03 May 2018
Launched on 5 May 2018, NASA’s InSight spacecraft will land on 26 November, just north of the Martian equator, and deploy its solar panels. SEIS, an instrument for recording seismic waves (left of image), and HP3, an instrument developed by DLR to measure the thermal conductivity of the Martian regolith and the heat flow from the interior of the planet (right of image), will be placed on the surface of the planet possibly before the turn of the year.
For the InSight mission, a landing area was sought that had to meet several scientific criteria, but above all space systems engineering criteria. For a secure energy supply from solar power and to avoid extreme diurnal and seasonal temperature variations, it could not be too far north or south of the equator, it had to be flat and, as far as possible, not covered by rocks. After a long selection process, engineers and scientists selected an area in a plain southwest of the large volcanic complex surrounding Elysium Mons. The chosen site is in Elysium Planitia, north of the Martian equator and the highland border – just a few hundred kilometres north of Gale Crater (below the ‘4’ in the latitude label), in which the NASA rover Curiosity has been driving since 2012. The image is a section of a global topographic map of Mars; blue and green are low-lying areas, yellow and red are elevated terrain. The image is about 5000 kilometres wide.
The InSight mission will investigate the internal structure of Mars and the processes at play inside the planet to acquire a better understanding of the formation and evolution of earth-like planets. Similar to the other terrestrial planets – Mercury, Venus, Earth and the Moon – Mars has a metallic core surrounded by a rocky mantle, over which lies a rocky crust. According to model calculations, the core has a temperature of about 1900 degrees Celsius and could still be molten if it contains a significant amount of sulphur. This is one of the questions that the InSight mission will address. The mission will also conduct a study of seismic activity and measure the meteorite impact rate on Mars.
DLR has contributed the HP3 experiment to the NASA InSight mission. HP3 stands for ‘Heat Flow and Physical Properties Package’ and the instrument was developed under the leadership of the DLR Institute of Planetary Research. The thermal conductivity of the material below the landing site and the heat flow from the interior of Mars to the surface will be measured using a penetrometer hammered five metres deep into the Martian regolith. The experiment is designed for an operational life of two Earth years. Essential components of HP3 are the ‘Mole’ and the ribbon cable with the temperature sensors, which the Mole will pull behind it into the ground to perform measurements.
InSight’s structural design is similar to that of NASA’s Phoenix lander from 2008. The main component is a platform two metres in diameter, on which most of the system components – the experiments in their ‘transport mode’, the antennas, the on-board computer, the thrusters, the propellant tanks and three telescopic legs are attached. A robotic arm will be deployed after landing and lift the experiments HP3 and SEIS from the platform onto the Martian surface. At the side of the platform are two solar panels, which produce a maximum of 700 watts, depending on the distance between Mars and the Sun. The RISE experiment is conducted from the platform itself.
A special system isolates the sensors from the impacts and in doing so minimises their exposure to stress. For this purpose, the STATIL system is fitted with specially patented double helix springs – also known as ‘galaxy springs’.
DLR (CC-BY 3.0).
The DLR HP3 experiment also includes the RAD radiometer, which is mounted on the lander platform. This determines the temperature of the Martian surface by observing its infrared radiation. The surface can reach a maximum of just over 20 degrees Celsius during the day, but can fall below minus 70 degrees Celsius at night. Knowledge of the surface temperature is important in order to be able to calculate disturbances in the temperature distribution in the subsurface. RAD was built at the DLR Institute of Optical Sensor Systems.
An engineer from Lockheed Martin Space, the corporation that constructed the InSight lander for NASA, places one of two silicon microchips on the Mars lander platform in a clean room. The names of 1.6 million people from all over the world have been engraved on an eight by eight millimetre area; these people registered to join the mission organised by NASA and will now take part in the almost 500-million-kilometre journey – and then remain on Mars forever. A second chip contains 800,000 additional names. NASA engineers used an electron beam to engrave them in extremely small font to accommodate the names of all the ‘passengers’. The lines are narrower than one-thousandth the width of a human hair, which themselves only have an average thickness of approximately 0.05 millimetres.
Last modified:15/05/2018 14:04:47