![Click here for Movie Clip of PIA11415](https://webarchive.library.unt.edu/eot2008/20090827054805im_/http://photojournal.jpl.nasa.gov/figures/PIA11415_fig1_thumb.jpg)
Click on the image for the movie
This animation illustrates how MASCS observed the tail region of Mercury's
exosphere during the mission’s second flyby of the planet. As MESSENGER
flew toward Mercury on the inbound leg of its trajectory, the spacecraft
rotated back and forth about the Sun-Mercury line. This nodding caused the
MASCS instrument viewing direction (i.e., the direction the instrument is
pointed) to move alternately north and south, building up an image in a
whiskbroom fashion. At two points, the scanning sequence was briefly
interrupted while the spacecraft reoriented to take an image; MASCS
observations continued during these times, but the observation direction
changed. After all the observations were processed, they were then
converted to an image of the emission intensity. In these images, the
color scale indicates relative intensity as a function of spatial
position. Images of the emission intensity of sodium and calcium (see
PIA11402) have been produced from data acquired during MESSENGER’s second
Mercury flyby and compared to similar sodium emission intensity
measurements from the mission’s first Mercury encounter (see PIA11407).
Date Acquired: October 6, 2008
Instrument: Mercury Atmospheric and Surface Composition Spectrometer (MASCS)
These images are from MESSENGER, a NASA Discovery mission to conduct the
first orbital study of the innermost planet, Mercury. For information
regarding the use of images, see the MESSENGER image use policy.