When it lands, InSight will have cruised 301,223,981 miles at a top speed of 6,200 mph, while being followed by two cube satellites. The suitcase-sized spacecraft, called Marco, is the first cube satellites to fly into deep space. Marco will try to share data about InSight when it enters the Martian atmosphere for the landing.
"We have studied Mars from orbit and from the surface since 1965, learning about its weather, atmosphere, geology and surface chemistry," said Lori Glaze, acting director of the NASA's Science Mission Directorate. "We will finally explore inside Mars and deepen our understanding of our terrestrial neighbor, and NASA is preparing to send human explorers deep into the solar system."
InSight will robotically guide itself through the landing, outside of a few last minute tweaks by the entry, descend and landing team to the algorithm that guides the lander to the surface.
"InSight team was busy making final preparations for Monday's landing," said Tom Hoffman of the Jet Propulsion Laboratory (JPL), who is InSight's project manager. "Landing on Mars is difficult and takes a lot of personal sacrifices, such as missing traditional Thanksgiving, but making InSight successful is well worth the extraordinary effort."
Only 40% of missions sent to the Red Planet by any agency have been successful. Part of this is due to the thin Martian atmosphere, which is only 1% of Earth's, so there's nothing to slow down anything trying to land on the surface.
Like the Phoenix spacecraft, InSight will have a parachute and retro rockets to slow its downfall through the atmosphere, and three legs suspended from the lander will attempt to absorb the shock of touching down on the surface.
But the engineers prepared the spacecraft to land during a dust storm if need be.
About 20 minutes before landing, InSight will separate from the cruise stage that helped bring it all the way to Mars and turn to position itself for entering the atmosphere.
At 2:47 pm ET, the entry, descent and landing phase is set to begin, and InSight will come in the air at 12,300 mph. Peak heating of the protective thermal shield will reach 2,700 degrees Fahrenheit two minutes later, which then decelerates. This is when the intense heat could cause temporary drops in the radio signal from the craft.
Then, the parachute will deploy, the craft will be separated from the heat shield, deploy its three legs and activate the radar to sense how far it is from the ground. After getting that radar signal, it will separate from the remaining shell and parachute, firing its descent engines known as retrorockets to help slow it down even more.
In ballet-like fashion, InSight will make a gravity turn to make sure the lander is in the right position before touching down. It will slow down until it reaches a steady 5 mph. Then, it will touch at 2:54 pm ET.
At 3:01 pm ET, InSight should send a signal to let scientists on Earth know that it's alive and well.
"It's been more than a decade to bring InSight from a concept to a spacecraft approaching Mars – and even longer since I was first inspired to try this kind of mission," said Bruce Banerdt of JPL and InSight's principal investigator. "But even after landing, we'll have to be patient for the science to begin."
What happens next
InSight's science mission will not start right away. It will take between two to three months for the robotic arm to place the mission's instruments on the surface. Meanwhile, mission scientists will photograph what can be seen from the lander's perspective and monitor the environment.
But on Tuesday afternoon, we can get the first image back from InSight of his new home on the surface of Mars. And Tuesday evening, the Mars Odyssey orbiter should confirm that the spacecraft's solar arrays have unfurled.
InSight will be landing at Elysium Planitia, called "the largest parking lot on Mars" by astronomers. Because it will not be roving over the surface, the landing site was an important determination. This spot is open, flat safe and boring, which is what scientists want for a stationary two-year mission.
After landing, InSight will unfurl its solar panels and robotic arm and study the whole planet from its parking spot. It's along the Martian equator, bright and warm enough to power the lander's solar array year-round.
The suite of geophysical instruments on InSight sounds like a doctor's bag, giving Mars its first "checkup" since it was formed. Together, these instruments will take measurements of Mars' vital signs, like its pulse, temperature and reflexes – which translates into internal activity like seismology and planet's wobble as the sun and its moons tugged on Mars.
These instruments include the Seismic Experiment for Internal Structures to investigate what causes seismic waves on Mars the Heat Flow and Physical Properties Package to burrow beneath the surface and determine the heat flowing out of the planet and the Rotation and Interior Structure Experiment to use radios to study the planet's core.
"Landing on Mars is exciting, but scientists are looking forward to the time after InSight lands," said Glaze. "Once InSight is settled on the Red Planet and its instruments are deployed, it will begin collecting valuable information about the structure of Mars' deep inside – information that will help us understand the formation and evolution of all rocky planets, including one we call home. "