The Lunascan Project


 Reprinted from IUR, July/August 1995
By Mark Rodeghier

The vast majority of scientists have been reluctant to investigate reports of UFOs or do research on the UFO phenomenon. Privately, scientists often express some interest in the subject, as Peter Sturrock found in his survey of astronomers and as I learned in my dissertation research, but this interest has not often been transferred into active research or case investigation. As a consequence, and also because of the conservative nature of science, scientific journals, especially those in the hard sciences, have published few papers on UFOs, and nearly all of these have had a negative slant.

Imagine my surprise, the, when I learned that the April 1995 volume of The Observatory, a serious astronomical journal published in Great Britain, contains an article about a potential extraterrestrial probe (read UFO) by an established astronomer. The author, Duncan Steel, is at the University of Adelaide in Australia and is an expert on the detection of small objects in near-Earth space. He has recently written about the danger posed to Earth by impacting objects, Rogue Asteroids and Doomsday Comets (New York: John Wiley & Sons, 1995). Steel has served on both the Detection Committee and the Intercept Committee that were created by NASA to consider the danger to mankind. One outcome of this concern is an outgoing program to detect objects passing near Earth, using the Spacewatch telescope at Kitt Peak Observatory.

The article by Steel, entitled "SETA and 1991 VG," has the typical dry title of most scientific papers. It is not highly technical, as is true of many articles published in The Observatory, so I encouraged those with a further interest in this topic to read the original (a good knowledge of astronomy will aid comprehension, however). The acronym "SETA" refers to the Search for Extraterrestrial Artifacts, a concious imitation of the Search for Extraterrestrial Intelligence (SETI).


Steel's main point is that an object discovered in late 1991 passing near the Earth is a candidate for an "alien probe". His article is based upon the discovery of a roughly 10-meter object in an orbit around the sun that passed by the Earth in December 1991 and was discovered by the Spacewatch telescope at Kitt Peak Observatory a month earlier. The object was given the name 1991 VG and was later observed in April 1992 by a larger telescope, also at Kitt Peak. These observations allowed a reasonably accurate determination of its orbit. Its size can only be estimated because it was too small to observe as anything but a point source. The size estimate of 10 meters is based on its spectral reflectivity and the assumption that it was an S-type asteroid: if it was a C-type asteroid it would be about 19 meters in greatest dimension. (C-type asteroids have a lower reflectivity, thus it takes a larger object to produce the same level of brightness.) Whatever its exact size, it is clearly a relatively small object.

Steel bases his conclusion on two unusual characteristics of 1991 VG, as well as two other factors. First, it exhibited rapid variations in brightness, which indicates that it has areas with very distinct and different reflectivity. This is highly unusual for small asteroids. Second, 1991 VG has an orbit that is very Earth-like, with low eccentricity and inclination, and an orbital size just slightly larger than Earth's. Additionally, Steel notes that 1991 VG passed close to Earth, slightly under 300,000 miles distant. This may seem quite far - it is greater than the Earth-Moon distance - but it is not far at all on an astronomical scale. Finally, he calculates the a priori probability of discovery of the object as one chance in 100,000 per year, which will become more meaningful below.

Steel considers these facts by determining how compatible they are with what he suggests are the only three visible possibilities for the nature of 1991 VG. These possibilities include an asteroidal body, a man-made spacecraft, and an alien artifact of some type.

The orbit of 1991 VG, calculated backwards, indicates that it closely approached Earth in 1975 and also sixteen years earlier in the late 1950s. By looking at spacecraft launched during these earlier periods, Steel concludes that no known man-made object could currently be following the orbit of 1991 VG (he looked both at spacecraft and at the expended rocket bodies that launched the craft, since some of these escape Earth's gravity).

Given the low probability of detection mentioned above, Steel further concludes that a priori chances of 1991 VG being a returning rocket body are small. Since only a few man-made objects have been injected into orbits around the sun, the likelihood of the Spacewatch telescope detecting one of these, given the small probability of detection each year of one in 100,000 of a similar object, is remote. This is statistical evidence that the object is not likely to be man-made.

As for the probability that 1991 VG is an asteroid. Steel argues against it for two reasons. The brightness of the object fluctuated rapidly, which is characteristic of artificial satellites rather than asteroids (satellites often have angled, highly reflective surfaces, and they rotate for stability, both of which together cause brightness fluctuations). Second, the orbit of 1991 VG would be unstable over a period of a few thousand years because of its similarity to Earth's orbit and close approaches to our planet. Consequently, 1991 VG can be in its current orbit only if it recently (in astronomical terms) entered that orbit. This makes its identification as an asteroid unlikely, and Steel estimates a low probability that 1991 VG is an asteroid.

This leaves the third hypothesis: that the object is alien in origin. Steel admits he has little evidence that 1991 VG is an alien artifact (what would one look like?), but he believes the prior probability of detection of such objects, including 1991 VG on its other conjectured near passes in the mid-1970s and late 1950s, was so small as to be nonexistent. This is chiefly because efforts like that of Spacewatch were just begun recently, and astronomers otherwise made few systematic searches for small objects passing near the Earth.

Steel is a cautious investigator, so he does not conclude the article by arguing that 1991 VG is definitely an alien probe. He calls for further investigation, especially an increase in surveillance programs to determine whether other asteroids have similar orbits and light curves as 1991 VG. He also suggests that candidate man-made objects be examined in more detail, since nongravitational forces might have altered their flight path sufficiently to bring them back to Earth in an orbit identical to that of 1991 VG (an example of a nongravitational force would be fuel leaking from a rocket body).

Steel goes on to state his personal bias that 1991 VG is a terrestrial object - an expendable rocket body launched some time ago and now returning to Earth - but he clearly enumerates the conditions Jthat must be met if such a hypothesis is correct, and those conditions are quite stringent and unlikely, as detailed above.


A UFO is a UFO, whether seen on the ground, flying in Earth's atmosphere, or detected in outer space. As the years have passed since 1947, the beginning of the modern era of UFO reports, the capability of scientific instruments to detect small objects in Earth orbit or near-Earth space has rapidly advanced.

The ability to detect such objects has been further enhanced because of the recent concern over the possibility that an asteroid or comet may strike the Earth and cause widespread devastation. Some argue that a similar event caused dinosaurs to become extinct about 65 million years ago. This concern led directly to the creation of the Spacewatch program, whose telescope detected 1991 VG. Any alien probe passing nearby much before the present era was extremely unlikely to be detected. To give you`an example of the difficulties,`1991 VGl at its closest approach, was about one million times too faint to be seen with the naked eye, and is now beyond the detection of the largest telescopes.

Nevertheless, since man's capability to detect small objects near Earth has increased by many magnitudes in recent years, its not too surprising that an alien probe passing near the Earth could be detected. This suggests that the UFO community has potentially fruitful links with the scientists conducting the Spacewatch program. And if there truly are alien probes passing near Earth, which some argue must be true given the likely number of extraterrestrial civilizations, then it should only be a matter of time until a more unequivocal detection is made.