Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: NASA has given the people of Earth a rare treat: A color mosaic that captures not only Saturn, but also the tiny dots of Earth and other planets in the background. The panorama, released Tuesday, was captured by the Cassini spacecraft on July 19, when the sun slipped behind the ringed planet. Earth appears as a bright blue dot to Saturn's lower right, just above Saturn's outer, halo-like E-ring. Venus is a dot to the upper left, with Mars appearing as a faint red dot above and to the left of Venus. This is the first image in which Saturn, its moons and rings, and Earth, Venus and Mars are all visible, NASA said. The image -- a panorama of 141 wide-angle pictures -- covers 404,880 miles across Saturn and its ring system.Image is Cassini's first showing Saturn, rings, moons, Earth, Venus and Mars at same timeThe collage is panorama of 141 wide-angle pictures taken July 19Image was possible that day because Saturn obstructed spacecraft's view of sun 
 Question:Cassini images showing both Saturn and Earth are rare because the sun is so close to Earth, that targeting the blue planet would damage _'s sensors, NASA says.

Cassini spacecraft