safe passage through the belt, and the closest the trajectory would take the spacecraft to any of the known asteroids was . One of the nearest approaches was to the asteroid 307 Nike on December 2, 1972. The on-board experiments demonstrated a deficiency of particles below a micrometer (μm) in the belt, as compared to the vicinity of the Earth. The density of dust particles between 10 and 100 μm did not vary significantly during the trip from the Earth to the outer edge of the belt. Only for particles with a diameter of 100 μm to 1.0 mm did the density show an increase, by a factor of three in the region of the belt. No fragments larger than a millimeter were observed in the belt, indicating these are likely rare; certainly much less common than anticipated. As the spacecraft did not collide with any particles of substantial size, it passed safely through the belt, emerging on the other side about February 15, 1973. Encounter with Jupiter On November 6, 1973, the Pioneer 10 spacecraft was at a distance of from Jupiter. Testing of the imaging system began, and the data were successfully received back at the Deep Space Network. A series of 16,000 commands were then uploaded to the spacecraft to control the flyby operations during the next sixty days. The orbit of the outer moon Sinope was crossed on November 8. The bow shock of Jupiter's magnetosphere was reached on November 16, as indicated by a drop in the velocity of the solar wind from to . The magnetopause was passed through a day later. The spacecraft instruments confirmed that the magnetic field of Jupiter was inverted compared to that of Earth. By the 29th, the orbits of all of the outermost moons had been passed and the spacecraft was operating flawlessly. Red and blue pictures of Jupiter were being generated by the imaging photopolarimeter as the rotation of the spacecraft carried the instrument's field of view past the planet. These red and blue colors were combined to produce a synthetic green image, allowing a three-color combination to produce the rendered image. On November 26, a total of twelve such images were received back on Earth. By December 2, the image quality exceeded the best images made from Earth. These were being displayed in real-time back on Earth, and the Pioneer program would later receive an Emmy