United Launch Alliance’s Atlas V rocket launched NASA’s Magnetospheric Multiscale (MMS) mission on Thursday. Launching from Cape Canaveral, the rocket placed the four-satellite constellation into a highly elliptical orbit, beginning a two-year mission to study reconnection in the magnetosphere. Launch occurred at the start of a thirty-minute window at 22:44 local time (02:44 UTC on Friday).
Atlas V launch:
The Magnetic Multiscale – or MMS – mission consists of four identical spacecraft which will be used to conduct plasma physics research in the environment of the Earth’s magnetosphere. The mission is intended to help scientists better understand a phenomenon called magnetic reconnection which has been observed in plasmas.
The phenomenon, which occurs naturally in the magnetosphere, results in the release of large amounts of energy as a result of intersecting magnetic field lines.
Flying in a tetrahedral formation, the MMS spacecraft will fly through the heart of reconnection events to allow three-dimensional mapping of how the particles and fields at hand interact.
The mission was conceived around 2003, with development of the spacecraft beginning in 2008. The MMS satellites were constructed by NASA’s Goddard Space Flight Center (GSFC) using a custom-made bus.
Octagonal in shape, the satellites measure 1.666 metres (5.476 feet) across by 1.230 metres (4.033 feet) high. Stacked together at launch, the combined spacecraft measure 4.920 metres (16.14 feet) in height.
During construction parts of the internal structures of the spacecraft were anodised different colours to help engineers distinguish them. Spacecraft number one was coloured orange, number two was coloured blue, number three green and number four pink.
The colours reportedly were intended to reflect the colours of the uniforms worn by The Beatles on the cover of their album Sgt. Pepper’s Lonely Hearts Club Band, as the spacecraft had been unofficially named John, Paul, George and Ringo after the members of the 1960s rock quartet.
Bound for highly elliptical orbits of 2,500 by 70,080 kilometres (1,600 by 43,500 miles, 1,300 by 37,840 nautical miles), following on-orbit commissioning the satellites will spend eighteen months studying reconnection events on the dayside boundary of the magnetosphere, where the magnetic fields of the Earth and Sun interact.
Following this the mission will enter a second phase with the spacecraft raising their apogees to 153,000 kilometres (95,000 miles or 82,600 nautical miles) in order to fly through the Earth’s magnetospheric tail and study events on the night side of the planet.
MMS builds on research conducted by several previous missions, particularly the European Space Agency’s four-satellite Cluster II mission and NASA’s five-spacecraft THEMIS constellation.
The Cluster II spacecraft were launched by a pair of Soyuz-U rockets in 2000, replaced the original Cluster spacecraft that were lost in 1996’s failed maiden flight of the Ariane 5.
THEMIS was launched by a single Delta II in 2007. While these satellites collected data on reconnection events they happened to observe, MMS will be the first mission whose primary objective relates to understanding reconnection.
Each of the four spacecraft carries three suites of instruments for a total of eleven experiments, with an identical loadout on all four vehicles.
The Hot Plasma Suite, designed to characterise the plasma environment in which reconnection events occur, consists of the Fast Plasma Investigation (FPI) and Hot Plasma Composition Analyzer (HPCA).
FPI uses particle filters to redirect fast-moving particles in the plasma onto sensor plates. Spectrometers will be used to analyse incident ions and electrons to characterise the quantities and energies of particles in the plasma.
FPI is designed to take fast, repeated measurements in order to collect as much data as possible as the spacecraft pass through reconnection events.
The Hot Plasma Composition Analyzer (HPCA) is a mass spectrometer which will be used to calculate the mass of incident particles from their speed. Measuring the time particles take to pass between two detector plates, the instrument will allow scientists to infer the presence of different types of atom or molecule from their masses.
The instrument will use radio emissions to block out most of the solar wind, allowing more accurate measurements of the particles already present in the magnetosphere.
The Energetic Particles Detector Suite, or EPD, is the second suite of instruments present aboard MMS and is intended to study the excitation of particles to extremely high energy levels as the result of magnetic reconnection.
Consisting of the Fly’s Eye Energetic Particle Sensor (FEEPS) and Energetic Ion Spectrometer (EIS), the EPD Suite will be used to test physicists’ theories about this excitation and whether it applies to particles heavier than electrons.
The FEEPS payload consists of two spectrometers per spacecraft, mounted on the top and bottom sides of the vehicles. Using solid state detectors to measure the energy imparted by particles which collide with the sensors, FEEPS will allow a picture to be built up of the particles present on either side of the spacecraft.
Some of the sensors in each instrument are optimised for detecting ions by using a detector plate so thin that electrons will pass through without interacting, while others are optimised for detecting electrons by using a foil covering to block larger particles from entering.
The Energetic Ion Spectrometer will be used to characterise the energy and velocity of incident ions, using similar solid-state sensors to those of FEEPS. The instruments will be used to interpolate the quantities of different types of particle, particularly oxygen ions and alpha and beta particles.
The final part of the MMS payload, the Fields Suite, consists of six instruments to conduct three-dimensional monitoring of the Earth’s magnetic field with a time resolution of up to one millisecond, integrated through the FIELDS Central Electronics, or CEB, data collection system.
Analogue Fluxgate magnetometers will be used to characterise changes in the strength of different parts of the magnetic field, while Digital Fluxgate magnetometers will also be used to complement their measurements.
The spacecraft also carries a Search Coil Magnetometer (SCM), an induction magnetometer which will record the electrical current induced in a coil of wire as it passes through the magnetic field.
The Electron Drift Instrument, or EDI, consists of two units mounted on opposite sides of each satellite that are equipped with electron guns and detectors.
The electron guns will emit beams of electrons into the magnetic field which will be curved by the presence of the field such that some of the electrons will be picked up by the detector on the other side of the spacecraft. By using the time taken for the electron beams to return to the satellite to calculate the distance they travelled, scientists will be able to measure the strength of the electromagnetic field.
EDI’s detectors can also be operated without the electron guns, allowing rapid measurements of naturally-incident electrons.
Magnetic Multiscale’s final instruments are the Spin-Plane Double Probe (SDP) and the Axial Double Probe (ADP), boom-mounted sensors intended to study the electric field around the satellites.
SDP consists of four electrodes mounted on the end of 60-metre (200-foot) booms extending from the sides of the spacecraft, while ADP uses electrodes on nine-metre (30-foot) booms protruding from the top and bottom surfaces. By measuring the electrical potential between the electrodes on opposing sides of the satellite, the electric field strength in each direction can be calculated.
A pair of Active Spacecraft Potential Control Devices (ASPOCs) are fitted to each of the satellites to reduce or cancel out the vehicles’ own electrical fields, which could otherwise affect observations and result in spurious data or experimental errors.
NASA selected United Launch Alliance to deploy the MMS mission, making use of an Atlas V rocket in the 421 configuration. Designated AV-053, the Atlas consists of a Common Core Booster (CCB) first stage augmented by two solid rocket motors.
A single-engine Centaur upper stage sits atop the CCB, with the satellites encapsulated within a four metre (13-foot) payload fairing.
Measuring four metres in diameter, the fairing is available in three different lengths; a Large Payload Fairing (LPF) is 12.2 metres (40 ft) long, with the Extended Payload Fairing (EPF) and Extra-Extended Payload Fairing (XEPF) adding one and two extra 90-centimetre (2.95-foot) sections respectively.
For Thursday’s flight, the Extra-Extended fairing was used.
The first stage of the Atlas burns RP-1 propellant, oxidised by liquid oxygen. A Russian-build RD-180 engine propels the stage, while two Aerojet AJ-60A solid rocket motors provide additional thrust during the earliest stages of the flight.
The Centaur is powered by a single RL10 engine which burns liquid hydrogen and liquid oxygen. For the MMS mission the Centaur will be sporting the older RL10A-4-2 engine which was used for the rocket’s first fifty flights before being replaced by the Delta IV-derived RL10C-1 on the most recent two launches.
Thursday’s launch took place from Space Launch Complex 41 (SLC-41) at the Cape Canaveral Air Force Station. The East-coast home of the Atlas V, SLC-41 was built in the 1960s for the Titan IIIC vehicle, and supported twenty-seven Titan IIIC, IIIE and IV launches between 1965 and 1998.
During the Titan era the complex shared its load with nearby Space Launch Complex 40 – now used by SpaceX to launch Falcon 9 rockets – as part of the Titan Integrate-Transfer-Launch complex that also consisted of a vertical integration building serving both pads.
Six months after its last Titan IV launch – an unsuccessful attempt to place a Defense Support Program missile defence satellite into geostationary orbit – work began at SLC-41 to accommodate the Atlas V.
The fixed and mobile towers used to support Titan launches were demolished to make way for the Atlas’ clean pad approach. By 2002 the complex had been refitted and was ready for the Atlas V’s maiden flight, which departed Cape Canaveral in August of that year carrying Eutelsat’s Hot Bird 6 communications satellite.
The deployment of MMS was the forty-third Atlas launch from Space Launch Complex 41 and the seventieth from the pad overall.
The facility has been earmarked for future use by manned missions to the International Space Station using Boeing’s CST-100 spacecraft launched atop an Atlas, with construction work on a new crew access tower beginning last month.
The MMS launch began with ignition of the Atlas’ RD-180 main engine, at the 2.7-second mark before liftoff. This was followed by solid rocket motor ignition and liftoff at around T+1.1 seconds, when the thrust generated by the engines exceeded the weight of the loaded vehicle.
Climbing away from its launch pad, AV-053 executed a series of pitch and yaw manoeuvres to establish its launch trajectory beginning 5.9 seconds into the mission. The vehicle headed East downrange over the Atlantic Ocean on an azimuth of 99.0 degrees.
As it accelerated through the atmosphere the Atlas reached a speed of Mach 1 48.9 seconds after liftoff, passing through the area of maximum dynamic pressure 13.6 seconds later.
The first major milestone in the mission was the separation of the two solid rocket motors at two minutes and 18.6 seconds elapsed time, the boosters having burned out approximately forty seconds previously.
First stage flight concluded with Booster Engine Cutoff (BECO), four minutes and 9.7 seconds after launch, with the RD-180 shutting down as it approached propellant exhaustion. Stage separation occurred six seconds after cutoff, with the RL10 beginning its prestart sequence.
Centaur ignition took place ten seconds after staging, commencing the first of two planned burns for the second stage.
This first burn lasted nine minutes and 3.3 seconds, placing the Centaur and its cargo into a parking orbit. About eight seconds into the burn the Atlas V’s payload fairing separated from around the MMS spacecraft at the nose of the rocket.
The burn was followed by a fifty-nine minute and 0.8 second coast phase before the RL10 restarted for its second and final burn of the mission.
This five-minute, 41.5-second burn established the initial deployment orbit for the MMS spacecraft, which separated at five minute intervals beginning fourteen minutes after the end of the final burn.
The target orbit for Thursday’s mission was an elliptical trajectory with a perigee of 585 kilometres (364 miles, 316 nautical miles), an apogee of 70,165 km (43,598 mi, 37,886 nmi), at an inclination of 28.77 degrees. From there the spacecraft will raise themselves into their operational orbits.
The second Atlas V mission of 2015 following January’s deployment of MUOS-3, Thursday’s launch was the twelfth of year worldwide – including the Vega launch in February which was not catalogued as an orbital mission despite the upper stage briefly reaching a low Earth orbit.
It is the fifth launch of the year from Cape Canaveral, following the previous Atlas V and three SpaceX Falcon 9 missions.
United Launch Alliance will next be in action towards the end of the month, with a Delta IV rocket carrying the GPS IIF-9 navigation satellite into orbit. The Atlas will make its next flight in May carrying the US Air Force’s AFSPC-5 payload, widely expected to be the fourth mission for the X-37B spaceplane.
(Images via ULA and NASA)