SETV (Search for Extraterrestrial Visitation)
Theory and observation connected with the possibility that extraterrestrial
probes may exist within the Solar System. Among the locations considered
most promising to search for such probes are Earth orbit, lunar orbit, libration
points, and the asteroid belt. Although SETV has a rational basis and is
clearly part of the overall quest for extraterrestrial intelligence (whether
this intelligence resides within the putative probes themselves or their
creators), it has long been sidelined by mainstream SETI
researchers. There are two main reasons for this exclusion. First, it has
been argued by a number of influential SETI workers, including Frank Drake,
that interstellar travel is not realistic
and that the most logical way to exchange information across interstellar
distances is by radio waves. Second, SETV is regarded by orthodox SETI as
being uncomfortably close to ufology (see unidentified
flying objects). This is unfortunate because the fundamental ideas behind
SETV are as reasonable and amenable to scientific testing as are those of
traditional microwave SETI.
The concept of "messenger probes," or Bracewell
probes as they became known, first arose in 1960, the year in which
Drake carried out his Project Ozma. The term
SETA (Search for Extraterrestrial Artifacts)
was first applied in 1985 by Robert Freitas
and Francisco Valdes to describe the attempt
to "detect [evidence] in the Solar System by telescopic, radar, infrared,
direct probe, or other available means". Freitas and Valdes were specifically
interested in the search for intra-Solar System extraterrestrial probes.
However, SETA has come to include speculation about hypothetical planetary
surface artifacts such as those on the Moon described by Alexey Arkhipov,
and on Mars.
The newer term SETV tends to be applied more restrictively to searches for
probes and appears to have arisen at the same time as a greater emphasis
on the design of practical search systems and the beginning of actual search
programs. JPL engineer Scot Stride describes
SETV even more specifically as a program to search for extraterrestrial
interstellar robotic probes by means of "passive autonomous data acquisition
platforms" using "commercial off-the-shelf" (COTS) hardware.
Other SETV researchers have mounted observational programs to collect data
on certain anomalous phenomena. For example, Project Hessdalen, under the
direction of engineer Erling Strand of Østfold College has been studying
anomalous luminous phenomena in the Hessdalen valley of Norway for over
15 years. A variety of instrumentation has been employed, including photography
and related optical and infrared systems, seismographs, radar, HF radio
spectrum analyzer, Geiger counter. The team has carried out similar measurements
in the Australian desert and at Mexico's Popocatepetl volcano, a well-known
focus of anomalous activity. Their work has led to a collaboration with
a team of Italian researchers headed by astrophysicist Massimo Teodorani
and to two Italian exploratory missions (EMBLA 2000 and 2001), which focused
on effects in the VLF and ELF portions of the radio spectrum and on new
aspects of the optical phenomenology including low-resolution spectroscopy.
At Kingsland Observatory in northwestern Ireland, Eamonn Ansbro
and Catherine Overhauser are developing instrumentation that builds on the
findings of the Hessdalen and EMBLA research projects. Their surveillance
system employs 11 cameras covering the whole sky hemisphere, with sufficient
intelligence to recognize and track targets, and to trigger a video tracking
system. They have also proposed ULF-VLF radio spectrum coverage, radar,
magnetometers, and other instrumentation, as well as a 30 mW, 532 nm laser
"for reaction tests on the target". Although SETV remains outside mainstream
SETI, it is beginning to be entertained as a viable paradigm, particularly
in Europe – for example, through publications and workshops of the
European Space Agency.
- Freitas Jr., Robert A.and Valdes, Francisco. "The Search for Extraterrestrial
Artifacts," Acta Astronautica, 12, No. 12, 1027-1034 (1985).
Abstract: The rationale for the use of interstellar artifacts
by intelligent life in the universe is described. The advantages of
using interstellar probes as a means of exploration and communication
are presented and shown to be significant enough to counter the time,
energy, and technology arguments generally raised against contact
via extraterrestrial artifacts. Four classes of artifacts are defined:
Those seeking contact, those seeking to avoid contact, those intended
to provide a passive technological threshold for detection, and those
for which detection is irrelevant. The Search for ExtraTerrestrial
Artifacts (SETA) is based on the latter two classes. Under the assumption
that an extraterrestrial probe will be interested in life in our solar
system, a near-Earth search space is defined. This search space is
accessible to us now with ground and satellite observing facilities.
The current observational status of SETA is reviewed and contrasted
with the achievable detection limits for the different parts of the
- Freitas, R. A. "The Search for Extraterrestrial Artifacts (SETA),"
Journal of the British Interplanetary Society, 36, 501-506
Abstract: The Artifact Hypothesis states that an advanced
extraterrestrial intelligence has undertaken a long-term programme
of galactic exploration via the transmission of material artifacts.
An attempt to verify this hypothesis experimentally, the search for
extraterrestrial artifacts (SETA), is proposed to detect such evidence
in the Solar system by telescopic, radar, infrared, direct probe,
or other available means.
- Freitas Jr., Robert A. "Interstellar Probes: A New Approach to SETI
Journal of the British Interplanetary Society," 33, 103-109 (1980).
Abstract: Interstellar transmissions via energy-markers
(photons) or matter-markers (probes) appear to be energetically indistinguishable
alternatives for advanced technical societies. Since only Type II
and Type III civilizations realistically can afford beacons or starprobe
technology, alternative distinguishability criteria suggest the possible
superiority of intelligent artifacts for contact and communication
missions among extraterrestrial cultures. A balanced, more cost-effective
Search for ExtraTerrestrial Intelligence (SETI) strategy is proposed.
- Freitas, R. A. "The Case for Interstellar Probes," Journal of the
British Interplanetary Society, 36, 490-495, 1983.
Abstract: Interstellar spacecraft are superior to electromagnetic
wave propagation for extrasolar exploration and communication. The
search for extraterrestrial intelligence (SETI) should include a search
for extraterrestrial probes. Arguments favouring, and various traditional
objections to, interstellar communications via messenger probe are
- Freitas, R. A., and Valdes, F. "A Search for Natural or Artificial
Objects Located at the Earth-Moon Libration Points," Icarus,
42, 442-447 (1980).
Abstract: Photographs in the vicinity of the Earth-Moon
triangular libration points L4 and L5, and of the solar-synchronized
positions in the associated halo orbits (A. A. Kamel, 1969, Ph.D.
dissertation, Stanford University), were made during August-September
1979, using the 30-in Cassegrain telescope at Leuschner Observatory,
Lafayette, California. An effective 2° square field was covered
at each position. No discrete objects, either natural or artificial,
were found. The detection limit was about 14th magnitude. The present
work extends traditional SETI observations to include the search for
- Freitas, R. A., and Valdes, F. "A Search for Objects Near the Earth-Moon
Lagrangian Points," Icarus, 53, 453-457 (1983).
Abstract: A photographic search of the five Earth-Moon
Lagrangian positions included the solar-synchro-nized positions in
the stable L4/L5 libration orbits, the potentially stable nonplanar
orbits near L1/L2, Earth-Moon L3, and also L2 in the Sun-Earth system.
Observations using the 61-cm Burrell Schmidt telescope at the Warner
and Swasey Observatory, Kitt Peak Station, spanned 60\'b0 along the
lunar orbital plane x 5° around Earth-Moon L5, 48" x 5° around
L4, 25° x 13° around L3, 15° x 24° around the Moon
(LI/L2). and 14° x 14° around Sun-Earth L2. Limiting magnitude
for the detection of libration objects near L3, L4, and L5 was 17-19th
magnitude, 10-18th magnitude for L!/L2 plates, and 14-16th magnitude
for Sun-Earth L2. No natural or artificial objects were found. An
automated search of selected priority plates was attempted using the
Faint Object Classification and Analysis System (FOCAS) software package.
- Freitas, R. A. Jr. "If They Are Here, Where Are They? Observational
and Search Considerations," Icarus, 55, 337-343 (1983).
Abstract: This paper discusses observational considerations
in a search for extraterrestrial intelligence (SETI) program to detect
extraterrestrial messenger probes in the solar system. Observable
artifacts will most likely be found in a search space consisting of
geocentric, selenocentric, Earth-Moon Libration, and Earth-Moon Halo
orbits, which may be searched to a limiting artifact size of 110 m
(pv = 0.1) using existing or foreseeable instrumentation.
- Papagiannis, M. D. "Are We Alone or Could They be in the Asteroid
Belt?," Quarterly Journal of the Royal Astronomical Society,
19, 277-281 (1978).
Abstract: The observations that life has a natural tendency
to expand into all available space, that advanced technological civilizations
should be able to engage with relative ease in interstellar travelling,
and that once this threshold is crossed the complete colonization
of the entire Galaxy will be accomplished in a very short interval
relative to the age of the Galaxy, lead us to the following dilemma:
either the entire Galaxy is teeming with intelligent life and hence
our solar system must have been colonized hundreds of millions of
years ago, or there are no other inhabitants in our solar system and
hence most probably neither any-where else in the Galaxy. Before accepting,
however, the bleak verdict that we are all alone in the Galaxy, we
must search carefully throughout the solar system for any signs of
other technological civilizations. The most logical place to look
for them seems to be the asteroid belt because of the many advantages
it offers to a galactic society living in space colonies.
- Steel, Duncan. "SETA and 1991 VG," The Observatory, 115,
No. 1125, 78-83 (April 1995).
Abstract: A ~ 10-metre object on a heliocentric orbit,
now catalogued as 1991 VG, made a close approach to the Earth in 1991
December, and was discovered a month before perigee with the Spacewatch
telescope at Kitt Peak. Its very Earth-like orbit and observations
of rapid brightness fluctuations argue for it being an artificial
body rather than an asteroid. None of the handful of man-made rocket
bodies left in heliocentric orbits during the space age have purely
gravitational orbits returning to the Earth at that time, and in any
case the a priori probability of discovery for 1991 VG was very small,
of order one in 100,000 per anmun. In addition, the small perigee
distance observed might be interpreted as an indicator of a controlled
rather than a random encounter with the Earth, and thus it might be
argued that 1991 VG is a candidate as an alien probe observed in the
vicinity of our planet.
- Vallee, J. P., and M. Simard-Normandin. "Observational Search for
Polarized Emission from Space Vehicles/Communication Relays Near the
Galactic Centre," Astronomy & Astrophysics, 243, 274-276
- Betinis, E. J., "On ETI Alien Probe Flux Density," Journal of the
British Interplanetary Society, 31, 217-221, 1978.
Abstract: An alien probe diffusion equation and corresponding
alien probe flux density are developed to see if earth or the Solar
System is being detected by technologically advanced extraterrestrial
civilisations. If such is the case, then data in the form of observed
probes, anomalous and alien as they may be, may possibly be reconciled
with data gathered by earth-based observers.
- Burke-Ward, Richard, "Possible Existence of Extraterrestrial Technology
in the Solar System," Journal of the British Interplanetary Society,
53,, 2-12, 2000.
- Cornet, Bruce and Stride, Scot L., "Solar System SETI Using Radio
Telescope Arrays," Proceedings of SETICon 03, The Third SETI League
Technical Symposium, The College of New Jersey, Ewing New Jersey, April