A microwave oven-size spacecraft took off on a four-month voyage to the moon Tuesday, the first step in a relatively low-cost pathfinder mission for NASA's planned Gateway lunar space station, a key element in the agency's Artemis moon program.
The solar-powered CAPSTONE spacecraft, owned and operated by Advanced Space of Westminster, Colorado, under a $20 million contract with NASA, also will measure the radiation environment and test techniques that one day might determine a moon-orbiting spacecraft's exact location without relying on Earth-based tracking.
The 55-pound Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment — CAPSTONE — was boosted into low-Earth orbit by Rocketlab's two-stage Electron booster, taking off from the company's Mahia, New Zealand, launch site at 5:55 a.m. EDT (9:55 p.m. local time).
The climb to orbit went smoothly and if all goes well, the rocket's Photon upper stage engine will repeatedly fire over the next five days to raise the high point of an increasingly elliptical orbit.
Finally, on flight day six, a final engine firing will boost the craft's velocity to 24,500 mph, fast enough to escape Earth's gravity and head for the moon.
"Congrats to the #CAPSTONE team for a successful launch this morning!" tweeted Thomas Zurbuchen, director of space science at NASA Headquarters.
Congrats to the #CAPSTONE team for a successful launch this morning! The spacecraft will explore a unique lunar elliptical orbit, the same orbit planned for @NASA_Gateway – a multipurpose outpost for long-term lunar missions as part of the @NASAArtemis program. pic.twitter.com/FRFcfy38WQ
— Thomas Zurbuchen (@Dr_ThomasZ) June 28, 2022
Along with $20 million for the spacecraft and mission operations, NASA paid about $10 million for the CAPSTONE launch, Rocketlab's 27th Electron flight and its first beyond low-Earth orbit. While expensive by everyday standards, a $30 million flight to the moon is a bargain when it comes to deep space exploration.
"I have to say, it's a pretty incredible feeling being able to work on a mission that's flying out to the moon," Jake Peery, an electrical systems engineer, said in a Rocketlab video. "Kind of puts you in a really exclusive club."
Following a path that will carry it more than 800,000 miles from Earth — more than three times the 240,000-mile distance between Earth and the moon — it will take the spacecraft four-and-a-half months to reach the planned lunar orbit on Nov. 13, an orbit that balances the gravitational effects of Earth and moon.
Viewed from Earth, the orbit around the moon's poles will trace out a huge ellipse, carrying CAPSTONE within about 1,000 miles of the north pole before sailing out to a point roughly 43,500 miles above the south pole and then falling back toward another north pole flyover.
CAPSTONE will take one week to complete one orbit and will remain in direct line of sight with Earth throughout. The spacecraft will not pass behind the moon and its solar cells will be in constant sunlight.
The "near rectilinear halo orbit," or NRHO, will be used for NASA's Gateway, a small multiport way station where Orion crew capsules and landers will dock. Astronauts will use Gateway to carry out detailed lunar observations, test equipment, carry out experiments and descend to the surface.
"NRHO enables global lunar access," said Nujoud Merancy, chief of the Exploration Mission Planning Office at the Johnson Space Center. "It's highly fuel efficient, especially when compared to other types of orbits around the moon.
"NRHO will give Gateway a continuous line of sight or view of Earth, so we get uninterrupted communication. And as the Gateway vehicle travels in deep space, its presence opens up a lot of opportunities for radiation (research) and the greater analysis of space weather on people and instruments for future exploration."
While it all works on paper, no spacecraft has ever been launched into such a halo orbit. NASA hopes to operate the Gateway station for 15 years or more and the agency is using CAPSTONE as a pathfinder, confirming the long-term stability of the trajectory.
Not that mission designers doubt it will work.
"If anything goes wrong (with the CAPSTONE mission), we have full plans that we can move forward with Gateway and really all of the Artemis missions that will use NRHO," said Merancy. "This data would be really valuable ... but it's not necessary or required to proceed."
That said, it's "always good to get more data and improve our modeling," she added. "But we have full confidence in the data that will be happening either way."
Along with giving the halo orbit a real-world test, the spacecraft, built by Florida-based Terran Orbital, also is equipped with communications gear enabling it to contact NASA's Lunar Reconnaissance Orbiter, circling the moon in a lower, more circular orbit.
By analyzing radio signals to and from the LRO as both spacecraft move around the moon, CAPSTONE should be able to calculate its general position in space without any Earth-based tracking. Future lunar satellites will improve the accuracy of the technique.
"This peer-to-peer information will be used to evaluate CAPSTONE's autonomous navigation software," NASA said on its website. "If successful, this software ... will allow future spacecraft to determine their location without having to rely exclusively on tracking from Earth.
"This capability could enable future technology demonstrations to perform on their own without support from the ground and allow ground-based antennas to prioritize valuable science data over more routine operational tracking."
The mission is expected to last at least six months.
Editor's note: This story has been updated to correct the date it's expected to reach orbit.