The mated Russian-built Zarya (left) and U.S.-built Unity modules are backdropped against the blackness of space and Earth's horizon shortly after leaving Endeavour's cargo bay. The photo was taken with an electronic still camera at 21:20:21 GMT, Dec. 13.
The Moon, left, Saturn, upper right, and Jupiter, lower right, are seen after sunset from Washington, DC, Thurs. Dec. 17, 2020. The two planets drew closer to each other in the sky as they headed towards a “great conjunction” on Dec. 21, where the two giant planets appeared a tenth of a degree apart.
If spacecraft are to visit the outer solar system, they must cross the asteroid belt between Mars and Jupiter. The Pioneer mission was faced with the question of just how dangerous this asteroid belt would be to a spacecraft passing through it.