Planetary Defence is defined as that activity concerned with protecting the Earth and its inhabitants from destruction due to impact by a large piece of space debris such as an asteroid or a comet.

The term "Planetary Defense" is believed to have first been used by Major Lindley N Johnson in a paper written for the Air University SpaceCast 2020 study in academic year 1993-1994 to explore required future space capabilities for the US Air Force. (Dr Johnson is now the NEO Observation Program Scientist at NASA HQ - 2004). A link to Johnson's paper can be found in the Links section of this web site.

However, the term received its wide use and promotion by Colonel Simon (Pete) Worden when he was commander of the US Air Force Space Command 50th Space Wing. It was a term used to indicate the realisation that we are under bombardment from outer space. Not from an alien agressor, but from a sporadic bombardment by naturally occuring objects in the solar system: asteroids and comets - fragmentary space debris - which occasionally are perturbed onto a collision course with Earth.

The term furthermore, is a recognition that our technology has now advanced to the point where not only can we search for and track such objects, but where we may also be in a position to deflect them from their intended path, and thus avert a disaster or catastrophe.

In the sense of a program, planetary defence then has three phases. The first phase is sometimes not stated, but it is really the most important of them all, for without it, the other two are doomed to fail.

The three phases may be described as:
1. Recognition of the threat or hazard of cosmic impact
2. Surveillance for detection of specific threats
3. Deflection or interception of the threat

North West Cape of Western Australia

Recognition is an awareness, by a broad spectrum of the population that there is a threat. It may be infrequent, but when it occurs it is devastating.

Surveillance of the near space environment is carried out by optical telescopes, aided by the new CCD imaging revolution. There are several programs, both large and small, around the world that are currently dedicated to searching the skies for potential impactors. Surveillance also includes the computer systems (both software and hardware) that keep track of the many tens of thousands of asteroids and comets that have been discovered, and search for possible orbital intersections with the Earth.

The third phase, of impact mitigation, has been much discussed, but there has been no universal consensus on how an impact threat should be handled. There are currently no programs anywhere in the world that have a defence in readiness.

Project Wormwood is a small program run by IPS Radio and Space Services (a unit of the Australian Government Department of Industry, Tourism and Resources) and established at Learmonth Solar Observatory to participate in the first two phases of Planetary Defence.


North West Cape of Western Australia

Learmonth Solar Observatory (LSO) is located on the North West Cape of Western Australia at approximate coordinates 22 degrees south and 114 degrees east.

Established in 1979, it is jointly managed by the US and Australian governments. It is staffed by four different organisations - the US Air Force Weather Agency, the US National Oceanic and Atmospheric Administration, the USAF 15th Communications Squadron (Maintenance), and the Australian IPS Radio and Space Services. It is a real-time space weather patrol observatory that monitors the near space environment. Two principal solar observatories, one hosting a suite of solar radio telescopes, and the other hosting an optical solar telescope, are on site. Ionospheric and geomagnetic sensors provide information on the geoeffectivenes of solar activity. Several international scientific research projects are also hosted at LSO. These include the GONG helioseismic laboratory run by the US National Solar Observatory, and a station of the Japanese 210 degree Magnetic Meridian network run by the Space Environment Research Centre of Kyushu University.

LSO has also hosted other programs from time to time, including a meteor radar from Genesis Software (Adelaide), to monitor the 2001 Leonid meteor storm.

Further information on LSO can be found at the IPS web site This includes a colour brochure on the Observatory in pdf format. Also available in near-real time is the space weather data acquired and processed at the Observatory. This includes a Solar Radio Spectrograph display which covers the frequency range of 25 to 180 MHz. As well as solar phenomenon, radio echoes (from distant transmitters) reflecting off meteors and re-entering space debris may occasionally be seen on this display.


Interest in Planetary Defence at Learmonth Solar Observatory and by IPS Radio and Space Services first started in 1995 following a visit to the site by then Colonel Simon (Pete) Worden, Commander of the 50th Space Wing of the US Air Force Space Command.

Colonel Worden briefed Observatory staff on his concept of Planetary Defense and outlined a small program to evaluate the use of the Learmonth site for detection and measurement of near Earth objects. The program was called RDOS for Rapidly Deployable Optical System. Details of the program can be found at RDOS installation. The choice of Learmonth for a site was primarily made on the basis of the high percentage of cloud free days experienced. A survey conducted by the US National Solar Observatory measured an average of 78% cloud free cover, and rated Learmonth second only to a mountain site in Chile (with 81% cloud free cover) with regard to this parameter, out of 15 sites surveyed worldwide.

Unfortunately, due to several manufacturing deficiences encountered with the telescope system, it was returned to the manufacturer after a few months. A dome to house the RDOS was received after this time, and this was erected on an antiseismic pad. Unfortunately, in the interim, there was a change of command at 50th Space Wing, and the telescope was never returned to Learmonth.

On March 22, 1999 Tropical Cyclone Vance, a maximal class category 5 cyclone swept over the North West Cape area, producing winds (recorded at the Learmonth Meteorological Office) up to 277 km/hour, the highest ever recorded on the Australian mainland. Destruction of LSO property was minimal, but the RDOS Observatory had its dome top removed and destroyed.

Rising from the ashes. A new Sirius Dome awaits construction, following the removal of the now destroyed RDOS dome.

In the year 2000, IPS funded for a new domed observatory, this one purchased from Sirius Observatories in Queensland. This was erected on the former pad.

In early 2001, IPS hosted a visit by two officers of the US Air Force Office of Scientific Research, Dr Clifford Rhoades and Major (Dr) Paul Bellaire. Following this, a research grant was made available by AFOSR to acquire equipment to restart observations of near Earth objects at LSO. Equipment selection and acquistion was also made possible by the very generous assistance of the US Spacewatch Project (Dr Robert McMillan and Ms Therese Lane). This led to the birth of Project Wormwood.

We should also acknowledge, at this stage, the Norcape Observatory, owned and operated by Alex Liu in Exmouth (36 km to the North of Learmonth, and the only town on North West Cape). His observing experience (with Schmidt Cassegrain telescopes) has been invaluable in our education in this field. Although Alex is primarily interested in occultations (of stars by asteroids) and variable star measurements, he has been persuaded from time to time to image near Earth objects.


"The third angel sounded his trumpet,
and a great star, blazing like a torch,
fell from the sky on a third of the rivers
and on the springs of water
- the name of the star is Wormwood."
Revelation 8:10-11

Telescope, mount, cameras and associated equipment arrived at Learmonth Solar Observatory and were initially set up in 2003.


Software Bisque Paramount ME Robotic Telescope Mount
Celestron 14" (0.35m) Schmidt Cassegrain Optical Tube Assenbly
SBIG STV CCD Camera (principally used as an e-Finder)


Latitude : S 22o 13' 7.4" ( -22.219 degrees )
Longitude : E 114o 6' 9.5" ( +114.103 degrees )
Altitude 12m MSL


John A Kennewell (PhD) - Principal Physicist IPS/LSO
Graham A Steward - Solar Physicist IPS/LSO


The majority of Project Wormwood activities will be follow-up astrometry (position measurements) that are required to obtain precise orbits for asteroids that have previously been discovered by other programs. However, we hope to also engage in some limited search activity for new asteroids. We will concentrate particularly on those areas of the sky with declinations south of -30 degrees. Although the asteroid population outside the declination range from +30 to -30 degrees is likely to be significantly less than the area inside this range (ie the range recommended by Spaceguard for NEO searches), it is also an area less accessible to the major Northern Hemisphere search programs, and thus offers a southern hemisphere site a search advantage. If possible, a small amount of time will also be devoted to asteroid light curve measurements (photometry) to help increase our knowledge of asteroid rotation rates. Specific activities will be posted in the ACTIVITIES section of this web site.


It has been previously stated that Project Wormwood will be involved in the first two phases of Planetary Defence. The Wormwood Observatory will cover the second phase. This web site will hopefully contribute to the first phase, with information in the form of short notes, papers, and references and links to other available relevant information.


IPS Radio and Space Services is the Australian Space Weather Agency, providing advice to customers in the Australasian area on the near-space environment, and the effects it has on communications, navigation, satellite operations, and other technological systems.

IPS maintains a network of stations in the Australasian, Antarctic and Pacific areas to monitor the state of the upper atmosphere, the ionosphere and magnetosphere, and the Sun, which directly or indirectly has the greatest influence on our near space environment.

Space weather has been defined as the application of space environmental studies to the interactions that occur between the space environment and the activities of humankind. In this definition, it is not only a phenomenon, but the appreciation and effects that phenomenon has on our lives.

An alternative definition might be: "Space weather is the state of the space environment, the appreciation of that environment, and the effects that environment has on our activities and ourselves."

While the Sun is the primary source of space weather, it is not the only source. An example of an extrasolar source of space weather is the natural space debris field (meteoroids) in which the Earth is continually immersed. This is not constant, but varies with diurnal, annual and longer cycles. This flux produces meteors (ionised trails in the mesosphere) when the meteoroids are trapped by the Earth's gravitational field, and ablate (burn up) in the upper atmosphere. These meteors can be used for specific communications in the lower VHF band. They can also be a source of interference in systems such as Over the Horizon Radars. They are thus a valid source of space weather.

It is only a short step to the realisation that space weather involves not only electromagnetic fields and microscopic (atomic) particles, but that it also includes macroscopic particles as well. And where does one draw the boundary on the size of a macroscopic particle? When does a meteoroid become an asteroid or a comet? We thus feel that planetary defence lies closely allied with the field of space weather. It certainly involves a part of the space environment that may significantly influence the course of human activities.

Further information on IPS can be found here.

[Wormwood Home] Go to Wormwood home page