GRAIL Probes Complete Primary Mission Ahead of Schedule

Zothecula writes with an update on NASA's lunar mapping probes. From the article: "After entering orbit around the Moon at the start of the year, NASA's twin GRAIL probes, Ebb and Flow, have completed their primary mission to study the Moon's interior structure ahead of schedule. Operating around the clock since March 8, NASA says the spacecraft have provided unprecedented detail about the interior structure and evolution of the Moon and the data they have gathered will provide insights into how Earth and its rocky neighbors in the inner solar system developed." And their extended mission? From NASA: "The extended mission goal is to take an even closer look at the moon's gravity field. To achieve this, GRAIL mission planners will halve their current operating altitude to the lowest altitude that can be safely maintained. 'Orbiting at an average altitude of 14 miles (23 kilometers) during the extended mission, the GRAIL twins will be clearing some of the moon's higher surface features by about 5 miles (8 kilometers),' said Joe Beerer of JPL, GRAIL's mission manager."

Re:This is more a JPL probe than a NASA one

[tlhIngan]

There are two NASAs: The Bad NASA that wastes billions on manned pork rockets to nowhere and the Good NASA (Jet Propulsion Lab) that has had one success after another with unmanned probes. I love it when the ex-pilots who run NASA try to take credit for JPL's success, even when they are trying to kill planetary exploration in favor of more manned pork.

There's actually a 3rd NASA. It's the "hidden NASA" that very few notice - I'll give you a hint - it deals with the first "A".

NASA actually does a lot of research/testing for aeronautics. It's just relatively low-key. If you're a pilot, you also keep a handy stack of NASA Aviation Safety Reporting forms with you (NASA is tasked as a neutral party to manage aviation safety issues - NASA anonymizes the forms before forwarding to the NTSB/FAA).

It's only the space parts that get all the glory. All the down-on-Earth parts work in relative obscurity.

Visualizing the insanely low altitude

[jheath314]

If you want to get a sense of how low that orbit is, fire up your favorite paint program and draw a circle 1000 px wide, representing the moon's average diameter (3,475 km). The circle representing the orbit is only 1013 px wide, just six pixels above the average surface and only two pixels away from the highest features.

Looking at this another way, the ratio of the craft's average altitude to the moon's diameter is slightly less than the ratio of an egg shell to the diameter of that egg.