NASA’s InSight lander has deployed its first instrument on the surface of Mars. On December 19th, the stationary lander used its robotic arm to deploy the SEIS (Seismic Experiment for Interior Structure), marking the first time a seismometer has been placed on the surface of another planet. This is a milestone for the mission, and one that comes well ahead of schedule.
InSight landed on Mars at Elysium Planitia on November 26th. Since then, it’s been checking out its immediate surroundings with its cameras to find the perfect spot to deploy the seismometer, and its other deployable instrument, the HP3 (Heat Flow and Physical Properties Package.) Mission planners allocated several weeks for instrument site selection, so this is well ahead of schedule.
“InSight’s timetable of activities on Mars has gone better than we hoped,” said InSight Project Manager Tom Hoffman, who is based at NASA’s Jet Propulsion Laboratory in Pasadena, California. “Getting the seismometer safely on the ground is an awesome Christmas present.”
Next to InSight’s harrowing descent and landing, instrument placement is the next critical step. To get it right, the engineering team relied on a unique testing facility here on Earth, at JPL. They built a test-bed as a mock-up of InSight’s location on Mars, and practiced placing the seismometer with InSight’s twin, ForeSight.
Pre-testing instrument placement here on Earth before issuing commands to InSight was crucial. The team created what they call a Martian rock-garden, raking and scooping gravel material into an exact replica of InSight’s landing spot. The team called it Marsforming.
Engineers used some sophisticated technology to get things just right at the test-bed. Using augmented reality headsets, the team projected Digital Terrain Models (DTM) onto the test-bed, and precision cameras measured each feature they replicated. It took them four hours to create the test-bed, down to any detail larger than about one half inch.
The test-bed also contains a full-scale working model of the InSight lander, called ForeSight. After recreating the real lander’s conditions on Mars at the test-bed, engineers practiced placing the seismometer with Foresight’s robotic arm. Engineers say they’re fortunate that InSight’s landing spot was nice and flat, and free of large rocks, which could damage the wires connecting the instruments to the lander.
“It’s the flat parking lot the landing team promised us.” – Marleen Sundgaard, JPL.
“It’s great for the science we want to do,” said JPL’s Marleen Sundgaard, who is guiding the test-bed work. “It’s the flat parking lot the landing team promised us. You calculate the probability of rocks in the area and hope the odds are in your favor.”
“All around us, there are rocks that were ejected from nearby craters. These can be launched miles across the landscape, depending on the impact size,” said Nate Williams, a JPL post-doctoral researcher working with the mission. “Thankfully, there just aren’t a lot of rocks right in front of us.”
The team spent several days practicing the instrument placement at the test bed. Wearing Microsoft HoloLens headsets, the team saw a glowing red Martian surface with the blue contour lines of the Digital Terrain Model from the actual terrain in front of InSight on Mars. This isn’t the first time that NASA has used the HoloLens for lander operations. For the last several years, scientists with NASA’s Curiosity rover have used the HoloLens in conjunction with custom software called OnSight. It lets them “walk” on Mars and make decisions about what to study next.
On the morning of Monday, December 17th, the engineering team at the rock garden was satisfied that they could get SEIS exactly where the science team wanted it. They had practiced all the movements for the instrument placement arm, and were confident they could place the instrument while keeping the instrument tether clear of rocks. They also confirmed that the Heat Flow Probe can be placed in its desired location, about 1.2 meters (4 ft.) to the left of the seismometer.
On Tuesday, Dec. 18th, the commands were issued to Insight to place SEIS on the Martian surface. On December 19th, InSight used its robotic arm to place SEIS in its chosen location, 1.636 meters, or 5.367 feet, away. This is about the furthest that the arm can reach.
According to the InSight team, placement of SEIS was critical to mission success. InSight has other instruments, but a failed placement would’ve hampered the mission significantly. There’s still some work required to level the seismometer. It’s sitting on ground that is tilted about 2 or 3 degrees. Once it’s levelled, data should start flowing.
It’ll take several additional weeks after instrument placement for scientists and engineers to make sure the data is as clear as possible. They may need to adjust SEIS’ tether to minimize noise, and in early January, they will place the thermal and wind cover over the seismometer. In late January, the InSight team plans to place the Heat Flow and Physical Properties Package.
“Having the seismometer on the ground is like holding a phone up to your ear,” – Philippe Lognonné, principal investigator of SEIS from Institut de Physique du Globe de Paris (IPGP) and Paris Diderot University.
SEIS will give us a look inside Mars. The instrument will listen for Marsquakes, and will analyze the seismic waves as they pass through the planet. The data will paint a picture of the interior structure. “Having the seismometer on the ground is like holding a phone up to your ear,” said Philippe Lognonné, principal investigator of SEIS from Institut de Physique du Globe de Paris (IPGP) and Paris Diderot University. “We’re thrilled that we’re now in the best position to listen to all the seismic waves from below Mars’ surface and from its deep interior.”
With SEIS in position and ready to get to work, and with a site for the HP3 selected, InSight is well on its way to meeting its science objectives. Another experiment, RISE (Rotation and Interior Structure Experiment) is already underway. RISE doesn’t use a deployable instrument. It’s a radio science experiment that uses the lander’s X band radio to provide precise measurements of planetary rotation. Data from RISE will be combined with data from other Mars landers and orbiters to calculate the size and density of Mars’ core and mantle.
InSight’s planned mission length is 709 sols, or 728 days. Once the mission is completed, we’ll have a lot more detailed knowledge of Mars’ deep interior. Hopefully, we’ll also learn a lot about how other rocky planets formed.