Space Sunday: insight on InSight

via Associated Press

On Saturday, May 5th, 2018, NASA commenced the latest in its ongoing robot exploration missions to Mars, with the launch of the InSight lander mission.

The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission is the first designed to carry out a detailed examination of the Red Planet’s interior – its crust, mantle and core.

Studying Mars’ interior structure can answer key questions about the early formation of the rocky planets in our inner solar system – Mercury, Venus, Earth, and Mars – more than 4 billion years ago. In addition, the data gathered may also help us to understand how rocky exoplanets orbiting other stars in our galaxy may have formed.

As well as potentially being a ground-breaking mission, InSight’s departure from Earth marked the first time any US interplanetary mission had been launched from the West Coast, rather than the more familiar Kennedy Space Centre in Florida. InSight started its six-month journey to Mars atop a United Launch Alliance Atlas V 401 launch vehicle from Space Launch Complex 3-East at Vandenberg Air Force Base, California, lifting-off at 04:05 PDT (07:05 EDT; 11:05 UTC) on May 5th, marking the end of a 2-year delay for the mission.

That delay had been caused by the repeated failure of a vacuum sphere forming a part of a set of seismometers called the Seismic Experiment for Interior Structure (SEIS) package, a crucial part of the mission’s science. Attempts to correct the issue with the French-developed package consistently led to further problems until, in December 2015, NASA was forced to call off InSight’s planned March 2016 launch while the unit was France for further repairs – a move that gave rise to fears the entire mission would be cancelled if a solution could not be found in time for InSight to meet the next launch opportunity in 2018 – such launch windows occurring every 26 months.

The mission critical vacuum sphere originally designed by CNES, and which kept failing tests and caused a 2-year delay in InSight’s launch. Credit: CNES

The mission was saved in March 2016 – a week after its original launch date in fact – when NASA’s Jet Propulsion Laboratory (JPL) reached an agreement with the French space agency CNES. This allowed JPL to design, build and test a new vacuum enclosure, with CNES taking responsibility for integrating it with the SEIS package, and testing the completed unit in readiness for integration with the lander in time for a May 2018 launch.

On May 5th 2018, the launch itself proceeded smoothly, with the Atlas V booster quickly obscured by pre-dawn fog shortly after clearing the launch complex. however, it was caught at altitude by a NAA observation aircraft, as it rose above the cloud tops. As well as InSight, the rocket carried within its payload fairings two “cubesats”, each roughly the size of a briefcase, called MarCO A and MarCO B.

Together, these tiny, self-contained satellites for the Mars Cube One (MarCO) technology demonstrator. Sent on their way to Mars alongside InSight, they both operate independently of the lander, carrying their own communications and navigation experiments. Their mission is designed to provide NASA with a temporary communications relay system during InSight’s  entry, descent and landing (EDL) mission phase, as it heads towards a (hopefully) soft-landing on Mars.

Currently, surface missions to Mars are generally monitored by the Mars Reconnaissance Orbiter, which monitors transmissions from a vehicle descending towards a landing on Mars. However, it cannot simultaneously transmit that information to Earth. This means that it can be as much as an hour before the data gathered during the critical EDL phase of a surface mission can be received on Earth. MarCO will be able to simultaneously receive and transmit EDL data sent by InSight to Earth, allowing mission engineers and scientists to have a more complete picture of this critical phase of the mission that much sooner. If successful, MarCO cover pave the way to a greater use of cubesats in the exploration of Mars.

An artist’s impression of MarCO A and MarCO B with their communications antennae deployed post-launch and on their way to Mars. Credit: NASA/JPL

Confirmation that both MarCO A and MarCO B (nicknamed “Wall-E” and “Eva” by their designers) had successfully deployed and were operating came shortly after they had separated from the launch vehicle, when each radioed mission control with a single word: “Polo”. Both will be monitored as they pass through the radiation fields surrounding the Earth to see how each  survives the passage.

If all goes according to plan, InSight will reach Mars in November 2018, after travelling some 485 million km (301 million mi), and is due to land on November 26th. This will be at 4.5°N 135.9°E, a point near the Martian equator in western Elysium Planitia, and some 600 km (370 mi) from where the Curiosity rover is operating in Gale Crater. Once on the ground, the lander will be subject to a series of checkout and calibration operations, prior to commencing its primary mission.

An artist’s impression of InSight on Mars, showing the SEIS and HP3 packages deployed. Credit: NASA / JPL

As noted above, by studying the size, thickness, density and overall structure of Mars’ core, mantle and crust, as well as the rate at which heat escapes from the planet’s interior, InSight will provide a glimpse into the evolutionary processes of all of the rocky planets in the inner Solar System.

Mars is perhaps the most ideal subject for this kind of in-depth study as it is believed the planet contains the most in-depth and accurate historical record of rocky planetary formation. This is because Mars is both big enough to have undergone the earliest accretion and internal heating processes that shaped the terrestrial planets, but also small enough to have retained signs of those processes.

We can’t gather this kind of information here on Earth because the planet is far too active; any evidence of what happened within the planet aeons ago has long since been erased. Similarly, while the Moon is inactive, it is so small that the processes that occurred inside it would likely be very different to those within a body the size of Mars or Earth. So Mars is effectively the “Goldilocks” world for these kind of studies – being “just right” for examination, simply because it has experiences similar processes of planetary differentiation to the Earth, but which came to something of an abrupt halt perhaps 20 to 50 million years after it was formed, and so have not be subsequently erased in the intervening aeons.

The two primarily elements of this science package are the aforementioned SEIS instrument suite, and the Heat Flow and Physical Properties Package (HP3). Both of these experiments are designed to be deployed away from the solar-powered lander, and placed directly on the Martian surface.

The French-designed SEIS will take precise measurements of quakes and other internal activity on Mars, and will also investigate how the Martian crust and mantle respond to the effects of meteorite impacts, offering further clues to the planet’s inner structure.

Artist’s illustration of InSight’s Seismic Experiment for Interior Structure (SEIS) instrument on the Red Planet’s surface. Credit: NASA TV/JPL

HP3, developed by the German Aerospace Centre (DLR), is a self-propelled heat flow probe nicknamed “the mole”. From its surface container, it can burrow up to 5 m (16 ft) below the surface to measure how much heat is coming from Mars’ core, helping to reveal the planet’s thermal history. As the probe digs into the Martian surface it trails a tether containing precise temperature sensors every 10 cm (3.9 in) to measure the temperature profile of the subsurface.

In addition, SEIS is supported by a suite of meteorological tools to characterise atmospheric disturbances that might affect the experiment. These include a vector magnetometer to measure magnetic disturbances  caused by the Martian ionosphere, and a suite of air temperature, wind speed and wind direction sensors. The HP3 instrument is supported by an infra-red radiometer measuring surface temperature. The remaining science payload instruments comprise:

  • The Rotation and Interior Structure Experiment (RISE), that uses the lander’s X-band radio to provide precise measurements of planetary rotation to better understand the interior of Mars. The data gathered will build on similar data obtained during the Viking missions and 1997’s Mars Pathfinder mission. The combined data should make it possible to calculate the size and density of the Martian core and mantle – something that would not only further our understanding of Mars, but also the formation of other rocky planets.
  • Temperature and Winds for InSight (TWINS), that will monitor weather at the landing site.
  • Laser RetroReflector for InSight (LaRRI), mounted on InSight‘s top deck to enable passive laser range-finding by orbiters even after the lander is retired, and designed to form a node in a proposed Mars geophysical network.
A map of the surface of Mars showing the InSight landing zone referenced against other NASA Mars surface missions. Credit: NASA

These experiments will be supported by three additional elements: the Instrument Deployment Arm (IDA), a 2.4 m long robotic arm that will be used to place the SEIS and HP3 instrument packages to Mars’ surface; the colour Instrument Deployment Camera (IDC) mounted on the IDA to image the instruments on the lander’s deck and provide stereoscopic views of the terrain surrounding the landing site; and the Instrument Context Camera (ICC), a colour camera mounted on the lander to provide wide-angle 120-degree panoramic views of the instrument deployment area.

There is one further payload element on InSight: two silicon wafers, each just 8 mm (0.3 in) across. Etched on to them in letters only ​11000 the width of a human hair, are 2.4 million names of people who applied to have their names flown to Mars with the mission. These include none other than the original James T. Kirk himself – actor William Shatner – and also the near-anonymous name of yours truly.

The solar arrays on NASA’s InSight lander are deployed in this test inside a clean room at Lockheed Martin Space Systems. This configuration is how the spacecraft will look on the surface of Mars. Credit: NASA/JPL / Lockheed Martin

The solar-charged batteries powering InSight are intended to operate for a minimum of 26 Earth months – a Martian year. During this period, it is thought the lander might detect as many as 100 quakes. However, it is hoped that like other Mars surface missions, InSight will operate well beyond its initial 26-month primary mission period – particularly as NASA’s other solar-powered mission, the Mars Exploration Rover Opportunity is still active more than 14 years after the end of its 90-day primary mission.

I’ll have more on InSight later in the year.


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