We have been busy working on several long term projects which will improve the power and scientific output of SETI@home. Most of our time over the past year has been applied to the task of building and releasing the next generation of SETI@home software using BOINC volunteer computing infrastructure. With this effort winding down, we will apply more resources to the following projects.

SETI@home Enhanced

Because Moore's law has been continually increasing the computing power of our volunteers, we developed a new SETI@home application with increased sensitivity. The original SETI@Home stepped coarsely through doppler drift rates. Because of this, there was a possibility of a Gaussian shaped or pulsed signal drifting out of a frequency bin during the duration of the analysis. These signals would be recovered later when the analysis is performed at lower frequency resolution. However, because more noise is included in the analysis performed at lower resolution, it decreases our sensitivity to such signals by a factor of two. Before now there wasn't enough computing power available to perform the full analysis at high resolution.

This new application is currently in beta-test. The BOINC core client will automatically update SETI@home to the new enhanced version once it is made available. Since there is more computing involved, users will notice a greatly increased turnaround time per work unit. Since BOINC credits by computation and not by workunit, this will not change the rate at which you receive credit. We will also extend the return deadlines since clients will be crunching on workunits for longer periods of time.

Multi-Beam Data Recorder

We are developing a high speed data recording system to take advantage of the new 7 beam ALFA receiver at Arecibo. Conceptually similar to the SETI@home I data recorder, it has been redesigned with a number of improvements.

It is capable of taking data much faster than the current recorder. While maintaining the sampling rate and instantaneous bandwidth of the SETI@home I recorder, the new system is more than capable of taking data from all 7 beams (better sky coverage) at both linear polarizations (more sensitivity). The current recorder takes data from beam at one polarization.

The new recorder will be able to monitor the pointing coordinates of the telescope. When the telescope is tracking a point on the sky, the frequency band being recorded will be periodically changed. This will give us greater frequency coverage rather than redundant coverage of just one part of the spectrum.

The new recorder will monitor the receiver state and when the ALFA receiver is off (for example, when AO is transmitting), data acquisition will be idled in order to conserve tape resources.

The data recorder consists of front end hardware, a host computer, an array of high speed disks, and an SDLT tape drive. The front end receives the analog signal from the receiver, converts it to a lower frequency and digitizes it. The host computer receives the digital data, collates it with timing and pointing data and writes it to tape, using the disk array as a buffer. It also makes decisions on whether or not to take data and controls frequency stepping.

Since the raw data will be organized in a different manner, we will be developing a new SETI@home application in order to analyze data in this new format.

Near Time Persistency Checker

After applications return signals they are validated and stored in our master database. The goal of SETI is to find similar signals that appear at the same frequencies and points in the sky, but at different times. With a database containing billions of singals, this is a rather large task to do all at once. In the past we had no choice - we didn't have enough resources to create a real-time data analysis pipeline that wouldn't clobber our entire project. In fact, as of August 2005 we still had over 50 tapes' worth of data that had yet to be validated and put into our master science database.

But now we are using BOINC, which has the ability to hand us reduced data for final analysis within minutes of client completion. Plus our new master science database is on a machine with more memory and faster disk throughput. For the first time since its inception, SETI@home has the potential for finding the most interesting repeating signals soon after these singals enter the database. We hope to have daily reports updated with the current "best" results when this system in put into place.

Read more about near time persistency checking here.

Astropulse

The current SETI@home application looks for signals that are narrow in frequency, but have long duration. That's one way that an extraterrestrial civilization can send a signal that stands up above the radio background noise. Another possibility is that they could put a lot of power into a short duration pulsed signal that has a wide bandwidth. As such a pulse travels through intestellar space, interactions with interstellar matter slow down low frequencies relative to high frequencies in a process called dispersion. This dispersion spreads the pulse out over time. If we know how much dispersion a pulse has experienced, we can correct for this effect. For an extraterrestrial signal we won't know how much interstellar matter the signal interacted with on its journey, therefore we have to try every possible dispersion measure. That takes a lot of computing time.

Astropulse is a SETI@home application that uses coherent dedispersion to search for pulsed signals. In addition to extraterrestrial signals we might see signs of evaporating black holes or discover new pulsars. You can read more about Astropulse here .