. 6) 7) 8) 9) 10) 11) 12) 13) 14)

• During the nominal operational lifetime, the Solar Orbiter operational orbit shall have the following parameters:

- Minimum perihelion radius larger than 0.28 AU to maximize the reuse of BepiColombo technology

- Perihelion radius within 0.30 AU in order to guarantee multiple observations close to the Sun

- Inclination with respect to solar equator increasing to a minimum of 25º (with a goal of 35º in the extended operational phase).

• At minimum perihelion passage, the spacecraft shall maintain a relative angular motion with respect to the solar surface such that individual solar surface features can be tracked for periods approaching one solar rotation.

• The Solar Orbiter system lifetime shall be compatible with a launch delay of 19 months (launch window locked to the next Venus gravitational assist opportunity).

Scientific requirements: The overarching objective of the Solar Orbiter mission is to address the central question of heliophysics: How does the Sun create and control the heliosphere? Achieving this objective is the next critical step in an overall strategy to address one of the fundamental questions in the Cosmic Vision theme: How does the Solar System work? To this end, the Solar Orbiter will use a carefully selected combination of in-situ and remote-sensing instrumentation, a unique orbit and mission design, and a well-planned observational strategy to explore systematically the region where the solar wind is born and heliospheric structures are formed.

The broad question that defines the overarching objective of the Solar Orbiter mission is broken down into four interrelated scientific questions:

1) How and where do the solar wind plasma and magnetic field originate in the corona?

2) How do transients drive heliospheric variability?

3) How do solar eruptions produce energetic particle radiation that fills the heliosphere?

4) How does the solar dynamo work and drive connections between the Sun and heliosphere?

Common to all of these questions is the requirement that Solar Orbiter make in-situ measurements of the solar wind plasma, fields, waves, and energetic particles close enough to the Sun that they are still relatively pristine and have not had their properties modified by dynamical evolution during their propagation. The Solar Orbiter must also relate these in-situ measurements back to their source regions and structures on the Sun through simultaneous, high-resolution imaging and spectroscopic observations both in and out of the ecliptic plane.

Basic mission requirements of Solar Orbiter:

- Total cruise phase duration < 3 years (goal) with valuable science during the cruise phase

- Orbital period in 3:2 resonance with Venus

- At least one orbit with perihelion radius < 0.25 AU and > 0.20 AU (science phase)

- Inclination with respect to solar equator increasing to a minimum of 30º

- During the extended operational lifetime, the Solar Orbiter operational orbit shall reach an inclination with respect to solar equator not lower than 35º (goal)

- Support a payload of 180 kg and 180 W (including 20% maturity margins) with a data rate of 100 kbit/s

- Provide onboard mass memory and communications with a single ESA deep-space ground station (New Norcia, Western Australia) in support of the science observations

- Fail-safe onboard autonomous operations during the perihelion passages (15 days without ground contact, in extremely harsh thermal environment).

The mission includes a nominal mission phase and a potential extended mission phase (corresponding to 6 solar orbits). The spacecraft consumables and radiation sensitive units shall be sized to meet the duration with extended phase: 9.5 years.

Solar Orbiter

Solar Orbiter joins NASA’s Parker Solar Probe in studying our star from closer than any spacecraft before them.

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