Atlas V launches MAVEN en route to Martian adventure

by William Graham

NASA’s MAVEN spacecraft has begun its journey to Mars following its launch atop the United Launch Alliance (ULA) Atlas V rocket Monday. Liftoff from Cape Canaveral’s Space Launch Complex 41 (SLC-41) occurred at 13:28 Eastern (18:28 UTC), at the start of what was a two-hour window.


The Mars Atmosphere and Volatile Evolution, or MAVEN, spacecraft is the second and final mission in NASA’s Mars Scout program. It will be placed into orbit around Mars, from where it is expected to study the planet’s atmosphere.

With a mass of 2,454 kilograms (5,410 lb), MAVEN is expected to operate for a year once it reaches Mars. The spacecraft is carrying 1645 kilograms (3627 lb) of propellant, with a dry mass of 809 kilograms (1,784 lb).

The spacecraft is powered by a pair of two-panel solar arrays, which will generate a minimum of 1.15 kilowatts. The spacecraft also carries two lithium ion batteries with capacities of 55 amp-hours which can be recharged by the solar arrays.

Propulsion is provided by six Aerojet MR-107N liquid rocket motors, with six smaller MR-106E thrusters for manoeuvring, and MR-103Ds for attitude control.

These are all monopropellant thrusters, fuelled by hydrazine propellant stored in the spacecraft’s central tank. MAVEN was manufactured by Lockheed Martin.

MAVEN carries eight scientific instruments to study the Martian atmosphere. Six of these instruments are collectively designated the Particles and Fields Package. The total mass of MAVEN’s instruments is 65 kilograms (143 lb).

Z9The Solar Energetic Particle experiment, or SEP, is part of the Particles and Fields Package designed to study the energies of hydrogen and helium ions emanating from solar storms which interact with Mars. Data collected will be used to help scientists characterise how these particles give energy to, and heat, the upper atmosphere of Mars.

These particles also have the effect of ionising particles in the upper atmosphere. SEP is similar to instruments previously flown on the WIND and THEMIS missions in Earth orbit, to study the interactions of solar particles with the Earth.

Led by the University of California at Berkeley, the SEP experiment utilises two sets of sensors mounted perpendicularly on the spacecraft. These consist of collectors which funnel ions through a magnetic field onto foil detectors.

The Solar Wind Ion Analyzer, or SWIA, is designed to study Mars’ interaction of the solar wind. Derived from instruments flown on the WIND, FAST and THEMIS spacecraft, SWIA will develop profiles of the temperature, velocity and density of ions in the solar wind, allowing scientists to calculate the rate at which Mars’ atmosphere is ionised by solar interactions. SWIA is part of the Particles and Fields Package.

The solar wind will also be studied by the Solar Wind Electron Analyzer (SWEA), which is another part of the Particles and Fields Package. Extended away from the body of the spacecraft by a short boom, measuring 1.7 metres in length, SWEA will study mid-energy electrons. It is designed to allow study of the distributions of energy and angular velocity amongst the electrons, helping to characterise their role in the ionisation of the upper atmosphere.

STATIC, the Suprathermal and Thermal Ion Composition experiment, is a third part of the Particles and Fields Package. It is designed to profile highly energetic charged particles in the upper atmosphere.

According to NASA it will study the velocities of the ionic forms of hydrogen, helium, oxygen and carbon dioxide. STATIC is similar to an instrument flown aboard the European Space Agency’s Cluster satellites, placed into Earth orbit by Soyuz rockets in 2000 following a failed Ariane 5 launch in June 1996.

Like SEP, the Solar Wind Ion Analyzer, Solar Wind Electron Analyzer and Suprathermal and Thermal Ion Composition experiments will be led by the University of California.

Z11Langmuir Probes and Waves (LPW) is another part of the Particles and Fields Package. Consisting of two sensors deployed away from the spacecraft on seven-metre (23-foot) booms, LPW will be used to conduct studies of Mars’ ionosphere.

An extreme ultraviolet imager is mounted on the body of the spacecraft for comparative observations. It is hoped that the experiment will better characterise the density of Mars’ ionosphere, and establish its boundaries. The experiment is led by the University of Colorado at Boulder.

The final part of the Particles and Fields Package is a pair of magnetometers mounted on the outside edges of the spacecraft’s solar arrays. The magnetometers are based on a design which has been used on NASA missions since the Voyager programme, while the arrangement of magnetometers on the solar arrays was previously flown on the Mars Global Surveyor mission.

Z11The primary objective of the magnetometers is to provide comparative data for the other instruments. NASA’s Goddard Space Flight Center is leading this part of the investigation.

An Imaging Ultraviolet Spectrograph (IUVS) will be used to study light emitted from particles in the upper atmosphere, thereby allowing scientists to determine its chemical composition.

The spectrometer has two openings, which will be used to study light reaching the spacecraft from different angles. Spectra will be produce which can then be studied to find information on the atmospheric composition.

Although primarily aimed at studying the upper atmosphere, the instrument can also be used to measure the amount of carbon dioxide in lower regions of the atmosphere. The University of Colorado will lead this experiment.

Z8MAVEN’s final instrument is the Neutral Gas and Ion Mass Spectrometer (NGIMS). This will be used to study the composition of the upper atmosphere in terms of low-energy ions and neutral, or unionised, gasses. It is hoped that by observing variations in composition by time or location data from other missions could be better calibrated.

It can also be used to produce data on the relative abundances of isotopes of particular elements, which could be used to establish the rate at which lower-mass particles are lost to space. NGIMS will be operated by NASA’s Goddard Space Flight Center.

A ninth payload aboard MAVEN is the 22-centimetre (8.7-inch) Electra communications array, which will be used to transmit data between spacecraft on the surface of Mars and ground stations back on Earth. Mars orbiters are often used to relay data from landers as not having to carry such a large communications array allows the mass of lander spacecraft to be reduced.

Z4NASA currently has two spacecraft operational on the surface of Mars; the ten-year-old Opportunity rover, and the Curiosity rover which arrived last year after launching in 2011.

Mars Scout is a NASA programme which was intended to conduct studies of Mars using comparatively low-cost spacecraft, providing dedicated funding for regular missions to the Red Planet compared to the more general Discovery Program, which funds many of NASA’s low-cost planetary missions.

The first Mars Scout mission was Phoenix, which was launched in August 2007. A lander, it touched down near Mars’ North Pole in May 2008, operating on the surface for over five months before the spacecraft’s solar arrays became unable to generate sufficient electrical power for the spacecraft.

The Phoenix mission, which was only expected to last 90 Martian days, or Sols, on the surface was completed successfully. Amongst the experiments it conducted, Phoenix dug into the surface, confirming the presence of water ice in the Martian soil.

In 2010 NASA announced the discontinuation of the Mars Scout programme after MAVEN, in favour of fewer, more expensive missions which could conduct complex surface missions, such as the Curiosity rover currently operating in Gale crater.

Z12NASA selected an Atlas V rocket, operated by United Launch Alliance, to send MAVEN on its way to Mars. The Atlas V used for this launch was AV-038; the forty-first Atlas V to fly since the type’s maiden flight in 2002.

Flying in the 401 configuration, with a four metre payload fairing, no solid rocket motors and a single-engine Centaur upper stage, the Atlas was tasked with delivering MAVEN into a heliocentric orbit: a hyperbolic trajectory in the Earth’s frame of reference with a characteristic energy of 12.2 kilometres squared per second squared.

The asymptote of the planned hyperbola has right ascension of 198.2 degrees, with declination of 17.7 degrees. It will be inclined 28.6 degrees relative to the Earth’s equator.

Monday’s launch was the first launch to heliocentric orbit since Curiosity on 26 November 2011.

India’s Mars Orbiter Mission, which was launched earlier this month, was placed into Earth orbit and will maneuver itself onto an escape trajectory.

At the time of MAVEN’s launch, MOM continues to orbit the Earth; as of 20:28 UTC on 15 November it was in a highly elliptical orbit with a perigee of 853 kilometres, an apogee of 194,683 kilometres and 19.42 degrees inclination.

Six engine firings have been conducted to raise the spacecraft’s orbit, the most recent at 20:07 on the 15th. A seventh, unplanned engine firing was made on 12 November after the burn two days earlier fell short of its planned duration.

Z7AV-038’s mission to loft MAVEN began with ignition of the first stage engine; an RD-180 built in Russia by NPO Energomash. The RD-180 powers the Common Core Booster; the first stage of the Atlas V; which is fuelled by RP-1 propellant and liquid oxygen oxidiser.

First stage ignition occurred at T-2.7 seconds; allowing the engine to build up thrust before liftoff. Around 3.8 seconds after ignition, at T+1.1 seconds, the thrust generated by the engine exceeded the mass of the rocket, and the Atlas V rose from its launch pad to begin the climb into orbit.

The rocket rolled to a launch azimuth of 94 degrees and perform a series of pitch and yaw maneuvers to attain the trajectory necessary for its target orbit, with the first maneuvers beginning at 17.3 seconds into the flight.

About 90.9 seconds after launch the vehicle experienced maximum dynamic pressure, or max-q, the point at which aerodynamic forces acting upon the rocket were at their greatest.

The first stage burn lasted until four minutes and 8.4 seconds into the mission, at which point Booster Engine Cutoff, or BECO, occurred. At this point the Common Core Booster exhausted its supply of propellant, and its engine was extinguished.

Z16Stage separation occurred six seconds later, with the upper stage detaching from the CCB to begin second stage flight.

The second stage of the Atlas V was a Single-Engine Centaur (SEC). This stage burns cryogenic propellants: liquid hydrogen and liquid oxygen, in a single RL10A-4-2 engine. Developed in the 1960s for used on Atlas and Saturn rockets, the Centaur has flown over 200 times in varying configurations as an upper stage on Atlas and Titan rockets.

Although traditionally Centaurs were powered by two engines, since the single-engine configuration was introduced with the Atlas III it has become the norm, and the Atlas V is yet to fly with a dual-engine configuration.

During Monday’s launch the Centaur made two burns. The first began 9.9 seconds after the first stage separates and lasted for nine and a half minutes.

Just under eight seconds into the burn the vehicle’s payload fairing separated from around the MAVEN spacecraft.

Z12The first Centaur burn culminated in Main Engine Cutoff 1, or MECO-1, 13 minutes, 48.3 seconds after liftoff. A coast phase then began, lasting for around 27 minutes and 36 seconds. At the end of the coast the Centaur began a second burn with a planned duration of five minutes, 28.9 seconds.

The completion of the second Centaur burn, SECO-2, marked the end of powered flight for AV-038.

Five minutes and 13 seconds later MAVEN separated from the upper stage to begin its journey to Mars.

From the countdown reaching zero to spacecraft separation, the Atlas’ mission lasted 52 minutes and 42.2 seconds.

Z6Following launch, MAVEN will begin a ten-month coast to Mars. Launch on 18 November would permit arrival at Mars on 22 September next year. The planned areocentric orbit has a periareon of 150 kilometres and an apoaereon of 6,220 km (93 by 3,860 miles).

A fifty-two week mission is planned; however up to six years of extended mission operations are possible, in addition to acting as a communications relay for spacecraft on the surface.

Following the end of its mission the spacecraft is expected to decay from orbit and enter the atmosphere of Mars, and as a result precautions have been taken to ensure it is sterilised in order to minimise contamination of the surface.

MAVEN is expected to launch during a 20-day window between 18 November and 6 December, although further, less desirable, opportunities are available until as late as 23 December. If the spacecraft cannot launch by that date, the planets will have moved out of alignment and another opportunity to launch will not occur until January 2016.

Z14AV-038 lifted off from Space Launch Complex 41 at the Cape Canaveral Air Force Station. Located in Florida on the East coast of the United States, Cape Canaveral was first used for the launch of a Bumper rocket in July 1950.

Launch Complex 41, as it was then called, was built in the 1960s for the Titan III rocket. A Titan IIIC was the first rocket to fly from the facility in December 1965.

Following several Titan IIIC launches, SLC-41 was used by the Titan IIIE and Titan IV rockets. In the late 1990s the complex was demolished and rebuilt to support the Atlas V. Monday’s launch is the sixty-second to make use of the complex.

MAVEN is the fifth Mars probe to launch from SLC-41.

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During the Atlas V’s tenure at the pad the Mars Reconnaissance Orbiter and Mars Science Laboratory (Curiosity) missions have been launched, while earlier Titan IIIE launches from the same pad deployed the two Viking probes in 1975.

Z15The deployment of MAVEN was the seventh and penultimate flight for the Atlas V this year; its only remaining mission before the end of 2013 is to deploy the classified NROL-39 payload for the US National Reconnaissance Office. Widely expected to be a Topaz radar imaging satellite, NROL-39 is scheduled for launch on 5 December.

Earlier this year, Atlas V rockets launched the TDRS-11 communications satellite for NASA, the Landsat 8 earth observation spacecraft, SBIRS-GEO-2, GPS IIF-4 and AEHF-3 for the US Air Force and MUOS-2 for the US Navy.

The next mission for United Launch Alliance is expected to be either the Atlas V launch of NROL-39, or a delayed Delta IV flight carrying the GPS IIF-5 satellite.

The GPS launch had been scheduled to occur last month but was delayed and no new launch date has been set.

(Images via L2, Philip Sloss/, Jacques van Oene/,Lockheed Martin, ULA and NASA).

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