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The Rocky Road To Space

Hipparcos Before Launch
ESA's Hipparcos Before Launch

The rocky road to space for a satellite named Hipparcos started in 1966 when it first was suggested by Pierre Lacroute of France's Strasbourg Observatory.

The name Hipparcos stood for High Precision Parallax Collecting Satellite. It was named for Hipparchus, a Greek astronomer who lived about 130 B.C.

Lacroute figured a precision satellite in orbit would be a great tool for drawing up a precise catalog of 120,000 stars visible from above Earth. However, European scientists weren't enthusiastic about what then was an unbelievable precision.

It took the European Space Agency time to get the project off the ground, but Lacroute won the argument and an Earth satellite named Hipparcos was approved in 1980. Construction began in 1984. Twenty years after its proposal, Hipparcos was completed in 1986 in Noordwijk, The Netherlands. The satellite eventually rode to space in 1989 on an Ariane rocket from Europe's launch pad in South America.

But first, a strange thing happened to the star-mapper on its way to space. Hipparcos almost didn't make it through a meteorite bombardment in Italy.

When ESA finished building Hipparcos in The Netherlands, the shiny new satellite was packed into a nitrogen-filled container and sent to the Aeritalia company in Turin, Italy, to wait for a ride to space.

The satellite was to have been launched in July 1988, but Ariane troubles delayed ESA launches. Rather than ship the satellite to French Guiana, ESA kept Hipparcos in the Turin warehouse. That's where a really odd coincidence appeared.

On May 18, 1988, a two-lb. meteorite smacked into the warehouse parking lot beside a tiny Fiat automobile parked there, missing Hipparcos by less than 1,000 feet. Excited astronomers rushed out to the space rock, grabbed the biggest remaining fragment, a one-lb. chunk they named Aeritalia-A, and hauled it into their lab for study.

Unscathed, Hipparcos was shipped to Toulouse, France, for passage to Kourou and launch to space on Ariane flight V-33.

Finally, Hipparcos was launched to an elliptical transfer orbit, but the rocky road hadn't ended. In its transfer orbit, the satellite ranged from 125 to 22,300 miles above Earth. From there, Hipparcos was to supposed to kick itself into a circular orbit 37 hours after launch.

Unhappily, the small solid-fuel rocket "kick motor" which was supposed to push Hipparcos to a stationary orbit over the equator above Africa failed, stranding the star-mapper in an elliptical orbit. ESA engineers were aghast.

For the next week, commands were radioed to the satellite to induce its kick motor to ignite each time the satellite sailed through the high point of its orbit. Each time the command failed.

Frustrated engineers finally used tiny thrusters designed for minor orbit corrections to shift the satellite a bit higher, to a safer orbit from 315 to 22,300 miles altitude, from which it wouldn't fall for a time.

Hipparcos had been built to spin so its telescope could scan the entire sky. Fortunately, the engineers were able to calculate how the satellite could complete most of its assignment from its low elliptical orbit. Hipparcos still would sweep 80 percent of the sky.

In the end, Hipparcos was able to get to work, cataloging the exact positions of 80 percent of the planned 120,000 stars.

The Hipparcos Space Astrometry Mission official ESA web site

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