.png) Artist depiction of MMS spacecraft | |
| Names | MMS |
|---|---|
| Mission type | Magnetosphere research |
| Operator | NASA |
| COSPAR ID | 2015-011A 2015-011B 2015-011C 2015-011D |
| SATCATno. | 40482 40483 40484 40485 |
| Website | www |
| Mission duration | Planned: 2 years Elapsed: 10 years, 7 months, 11 days |
| Spacecraft properties | |
| Manufacturer | Goddard Space Flight Center |
| Launch mass | 1,360 kg (3,000 lb) |
| Dimensions | Stowed: 3.5 × 1.2 m (11.5 × 3.9 ft) Deployed: 112 × 29 m (367 × 95 ft) |
| Power | 318watts |
| Start of mission | |
| Launch date | 13 March 2015, 02:44UTC |
| Rocket | Atlas V 421 AV-053 |
| Launch site | Cape Canaveral,SLC-41 |
| Contractor | United Launch Alliance |
| Entered service | September 2015 |
| End of mission | |
| Last contact | 2040 (planned) |
| Orbital parameters | |
| Reference system | Geocentric orbit |
| Regime | Highly elliptical orbit |
| Perigee altitude | 2,550 km (1,580 mi) |
| Apogee altitude | Day phase: 70,080 km (43,550 mi) Night phase: 152,900 km (95,000 mi) |
| Inclination | 28.0° |
 Large Strategic Science Missions Heliophysics Division | |
TheMagnetospheric Multiscale (MMS) Mission is aNASA robotic space mission to study theEarth's magnetosphere, using four identical spacecraft flying in atetrahedral formation.[1] The spacecraft were launched on 13 March 2015 at 02:44UTC.[2] The mission is designed to gather information about themicrophysics ofmagnetic reconnection, energetic particle acceleration, andturbulence — processes that occur in many astrophysicalplasmas.[3] As of March 2020, the MMS spacecraft has enough fuel to remain operational until 2040.[4]
The mission builds upon the premise of theESACluster mission, but MMS instrumentation surpasses it in spatial resolution and in temporal resolution, allowing for the first time measurements of the critical electron diffusion region, the site where magnetic reconnection occurs. Its orbit is optimized to spend extended periods in locations where reconnection is known to occur: at the daysidemagnetopause, the place where the pressure from thesolar wind and the planets' magnetic field are equal; and in themagnetotail, which is formed by pressure from the solar wind on a planet's magnetosphere and which can extend great distances away from its originating planet.
Magnetic reconnection inEarth's magnetosphere is one of the mechanisms responsible for theaurora, and it is important to the science of controllednuclear fusion because it is one mechanism preventingmagnetic confinement of the fusion fuel. These mechanisms are studied in outer space by the measurement of motions of matter in stellar atmospheres, like that of the Sun. Magnetic reconnection is a phenomenon in which energy may be efficiently transferred from a magnetic field to the motion of charged particles.[5]
The MMS mission consists of four spacecraft. Each has a launch mass of 1,360 kg (3,000 lb).[6] In their stowed launch configuration, each are approximately 3.5 by 1.2 m (11.5 by 3.9 ft), and when stacked together they have a total height of 4.9 m (16 ft).[6] After being deployed in orbit, a total of eight axial and wire booms are deployed, including four Spin-Plane Double Probe (SDP) wire booms each 60 m (200 ft) long.[6]
The MMS spacecraft are spin stabilized, turning at a rate of three revolutions per minute to maintain orientation. Each spacecraft contains 12 thrusters connected to four hydrazine fuel tanks. Position data is provided by highly sensitive GPS equipment, while attitude is maintained by fourstar trackers, twoaccelerometers, and twoSun sensors.[6]
The mission is broken into three phases. The commissioning phase will last approximately five and a half months after launch, while the science phases will last two years. The first science phase will focus on the magnetic boundary between theEarth andSun (day side operations) for one and a half years, with the spacecraft formation orbiting the Earth at 2,550 by 70,080 km (1,580 by 43,550 mi). The second science phase will study reconnection in Earth's magnetic tail (night side operations) for half a year, increasing the orbit to 2,550 by 152,900 km (1,580 by 95,010 mi).[6]
Each spacecraft carries several experiments, divided into three suites: the Hot Plasma Suite, the Energetic Particles Detector Suite, and the Fields Suite.[7]
The Hot Plasma Suite measuresplasma particle counts, directions, and energies during reconnection. It consists of two instruments:
The Energetic Particles Detector Suite detects particles at energies far exceeding those detected by the Hot Plasma Suite. It consists of two instruments:
The Fields Suite[9] measures magnetic and electric field characteristics. It consists of six instruments:
Theprincipal investigator is James L. Burch ofSouthwest Research Institute, assisted by an international team of investigators, both instrument leads and theory and modeling experts.[12] The project scientist is Thomas E. Moore ofGoddard Space Flight Center.[13] Education and public outreach is a key aspect of the mission, with student activities, data sonification, and planetarium shows being developed.
The mission was selected for support by NASA in 2005. System engineering, spacecraft bus design, integration and testing has been performed byGoddard Space Flight Center inMaryland. Instrumentation is being improved, with extensive experience brought in from other projects, such as theIMAGE,Cluster andCassini missions. In June 2009, MMS was allowed to proceed to Phase C, having passed aPreliminary Design Review. The mission passed itsCritical Design Review in September 2010.[14] The spacecraft launched on anAtlas V 421 launch vehicle,[15] in March 2015.[2][16]
In order to collect the desired science data, the four satellite MMS constellation must maintain a tetrahedral formation through a defined region of interest in a highly elliptical orbit. The formation is maintained through the use of a high altitude ratedGPS receiver,Navigator, to provide orbit knowledge, and regularformation maintenance maneuvers.[17] ThroughNavigator, the MMS mission broke theGuinness World Record twice for highest altitude fix of a GPS signal (at 70,000 km (43,000 mi) and 187,200 km (116,300 mi) above the surface in 2016 and 2019 respectively).[18][19]
In 2016, the MMS mission was the first to directly detectmagnetic reconnection, the phenomenon which drivesspace weather in the Earth's magnetosphere.[20][21]
MMS has since detected magnetic reconnection occurring in unexpected places. In 2018, MMS made the first-ever detection of magnetic reconnection in themagnetosheath, a region of space previously thought to be too chaotic and unstable to sustain reconnection.[22]Magnetic flux ropes andKelvin–Helmholtz vortices are other phenomena where MMS has detected reconnection events against expectations.[4]
In August 2019, astronomers reported that MMS made the first high-resolution measurements of aninterplanetary shock wave from the Sun.[23]
A 2025 paper reported detection of amagnetic switchback in Earth's magnetic field with data from MMS.[24]
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