A trio of 200-pound scientific probes was directed yesterday at Venus from a spot in space less than 6 million miles from the planet, the second such successful maneuver in the last four days.
The three probes were "sprung" out of the Pioneer Venus space bus at 8:08 a.m. EST by remote signals sent to the bus from California's Ames Research Center, where the flight of two Venus-bound Pioneer spacecraft is being directed by the National Aeronautics and Space Administration.
The smaller probes are now following a path that will take them into the atmosphere of Venus at spots 6,000 miles apart on Dec. 9. A larger, 700 pound probe was released by the bus and directed at Venus last Thursday and should enter the atmosphere of Venus only a few minutes ahead of the three smaller probes.
If projected on a map of the earth, the four probes would enter at points corresponding roughly to Oslo, the Malagasay Republic in the Indian Ocean, the mouth of the Amazon River in Brazil and a spot at Uruguay on the east coast of South America.
One small probe will enter on the night side of Venus and descend into the regions of the planet's North Pole. A second small probe will fly into the day side at mid-southern latitudes, and the third small probe into the night side at the same mid-south latitudes.
The three aim points will be reached only if the probes were spun off at precisely the same time toward Venus yesterday by the Pioneer bus. All flight controllers could say yesterday when the probes were released was that "the maneuver appeared to go as commanded."
Before the maneuver, the bus was pitched down and away from earth, then was commanded to increase its spin rate from 15 revolutions per minute to 48. When it had done this, an order was given to release the probes. Each probe flew in a slightly different trajectory because the bus was spinning.
The 700-pound probe will enter the atmosphere of Venus at the planet's Equator and carries seven instruments - four more than the smaller probes do. All four of the probes will take the first detailed measurements of the mysterious and thick clouds of Venus, including temperature, pressure and density, all the way to the planet's surface.
None of the probes is expected to survive anticipated hard landings on the surface of Venus, though there is a possibility the probes could continue to transmit signals from the planet's surface. None of the probes is equipped with cameras to photograph the surface.