The Project Phoenix Targeted Search System (TSS) returned to the world's largest telescope after an eventful six years. In 1992, when the SETI Institute was last observing in Puerto Rico, the TSS had less than half its current capability and was operated as part of NASA's High Resolution Microwave Survey. Since then, the U.S. Congress cancelled the HRMS, Project Phoenix was born, and Arecibo was closed for several years for major upgrades.
During those six years, Project Phoenix has raised funds to continue and improve upon the Targeted Search portion of NASA's HRMS. Based on the experience of the initial observations at Arecibo, Phoenix engineers doubled the number of channels and added a follow-up detection system. The improved TSS was up and running at the Parkes Observatory about a month later than was originally envisioned for the NASA program. After a six month stay at the largest radio telescope in the Southern Hemisphere, the TSS came back to the SETI Institute for more upgrades. In September 1996, the TSS traveled from California to West Virginia. It was installed next at the NRAO 140 Foot telescope, only a few hundred meters from the site of the first (1960) modern SETI program, Project Ozma. A total of 24 weeks of observations were conducted over a span of 18 months at Green Bank.
The upgrades to Arecibo were finished in early 1998, and the telescope was once again ready for astronomical work. After six years away, we were ready to go back.
Since Arecibo is a massively large antenna, a similarly imposing instrument is needed for use as the follow-up device, to sort out terrestrial interference from the signal that we're hoping to find. During our run at Arecibo, our secondary 'scope will be the 250 foot telescope at Jodrell Bank.
Pioneer 10 at Arecibo
With a system designed to pick up interstellar communication signals operating with the world's largest telescope, it's not surprising that we can detect our own technological civilization. In this page we will present some examples of terrestrial signals.
Our favorite signal (until we get the one from ETI) is from the Pioneer 10 spacecraft. Launched in 1972, it now at a distance of roughly 10,000,000,000 kilometers. Its aging transmitter broadcasts with a power of only a few watts. The huge collecting area of the Arecibo antenna brings it in loud and clear.
Pioneer 10 is now at a distance of more than 11,000,000,000 km (about 6.9 billion miles). It takes more than 10 hours for its radio signal, travelling at the speed of light, to reach the Earth. After more than 10,000 days of continuous operation, the electronics in its transmitter are beginning to deteriorate. In spite of this, the signal from Pioneer 10 is still an excellent test for our system.
This plot shows the power in 924 channels over time. Each horizontal row of dots gives a snapshot of the amount of power in each of the channels at a specific time. The larger the dot, the more power in that channel. Every 0.7 seconds a new row of dots is added. Over about two minutes the picture shown to the left builds up. If a particular channel always had a signal in it, we would see a vertical line since that channel would always have a more power than the other channels, and so would tend to have larger than average dots.
The signal from Pioneer 10 drifts in frequency and so moves from channel to channel over time. The plot shows the "carrier wave" portion of the Pioneer signal as a narrow line to the left of center and beginning about a quarter of the way up from the bottom. After about a minute, we shifted to a different frequency to display one of the "side bands". This shows the data being transmitted by the spacecraft.