Echo satellite

The satellite also aided the calculation of atmospheric density and solar pressure due to its large area-to-mass ratio. Each spacecraft was designed as a metallized balloon satellite acting as a passive reflector of microwave signals.

Schjeldahl Company in Northfield, MN. Echo 2, a 41.1 m diameter metalized PET film balloon with an improved inflation system to improve the balloon s smoothness and sphericity, was launched January 25, 1964 on a Thor Agena rocket. The Echo satellites were NASA s first passive communications satellite experiment.

Echo 2 reentered on June 7, 1969. The Echo satellite program also provided the astronomical reference points required to accurately locate the Russian city of Moscow geographically. This improved accuracy was sought by the US military for the purpose of targeting intercontinental ballistic missiles.

The 30.5 meter (100 foot) diameter balloon was made of 0.127 mm (0.005 inch) thick metalized Mylar polyester film and was successfully used to redirect transcontinental and intercontinental telephone, radio, and television signals. It was used for more passive communications experiments, and also to investigate the dynamics of large spacecraft and for global geometric geodesy.

After it was placed in a low orbit of the Earth, a signal would be relayed to Echo, reflected or bounced off its surface, then returned to Earth. NASA abandoned passive communications systems in favor of active satellites following Echo 2.

. Brighter than most stars, it was probably seen by more people than any other man-made object in space.

Communication signals were bounced off of it from one point on Earth to another. Following the failure of the Delta rocket carrying Echo 1 on May 13, 1960 Echo 1A (commonly referred to as just Echo 1) was successfully put in a 1,519 to 1,687 km (944 to 1,048 mi) orbit on August 12, 1960. The spacecraft was nicknamed a satelloon by those involved in the project. The Echo 1 satellite was built by Gilmore Schjeldahl s G.T.

As its shiny surface was also reflective in the range of visible light, Echo 1A was visible to the unaided eye over most of the Earth. Echo 1A reentered Earth s atmosphere and burned up on May 24, 1968.

Of note is that both the Echo 1A and Echo 2 experienced a solar sail effect due to their large size Echo 1 was a passive communications satellite: it functioned as a reflector, not a transmitter. Echo 1 was visible to the eye because of its shiny surface, but also because of its low orbit; it would appear from below one side of the horizon, cross the sky, then disappear below the opposite horizon after crossing the sky, as happens with all LEO satellites.