ERAU Prescott Observatory

ERAU Long Wavelength Astronomy

Over most of the electromagnetic spectrum the earth's atmosphere absorbs radiation emanating from extraterrestrial sources. However, there is an atmospheric window for wavelengths from 10 meters through 1 millimeter. Most radio telescopes operate at the shorter wavelengths of less than 0.3 meters.

A relatively new field of astronomical observations is emerging for long wavelength radio emissions with wavelengths greater than 1.0 meter. At these long wavelengths, relatively low cost receiving stations can be built and dispersed to many locations around the world.

With the use of inexpensive omni-directional antennas and receiving stations, a phased array aperture synthesis telescope can be created. The direction of observation ("beam") is chosen electronically by phase delays between the antennas.

Multiple receiving stations outputs can be cross-correlated to greatly improve the signal to noise ratio of the receiving system. With very long base lines between stations, observations can be made emulating a telescope with a size of the baseline, and with many stations combining their outputs, an extremely sensitive astronomical observatory can be constructed.

Observation Targets

Many astronomical objects emit radiation at long wavelengths, allowing the following observations to be made:

ERAU Long Wavelength Telescopes

ERAU has several long wavelength projects underway. These include the following telescopes:

Distributed Array Radio Telescope - DART

The DART system consists of three 5 by 5 meter arrays of 16 crossed dipole antennas (a Tile) with associated beamformers covering the frequency range from 80 to 300 MHz. The signals from the beamformers are fed to a signal conditioning system which provides a command interface for such things as beam forming, dc voltage to the arrays and signal conditioning. The signals can then be routed to three sets of dual-channel wideband receivers for detection and recording. The capability will be provided to remotely steer the telescope and collect data both locally or review the received signals real-time locally or remotely.

Distributed Array Radio Telescope - DART DART Position
DART Tile DART Position

For more information about DART, click here.

Long Wavelength Telescope - LWT

The LWT consists of two cross-dipole antennas and active baluns covering the frequency from 20 to 100 MHz.  One antenna is a LWA antenna from the NRAO VLA Observatory, Socorro, NM and the other is a copy of the European LOFAR low frequency telescope antenna.  Together they are the antennas that make up the observatory’s Long Wave Telescope. The four crossed signals are provided to a signal conditioned system with their outputs available to the observatory’s receiver systems which then make up the long wavelength telescope.  The telescope can be remotely controlled by students and the data can be viewed real-time or stored for off-line analysis either locally at the observatory or remotely, as desired.

LWT Antenna LOFAR Antenna
LWA Antenna LOFAR Antenna

Hydrogen Epoch of Reionization Array - HERA

HERA Antenna 1

ERAU has agreed to assist the ASU Earth and Space Center, Cosmology initiative by hosting one of their HERA 15-meter telescopes. The HERA telescope will be located near DART Tile #2 and will use the DART infrastructure to return signals to the observatory control center. The primary use of the single HEAR antenna will be in testing. One requirement is to characterize the antenna pattern. To do this a drone equipped with appropriate transmitter will be flown in a constrained and known pattern above the antenna.

Beginnings of HERA Antenna

This photo shows the beginning of the HERA dish at ERAU, Prescott.

Field Testing with a Drone

A side benefit of installing and testing a HERA dish at the ERAU Prescott observatory is that we will be able to characterize the DART tiles in a similar way as the frequencies are similar.