Sudan.Chali · missionaries see a silvery cloud cross the sky

On the night of Thursday, November 1, 1962, American missionaries at Chali, a village in southeastern Sudan near Kurmuk and the Ethiopian border, some ten degrees north of the equator, saw something strange in the sky. Around 7:30 p.m. local time (17:30 GMT) what looked like a small cloud seemed to rise in the west. According to the letter, the sun had set about 5:30 p.m. local (15:30 GMT), two hours earlier. The mass moved until it passed overhead, seemed to turn north and, without getting far in that direction, gradually faded away. From the time they saw it until it disappeared about twenty minutes passed.

Six days later, on November 7, one of them wrote a letter to the "Atomic Testing Commission, Cape Canaveral, Florida," asking for an explanation and suggesting it might be the result of an American test. He described a round mass, like a cloud, that stayed together. The night was clear and starry, with a sliver of moon. To estimate its size they held up a six-inch saucer and moved back until it just covered the mass: the saucer was then about twelve feet (3.7 m) away.

They had no idea how high it was, but it was much higher than the clouds and looked somewhat like a moon, though it did not keep one constant shape. It was almost colorless, a smoky silver. They supposed the mass was traveling east around the Earth and that, as it passed overhead, it was moving out of the Sun's rays, hence disappearing; but they could not understand why it had turned north.

They made two guesses: that it was the cloud formed by the water released in one of the American experiments (on April 25, 1962, on the Project Highwater flight SA-2, NASA released a Saturn rocket's water ballast into the upper atmosphere; the letter does not name the project), or a cloud of radioactive fallout from some recent nuclear test. They also said some local people thought it was a spirit and came running, frightened, to ask what it was. The letter, stamped at Cape Canaveral on November 27, ended up with the U.S. Air Force's Project Blue Book.

The Blue Book card summarizes the observation, checks "Other: cloud" and notes that, from the description, the object was "probably a noctilucent cloud," which disappeared when it stopped reflecting sunlight. In the date-time box, the card enters 01/1530Z, that is, 15:30 GMT on November 1: the time the letter gives for sunset, two hours before the sighting. According to NASA, noctilucent clouds form at about 80 kilometers and are seen in summer and at high latitudes, though they are now also seen at lower latitudes; Chali is about ten degrees from the equator and the sighting was in November.

Jonathan McDowell's satellite catalog points to something else. That same day, November 1, 1962, the Soviet Union launched the Mars 1 probe from Baikonur on a Molniya rocket. The catalog records the launch at 16:14 GMT, the launch vehicle in parking orbit (a temporary low orbit) around 16:23 and the probe separating, after that stage fired to escape Earth orbit, at 17:19 GMT: eleven minutes before the missionaries saw their "cloud," if the letter's time is used.

The missionaries described a round, smoky-silver mass far above the clouds, appearing in the west two hours after sunset, crossing the sky and fading as if leaving the sunlight. No source proposes it, but that is what one would see if a rocket engine's exhaust, or a chemical payload, expanded in the vacuum hundreds of kilometers up and stayed lit by the Sun while the ground was already dark. The missionaries themselves thought of a cloud of water released by an American experiment.

The separation of the Mars 1 probe happened eleven minutes before the time in the letter, and an exhaust cloud at high altitude can stay visible for much longer. The catalog does not give the stage's position when it fired its engine or its track over Africa. A rough calculation, not taken from any source, using the 65° inclination of the parking orbit and the time the catalog gives for the escape stage, puts that firing at very southern latitudes of the Atlantic, some 10,000 km from Chali, where a cloud at that height would not rise above the horizon. With that, the identification with Mars 1 stays a weak hypothesis.