With a thunderous roar, NASA’s Mars Atmoshere and Volatile EvolutioN (MAVEN) spacecraft rocketed into space today on time at 1:28 p.m. EST and the opening of a 20-day launch period. Nestled atop a United Launch Alliance Atlas V-401 rocket, MAVEN lifted off from from Space Launch Complex-41 at Cape Canaveral AFS and quickly sliced through partly cloudy skies, thrilling crowds gathered along the causeways and beaches to watch NASA’s newest emissary to the Red Planet break the bonds of Earth’s gravity. Less than an hour later, MAVEN was cast free from the Atlas upper stage to begin a nearly year-long cruise to Mars and an ambitious mission to understand the history of the Martian atmosphere, present-day processes and add another piece to the question, Where did Mars water go?
“We’re currently about 14,000 miles away from Earth and heading out to the Red Planet right now,” said MAVEN Project Manager David Mitchell of NASA’s Goddard Space Flight Center.
“Safe travels, MAVEN,” Mitchell said. “We’re with you all the way.”
The 191-foot tall Atlas rocket sported a four meter diameter payload fairing atop the second-stage powered by a single-engine Centaur. Atlas provided 933,406 pounds of thrust to lift MAVEN out of Earth’s atmosphere before the Centaur took over to provide 22,300 pounds of thrust and the energy to propel the MAVEN on an escape trajectory toward Mars.
Following launch at T-0, the Atlas’ Russian-built RD-180 first stage fired for 250 seconds before shutting down and separating from the second stage. Shortly before first stage shutdown, at T+4.5 minutes, the payload fairing was released, jettisoning its added weight since it was no longer necessary to protect the spacecraft from the dense lower atmosphere.
The Centaur upper stage, powered by its RL-10B cryogenic engine, conducted two burns to place MAVEN on a trajectory that will intercept Mars in September, 2014. The first burn, lasting 9.5 minutes was followed by a 30-minute coast phase before Centaur fired again for approximately 5 and a half minutes.
Separation from the Centaur’s payload adapter occurred at approximately T+53 minutes. Deployment of the twin solar arrays took place five minutes later and ground controllers received the first communication with MAVEN over it’s Low-Gain communication system.
“MAVEN joins our orbiters and rovers already at Mars to explore yet another facet of the Red Planet and prepare for human missions there by the 2030s,” NASA Administrator Charles Bolden said. “This mission is part of an integrated and strategic exploration program that is uncovering the mysteries of the solar system and enabling us to reach farther destinations.”
Two to three weeks after launch, most of MAVEN’s instruments will power up for the first time and perform a post-launch checkout. The spacecraft will not extend any of its booms and the NGIMS and the IUVS instruments will power down following this early checkout procedure. The Particles & Fields package will remain on and will collect data during the cruise phase.
“After 10 years of developing the mission concept and then the hardware, it’s incredibly exciting to see MAVEN on its way,” said Bruce Jakosky, principal investigator at the University of Colorado Boulder’s Laboratory for Atmospheric and Space Physics (CU/LASP) in Boulder, Colo. “But the real excitement will come in 10 months, when we go into orbit around Mars and can start getting the science results we planned.”
“We’ve managed to work together as a team in a way I never would have imagined possible,” Jakosky said.
During the cruise phase, flight operations will execute at least four trajectory correction maneuvers (TCM). The first will use the spacecraft’s six orbit insertion thrusters. Following TCMs will utilize the spacecraft’s six smaller vector control thrusters. After the first TCM, the team will turn on and checkout all the instruments over a one week period. By approximately day 89, MAVEN will be oriented toward Earth and will activate its high-gain antenna. All activities not related to orbital insertion will conclude 60 days before insertion.
Entry Into Martian Orbit
MAVEN will enter Martian orbit on or around Sept. 22, 2014. Six orbital insertion thrusters, each with 45 pounds of thrust, will fire for 38 minutes to slow the craft and establish a 35hour orbit at a 75-degree inclination. During this phase, the closest point in its orbit, known as periapsis, is 236 miles (380 km).
During a five-week “commissioning phase,” MAVEN will carry out five maneuvers to settle into its final, 4.5-hour scientific mapping orbit. The spacecraft will also power up and test all instruments before commencing its scientific mission. Spacecraft booms will be deployed during the commissioning phase.
“The team overcame every challenge it encountered and still kept MAVEN on schedule and on budget,” said David Mitchell, MAVEN project manager at NASA’s Goddard Space Flight Center in Greenbelt, Md. “The government, industry and university partnership was determined and focused to return to Mars sooner, not later.”
MAVEN’s orbit is designed so that the craft will visit a wide range of Martian latitudes at periapsis and encounter all of the different solar-wind-interaction regions at apoapsis. During routine scientific orbits, periapsis will be around 93 miles (150 km) and apoapsis at around 3,860 miles (6,220 km).
While in its nominal science mapping orbits, MAVEN’s solar panels will face the Sun much of the time. The articulated payload platform will continually move to orient its three instruments correctly. This orientation will vary depending on MAVEN’s position in its orbit. Close to periapsis, though, the platform will orient NGIMS in the ram direction, IUVS facing the planet, and STATIC perpendicular to the orbital plane.
MAVEN will execute five Deep Dip campaigns, each lasting 20 orbits. During a Deep Dip, MAVEN will descend to a lower periapsis altitude of around 77.6 miles (125 km) to sample a denser region of the upper atmosphere. At this elevation, the atmosphere is around 30 times denser than at nominal science mapping periapsis.
The spacecraft’s solar panels are bent at a 20-degree angle. As MAVEN travels through the upper atmosphere, the air pressure will increase to a point that could disrupt flight dynamics if the solar panels were flat. MAVEN’s bent solar panels shift the center of air pressure away from the spacecraft’s center of gravity, providing a selfstabilizing configuration for atmospheric flight . The effect is similar to the self-stabilization provided by feathers on a badminton shuttlecock.
MAVEN’s primary mission lasts for one Earth year. MAVEN is expected to be able to fully satisfy its science objectives during this time period and mission managers are hopeful of getting an extension to the prime mission. If the mission continues for a second Earth year, MAVEN will be able to enhance its science investigations by observing all of Mars’ seasons through a full Martian year (98 weeks). Further mission extensions could cover a greater period of the Sun’s 11-year solar cycle and provide data on year-to-year variability in both Martian weather and space weather.
During a long-duration extended science mission, ground crews will raise MAVEN’s periapsis altitude to 137 miles (220 km). At this altitude, MAVEN can continue science observations for another six years with minimal fuel use and continue to serve as a communications relay for ground-based Mars spacecraft via its Electra antenna.
After MAVEN’s fuel is depleted, the spacecraft will eventually fall to the surface of Mars. Planetary protection precautions have been taken to ensure that, when it impacts, the spacecraft will not contaminate the surface of Mars with terrestrial organisms.
MAVEN’s Science Objectives
MAVEN’s goal is to determine the role that loss of volatiles from the Mars atmosphere to space has played through time, exploring the histories of Mars’ atmosphere and climate, liquid water, and planetary habitability.
To achieve this, the mission has three stated objectives:
MAVEN investigates the processes whereby atmospheric gases may have escaped from Mars. In order to escape, gas molecules must attain sufficient energy to break free of the planet’s gravity. These escape processes can be classified according to the underlying physics and chemistry driving them.
Atmospheric atoms and molecules naturally bounce around, colliding with one another in random directions and with random energies. The higher-energy atoms at the top of the atmosphere may have enough kinetic energy to jump right out of the atmosphere.
This process, dubbed “Jeans escape” after English astronomer James Jeans, may account for the loss of most neutral (non-ionized) hydrogen from Mars. and therefore is equivalent to tracking the loss of water on the planet.
Solar ultraviolet light can eject electrons from atoms and molecules, creating positive ions. When some molecular ions (such as ionized oxygen, carbon and nitrogen) re-combine with electrons, the reaction releases energized atoms at escape speeds.
Charged molecules in Mars’ upper atmosphere follow magnetic field lines carried by the solar wind. These ions can be accelerated to velocities up to hundreds of miles per second and many are carried away into space.
Not all of these pickup ions escape Mars, however. Some are flung back down into the atmosphere with terrific speed, transferring their energy to other molecules. This process, called “sputtering,” can account for the loss of heavier neutral atoms.
MAVEN’s instruments will also measure the amount and types of gas particles escaping Mars’ atmosphere today. Over the course of MAVEN’s mission, scientists will monitor how escaping gas composition changes in reaction to different energy inputs.
MAVEN’s science payload consists of eight instruments in three packages.
Solar Energetic Particle (SEP) measures the energetic ions of hydrogen and helium emitted by the Sun during storms, flares, and coronal mass ejections. The instrument characterizes the particles’ energy and direction.
SEP is a near-exact duplicate of instruments on the THEMIS (launched 2007) and Wind (launched 1994) missions, which both studied how the solar wind interacts with Earth’s atmosphere. SEP consists of two identical instrument boxes, mounted at 90-degree angles to each other on opposite sides of the spacecraft. The offset angle allows the twin SEP sensors to record differences in energetic particle impacts from different directions.
Solar Wind Ion Analyzer (SWIA) measures the density, temperature, and velocity of solar wind ions, both in the undisturbed interplanetary medium and as they encounter the Martian environment. Using these data, MAVEN scientists can derive the rate at which neutral atmospheric atoms are ionized by the solar wind, and the acceleration of these new ions in the magnetic and electric fields around Mars.
SWIA’s design heritage comes from instruments on the FAST, Wind and THEMIS missions, (the latter two still operating after 19 and six years, respectively). SWIA is mounted on the spacecraft body and is oriented toward the Sun, ensuring good coverage of the solar wind. The instrument operates continuously except during the “deep dips” into the Martian upper atmosphere.
STATIC (SupraThermal and Thermal Ion Composition) measures the composition and velocity of high-energy ions in Mars’ upper atmosphere. Mounted on the articulated payload platform, STATIC provides a profile of high-velocity ions at different altitudes and quantifies how many of these ions are carried away by solar winds. These high-speed ions may leap out of the atmosphere into space to be lost, or they may plunge back down into the upper atmosphere, causing sputtering loss. The instrument measures the densities and velocities of hydrogen, helium, oxygen, and carbon dioxide ions.
The LPW (Langmuir Probe and Waves) instrument has two sensors, one that is the Langmuir probe and Waves sensor and a second that measures Extreme Ultraviolet (EUV) light coming from the Sun.
LPW’s measurements allow MAVEN scientists to delineate the boundaries and the density of the ionosphere. The instrument will also measure the temperature of ionospheric electrons. These data will allow scientists to derive photochemical reaction rates, which control atmospheric escape.
The instrument design draws on forerunner instruments used on STEREO and THEMIS missions. During launch and interplanetary cruise, the booms remain coiled within a canister. Upon arrival at Mars, the booms will uncoil and expand from approximately 1.5 feet in length to their full length. MAVEN’s two LPW sensors are oriented such that the spacecraft’s wake obscures no more than one sensor at a time.
Solar Wind Electron Analyzer (SWEA) measures the energy and angular distributions of electrons with mid-range energies, which helps to fulfill several of MAVEN’s scientific objectives.
Neutral atmospheric gases can become ionized by solar ultraviolet light and by collisions with energetic ions and electrons. SWEA measures the influx of those solar wind and ionospheric electrons with sufficient energy to cause ionization on impact.
Over the course of the mission, as the MAVEN orbit samples different altitudes and latitudes, SWEA measurements can be used to map the solar wind regions both “upstream” and “downstream” of the planet, and characterize the ionosphere on both the day-side and night-side of Mars.
Positioned at the far ends of MAVEN’s solar panels, dual magnetometer sensors (MAG) provide information about the magnetic environment as the spacecraft travels through the solar wind, the Martian ionosphere, or the magnetic field near one of the regions of magnetized crust on the surface. This information provides MAVEN’s other instruments with appropriate context, since magnetic fields affect many upper atmosphere processes. MAG assists LPW and SWEA in determining the structure of Mars’ ionosphere and magnetic cusp regions formed by Mars’ crustal magnetic fields.
Neutral Gas and Ion Mass Spectrometer (NGIMS) will measure the composition of neutral gases and thermal (or cold) ions in the Martian upper atmosphere, sorting them by electrical charge and isotopic mass. These measurements will provide basic information on the composition and structure of the Martian upper atmosphere and how it varies around the planet and throughout the MAVEN mission.
In addition to measuring the abundance and composition of both neutral gases and ions, NGIMS’ data also measures the isotope ratios for atmospheric gases. The isotopes of different atoms have the same composition but different masses.
MAVEN measures atmospheric processes’ impact on isotopes so that surface explorers, such as Curiosity, can better interpret their own isotopic measurements. Gas enters the instrument and is ionized in an electron beam. The ionized gas is then filtered by four electrostatic rods, which sort atoms by weight and charge. Detectors at the far end of the rods measure the amounts of the filtered fractions of ions. NGIMS will measure isotope ratios of carbon, nitrogen, oxygen, and argon.
The ultraviolet portion of the electromagnetic spectrum contains valuable information about the chemical makeup of planetary atmospheres. Imaging UltraViolet Spectrograph (IUVS) will use UV light to chemically map the composition of Mars’ upper atmosphere and measure the rate that hydrogen atoms escape from the planet.
In addition to its science payload, MAVEN also carries Electra, an ultra-high-frequency transceiver. Electra will serve as an additional backup communications relay for the Curiosity and Opportunity rovers. The rovers are able to return much more data to Earth through a relay than they could with direct-to-Earth communications.