Polar orbiting satellites

¡SkyCaramba! Weekly astronomy blog for the week ending February 22, 2014

At the end of February is an anniversary whose remembrance informs us of how much things have changed in science, technology, and politics. On February 28, 1959, the United States tried to launch a satellite into polar orbit. Most people didn’t know at the time that the mission failed.

In the 1950s, the American military kept an eye on the Soviet Union’s readiness for war by sending spy plane pilots deep into Soviet airspace. Pilots took pictures of suspected military bases and missile sites at considerable risk of being killed or imprisoned. Even though the airplanes could fly higher than the era’s anti-aircraft weapons could reach, a malfunction could kill a pilot or land him in the enemy’s custody.

President Dwight Eisenhower had a vision of spy satellites passing over the U.S.S.R. They would be even higher out of the reach of anti-aircraft missiles. Without people in them, malfunctions wouldn’t endanger a pilot. And once in orbit, they could stay on the job until they ran out of film.

That’s right. Instead of storing pictures electronically and transmitting them to ground stations, the first satellites took pictures on film rolls that were dropped in capsules back to Earth. Depending on the situation, an airplane pilot would catch the capsule as it fell with an open parachute or a naval team would retrieve it from the ocean.

The satellite launched at the end of February 55 years ago didn’t even have a camera. It went up as a test just to see what it would take to put a satellite into polar orbit and keep it there. Unfortunately, it never made it. Analysts familiar with the project think it crashed in the Antarctic after liftoff from California. At the time, the U.S. Air Force told the public the satellite named Discoverer 1 made it to orbit, transmitted some measurements, and then shut down as planned. That seemed believable, because satellites in those days didn’t last long anyway. Batteries lasted just days or weeks. Many satellites reentered the atmosphere and burned up.

Documents declassified in 1995 reveal that the satellite’s secret name was Corona 1 and its successors did carry cameras that took lots of pictures over Soviet territory. Among the declassified items is a Central Intelligence Agency movie in which people involved in the Corona project described the steep learning curve. Every time they solved a problem, they ran right into another.

But they overcame. By 1972, satellite launches were ordinary enough that the technicians who’d been there in the early days had trouble explaining to newcomers how hard it all was. Eventually, satellites didn’t need film anymore. Reusable magnetic tape, along with rechargeable batteries, could keep a mission going for years instead of mere weeks.

A satellite in a polar orbit can photograph nearly the entire planet in a day or two. So not only spy satellites, but also those that may need to image any part of the earth will often be in polar orbits. Besides looking for enemy missile silos, satellites are used for map making, studying geography, and monitoring weather systems. It’s worth noting, however, a few are in polar orbits primarily to study phenomena that happen at the poles. Analyzing the aurorae and watching upper atmospheric ozone levels come to mind.

Now you know something about the secret space pioneers of a couple generations ago. ¡SkyCaramba!