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Emily LakdawallaSeptember 29, 2009

A little drama during the MESSENGER Mercury flyby

Just minutes after closest approach, MESSENGER's radio signal was lost unexpectedly, several minutes before the expected blackout due to it passing behind Mercury. Then, of course, came the expected 52-minute blackout period, so for about an hour there things were pretty tense as all of us who were paying attention wondered if MESSENGER would be talking again as it came out on the other side of Mercury.

Well, the signal was reacquired, and the early indications are that the only experiment that was affected was the gravity experiment, which uses Doppler tracking of the spacecraft's radio signal as a probe of the planet's gravity field. The unexpected loss of signal means a sad loss of the closest-approach data. But never mind; the spacecraft is otherwise healthy and should now be gathering stacks and stacks of photos of Mercury, which is receding from MESSENGER's view.

What's better, it so happens that now Mercury and Earth are in almost exactly the same part of the sky as seen from MESSENGER, which means that before too long it'll be able to carry on taking data at the same time as it starts relaying data back to Earth. We should have images on the ground from the spacecraft much faster than usual (though I don't know what the MESSENGER team's plans are regarding public release of those images).

At any moment now I'll be called away from my computer to feed one baby, pick up another from school, get her dinner, etc etc etc. So I think I'll probably wrap up my color commentary of the flyby now. I'll check back periodically though to see what the spacecraft's saying about its health! Detailed telemetry should start up again from the spacecraft in a little over two hours.

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Emily Lakdawalla

Senior Editor and Planetary Evangelist for The Planetary Society
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Emily Lakdwalla
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