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MESSENGER's camera takes over
for the Webcam in this week's image, snapping the above photo
during recent instrument alignment checks at NASA's Goddard Space
Flight Center. Taken by the Mercury
Dual Imaging System's wide-angle camera, the picture shows
an engineer using a theodolite - an
instrumented telescope used to measure angles - to check the
camera's bore sight. This alignment test shows the team exactly
where the camera is pointing in relation to the spacecraft's
three directional axes.
The picture appears blurry because
the wide-angle camera is designed to focus on objects at least
200 kilometers (124 miles) away. The theodolite projects an illuminated
cruciform - the white crosshairs in the center of the image -
and since its optics make the cruciform appear far away, the
crosshairs are in focus when viewed by the wide-angle camera.
(If you look closely you can also see a small-but-sharper image
of the engineer in the telescope's eyepiece.)
Careful alignment of each MESSENGER
instrument is crucial for planning future science observations,
but operators will also use the camera for navigation during
MESSENGER's flight. In particular, when MESSENGER prepares to
enter orbit about Mercury, the navigation team will take distant
images of the planet and starry background to refine the spacecraft's
exact position in space - knowledge key to pointing the spacecraft
correctly during critical engine burns.
Click here to see the image at
full resolution.
Last updated: February
11, 2004
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