The second of two probes built by UC Berkeley successfully entered orbit around the moon on Sunday, after a two-year journey from its original orbit around Earth.
The probe is part of the National Aeronautics and Space Administration’s ARTEMIS mission, the first mission to ever use a pair of satellites to observe the lunar surface, its magnetic field and the surrounding magnetic environment.
“With two spacecraft orbiting in opposite directions, we can acquire a full 3-D view of the structure of the magnetic fields near the moon and on the lunar surface,” said Vassilis Angelopoulos, principal investigator and UCLA professor of space physics, in a statement.
Engineers at UC Berkeley’s Space Sciences Laboratory, in collaboration with NASA, developed and orchestrated the journey from Earth to the moon. Manfred Bester, director of operations for the lab, said UC Berkeley “had a very large responsibility in the mission, from building everything to operating the spacecraft in orbit.”
“We had a team working on various aspects of accomplishing those mission control functions, overseeing trajectory planning and maneuver operations for this lunar mission extension,” Bester said.
The spacecraft are from a former mission called THEMIS, featuring five in-orbit spacecraft investigating the changes in atmospheric auroras. However, the outermost two were in danger of falling into Earth’s shadows and freezing, preventing them from re-entering orbit.
As a result, Angelopoulos came up with a plan to get the spacecraft away from the Earth and out into the moon’s orbit, said David Sibeck, project scientist at NASA’s Goddard Space Flight Center.
“Angelopoulos wrote a proposal that we would study the environment of the moon and the interior structure of the moon, its magnetic fields and even its composition,” Sibeck said.
After NASA approved the proposal in July 2009, the spacecraft began moving out to the moon. Just last month, the first ARTEMIS probe went into lunar orbit, and Sunday, the second probe also started circling the moon.
“We had fuel preserved that allowed us to go on this complex trajectory to the moon,” Bester said. “We used gravity assist, which changed the flight path of the probes and allowed us basically to get to the moon from an angle where the spacecraft would follow the moon on its own path around Earth.”
However, the scientists and engineers involved in the mission ran into challenges, as the spacecraft were designed for an Earth orbiting mission, not to fly around the moon.
“By venturing out, we had to pull all kinds of tricks out of our hats to make this work,” Bester said. “In some ways, if this mission had been designed to be a lunar mission, we would have gone about it differently. On the bright side, we changed one mission to another mission at little cost, which is definitely something we can be proud of.”
The spacecraft are equipped with instruments that can measure sensitive variations in magnetic fields, allowing scientists and engineers to study both the moon’s composition and environment.
“When it comes to the moon itself, if we understand its composition and its internal structures, and if we understand when and where there are magnetic fields, that can tell us a lot about the history of the moon and how it was formed,” Sibeck said. “So in the big picture, we learn more about our solar system, and we learn more about space weather in the vicinity of Earth.”