By 2024, NASA will land astronauts, including the first woman and the next man, on the moon as part of the Artemis lunar exploration program. This will not be the first time that NASA has taken the name Artemis on the Moon. Two robotic spacecraft orbiting the Moon today were originally known as ARTEMIS – short for Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun. Since 2011, these spacecraft have been sending scientists valuable information about the lunar environment and laying the groundwork for humans to return to the moon.
The mission, now renamed THEMIS-ARTEMIS, uses spacecraft that were originally part of the mission known as the Time History of Macroscopic-Scale Events and Interactions During Substorms, or THEMIS , for short, who launched five spacecraft in 2007 to uncover the physical processes that happened to the events that cause the Northern Lights.
“THEMIS-ARTEMIS has been a pioneer in technologies that will be important to NASA’s new Artemis program,” said Jasper Halekas, THEMIS-ARTEMIS scientist and researcher at the University of Iowa in Iowa City. “Some of the work we have done in terms of navigation and operations will be used by future missions.
A mission in two
The five THEMIS spacecraft were sent into carefully designed orbits that lined them up every four days. After two productive years of discoveries about radiation and particles in the near-Earth environment, the orbits of spacecraft had either precessed or drifted considerably. Precession of the orbit is a natural and expected phenomenon for spacecraft that does not generally affect scientific studies. But in the case of THEMIS, that meant the spacecraft would no longer line up every four days.
Knowing that orbits would eventually precede, THEMIS scientists, in a joint effort coordinated by NASA and the University of California, Berkeley Space Science Lab, decided in advance to do something new with two spaceships. Instead of spending the remaining fuel to reset the orbits, they would send them in a radically new direction – towards the Moon.
“NASA’s Jet Propulsion Laboratory and Goddard Space Flight Center came up with a wonderful orbit navigation design for us and came up with these very smart orbits that got us to the moon,” Halekas said. “And we’re still here.
This is how the THEMIS-ARTEMIS mission was born. The acronym for the mission was created to reflect her science and her position on the Moon, as in Greek mythology, Artemis was the moon goddess. Artemis was also Apollo’s twin. NASA administrator Jim Bridenstine recently named the new lunar program Artemis for these reasons, in addition to the fact that the agency will send the first woman to the moon as part of the program.
“THEMIS-ARTEMIS is NASA’s only long-term monitor of conditions in and around the lunar environment,” said David Sibeck, THEMIS project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The spaceship reborn
With the same instruments it used to research events around Earth, the new mission uses the two spaceships to learn how the Moon interacts with the space around it.
“Before THEMIS-ARTEMIS was on the Moon, most people had the idea that the Moon was just a big boulder in the sky and didn’t interact much with its surroundings,” Halekas said. . “The understanding we have gained over the past eight years is that the Moon is truly connected to the space environment around it. The space environment affects the Moon and vice versa. “
Over the years, scientists have made discoveries about the solar wind and its impact on the surface of the Moon, interplanetary electromagnetic fields, the structure of the lunar interior, and particles of the thin lunar atmosphere and the ionosphere.
In addition to deepening our understanding of the Moon, the measurements made by THEMIS-ARTEMIS will be useful for future missions, including the Artemis program.
“When we design robotic systems and systems for humans on the Moon, we need to understand the conditions to which they will be exposed,” Halekas said. “THEMIS-ARTEMIS measurements have helped us to find out what these conditions are and how they change over time.”
THEMIS-ARTEMIS could provide real-time measurements of highly energetic particles that can be dangerous for spacecraft and astronauts. It will also provide valuable information for instruments placed on the lunar surface. Just as a weather satellite can provide information about incoming storms, THEMIS-ARTEMIS can provide information about the space environment to help contextualize discoveries made on the surface.
“THEMIS-ARTEMIS would be a natural partner for any heliophysical mission sent to the moon either on a spacecraft or on the lunar surface,” said Sibeck. “Both ships are performing very well, taking their full sets of measurements, and could last a very, very long time in this environment.”
As part of the Lunar Payload Commercial Services initiative under the Artemis program, NASA will send a series of new instruments and technology demonstrations to study the Moon before a human return. The first two lunar deliveries on commercial landers are expected to launch in July 2021. While many of these investigations focus on lunar science, some point to THEMIS roots in the science of heliophysics, the study of interaction of the Sun with the solar system. The lunar surface electromagnetic experiment, or LUSEE instrument, will examine electromagnetic phenomena on the lunar surface. The Heliospheric X-ray Lunar Environment Imager, or LEXI instrument, will plant a telescope on the Moon to study the Earth’s magnetosphere and its interaction with the solar wind.
In the years to come, THEMIS-ARTEMIS, along with the agency’s Lunar Reconnaissance Orbiter, will continue to provide invaluable information to NASA as preparations continue to send astronauts to the Moon, and ultimately to Mars.