Scientists eager for answers to long-standing questions about the geology of Mars will get a lift Saturday with the blastoff from California of an Atlas 5 rocket with NASA’s InSight mission, a robotic landing craft that will take the pulse and temperature of the red planet.
With two experimental deep space communications relay CubeSats riding along, the InSight spacecraft and the Atlas 5 rocket are scheduled for liftoff at 4:05 a.m. EDT (7:05 a.m. EDT; 1105 GMT) Saturday from Space Launch Complex 3-East at Vandenberg Air Force Base, California.
InSight’s arrival at Mars is fixed on Monday, Nov. 26, 2018, when the robot will plunge into the Martian atmosphere, using a combination of a supersonic parachute and braking rockets to touch down with the aid of three shock-absorbing landing legs in Elysium Planitia, a broad equatorial plain with few boulders or craters that could pose a hazard during the spacecraft’s final descent.
Once on the Martian surface, InSight will unfurl solar arrays and place two instruments on the ground using a robotic arm to listen for tremors and measure the heat flow coming from the planet’s super-heated interior.
“In this mission, we’ll probe the interior of another terrestrial planet, giving us an idea of the size of the core, the mantle, and the crust, and our ability to then compare that to the Earth,” said Jim Green, NASA’s newly-appointed chief scientist, and former head of the space agency’s planetary science division. “This is of fundamental importance for us to understand the origin of the solar system, and how it became the way it did today.”
“The goal of InSight is nothing less than to better understand the birth of the Earth, the birth of the planet we live on, and we’re going to do that by going to Mars,” said Bruce Banerdt, InSight’s principal investigator from the Jet Propulsion Laboratory.
Saturday’s predawn launch will be the first time a mission to another planet has left Earth from Vandenberg, the primary launch base on the West Coast.
The 188-foot-tall (57-meter) Atlas 5 rocket, built by United Launch Alliance, will initially send the InSight spacecraft toward the south-southeast over the Pacific Ocean, with the booster stage’s kerosene-fueled RD-180 engine generating around 860,000 pounds of thrust. The Atlas 5’s Centaur upper stage will ignite its RL10 main engine, burning a mixture of hydrogen and oxygen, two times to place InSight into low Earth orbit, then hurl the science probe toward Mars.
The Centaur upper stage will release the 1,530-pound (694-kilogram) InSight spacecraft, built by Lockheed Martin, around 93 minutes after liftoff. Two briefcase-sized interplanetary CubeSats, part of the Jet Propulsion Laboratory’s Mars Cube One technology demonstration mission, will spring out of carriers on the Centaur stage moments later to chart their own path toward the red planet.
The twin Mars Cube One, or MarCO, nanospacecraft will become the first CubeSats to travel into interplanetary space, providing a radio relay capability to beam telemetry from InSight directly to Earth as the lander drops into the Martian atmosphere.
But InSight does not need the MarCO CubeSats to make a safe landing. The entry, descent and landing maneuvers will be pre-programmed into InSight’s on-board computer for the make-or-break arrival at Mars in November.
A blanket of fog forecast at the Vandenberg launch site early Saturday may inhibit viewing of the Atlas 5’s climb into space from nearby observation posts, but the reduced visibility is not likely to prevent liftoff, officials said Thursday.
The Air Force levies a constraint for favorable visibility during an Atlas 5 launch to meet range safety requirements, but Air Force officials said they have workarounds to gather data on the rocket’s trajectory after liftoff with other tracking assets. The fog would only become a problem if the other range safety capabilities were offline.
Ground crews at the SLC-3E launch pad, perched on a hillside overlooking the Pacific Ocean, will switch on the Atlas 5’s avionics late Friday for pre-flight checks, then retract the towering mobile gantry shortly before midnight, Pacific time, to reveal the rocket on its launch mount.
The launch team will load cryogenic liquid oxygen and liquid hydrogen propellants into the two-stage Atlas 5 rocket during the final hours of the countdown.
A final pre-planned hold in the countdown is scheduled at T-minus 4 minutes, giving managers time to complete final polls of the launch team before clocks resume at 4:01 a.m. PDT (7:01 a.m. EDT; 1101 GMT).
InSight has launch opportunities available every five minutes during Saturday’s two-hour launch window. If technical or weather concerns prohibit liftoff Saturday, the mission has launch dates available through June 8, and still reach Mars on Nov. 26.
NASA’s 20 previous Mars missions have all departed from Cape Canaveral, taking advantage of Earth’s rotation by launching toward the east. The extra momentum gives rockets an additional boost.
Vandenberg Air Force Base is typically host to launches into polar orbit, a type of orbit usually tailored for climate research missions, spy satellites and some communication applications.
But InSight is small, with a mass well below the lift capability of the United Launch Alliance Atlas 5 rocket, which will fly in its basic “401” configuration with a four-meter payload fairing and no solid rocket boosters.
That means the Atlas 5 will not need the extra energy imparted during an eastward launch from Cape Canaveral, and ULA and NASA agreed to launch InSight from Vandenberg. The launch contractor proposed to base the mission from the West Coast because fewer Atlas 5 missions are scheduled from Vandenberg, so officials wanted to reduce the workload at ULA’s busier launch base in Florida.
“There’s one optimal launch time per day in order to get to Mars,” said Jen Krupp, a ULA flight design engineer. “While there may be on optimal launch time, we can achieve a two-hour launch window by steering slightly more inefficiently toward the edges of the optimal time in order to still hit the same target.”
The final burn of the Centaur upper stage will give InSight enough speed to escape the bonds of Earth’s gravity, sending the spacecraft into the solar system on a trajectory mimicking the course the mission would have followed if launched from Florida.
“I use the baseball analogy for this one,” Krupp said. “From Florida, the baseball pitcher is throwing sidearm. they’re going on an easterly trajectory going toward Mars, and they’re throwing sidearm. For InSight, we’re going to fly southerly in a polar mission, and (as) we come over the north pole, the pitcher is throwing overhand and releasing the spacecraft to Mars.”
To complete the analogy, sidearm and overhand pitches can both deliver the baseball to a narrow strike zone 60 feet away. In InSight’s case, the Atlas 5 can deliver the lander to Mars from either coast.
Designers based the InSight lander on NASA’s Phoenix probe, which launched in August 2007 and touched down on the northern polar plains of Mars in May 2008. Diminishing solar power and cold temperatures limited Phoenix’s lifetime to about five months — two months longer than its three-month prime mission.
InSight will head for a broad plain near the Martian equator with ample sunlight year-round, providing enough warmth and solar power to keep the mission operating for nearly two years, or a little more than one Martian year.
Assuming the mission takes off Saturday, InSight will embark on a 301-million mile (485-million-kilometer) journey. Several course-correction maneuvers are planned during the trip, setting up for InSight’s fiery descent through the Martian atmosphere.
Employing a similar entry, descent and landing profile as the Phoenix mission a decade ago, InSight will approach the target landing zone in Elysium Planitia, with its heat shield absorbing blistering temperatures up to 2,700 degrees Fahrenheit, before unfurling a parachute and firing downward-facing rocket thrusters to settle to a gentle touchdown.
Mission managers selected the nearly featureless landing target because of its safety. There are few surface hazards that could spell doom for InSight, and Banerdt, the mission’s chief scientist, calls it the “biggest parking lot on Mars.”
InSight was originally supposed to launch in March 2016, but problems sealing a vacuum enclosure containing one of the lander’s primary instruments, a French-developed seismometer, forced officials to postpone the mission. Mars launch opportunities come once every 26 months, when the planets are in the proper positions in the solar system, so the next chance to send InSight to the red planet opens Saturday.
Engineers redesigned the vacuum enclosure to eliminate an air leak in a feed-through, or wiring interface, used route data between the seismic sensors inside the instrument and electronics and communications equipment aboard the InSight spacecraft.
The protective enclosure keeps out wind and other environmental conditions that could disrupt the sensitive seismic measurements. It must keep a seal through the large temperature swings on Mars.
“One of these feed-throughs was not capable of maintaining itself through the large temperature extremes,” Banerdt said. “When we actually tested at Mars conditions going down to minus 100 or minus 120 degrees Celsius (minus 148 to minus 184 degrees Fahrenheit). It developed a very tiny crack and started leaking — started allowing some air to come in.
“This was enough to upset the whole apple cart in terms of the sensitivity of the seismometer,” Banerdt said.
JPL took over responsibility for fabricating a new enclosure, while the French space agency, CNES, remained in charge of the instrument’s internal sensors.
The seismometer is now healthy, their enclosure sealed, and are ready for launch. The InSight spacecraft itself, along with a German-built heat probe sensor and the United Launch Alliance Atlas 5 rocket, were all in position at Vandenberg for the March 2016 launch when NASA managers decided in December 2015 to keep the mission on the ground.
The two-year delayed added roughly $150 million to InSight’s cost, which now sits at more than $993 million, including launch and operations expenses. That figure includes an investment valued at approximately $180 million from the French and German space agencies.
The twin MarCO spacecraft cost another $18.5 million, according to NASA.
One of InSight’s first jobs will be to take panoramic pictures to survey the landing site, a region unexplored by past Mars missions. InSight carries cameras based on technology originally developed for the Opportunity and Curiosity rovers, but with added capability for color imagery.
A nearly 8-foot-long (2.4-meter) robotic arm will place the seismometer and heat probe on the Martian surface next to the lander after touchdown. InSight’s robotic arm was originally built for the canceled Mars Surveyor lander that was supposed to launch in 2001.
Other leftover parts on InSight include a landing radar originally built as a spare for the Phoenix mission, and surplus structural booms from the Curiosity rover repurposed for a Spanish-built weather station on InSight to collect temperature and wind data.
Once placed on the surface of Mars, the German-made Heat Flow and Physical Properties Package, know as HP3, will hammer to a depth of 16 feet, or 5 meters, a process expected to take around six weeks with roughly 10,000 individual hammer blows, accounting for several planned pauses to allow the instrument to record thermal conductivity measurements.
“If you have an astronaut on the planet, you can do this in maybe 20 minutes or half an hour,” Banerdt said of the heat flow experiment. “But if you want to do it robotically, you have to get a little bit more clever.”
A metallic mole will probe deeper into the Martian crust than any past lander.
“We think this remote probe can actually go down about 15 feet, which gives us a better baseline to measure the temperature increase with depth and be able to estimate the amount of heat coming out of Mars,” Banerdt said.
“And that amount of heat is tied to the geological activity of the planet. It’s the heat engine of the planet that drives volcanism, 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.”
“We switch on the temp sensors and record the temperature over depth and time for up to two years,” said Tilman Spohn, HP3 investigation lead from DLR, the German Aerospace Center, in Berlin. “Taking the temperature gradient, or the rate at which the temperature increases (with depth), gives us the heat flow. Very simple and straightforward, but as planetary science often is, very difficult. The devil is in the details.”
The seismometer will get to work listening for marsquakes.
“Sensitive is really an understatement,” Banerdt said of the seismometer. “Tt’s an exquisitely sensitive device for measuring the motion of the ground. And when we talk about motion, we’re talking about vibrations that have an amplitude comparable to the size of an atom.
“These are waves that were generated, maybe, by a marsquake on the other side of the planet, have traveled all the way through the planet, getting their waveform modified as they go through the planet and picking up information about the deep interior structure, and then we are able to pick it up when it comes back up to the surface under the seismometer,” Banerdt said.
The seismic sensors aboard InSight evolved from mission concepts in the 1990s and 2000s that would have dispatched multiple small probes to Mars, creating a global geophysical network. InSight will be just one seismic station, but scientists have developed techniques to glean information about the interior of Mars, even with a single seismometer.
Researchers have attempted seismic detections on Mars before, but seismometers on NASA’s Viking landers in the 1970s provided inconclusive results. The instruments were mounted the decks of the landers, making them susceptible from interference from spacecraft vibrations and winds.
“Not only do you have to have a very sensitive device for measuring those motions but you have to protect it from everything else that might affect it,” he said. “We have several different layers of protection, it’s sort of like a Russian doll.”
An electrical and data cable will connect the seismometer to the InSight lander.
Philippe Lognonné, head of the InSight seismic investigation team at the Institut de Physique du Globe de Paris in France, said scientists do not have a confirmed detection of marsquake, but evidence suggests weak tremors occur on the red planet.
“We have no clear data on seismic activity on the planet,”Lognonné in an interview with Spaceflight Now. “We imagine it because we see faults on the surface. In some places, we have seen where a boulder may have fallen down from a scarp. But again, we have no data.”
Lognonné said, based on existing theoretical models, the seismometer could register around 20 or 30 quakes per year, sensing ripples from all types of seismic waves moving through the planet.
“We cover all the seismic waves, and we even have sensitivity to tides, the Phobos tide especially,” Lognonné said. “We cover all the signals to be generated by a quake.”
“but we can measure that, and extrapolate it down. So if you have an astronaut on the planet, you can do this in maybe 20 minutes or half an hour. But if you want to do it robotically, you have to get a little bit more clever.
“We have something we call a MOLE, because it’s something that burros down into the surface, and what it is is it’s a little torpedo with a hammer on the inside that gets wound up on a motor and about every three seconds, hammers this thing down and finally, it should go down five meters or so, which is about 15 or 16 feet, and it pulls behind itself a cable that has temperature sensors along the cable. So instead of only going down a few feet, we think this remote probe can actually go down about 15 feet, which gives us a better baseline to measure the temperature increase with depth and be able to estimate the amount of heat coming out of Mars.
“And that amount of heat is tied to the geological activity of the planet. 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.
“then we switch on the temp sensors and recrd the temp over depth and time fr up to two years. by taking the temp gradient, or the rate at which the tmep incrases, tyimes the thermal conductivity that we measured, gives us the heat flow. very simple er straightfoward, but as planetary science often is, very difficult. the devil is in the details.”
Scientists will also measure Mars’ polar wobble by analyzing radio signals transmitted between InSight and Earth-based antennas.
“By the timing of that signal, we can track the location of the spacecraft at Mars … with an accuracy of something around a foot or so, maybe a little bit less,” Banerdt said. “To me, that’s the closest we can get to magic with science.”
With that information, scientists can determine which way the Martian north pole is pointing as the planet rotates.
“Over the course of a year, we can watch the north pole wobble just a little bit because of the core sloshing around inside of the planet, and that will give us a very, very tight constraint on the size of that core and 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 this into our mdoels, extrapolate it to Earth, and understand how the Earth formed four-and-half billion years ago.”
Much of the ancient geologic record on Earth has eroded away, but Mars may still hold clues about how it was born, accreted rock and dust, and formed a hot, high-pressure mantle and core as heavier elements sunk deep beneath its surface.
“How we get from a ball of featureless rock into a planet that may or may not support life is a key question in planetary science,” Banerdt said. “And these processes that do this all happen in the first tens of millions of years.”
Discoveries made by InSight at Mars could inform scientists how the Earth formed and evolved.
“Mars is a smaller planet,” Banerdt said. “It’s less active than the Earth, so it has retained the fingerprints of those early processes in its basic structure — the thickness of the crust, the compositon of the mantle, the size and composition of its core,” he said. “By mapping out these boundaries, these various different sections of the inside of the planet, we can then understand better how the planet formed, and how our planet got to be the way it is.”
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