Artist illustration of NASA's CAPSTONE, a 'cubesat' that will scout out the orbital trajectory planned for the Gateway space station, and test new navigational technologies to aid upcoming missions. (Courtesy of NASA)
The last time humans landed on the moon, “The Godfather” was a hit movie and Roberta Flack and Don McLean had hit songs. Apollo 17 Commander Eugene Cernan and Lunar Module Pilot Harrison Schmitt were the last people to leave footprints on the moon’s cratered surface.
The next time humans land on the moon might be only three years from now with NASA’s Artemis missions, and this time a woman and a person of color will step down from the landing capsule onto the dusty ground.
To get ready for the adventures of Artemis, NASA has a lineup of robotic missions to map the trail, testing everything from the orbital mechanics for a space station to navigational technologies that will allow future spacecraft to operate with less dependence on controllers back on Earth.
One robotic scout is CAPSTONE, a 55-pound “cubesat” no larger than a desktop computer. CAPSTONE is scheduled to launch this Saturday, on March 19, on a Rocket Lab “Electron” rocket from New Zealand.
Then, possibly as early as April, the first Artemis test flight is set to launch from Kennedy Space Center on NASA’s new Space Launch System (SLS) rocket. Artemis 1 will send an uncrewed Orion spacecraft to within 60 miles of the moon’s surface, testing the system’s flight readiness and orbital trajectories before returning to Earth three weeks later.
Mapping a trail for Artemis
CAPSTONE (ready for this? It’s: Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment) will, among other things, scout out a unique trajectory planned for a moon-orbiting space station, literally breaking trail for the lunar space station. The station, which NASA calls Gateway, will be a home base for astronauts to live between flights to and from Earth, and landings on the lunar surface.
CAPSTONE will maneuver into and maintain this orbit for at least six months, verifying the mathematics and orbital mechanics prior to Gateway’s construction.
NASA has plotted Gateway’s path with special considerations in mind.
The orbit is a highly elongated ellipse, swooping to within 1,000 miles of the moon’s southern polar region and then flinging to a far distance of 43,500 miles, circling the moon every seven days. The orbit takes advantage of the point of balance between the gravity of Earth and the moon, which means it’s a very stable orbit that requires minimal fuel for a spacecraft to maintain over time.
Gateway’s orbit will make it easier for spacecraft flying to and from the moon’s surface — particularly the south polar region that NASA is interested in exploring — to rendezvous with the station. And at the far end of the loop, away from the moon, spacecraft departing for Earth (and future destinations like Mars) won’t need to burn as much fuel to break free of the moon’s gravity.
Another advantage of Gateway’s orbit is that it keeps an almost constant line of sight with Earth, allowing near continuous communication between the station and controllers at home. The orbit also provides coverage to the moon’s far side, where the body of the moon blocks radio signals from Earth. For future missions that will land on the far side of the moon, Gateway will serve as a Wi-Fi connection in the sky.
Untethering (a little) from Mission Control
Another of CAPSTONE’s goals is to test new navigational technologies that will help future moon-bound spacecraft to operate with less dependence on controllers back on Earth.
As part of this test, CAPSTONE will communicate directly with the Lunar Reconnaissance Orbiter, which has been circling the moon for over a decade now, making a high-resolution image survey of the lunar surface.
CAPSTONE will use this orbiter as a form of lunar GPS, a navigational reference to determine its own location and orbital trajectory.
Coming up: astronauts aboard Artemis
Named for the Greek moon goddess and twin sister of the sun god Apollo, the Artemis missions mark not only the first human-crewed expeditions to the moon since Apollo 17, five decades ago, but also the first time humans have ventured farther than 300 miles from Earth’s surface since that time.
Artemis 2, planned to launch in May 2024, will carry human astronauts around the moon, then back home again.
Artemis 3 will land astronauts on the lunar surface as early as 2025. NASA has announced that the spacecraft will carry the first woman and first person of color to the moon’s surface. The plan is to send the two astronauts to a site in the moon’s southern polar region, where they will explore for about a week. A third astronaut will remain aloft in Gateway.
Why are we going to the moon?
Good question. The moon is a valuable resource, not only as a place for humans to explore, or a repository of natural resources to fuel missions on the moon and destinations beyond, such as Mars, but also as a unique platform for scientific observation of the universe.
The far side of the moon, which always faces away from Earth, is protected from the radio noise that human civilization generates and spews into space, a natural shelter where sensitive radio observatories may probe the cosmos.
But, until the exciting human expeditions of Artemis come to pass, we can look forward to the adventures through the exploits of our robotic explorers.
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