Introduction to the Learmonth Solar Observatory

However, another mostly unseen aspect of the Sun's influence is its effect on the Earth's upper atmosphere and the near-space environment. This space weather is becoming increasingly apparent as society becomes more technologically dependent. Areas as diverse as radio communication and navigation, satellites and space exploration, geophysical prospecting, submarine detection, long pipelines and large electric grid networks, aroura and animal migration are affected. It is the task of the Learmonth Solar Observatory to monitor the variability of the Sun, the source of these natural effects, on a diverse range of human activity.

The image on the right shows the radiotelescope observatory at Learmonth. The 1m antenna and its drive are mounted on the ground on the far right. The 2.4m dish is mounted on a platform on top of the observatory building. The 8.5m parabolic antenna is mounted on a tower south of the observatory in the background.

Establishment and Operation

The Observatory was established by agreement between the Australian and United States Governments in October 1977 and operations commenced in April 1979.
Joint operation is conducted by IPS Radio and Space Services, an Australian government agency under the Department of Trade, Tourism and Industry, and the
United States Air Force (USAF).

Located on North West Cape, Western Australia (22.2 S, 114.1 E), the site overlooks Exmouth Gulf to the east and Cape Range to the west. It is part of a network of solar
observatories (the Solar Electro-Optical Network, SEON) established by the USAF in various locations around the world, and one of two solar patrol observatories in
Australia (the other being in Culgoora, NSW). Chosen for clear skies, the site averages over 9 hours of sunshine per day.

The Observatory is staffed seven days per week, from sunrise to sunset. Staff include analysts to monitor and interpret observations, maintenance technicians,
scientists and administrators.

Learmonth Observatory operates optical and radio telescopes to monitor the Sun. In collaboration with Geophysics Australia, magnetometers are operated to sense
geomagnetic effects of solar activity. An ionosonde is also used to probe the state of the Earth's upper atmosphere.

This is an interior view of the RSTN Observatory at Learmonth. In the background 5 racks of equipment can be seen. From left to right these are: - 1m antenna controller - 2.4m antenna controller - 8800 MHz radiotelescope - 4995 MHz radiotelescope - 2695 MHz radiotelescope At the operator's desk are eight monitor screens. These are the Solar Radio Spectrograph (SRS) monitor, three communications monitors, a small video monitor showing a live solar image from the SOON observatory, a GONG monitor showing a live image of the Sun in hydrogen alpha, HP1000 graphics terminal, HP1000 interactive terminal and the RSTN Rehost terminal.

Data Collection, Distribution and Use

Information collected at Learmonth is reported directly to forecast centres in both Australia and the USA. The IPS Australian Space Forecast Centre in Sydney
provides space environment forecasts to clients within the Australasian area. In the USA, the NOAA Space Environment Center at Boulder, Colorado, and AFWA
at Colorado Springs and Omaha, Nebraska receive data. Data produced at the Observatory is also archived at IPS in Sydney and the World Data Center in Boulder
where it is freely available to researchers anywhere in the world.

Another interior view of the RSTN Observatory at Learmonth. The first four racks of equipment from right to left show: - 8m antenna controller - 245 MHz radiotelescope - 410 MHz radiotelescope - 610 MHz radiotelescope

Monitoring The Space Environment

The Sun is the primary source of variations in the space environment through which the Earth moves. In a sense, the Earth is immersed in the Sun's outer atmosphere which consists of the solar wind that is constantly flowing from the Sun. It not only emits large quantities of light and heat, but other electromagnetic radiation such as radio waves, ultraviolet light and X-rays. Huge eruptions occurring on the Sun (Coronal Mass Ejections) can eject large clouds of plasma into space. These, preceded by shock waves may impinge on the Earth's magnetic field and inject plasma particles, creating a geomagnetic storm.

The Learmonth optical telescope monitors solar surface features. These include susnpots, plage, filaments, fibrils, prominences and magnetic fields. These features change constantly and may appear and disappear on time scales from minutes to months. One of the most spectacular events to be viewed on the Sun is a flare, an explosive release of incredible amounts of constrained magnetic energy. The optical telescope, includes many subsystems to monitor all the above phenomena for any potential impact that they might have on, or around, the Earth.

The radio telescopes monitor emissions from the Sun that complements information gained from the optical systems. Different radio frequencies indicate different potential effects on the Earth. Mid-microwave frequencies indicate the emission of X-rays from the Sun. This affects the Earth's ionosphere which supports high frequency (HF) radio communication. Variations in X-ray emissions control the range of frequenciesHF radio communicators may use. The radio telescopes can also track ejected material as it travels up through the Sun's atmosphere which can assist in predicting those events likely to have an impact on Earth.

Magnetometers, another instrument at LSO monitor very small changes in the Earth's magnetic field, detect interplanetary shock waves and monitor the course of geomagnetic storms.

An ionosonde is a vertically directed HF radar providing information on the ionosphere. This data is useful to support radio communications and navigation, both ground and satellite based.