The main goals of the Parkes Pulsar Timing Array (PPTA) project are to 1) detect ultra-low-frequency gravitational waves, 2) improve the solar system planetary ephemeris and 3) provide a long-term, stable time standard. In this paper, we highlight the main results from the project so far and discuss our expectations for the future.

ABSTRACT
1. INTRODUCTION
2. THE PPTA DATA SETS
3. NEW TECHNIQUES
4. GRAVITATIONAL WAVES
5. THE SOLAR SYSTEM EPHEMERIS
6. A PULSAR-BASED TIME STANDARD
7. DATA ACCESS
8. THE INTERNATIONAL PULSAR TIMING ARRAYAND FUTURE TELESCOPES
9. CONCLUSIONS
REFERENCES

• George Hobbs(CSIRO Astronomy and Space Science)