NASA’s InSight mission began a six-month journey to Mars on Saturday with liftoff aboard United Launch Alliance’s Atlas V rocket. The first interplanetary mission to launch from the West Coast of the United States, InSight departed from California’s Vandenberg Air Force Base at the opening of a two-hour launch window that opened at 04:05 local time (11:05 UTC).
InSight will land on Elysium Planitia, an equatorial region or Mars, from where it will perform experiments aimed at gaining a better understanding of the Red Planet’s interior. The twelfth mission of NASA’s Discovery program, InSight will be joined on its journey to Mars by Mars Cube One (MarCO) a pair of small satellites that will test the operation of miniaturized spacecraft technology in deep space and help to relay data from the InSight lander as it descends into the Martian atmosphere.
InSight – Interior Exploration using Seismic Investigations, Geodesy and Heat Transport – is the first mission dedicated to understanding the internal structure of Mars. The mission is expected to last at least about two Earth years – or one Martian year. Originally named the Geophysical Monitoring Station (GEMS), and also known as Discovery 12, the InSight mission is led by NASA’s Jet Propulsion Laboratory (JPL) with Bruce Banerdt is principal investigator.
The primary goals of the InSight mission are to help gain an understanding of how the terrestrial planets formed and evolved by studying the interior of Mars, and to determine current seismic and impact activity on Mars. The specific objectives of the mission are to determine the thickness and structure of Mars’ crust, the composition and structure of its mantle and the size, composition and physical state of its core. Other key objectives are to characterize the thermal state of the planet’s interior, to measure seismic activity and the rate of meteorite impacts on the surface.
To achieve these objectives, InSight carries a suite of scientific instruments.
The Seismic Experiment for Interior Structure (SEIS) is a seismometer consisting of three very broad-band sensors to detect medium-to-low frequency seismic activity and three short-period sensors to detect more high-frequency activity. The SEIS instrument package will be deployed onto the surface of Mars, with an umbilical connection to InSight providing electrical connections for power and data. SEIS will detect and measure seismic activity, including “mars-quakes”, surface impacts and gravitational interactions with Mars’ larger moon, Phobos. The instrument was built by an international consortium involving several European nations and led by French Space Agency CNES.
The Heat Flow and Physical Properties Probe, or HP3, will tunnel into the Martian surface to study the amount of internal heat escaping from the interior of Mars through its surface. HP3 will deploy a device called a self-hammering mole, which will use a spring-loaded tungsten block to force itself under the surface.
The probe is an aluminum cylinder measuring 2.7 centimeters (1.1 inches) in diameter by 40 centimeters (16 inches) in length, which is expected to reach a depth of 3 to 5 meters (10-16 feet). The hammer, which is driven into the inside of the probe’s tip, can fire every 3.6 seconds and will take about 30-40 days to sink the mole to its maximum depth. During the burrowing process, the mole will stop every 15 centimeters (5.9 inches) to allow data to be collected.
HP3’s probe carries heaters that will be used to allow a study of how long it takes heat to propagate through the surface to temperature sensors in the probe itself and embedded in the umbilical that connects the probe to its support assembly on the surface. The probe will also measure the ambient temperature of the Martian sub-surface environment and carries a tilt sensor that will allow its depth to be more accurately determined from the angle of its descent. HP3 was built by the German Aerospace Centre, while the Polish Academy of Sciences developed its burrowing mechanism.
The Rotation and Interior Structure Experiment (RISE) will aim to characterize in Mars’ axis of rotation. By understanding perturbations in the rotation of Mars, scientists will be able to gain an understanding of the size, density and state of Mars’ core. The investigation will NASA’s Deep Space Network (DSN) to communicate with InSight’s X-band transponder, with the radio signals being used to determine the spacecraft’s position to within 10 centimeters (4 inches) and to look for changes as Mars rotates. The experiment builds on research conducted by the Mars Pathfinder mission in 1997.
InSight’s Auxiliary Payload Sensor Subsystem (APSS) consists of additional instruments to monitor the environment around the spacecraft. This includes a fluxgate magnetometer – the first magnetometer to be carried by a Mars lander – which will monitor the magnitude and orientation of Mars’ magnetic field at InSight’s landing site. Other instruments in this suite include Temperature and Wind for InSight (TWINS), a pair of booms carrying temperature and wind sensors to monitor atmospheric conditions and atmospheric pressure sensor.
The magnetometer aboard InSight was built by the University of California, while the TWINS instrument was provided by Spain’ Centro de Astrobiología (CAB) and the pressure sensor was produced by Tavis Corporation of California. TWINS was originally built as a flight spare for the Curiosity rover and has been refurbished for the InSight mission. The electronics that integrate APSS and facilitate data collection were built by NASA’s Jet Propulsion Laboratory.
In addition to APSS, the HP3 instrument and cameras aboard InSight spacecraft will also help to gain an understanding of conditions at the landing site, tracking variations in surface temperature and monitoring dust that is picked up by the wind respectively.
The Italian Space Agency, ASI, has provided the Laser Retroreflector for Mars, LaRRI, which InSight will carry to the surface. LaRRI is a 5-centimeter (2-inch) diameter retroreflector array, incorporating eight reflectors. The retroreflectors reflect incoming light directly back at its source, which will allow future orbiter missions to measure the lander’s position with great precision.
The SEIS and HP3 instruments will need to be placed directly onto the surface of Mars. To facilitate this, InSight’s Instrument Deployment System (IDS) consists of a 2.4-metre (7.8-foot) three-jointed robotic arm and cameras to identify suitable deployment sites for the instruments and monitor the process of lowering them to the surface. The Instrument Deployment Arm (IDA) will place SEIS and HP3 onto the surface and will also be used to place a shield around SEIS to protect it from wind and thermal conditions.
IDS incorporates two one-megapixel engineering cameras – the Instrument Deployment Camera (IDC) and the Instrument Context Camera (ICC). The IDC is mounted between the elbow and wrist joints of the lander’s robotic arm, while ICC is mounted under the deck of the lander, allowing it a view of the area to the south of the lander where the instruments will be placed.
Lockheed Martin was the prime contractor for the InSight mission, with construction beginning in May 2014. The spacecraft has a mass at launch of 694 kilograms (1,530 lb). Its lander will stand 83 to 108 centimeters tall (2.7 to 3.5 feet), depending on how much its legs compress after landing, with the spacecraft measuring 1.56 meters (5.12 feet) in width, or 6 meters (19.69 ft) across with its solar panels fully deployed.
The InSight spacecraft is based on the design of an earlier lander, Phoenix, which was also developed by Lockheed Martin. The Phoenix spacecraft was originally built as part of NASA’s Mars Surveyor 2001 program. The mission was to have consisted of both an orbiter and a lander, launched separately aboard Delta II rockets. Mars Surveyor 2001 was canceled following a review of NASA’s Mars exploration plans after the Mars Polar Lander probe was lost on landing in December 1999, although its orbiter was still launched as the highly-successful Mars Odyssey mission. The Mars Surveyor lander was mothballed until the University of Arizona proposed re-purposing it to explore the Northern polar region of the red planet.
The revised project was named Phoenix and became the first mission of NASA’s Mars Scout program. Launched by a Delta II rocket in August 2007, Phoenix touched down on Mars on 25 May 2008. Phoenix was designed to operate for ninety days on the surface of Mars – with its mission duration limited by the Martian winter, which the spacecraft was never expected to survive due to a lack of sunlight and the spacecraft becoming encased in dry ice. Phoenix continued to operate until 2 November 2008.
InSight’s robotic arm uses hardware that was originally built for the 2001 mission.
In addition to the lander itself, InSight consists of a coast stage and an aeroshell, which will support the spacecraft during the journey to Mars and its entry into the Martian atmosphere respectively. The lander has a mass of 358 kilograms (890 lb), not including 67 kilograms (148 lb) of propellant, while the aeroshell weighs 189 kilograms (418 lb) and the cruise stage has a mass of 79 kilograms (174 lb).
InSight’s cruise stage provides power – via solar panels – and communications during the journey to Mars. It is equipped with star trackers and sun sensors to help guide the spacecraft, but does not carry any propulsion systems. Instead, engines on the lander will be used for attitude control and course corrections during the mission’s coast towards Mars. Although the lander is encapsulated within its aeroshell, cut-outs allow some of the spacecraft’s thrusters to operate prior to aeroshell separation. The aeroshell itself includes a back shell and heat shield.
The lander is equipped with twenty engines – twelve 302-newton (68 pound-force) descent engines to perform its landing, four 22-newton (5 lb) trajectory correction thrusters for performing maneuvers during the coast phase and four 4.4-newton (1 lb) reaction control system (RCS) thrusters for attitude control. Only the trajectory correction and RCS thrusters will be used during the coast phase. All of these thrusters are monopropellant, using hydrazine that is passed over a heated catalyst to generate thrust without requiring a separate oxidizer.