For about nine years two tag-team satellites, collectively called the Gravity Recovery and Climate Experiment or GRACE, have zipped around Earth in formation. Their course deviations reveal precisely the varying concentration of mass in the Earth, allowing mapping of its interior by density. Its focus is on things that change over time. Grace, a joint NASA and German project, will get two little sisters with about the same job to do but  at the Moon even if not much changes there. The first gets there on New Year’s eve and the second January 1. Collectively the are GRAIL, for Gravity Recovery and Interior Laboratory. They have been on separate but similar long, roundabout, and energy-saving marches almost any way but moonward, feinting first toward the Sun and past gravity-kink Libration Point 1 since their launch Sept. 10 from Cape Canaveral.

   Several outlets have advance stories, or curtain raisers, out on the scheduled operating deployment of the GRAIL birds. It’s mildly peculiar that none that came into view allude to GRACE, an obvious relative of the new program. The missions share several top scientists. GRACE affords a convenient avenue for explaining that this sort of research comes naturally to planetary geophysicists. One might dig up a few GRACE examples to show how powerful the method is. GRACE already has, for instance, measured the displacement of mass in Earth’s crust by large earthquakes and the deflection of the surface by the weight of floods in Bangladesh. Now it’ll chart the Moon’s mass deviations to similar or better accuracy. Perhaps the oversight has easy explanation, if not excuse: a press release from NASA’s Jet Propulsion Lab does not make the association either.

Stories:

• AP – Alicia Chang: NASA probes to arrive at the moon over New Year’s ;
• Space.com – Mike Wall: NASA’s twin moon probes to enter orbit this weekend ; Nice description (if not ‘graceful’) of the ambition to get these things down to where they’re nearly buzzing the craters’ rims.
• NPR – Eyder Peralta: Twin NASA Probes Will Arrive At The Moon By New Year’s ; Not much – rewrite with citations of other outlets, presumably of the handout too.
• AFP: Twin NASA probes approach lunar orbit ;
• Register (UK) Lewis Page: NASA to place twin proes in Moon orbit as you snog beneath mistletoe ; Catchy hed but not much else – except for noting that these craft keep such close watch on one another that they can tell when their separation has changed by as little as a micron or, as Page writes, the diameter or a red blood cell.
• Universe Today – Ken Kremer: NASA’s Unprecedented Science Twins are GO to Orbit our Moon on New Year’s Eve ; Unprecedented to the moon, maybe, but what about GRACE?!
• Orange County Register – Pat Brennan: Twin moon probes to make New Year’s arrival ;
• Denver Post – Ann Schrader: Lockheed-built twin Grail spacecraft eneter orbit around moon this weekend ;

Just to show that the GRAIL-GRACE Nexus is not obscure, some digging reveals this that ran just prior to mission launch:

• Aviation Week (Sept 8, 2011) Frank Morring Jr. : NASA Readies Twin Lunar Spacecraft; Anybody planning on covering the onset of science operations might, even before reading the press kit  stem to stern, read this savvy account.

Grist for the Mill: NASA-JPL GRAIL mission ; NASA Press Release ; NASA Press Kit ;

- Charlie Petit

Stories:

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