A good general reference for those interested in learning more about the LWA project is From Clark Lake to the Long Wavelength Array:   Bill Erickson's Radio Science [ASP Conference Series, Vol. 345, Proceedings of the Conference held 8-11 September, 2004 in Santa Fe, New Mexico, USA. Edited by N. Kassim, M. Perez, M. Junor, and P. Henning]. These Proceedings contain a variety of papers which review scientific and technical aspects of the project during its early stage, including one on The Legacy of Clark Lake (pdf file by N. Kassim) from which some of the photos shown here were taken.

The Jansky telescope

Bill Erickson was born about a year before Karl Jansky discovered cosmic radio waves in 1931 and ushered in the birth of radio astronomy. Jansky's antenna, pictured here, was designed to receive radio waves at a frequency of 20.5 MHz.

ASP Conference Series V345 mentioned above also includes a copy of one of Jansky's now famous early publications, together with reproductions of several other historical papers from the birth of radio astronomy at low frequencies.

The History of the Clark Lake Observatory

In the late 1950s, Convair Scientific Research Lab created CSRL in San Diego. Bill Erickson, former student of Director Critchfield, was hired to begin work at Clark Lake. By the early 1960s, Convair transfers the CSRL to the University of Maryland.

The Clark Lake Teepee-Tee Telescope was a broad-band (10-123 MHz) instrument with a reasonable collecting area. It was fully electronic, fast and versatile. However, it was closed in the late 1990s because the TPT could not compete with the longer baselines of the VLA and the improved resolution of ~2" at 1400 MHz of the VLA compared to ~900" resolution at 30 MHz of the TPT.

The 74 MHz system on the Very Large Array

The first proposal to extend earlier techniques to frequencies below 100 MHz with a connected element, synthesis imaging array was made shortly after self-calibration was first introduced, when Rick Perley and Bill Erickson proposed development of a large, dipole-based array to work alongside the VLA in New Mexico. (G. Swarup's original concept for the GMRT also appeared at about this time.) Funding to implement the sensitive, broad-band, ambitious system originally envisaged in VLA Technical Memorandum #146 (Perley and Erickson 1984) was not readily available at that time. However their proposal inspired the Naval Research Laboratory (NRL) and National Radio Astronomy Observatory (NRAO) to work together in the early 1990s to implement a narrow-band, modest version of the Perley-Erickson proposal using the existing VLA dishes and infrastructure.

The full system of 74 MHz receivers on all 27 VLA antennas became operational in 1998. It attracted a wide variety of scientific projects in the areas of solar system (planetary emission, solar bursts), Galactic (supernova remnants, ISM), and extragalactic (clusters, radio galaxies) astrophysics. An ongoing major project is the VLA Low Frequency Sky survey (VLSS) a 74 MHz complement to the successful NVSS 20 cm VLA sky survey.

The Bruny Island Radio Spectrometer (BIRS)

Bruny Island lies off the south-eastern corner of Tasmania, Australia. Since 1 January 1998 low frequency solar radio burst observations have been made daily with the Bruny Island Radio Spectrometer (BIRS) developed by Bill Erickson. Since 15 September 2006, the solar burst data appear on the Green Bank Solar Radio Burst Spectrometer website . Earlier data were on a University of Tasmania web site and can be made available only by contacting bill.erickson @ utas.edu.au.

The frequency range of the observations is from the low frequency ionospheric cutoff to 62.5 MHz. The ionospheric cutoff occurs at a frequency at which radio waves from the Sun suffer total reflection by the Earth's ionosphere and is normally between 7 MHz and 12 MHz: it is a strong function of the local elevation of the Sun. Only the 12 to 62 MHZ frequency range is normally displayed on the website.


The solar emissions are received with the wide-band, droopy, active dipole shown in the accompanying photo above. This antenna may be considered one of the first bona fide LWA prototype antennas!

The Grote Reber Medal

In 2005, the Inaugural   Grote Reber Medal   was awarded to Bill Erickson, Professor Emeritus at University of Maryland and Honorary Research Associate at the University of Tasmania. Professor Erickson was recognized for his innovative contributions to radio astronomy, especially for his many novel techniques which have been the forerunner of the new generation of metre-wavelength radio telescopes. Currently he operates his own private radio observatory on Bruny Island in Tasmania. (Photo from the cited website article.)