Significant new opportunities for astrophysics and cosmology have been identified at low radio frequencies. The Murchison Widefield Array is the first telescope in the southern hemisphere designed specifically to explore the low-frequency astronomical sky between 80 and 300 MHz with arcminute angular resolution and high survey efficiency. The telescope will enable new advances along four key science themes, including searching for redshifted 21-cm emission from the EoR in the early Universe; Galactic and extragalactic all-sky southern hemisphere surveys; time-domain astrophysics; and solar, heliospheric, and ionospheric science and space weather. The Murchison Widefield Array is located in Western Australia at the site of the planned Square Kilometre Array (SKA) low-band telescope and is the only low-frequency SKA precursor facility. In this paper, we review the performance properties of the Murchison Widefield Array and describe its primary scientific objectives.

Since the image separations produced by microlensing are inaccessible to observation, we are left to observe either a change in total amplitude or the time delay between the images. Spillar (1993) has suggested that a time delay might be observed in the autocorrelation of a microlensed signal. The time delays are of order a few microseconds and are easily accessible to a sufficiently wide bandwidth system. We calculate expected observational results using the Green Bank Telescope with a VLBA recording system, and find that brightness temperatures exceeding the Compton limit are required for detection.