National Geographic : 1962 Feb
gravity and put it into orbit? Too much speed would thrust the capsule far out into space; too little speed would let it drop back to earth." During one of the many Mercury tests I witnessed, a Bermuda engineer explained how they "find" an orbiting spacecraft. "We know where to expect the capsule," he said, "so we point our antennas in that direction." As he spoke, the station's four pronged antennas and the radar dishes all slued around in unison to face the western horizon in mute anticipation. Stations Listen for Signal From Space As word came from Canaveral that the launch had started, the engineer took me to a device known as the acquisition aid. "This is the 'ears' of our station," he said. "It listens for the telemetry signal-the radio KODACHROMESW NATIONALGEOGRAPHICSOCIETY 196 signal from the capsule that tells how the man and machine in space are performing." About three minutes after the imaginary rocket and capsule had soared from the pad at Canaveral, the engineer pointed to a fuzzy band of pulsating yellow light on the acquisi tion aid screen. Suddenly it erupted in a steep yellow peak, flickering like a volcanic out burst (page 200). "That peak tells us that the acquisition aid has caught the capsule's signal," the engineer said. "Now it will guide our radars. When they make contact, they will trigger answering signals from a device in the capsule known as a transponder. We can tell how far away the capsule is by measuring the time in mil lionths of a second from the moment our sig nal goes out until the response comes back." Only ten minutes after launch, the man in space passes beyond the normal reach of Bermuda. But he has little chance to feel lonely. No sooner does he say goodbye to Bermuda than he begins talking to the Atlantic Ocean ship Rose Knot, station No. 3. Then, only 18 minutes after lift-off, he has al ready spanned the ocean and finds himself nearing the Spanish island of Grand Canary. The Mercury station on Grand Canary lies just off the coast of Af rica, so close that the sand dunes of the Spanish Sahara can be seen on its radar screen (page 190). At the main city of Las Palmas to the north, an overcast sky often hides the sun. But 40 miles by coastal road to the south, brilliant sunshine bathes the Mercury station almost every Decorative horns jut above sculptured mud walls of a house in Kano, an old caravan center in northern Nigeria. Sunbaked walls seem almost as hard as concrete blocks, but eroding rains necessi tate periodic repairs. Helter-skelter streets in Kano's adobe maze restrict automobile traffic; most residents travel by foot, donkey, or bicycle. In the dis tance, 40-foot pyramids of shelled peanuts await shipment to mar ket. Green tarpaulins protect the mounds from rain.