Spaceflight Now: Breaking News

Earth strains to hear Pioneer 10 some 7 billion miles away
BY STEPHEN CLARK
SPACEFLIGHT NOW

Posted: July 11, 2000

  Jupiter
An artist's concept of Jupiter encounter. Photo: NASA
 
After 28 years in space, Pioneer 10 continues to function as it cruises through interstellar space but Earth is having an increasingly difficult time hearing the venerable craft.

Pioneer 10's weak signal is still being tracked by NASA's Deep Space Network (DSN) system on Earth. However, with the probe over 7 billion miles away and still heading outward, officials say keeping in contact will be a challenge.

Data being received from Pioneer 10 has a signal strength of -178 dBm, which very close to the receiver's limitation of -180 dBm.

Program managers warn the DSN might be unable to lock onto Pioneer as the so-called signal-to-noise ratio continues to decrease.

"Even though in a year the DSN may still be able to get good telemetry lock, being this close to the receiver threshold and losing about 0.3 dBm/yr due to range, maintaining contact will be a challenge," a recent status report said.

The probe's four Radioisotope Thermoelectric Generators (RTGs) are still producing electrical power as a by-product of a form of plutonium. Enough electrical power is still being generated for the operation of craft's transmitter, receiver, command and data handling systems, attitude control system, and one of the original eleven science experiments. The RTGs are currently producing 65 Watts of power, or about 42 percent of the 155 Watt launch value.

Pioneer 10 is being readied for an upcoming firing of the attitude control system thrusters. These are done twice a year in order to point the spacecraft toward the Sun. The last such maneuver was performed in February.

Also, despite the lack of warmth in its current environment, Pioneer 10's outer hull remains at an acceptable temperature of -41 degrees F.

As of July 1, 2000, Pioneer 10 was 7.111 billion miles (11.44 billion kilometers) from Earth and was traveling at 27,380 miles per hour (12.24 km/sec). It takes light and radio signals 21 hours 11 minutes to make the round-trip from Earth, to Pioneer 10, and back. Pioneer is headed toward the constellation Taurus. It should arrive at one of the constellation's stars in around 2 million years.

Pioneer 10 was launched aboard an Atlas/Centaur rocket on March 2, 1972, from Cape Canaveral. It's trajectory took it through the asteroid belt and by Jupiter and Saturn before heading into interstellar space.

Its sister ship, Pioneer 11, was launched a year later and took nearly the same path. Pioneer 11's RTGs failed in 1995 and brought the mission to an end.