The Magnetospheric Multiscale (MMS) mission is a Solar Terrestrial Probes Program mission within NASA’s Heliophysics Division. The MMS mission, consisting of four identically instrumented spacecraft, uses Earth’s magnetosphere as a laboratory to study magnetic reconnection, a fundamental plasma-physical process that taps the energy stored in a magnetic field and converts it—typically explosively—into heat and kinetic energy in the form of charged particle acceleration and large-scale flows of matter.
The four MMS spacecraft carry identical suites of plasma analyzers, energetic particle detectors, magnetometers, and electric field instruments as well as a device to prevent spacecraft charging from interfering with the highly sensitive measurements. The plasma and fields instruments measure the ion and electron distributions and the electric and magnetic fields with unprecedented high (millisecond) time resolution and accuracy. These measurements enable MMS to locate and identify the small (tens of km) and rapidly moving (10—100 km/s) diffusion regions, to determine their size and structure, and to discover the mechanism(s) by which the plasma and the magnetic field become decoupled and the magnetic field is reconfigured. MMS is collecting the first unambiguous measurements of plasma composition at reconnection sites, while energetic particle detectors remotely sense the regions where reconnection occurs and determine how reconnection processes produce large numbers of energetic particles.
The four satellites launched together on an Atlas V-421 launch vehicle and were successfully inserted sequentially—at five-minute intervals—into Earth orbit. As they explore the dayside and nightside reconnection regions, the spacecraft fly in a tetrahedral (pyramid) formation, allowing them to capture the three-dimensional structure of the reconnection sites they encounter. Onboard propulsion is used to adjust the separation among the spacecraft—from hundreds of kilometers to as close as 10 kilometers—to achieve the optimum inter-spacecraft separation for probing the diffusion region.
The overarching goal of the MMS mission is to measure the plasma and the electric and magnetic fields inside the diffusion regions in Earth’s magnetosphere in order to answer the following fundamental questions:
- What conditions determine when reconnection is initiated and when it ceases?
- What determines the rate at which reconnection occurs?
- What is the structure of the diffusion region?
- How do the plasma and magnetic fields become decoupled in the diffusion region? In particular, what role do the electrons play in facilitating reconnection?
- What is the role of turbulence in the reconnection process?
- How does reconnection accelerate particles to high energies?
- LASP serves as the mission Science Operations Center (SOC), which includes science operations planning, instrument command sequence development, and science analysis support
- Science data for all MMS measurements is hosted at LASP and centrally disseminated to the science community
- LASP Director, Dan Baker, serves as the SMART (Solving Magnetospheric Acceleration, Reconnection, and Turbulence) Science Operations Center Lead
LASP built several key components to the MMS FIELDS investigation instruments. This includes the door and preamplifier assemblies for the Spin-plane Double Probe (SDP) electric field instrument, the Axial Double Probe (ADP) electric field instrument including booms, sensors, and preamplifiers, and the Digital Signal Processor (DSP) electronics that support onboard capture and processing of the ADP, SDP, and Search Coil Magnetometer (SCM) electric and magnetic field measurements.
Launch date: March 12, 2015
Launch location: Kennedy Space Center, Cape Canaveral, Florida
Launch vehicle: Atlas V-421
Mission target: Earth orbit
Mission duration: 2 years + 6 months
Other organizations involved:
- NASA’s Goddard Space Flight Center
- Southwest Research Institute
- University of New Hampshire
- Johns Hopkins University Applied Physics Laboratory
- Rice University
- Austrian Academy of Sciences
Click on the image to view a PDF (721 KB) of MMS FAQs.