NASA’s “Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight)” mission has received another boost ahead of launch, as the spacecraft passed its Thermal vacuum (TVAC) milestone in Colorado. The mission remains on track for May of next year, which will involve the first interplanetary launch from the West Coast.
The latest battery of tests was designed to validate the spacecraft could survive the six month journey to Mars and carry out of its important work on the Red Planet.
The United States is the world champion at successfully sending spacecraft and landers to Mars, a task that remains incredibly difficult to pull off. Landing them in a healthy condition is even more difficult.
Thermal vacuum (TVAC) testing is the most comprehensive testing you can perform on a fully assembled spacecraft prior to its launch.
Using a special depressurized chamber, TVAC stresses the design and assembly of the system, validating its integrity and operational capabilities in a simulated, harsh, space-like environment.
“This milestone came after a long stream of rigorous tests including solar array deploy and electromagnetic interference and compatibility testing,” noted Lockheed Martin, in a release on Wednesday.
Passing this phase of testing is a big milestone for the mission, not least because a leak was discovered during an earlier test period.
During the environmental testing phase, the lander was exposed to extreme temperatures, vacuum conditions of nearly zero air pressure simulating interplanetary space, and a battery of tests.
One of the tests was designed to ensure the seismometer instrument’s main sensors can operate within a vacuum chamber to provide the exquisite sensitivity needed for measuring ground movements as small as half the radius of a hydrogen atom.
A leak had previously prevented the seismometer from retaining vacuum conditions, but was repaired, and the mission team was hopeful that fix would prove to be successful. However, during follow-up testing in extreme cold temperature (-49 degrees Fahrenheit/-45 degrees Celsius) the instrument again failed to hold a vacuum.
The discovery of the issue with the Seismic Experiment for Interior Structure (SEIS) instrument was the responsibility of CNES, not Lockheed Martin.
Now, with the TVAC testing a success, the spacecraft can look forward to preparations for the shipping to the launch site for integration with its launch vehicle.
“With InSight coming out of TVAC, the team at Lockheed Martin has successfully completed the environmental testing phase and will be finalizing launch preparations over the coming months,” added the company.
The launch is set for a five-week window that opens on May 5, 2018. The journey to Mars will result in a landing the Monday after Thanksgiving in 2018.
The spacecraft will be launched by the United Launch Alliance (ULA) Atlas V rocket flying in her 401 configuration.
This type of flagship mission is something ULA rockets excel in, with every launch conducted by the company riding uphill without issue.
However, this will be the first time an interplanetary mission will have been launched from a West Coast launch site. The only other deep space launch of note from the West Coast was the Clementine mission that was launched to the Moon by a Titan II rocket on January 25, 1994.
Due to the trajectory requirements for spacecraft launched for such missions, the East Coast is normally the primary site. However, the option to launch from the West Coast was taken due to the relatively small mass of the spacecraft, allowing the powerful Atlas V to have margin left over to conduct the launch from her SLC-3E West Coast launch site at Vandenberg Air Force Base.
Using the less busy West Coast site also aids the launch window, with multiple opportunities available without the distraction of other rockets, of which there are many on the Eastern Range.
The InSight mission draws upon a strong international partnership led by Principal Investigator Bruce Banerdt of JPL. The lander’s Heat Flow and Physical Properties Package is provided by the German Aerospace Center (DLR).
While the spacecraft features numerous elements, a striking feature of the lander is a probe that will hammer itself to a depth of about 16 feet (5 meters) into the ground beside the lander, providing – as the mission’s name suggests – major insight into the interior of Mars.
Called the Heat Flow and Physical Properties Package (HP³) and designed by The German Aerospace Institute (DLR), it will hammer into the Martian surface, further than any probe has ever peered into Mars’ interior, and take subterranean temperature readings.
“HP3 consists of a so called ‘Mole’, which will hammer itself into the subsurface. The mole pulls an instrumented tether behind it, which is equipped with temperature sensors to determine the thermal gradient in the ground,” noted DLR information.
“The mole is targeted for a depth of 5 m below the surface. In addition to the temperature sensors, the mole is equipped with heating foils, which will be used to determine the thermal conductivity of the regolith by operating the mole as a modified line heat source.”
A lander-mounted radiometer, which will measure surface temperatures at the landing site, will complement HP³. Surface temperature readings will allow scientists to better interpret temperature variations HP³ encounters as it probes below the Martian surface.
For instance, a shadowed area of surface may cause cooler temperature readings in the soil below it. In addition, the radiometer will detect the dust coverage and soil compaction of the surface.
HP³ is derived from the designs of both the Multi-Purpose Sensor (MUPUS) aboard ESA’s Rosetta spacecraft and the Planetary Underground Tool (PLUTO), which would have peered beneath the Martian surface from the ill-fated Beagle 2 lander.
The mission will further aid our understanding of Mars which is an ongoing process, not least after this week’s news that the dark features previously proposed as evidence for significant liquid water flowing on Mars has now been identified as granular flows, according to the U.S. Geological Survey.
(Images via Lockheed Martin, NASA and DLR).