ATNF OBSERVATORY RFI INFORMATION

Peter Hall, 23 February 1998
 

Introduction

This page contains links to graphical and tabular summaries of external interference at the ATNF's observatories at Parkes and Narrabri. The information is derived from several spectrum licence databases and this first-round study is undoubtedly incomplete. Nevertheless, observers and ATNF staff will most likely find the summaries useful.

Interference information has been derived from two major databases which have recently been made available in electronic form. Information about terrestial interferers within ~120 km radius of the Observatories has been extracted from the CD ROM database maintained by the Australian Communications Authority, the sole spectrum licensing body for the continent. Much of this information is available on-line at the ACA site. If you do wish to access the on-line material, recall that the Parkes and Narrabri postcodes are 2870 and 2390 respectively.

Satellite interference information has been gleaned from the database compiled and maintained by the SETI Institute and the Georgia Institute of Technology. The database may be downloaded from a Georgia Tech Web site. At present, extraction from this database is done manually (and somewhat tediously). This first ATNF study therefore uses a single set of satellite data derived for Parkes; the error involved in representing the Narrabri situation is small.

For a more complete description of the assumptions made in compiling the ATNF Observatory databases, see the paper Interference Characterization of Australian Astronomy Sites by Hall, Mohan and Soretz (Proc. URSI Large Telescope Working Group, Sydney, December 1997).

Interference Plots

Plots are available in Adobe Portable Document Format (PDF) and are sized for easy printing on an A4 page. The ordinate quantity is logarithmic flux density, with 0 dB representing 1 mW m-2. Satellite visibility is averaged over a 1-day period and, for low earth orbit and polar orbiting satellites, the vertical bars show the maximum and minimum levels, the actual level for a given pass being dependent on pass geometry. See the paper referred to above for details.

To obtain a full-spectrum (100 kHz - 100 GHz) plot for Parkes, click here .
To see the Parkes plot in expanded form (100 MHz - 3 GHz), click here .

The complementary Narrabri full spectrum and expanded scale plots are also available.

Interference Databases

The ATNF Observatory databases are also available in tabular format. The format is plain text, with columns delimited by tabs. This format is easily imported into a variety of spreadsheet or similar programs. Once imported, it is straightforward to sort on the basis of frequency, distance to transmitter, etc. Column headings are fairly self-explanatory but reference to the Australian Communication Authority material and the paper cited above will clarify matters for some readers.

You can view the text files by double-clicking on the links below. However, because of the large number of parameters and data entries, it makes more sense to invoke your browser's "save as" function, then import the file into whatever application you choose.

Click here to access the database of terrestial interferers at Parkes.
Click here to access the database of terrestial interferers at Narrabri.
Click here to access the database of geostationary satellites visible from the observatories.
Click here to access the database of visible low earth orbit and polar orbiting satellites.

Note: the Narrabri database has been updated manually to account for the Mt. Dowe MDS pay TV service. In doing the update, I have appended vision carrier information to the start of the file. While future (automated) database updates will be more comprehensive and include the lower-power adjacent sound carrier, using the vision carrier alone gives a fair indication of band occupancy.

Acknowledgements

I thank Ananda Mohan and Robert Soretz (from the University of Technology, Sydney) for their help in establishing the interference mitigation project which spawned the ATNF interference lists. Paul Steffes from the Georgia Institute of Technology provided references to the SETI Institute satellite database. Without the Australian Communications Authority database this work would not have been possible; I urge overseas colleagues to exhort their own national regulatory bodies to publish similar compendia.

Page created by Peter Hall 23 February, 1998.