Solar Helioshperic Research Group

Messenger

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) became the first spacecraft to orbit the planet Mercury on March 18, 2011. It was sent to answer very fundamental questions about the innermost planet and its harsh environment, e.g., What is Mercury's geologic history? What is the state of Mercury's core? What are the sources and sinks for its atmosphere? Sending a spacecraft so close to the Sun is not easy. In fact, prior to MESSENGER, Mercury had only been visited during the three flybys of the Mariner 10 spacecraft in the mid-1970's. Launched in 2004, it had taken 7 years and 6 gravity assist maneuvers for MESSENGER to begin orbiting Mercury, flying by the Earth, Venus (twice), and Mercury itself (3 times). In order to complete the long journey, MESSENGER carried over 500 kg of fuel, more than half of the spacecraft mass at launch. As a consequence of Mercury's proximity to the Sun, MESSENGER has a large sunshade to protect the instruments from solar radiation, which is 10 times more intense at Mercury than at Earth. The spacecraft is outfitted with a full complement of scientific instruments: two high resolution cameras to photograph the surface, several spectrometers to measure the elemental composition of the planet's crust, a laser altimeter to measure topography, a magnetometer to measure Mercury's intrinsic magnetic field, and two instruments to measure high-energy ions in its space environment.

The Solar and Heliospheric Research Group contributed one of those instruments, the Fast Imaging Plasma Spectrometer (FIPS). FIPS was designed and built here at the University of Michigan in conjunction with the Space Physics Research Laboratory. When compared with its predecessors, FIPS is much smaller, lighter, and uses much less power, properties which were required to fit aboard the MESSENGER spacecraft. Its primary function is to measure ions from Mercury itself, created from the ionization of the planet's very thin atmosphere or via collisions of micrometeroids and high energy ions from the solar wind with its surface. FIPS can measure ions ranging from hydrogen through iron on the periodic table and at energies up to 13 keV, which, for protons, corresponds to speeds of up to 3.4 million miles per hour. FIPS uses several key technologies to make these measurements, such as a precisely designed ion path including a 15-kV acceleration region and an electrostatic mirror, microchannel plate detectors capable of detecting single electrons, and fast electronics which can measure times of flight for these ions down to 1 ns.

Ulysses

Ulysses, launched by the Shuttle Discovery on October 6, 1990, is a joint ESA-NASA deep-space mission. Its primary scientific goal is to make the first-ever measurements of the unexplored region of space above the Sun's poles, and to reveal the 3-D the structure of the heliosphere, which is the region of space influenced by the Solar wind and its magnetic field.

To reach high solar latitudes, Ulysses flew by Jupiter on February 8, 1992, so that Jupiter's large gravitational field would accelerate it out of the ecliptic plane to high latitudes, regions which had never been studied before. Equipped with a comprehensive range of scientific instruments, Ulysses is able to detect and measure solar wind ions and electrons, magnetic fields, energetic particles, radio and plasma waves, dust and gas, X-rays, and gamma rays. This combination of experiments helped scientists understand the Sun and the heliosphere. Ulysses discovered the fast (600?800 km/s), cold (in electron temperature) and steady solar wind originating from the polar coronal holes of the Sun fans out to fill a significantly large portion of the heliosphere. Those fast winds are dramatically different from the slow, hot and variable wind that emerges from the Sun's equatorial zone and have constantly been observed by the spacecraft observed on the ecliptic plane (e.g. ACE and WIND).

On 30 June 2009, the Ulysses mission ended after 6842 days (18 years 8 months 24 days) in orbit.

ACE

The Advanced Composition Explorer, launched to the L1 point in 1997, is a space-based observatory of plasma from solar, interplanetary, and interstellar sources. Since science observations began, ACE has served as a real-time solar wind monitor and a warning system for extreme space weather events.

The Solar Wind Ion Composition Spectrometer (SWICS) and the Solar Wind Ions Mass Spectrometer (SWIMS) instruments on ACE are optimized for measurements of the chemical and isotopic composition of solar and interstellar matter. Both instruments are time-of-flight mass spectrometers with electrostatic analyzers, though each is optimized for different measurements. SWICS determines the chemical and ionic charge state composition of the solar wind and resolves H and He isotopes of both solar and interstellar sources. SWICS also measures the distribution functions of both the interstellar cloud and dust cloud pickup ions up to energies of 100 keV/e. SWIMS measures the chemical and isotopic composition of the solar wind for every element between He and Ni, up to 10 keV/e.

WIND

WIND was launched in 1994 as part of the International Solar Terrestrial Physics (ISTP) program. WIND, combined with the POLAR spacecraft were slated to take coordinated measurements of the near Earth space environment. The main science goal of the Wind mission was to observe the upstream conditions in front of the magnetosphere as well as observe the interaction with the solar wind as far downstream as inside the magnetotail. WIND spend the first 10 years of its mission lifetime executing a series of petal orbits that took it in and out of the magnetosphere and magnetotail as it precessed around the Earth. In 2005, WIND engaged its thrusters and set off for a new orbital position centered around the 1st lagrangian point, the gravitational saddle point between the Sun and the Earth. Since 2005, WIND has been constantly immersed in the solar wind, orbiting nearby the ACE spacecraft, providing a real-time platform for solar wind monitoring.

The SHRG maintains and operates the Solar wind/Suprathermal Mass Spectrometer (SMS) instrument suite, which consists of three sensors, one of which is the SupraThermal Ion Composition Spectrometer (STICS). STICS is a time-of-flight mass spectrometer that does not contain a post-acceleration region, thereby only accepting particles in the range of 6-230 keV/e. This energy range is ideal for observing the suprathermal ion population.

COSMO

The COronal Solar Magnetism Observatory (COSMO) facility consists of a suite of instruments that allows the measurement of the magnetic field, large-scale structure and thermodynamic properties of the solar corona with unprecedented detail and accuracy. The primary instrument is a 1.5-meter coronagraph which observes the Sun at multiple wavelengths in the visible range, allowing the measurement of spectral line profiles and magnetic field vector simultaneously in the entire field of view. Supporting instruments are a white-light K-coronagraph, and a chromosphere and prominence magnetometer. COSMO will provide the first large-scale, accurate measurements of the magnetic field of the solar corona and of its evolution over multiple time scales, as well as supporting determinations of coronal, wind and CME plasma density, thermal structure, and dynamics. COSMO will make it possible to study solar coronal heating, solar wind acceleration, and CME thermal and dynamic evolution close to the Sun in real time including, for the first time, the direct determination of the key player in solar structuring, heating and wind acceleration: the magnetic field.

Solar Orbiter

Solar Orbiter (SO) is a European Space Agency led mission, in partnership with NASA. SO will, for the first time, study the Sun with a full complement of instruments that will combine in-situ measurements along with imaging and spectral measurements of the Sun extending to high latitudes (>25 degrees out of the ecliptic) and in the inner heliosphere (perihelion is 0.28 AU). At times, Solar Orbiter's orbit will allow it to sweep very slowly across longitudes, enabling extended observations of confined areas on the Sun. Solar Orbiter will launch in 2017 has a nominal mission lifetime of 7.5 years.

The SHRG is involved in building the Heavy Ion Sensor (HIS), part of the Solar Wind Analyzer (SWA) instrument suite. HIS is a time of flight mass spectrometer which combines an electrostatic analyser with ion steering (EA-IS) which selects particles within a range of trajectories into the time of flight telescope. Ions that enter the time of flight telescope impact an energy resolving solid state detector after registering a time of flight (related to the ion's velocity) on microchannel plates. HIS will measure and characterize the heavy ion composition of the solar wind in an energy range extending from 0.5 keV/e up to 85 keV/e. The key science questions that HIS and SO will address are:

What mechanism and source regions are responsible for generating the solar wind and magnetic field in the corona?
How does heliospheric variability related to solar transients
How is solar energetic particle radiation generated by solar eruptions?
How does the solar dynamo drive connections between the Earth and the Sun?

Solar Probe Plus

Two puzzles about the Sun continue to defy explanation more than half a century after their discovery. Why is the atmosphere of the Sun, or corona, thousands of times hotter than the surface of the Sun beneath it? And how is a fraction of the Sun\'s atmosphere accelerated to escape as the solar wind? The best way to understand what causes the observed heating and acceleration is to send a probe directly into the solar corona, and advances in technology and mission design have finally made this possible.

Solar Probe Plus is a NASA mission designed to plunge directly into the atmosphere of the Sun for the first time in history. Reaching 4 million miles from the surface of the Sun, the spacecraft will enter a completely unexplored region of space. At these distances the Sun will be over 500 times brighter than it appears at Earth and particle radiation from solar activity will be harsh. In order to survive the spacecraft folds its solar panels into the shadows of its protective solar shade, leaving just enough of the specially-angled panels in sunlight to provide power closer to the Sun

The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation is the set of instruments on the spacecraft that will directly measure the properties of the plasma in the solar atmosphere during these encounters. A special component of SWEAP is a small instrument that will look around the protective heat shield of the spacecraft directly at the Sun. This will allow SWEAP to sweep up a sample of the atmosphere and touch the Sun, our star, for the first time.

The SWEAP Investigation is lead by Prof. Justin C. Kasper of the University of Michigan and the Smithsonian Astrophysical Observatory. Institutions participating in SWEAP include the Smithsonian Astrophysical Observatory, the University of California, Berkeley Space Sciences Laboratory, the University of Michigan, NASA Marshall Space Flight Center, the University of Alabama Huntsville, NASA Goddard Space Flight Center, Los Alamos National Laboratory, University of New Hampshire, and the Massachusetts Institute of Technology.

http://www.cfa.harvard.edu/sweap/
http://solarprobe.jhuapl.edu/

MWA

The Murchison Widefield Array (MWA) is an 8,000-antenna, 80-300 MHz, imaging radio array under construction in Western Australia. MWA is composed of hundreds of "tiles", which are 4 by 4 arrays of dipole antennas. Some of the key performance features of MWA are a large field of view (up to 50 degrees), high sensitivity (11,000 square meters of collecting area at 150 MHz), and accurate real-time polarization and intensity calibration. Key science projects of the MWA are understanding structure in the early universe through the detection of the Epoch of Reionization and remote imaging of magnetic and density structure in the solar corona and inner heliosphere. The performance required to meet the goal of our solar and cosmology science goals also makes MWA well-suited for blind searches for astrophysical radio transients.

For more information about MWA, including the status of the project and recent results, visit the main MWA web site http://mwatelescope.com/

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