Following a two-year delay, NASA's Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport (InSight) Mars lander is back on track. Previously grounded due to a faulty seismometer, the unmanned spacecraft is now scheduled to lift off during a launch window that starts on May 5, 2018 for a landing on the Red Planet on November 26, 2018.

According to NASA, today's announcement comes after a meeting with France's space agency, Centre National d'Études Spatiales (CNES), which built the Seismic Experiment for Interior Structure (SEIS) experiment. This is a seismometer that can detect ground movements on an atomic scale thanks to three main sensors sealed in a vacuum.

However, on December 22, 2015, NASA abandoned the original March 2016 launch date due to a persistent leak in the vacuum chamber of the SEIS that would have rendered the instrument useless by the time it reached Mars. It was therefore decided to return the probe from Vandenberg Air Force Base in California to Lockheed Martin's Denver facility, where the spacecraft was built and tested.

InSight undergoing acoustics testing(Credit: NASA)

NASA says that the plan for the redesign has been approved and the SEIS experiment will be modified by NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, with CNES providing instrument level integration and test activities. The end result will be an improved vacuum chamber that can withstand launch, landing, deployment, and a two-year prime mission on the surface of Mars.

The reason for the two-year delay is that, unlike missions to Earth orbit, which have launch windows that can recur every day, and ones to the Moon that can recur monthly, planetary missions involve a complex ballet of two bodies revolving about the Sun. For missions to Mars, the best conditions only appear during a period of a few weeks every 26 months.

The InSight stationary lander is based on NASA's Phoenix lander, which set down at the Martian North Pole in 2008. It is designed for a 720-day primary mission near the Martian equator and features a robotic arm for placing instruments, including hammering a heat-flow meter up to 15 ft (4.5 m) into the ground. Its purpose is not only to study Mars, but also to gain insights into the formation of rocky planets in the inner Solar System.

NASA says that the InSight will remain in storage with Lockheed until the SEIS experiment is tested and launch preparations resume in 2017.

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