Slamming into the thin Martian atmosphere at more than 13,000 mph, NASA’s InSight lander pulled off a blazing six-and-a-half minute, 77-mile plunge to the surface of Mars Monday, using a huge parachute and then 12 pulsing rocket thrusters to settle to a gentle 5-mph touchdown in a billion-dollar mission to study the red planet’s hidden interior.
Utilizing the same entry, descent and landing system successfully employed by NASA’s Phoenix lander in 2007, InSight began its nail-biting descent at 2:47 p.m. EST (GMT-5) and landed on a broad plain known as Elysium Planitia at 2:54 p.m. EDT.
When signals reached Earth confirming a successful touchdown, anxious flight controllers, engineers and scientists gathered at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., burst into welcome cheers, hugs and applause.
They erupted again when an initial photograph was beamed down, showing the martian horizon through a lens cover speckled with dust kicked up during landing. The photo served as confirmation the spacecraft was working properly after its fiery descent to the surface.
“We spend most of our time visualizing all these bad things that can happen, but sometimes things work out in your favor,” said Rob Manning, chief engineer at JPL and a Mars landing veteran. “It certainly looked like it was a very successful and perfect landing.”
Vice President Mike Pence tweeted his congratulations to NASA and Lockheed Martin, InSight’s builder, along with “all who made today’s (landing) possible. This marks the 8th time the US has landed on Mars & the 1st mission to study its deep interior. Incredible milestone!”
Congratulations to @NASA, @LockheedMartin, @ulalaunch, & all who made today's @NASAInSight #MarsLanding possible! This marks the 8th time the US has landed on Mars & the 1st mission to study its deep interior. Incredible milestone! https://t.co/plgJch3Vpc
— Vice President Mike Pence (@VP) November 26, 2018
The team had good reason to celebrate given the challenges the spacecraft had to overcome.
InSight’s protective heat shield endured temperatures up to 2,700 degrees Fahrenheit, the vehicle “felt” an atmospheric braking force of 7.5 times the force of gravity on Earth and still more as its 39-foot-wide supersonic parachute inflated with a force of 12,500 pounds per square foot.
After slowing to subsonic velocities, InSight fell free of its parachute and upper support structure for the final mile to the surface, using a dozen small rocket motors to reduce its descent rate to about 5 mph before settling to the surface atop three shock-absorbing landing legs.
InSight did not have the ability to send telemetry directly back to Earth during its plunge to the surface, but flight controllers at JPL were able to follow along thanks to a pair of small, experimental “CubeSats” known as MarCO A and B that were launched along with InSight last May as part of a technology demonstration project.
As the lander descended, a UHF radio sent telemetry up to the MarCOs, which then relayed it directly back to Earth. As a backup, the entry was timed to coincide with the passage of NASA’s Mars Reconnaissance Orbiter overhead. The satellite was programmed to record the full suite of InSight telemetry for relay back to Earth about three hours after touchdown.
But thanks to the MarCOs, the flight control team already knew the lander had made it safely to the surface, albeit 8.1 minutes after the fact. That’s how long it took for radio signals from Mars to cross the 90-million-mile gulf to Earth.
And it was an exciting, action-packed few minutes. InSight engineers were on the edges of their seats listening to Christine Szalai, an entry, descent and landing engineer at JPL, call out the milestones as the telemetry came in, painting a picture of events taking place 90 million miles away.
“InSight has passed through peak deceleration,” she reported. “Telemetry shows the spacecraft saw about eight Gs.”
A moment later, radio signals resumed after a brief blackout during peak heating.
“InSight is now traveling at a velocity of about 2,000 meters per second (4,473 mph),” Szalai said.
“It seems to have passed this very critical point of peak heating, peak deceleration,” Manning observed. “The next big step is parachute inflation.”
“InSight is now traveling at 1,000 meters per second (2,237 mph),” Szalai reported. “Once InSight slows to about 400 meters per second (895 mph), it will deploy its 12-meter diameter supersonic parachute. The parachute will deploy, nominally, at about Mach 1.7. Standing by for parachute deploy…”
“Radio science reports a sudden change in doppler,” another engineer added, meaning a change in the frequency of the incoming signals indicated a sudden change in InSight’s velocity.
“Ground stations are observing signals consistent with parachute deploy,” Szalai said, prompting a thunderous round of applause. “Telemetry shows parachute deployment, radar powered on. Heat shield separation commanded.”
“This is really good news so far,” Manning, serving as a commentator on NASA TV, said under his breath, listening like everyone else to the telemetry calls. “Ahh, I’m on pins and needles!”
“We have radar activation where radar is beginning to search for the ground,” Szalai said a moment later. “Once the radar locks on the ground and Insight is about one kilometer above the surface the lander will separate from the backshell and begin terminal descent using its 12 descent engines.”
She continued a few seconds later: “Altitude convergence, the radar has locked on the ground (applause)! Standing by for lander separation… lander separation commanded. Altitude 600 meters… gravity turn, altitude 400 meters… 300 meters.. 200 meters… 80 meters… 60 meters… 50 meters, constant velocity, 37 meters… 30 meters… 20 meters… 17 meters, standing by for touchdown.”
And then came the words everyone in the room was waiting to hear: “Touchdown confirmed! InSight is on the surface of Mars!” Szalai called out as the JPL team burst into cheers.
But one last milestone remained: confirmation of solar array deployment. The arrays were expected to begin opening up about 16 minutes after touchdown. The MarCO spacecraft were out of range by that point, but telemetry confirming solar panel deploy was expected Monday night after a pass by NASA’s Mars Odyssey orbiter.
InSight — the acronym stands for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport — is the ninth lander sent to Mars by the United States since the twin Viking spacecraft touched down in 1975. One of the eight previous landers crashed to the surface in 1999, but InSight’s descent marked NASA’s fifth success in a row.
Overall, NASA has spent an estimated $22.7 billion sending 23 spacecraft to Mars since the initial — and unsuccessful — Mariner 3 flight in 1964. Only 24 of the 57 missions launched so far by any nation, including combination lander/orbiter flights, have been successful, but NASA’s batting average tops the list with 17 successes in 23 attempts.
Unlike previous projects that primarily studied the surface of Mars to probe its geology, history and past habitability, InSight is focused on the red planet’s interior, using an ultra-sensitive seismometer and a sophisticated thermometer to map out the sub-surface architecture all the way down to the core 2,000 miles below the landing site.
But science observations are not expected to begin until next spring. First, the Seismic Experiment Interior Structure — SEIS — seismometer, provided by the French space agency, CNES, and the Heat Flow and Physical Properties Probe — HP3 — provided by the German Aerospace Agency, DLR, must be placed on the surface using the lander’s robot arm.
“We have a picture of the ground, and now the work to deploy the seismometer is beginning,” said Philippe Laudet, SEIS project manager with CNES. “The deployment is going to take about two or three months. Of course, we will have some data during the deployments, but the best data to make the best science will be about the beginning of March.”
Engineers plan to spend weeks photographing the surrounding landscape to identify the best spots near the spacecraft to place the instruments, looking for the smoothest, flattest-possible terrain.
Then, they plan to rehearse operations with InSight’s robot arm to make sure every step in the instrument-lowering procedure is well understood. An engineering mockup of InSight is available in a simulated Mars environment at JPL that will be used to test the hardware and software needed to get the job done.
But getting the instruments to the surface is just half the job. The heat probe must then hammer its way into the crust up to a depth of about 15 feet, a procedure that will take still more weeks to complete. Only then will science operations commence.
Bruce Banerdt, the InSight principal investigator, said the seismometer “is really the heart of the InSight mission.” It is capable of measuring vibrations that measure less than the width of a hydrogen atom. As seismic waves from marsquakes or meteor impacts travel through the planet, different types of soil and rock will also their shape.
“Scientists understand how to take the shapes of those wiggles, their frequency, their amplitude, the polarization, the timing, all kinds of properties of those waves and pull that information out and finally, after we’ve gotten many, many marsquakes from different directions, we can put together a three-dimensional view of the inside of Mars,” Banerdt said.
The German heat probe will use a spring-driven internal hammer-like device to pound its way down into the martian soil trailing a cable carrying sensitive temperature sensors. After some 10,000 hammer blows, the probe should reach a maximum depth of about 15 feet, pausing along the way to measure the thermal conductivity of the soil at different depths.
By precisely measuring that thermal conductivity, scientists will be able to extrapolate the temperature profile all the way to the core.
“And that amount of heat is tied to the geological activity of the planet,” Banerdt said. “It’s the heat engine of the planet that drives vulcanism, it drives tectonic activity, it drives mountain building. So all the geological processes that happen on a planet are driven by its heat engine, and we want to measure sort of the vigor of that heat engine.”
While the surface instruments are measuring Mars’ internal structure, scientists will be studying the spacecraft’s radio signals, noting how the planet’s rotation affects them. They hope to use those data to pinpoint the orientation of Mars’ polar axis and how it changes over time.
“Over the course of a year, we can watch that north pole wobble just a little bit because of the core sloshing around inside the planet, and that will give us a very, very tight constraint on the size of that core, its density and so its composition,” Banerdt said.
“That tells us the structure of Mars, the structure of Mars tells us something about the processes that put that structure together, we can put that into our models, extrapolate to the Earth and understand how the Earth formed four and a half billion years ago. And that’s really the crux of the science behind this mission.”