Twin probes in lunar orbit
5 Jan 2012 by Evoluted New Media
NASA rang in the new year with the successful arrival of twin probes designed to study the Moon from crust to core.
Grail-B probe entered lunar orbit on 1st January after a 40 minute orbital-insertion burn, joining its twin – Grail-A – which arrived via a similar manoeuvre the previous day. The Grail probes – short for Gravity Recovery And Interior Laboratory – will begin studying the Moon in March to construct details about its gravitational field.
Despite more than 100 moon missions over the years, scientists still know very little about the lunar body.
“You might think that, given all of these observations, we would know all there is to know about the moon,” said principal investigator Maria Zuber, from MIT. “Of course that’s not the case.”
The washing machine-sized probes will spend the next two months circling down to super-low orbits before settling at 34 miles above the lunar surface. They will then zip around the Moon in tandem, mapping its lunar gravity field in unprecedented detail.
They will chase each other around the Moon for 82 days, staying between 75 and 225 miles apart: regional differences in the lunar gravitational field will cause them to alter their speeds and change the distance between them. By bouncing microwave signals back and forth off each other, they will measure these tiny distance variations constantly.
Scientists will use the twin probe measurements to construct detailed maps of the lunar gravitational field. These maps are expected to reveal much about the composition of the Moon, allowing scientists to debate how the Moon was formed and how it has changed over time.
Primarily, researchers hope to explain why the far side of the Moon is so different to the nearside, the side visible from Earth.
“We don’t actually know why the nearside and the far side of the Moon are different,” Zuber said. “We think that the answer is locked in the interior.”
In August, scientist proposed a second moon slammed into the Moon’s far side, spreading itself over the surface, causing the more mountainous regions we now see. The Grail probes’ observations could help determine whether this scenario is accurate.
