The cessation at the end of 1994 of the photographic NEO programs
conducted by Eleanor Helin and by Gene Shoemaker with the 0.46-m Schmidt
telescope at Palomar Observatory in California produced a noticeable
perturbation in the rate of discoveries of comets and near-earth asteroids.
This effect was particularly evident during 1995, before Helin's
NEAT
(Near-Earth Asteroid Tracking) program using a JPL CCD camera
on a
GEODSS telescope operated by U.S. Air Force personnel in Hawaii, as well
as other more recent CCD surveys, got underway. Only the University of
Arizona's scanning-CCD
Spacewatch
search and the Australian program
involving the examination of U.K. Schmidt plates and CCD follow-up were
active during 1995, and the latter was operating at a rather low level
prior to its final surge before the program was terminated in late 1996.
The fact that one of the intrinsically brightest comets in history could
be discovered visually by amateur astronomers when it was only 22 degrees
from opposition is testament to the rather sorry state of NEO activities
in 1995. NEAT and the Australian program, as well as the high-latitude
photographic program carried out by T. B. Spahr and C. W. Hergenrother
with a 0.4-m Schmidt in Arizona and two photographic programs for more
general studies of asteroids with the 1-m Schmidt at the European
Southern Observatory, nicely supplemented Spacewatch in 1996 and brought
the number of discoveries back to the 1994 level.
1997 dawned with Spacewatch still dominating the field with its
discovery of four of the seven comets, six of the 12 Apollos and Atens
(i.e., asteroidal objects with their perihelia inside the orbit of the
earth), and all but one of the five Amors (further asteroidal objects out to
a perihelion distance of 1.3 AU) reported before the end of April. The NEAT
program suffered from unusually poor weather and from a cutback in operation
that allows it a maximum of only six observing nights each month, in
contrast to Spacewatch's 18. Nevertheless, NEAT discovered one comet, one
Aten and the remaining Amor during the four-month interval.
The sixth of the comet discoveries was by a Japanese amateur using a CCD,
and the seventh was a "traditional" photographic discovery during the second
Palomar Sky Survey. Of the remaining Apollo discoveries, one was found in
the course of a CCD observation with the 1.0-m Schmidt telescope at the Kiso
Station of the National Astronomical Observatory of Japan, one in the course
of an asteroid survey operated by students with the Beijing Observatory's
0.6-m Schmidt at Xinglong, one was found by an Italian amateur astronomer,
and two were found in the course of LINEAR, the Lincoln Laboratory's
Near-Earth Asteroid Research survey, which operates on a GEODSS telescope in
New Mexico.
LINEAR is an important new search program that promises to be a
very significant contributor to the NEO cause. While its faintest
detections of main-belt asteroids, at around V = 20.5 comparable to that in
the NEAT program, are more than one magnitude brighter than the faintest
detections by Spacewatch, LINEAR's strength comes from its fast-readout CCD,
which typically allows the saturation of several search areas extending for
8 degrees along the ecliptic and perhaps 9 degrees in latitude., spread over
an average of six or seven clear nights each month. In contrast, the
Spacewatch latitude range is typically only 2 degrees, while NEAT coverage
falls in between but with less continuity than in the other two programs.
Of course, there is no value to making a discovery that is not followed
up with further observations. Initial information about many of the
objects discussed above, as well as other candidate NEOs that could not be
confirmed, is routinely placed in
The NEO
Confirmation Page maintained on
the World Wide Web by the
Minor Planet Center,
even on the basis of
single-night detections. Key confirmation and other early follow-up
observations have been obtained, most notably by Dave Balam and Chris Aikman
with the 1.8-m reflector at the Dominion Astrophysical Observatory in
British Columbia and by Jana Ticha and her associates with the 0.6-m
reflector at the Klet Observatory in the Czech Republic. A handful of
amateur astronomers in the U.S. and Italy are also involved in this work, as
are several Japanese amateurs, particularly when the follow-up is of a
comet. Initial information about comets has been
published on the
IAU
Circulars. As soon as the orbit of an Aten, Apollo or
Amor is tolerably determined, this information has been routinely supplied
in the
Minor
Planet Electronic Circulars, with subsequent updates appearing
in some cases as the orbital solutions are improved.
Although observations may sometimes be obtained over a span of several
months at the discovery opposition, it is--at least, in the absence of
radar data or a chance identification of observations from earlier
years--essential to recover an object at the next suitable opposition
(or reasonable elongation from the sun) before one can really say that an
orbit is "established", in the sense that reliable predictions for the
object in the future are guaranteed. In addition to new discoveries, the
Minor Planet Electronic Circulars carry information about NEOs (or the IAU
Circulars in the case of comets) at their crucial second apparitions.
During the first four months of 1997 there were four Apollos and five Amors
in this category. Six of these nine recoveries were made by Hergenrother,
generally with the 1.2-m reflector at the Smithsonian Astrophysical
Observatory's Whipple Observatory in Arizona. This is another new
observing program that has been initiated only during the past year, and it
replaces the follow-up program conducted with the 1.5-m reflector at the Oak
Ridge Observatory in Massachusetts--a program that was carried out by
Richard McCrosky for very nearly a quarter of a century and one of the
earliest successes of which was the 1973 recovery of (1862) Apollo itself
after it had been lost since its discovery opposition 41 years earlier.
While there is value to well-conducted observational programs involving
comets and asteroids generally, few of the objects discovered are even
remotely likely to be an actual threat to the earth during the foreseeable
future. All of the comets of 1997 have perihelion distances well in excess
of 2 AU. It is useful to define a category of PHAs ("potentially hazardous
asteroids") that currently have the possibility of passing within 0.05 AU
and have an absolute visual magnitude brighter than 22 (so as to include all
objects likely to be 200 meters across). There are currently 98 objects in
this category, of which 13 were discovered in 1994, three in 1995, 11 in
1996 and five during the first third of 1997. One of the points about the
Spacewatch discoveries is that many of them are intrinsically very faint
objects close to the earth but too small to survive passage through the
atmosphere--or at least do more than very local
damage. Even so, Spacewatch has consistently been the most important
contributor to PHA discoveries in recent years, with six in 1994, all three
in 1995, four in 1996 (with three each by NEAT and the Australian program)
and two so far in 1997.
A new search and tracking program has been initiated in Italy. The
program (CINEOS: Campo Imperatore NEO Survey) is a component of the
national ITANET project, aimed at building and testing a small-scale
network for NEO observations. The program, in which seven Italian
institutions participate, uses at the moment the Schmidt telescope of
the Campo Imperatore station (Observatory of Rome), on the Gran Sasso
massif at an altitude of 2180 meters. This is a 90/60 cm f/3 instrument
with a 2k x 2k CCD in the focal plane. Its FOV is of about one square
degree. With optimal conditions the instrument is able to reach mag
21. The primary objective of the program, mainly thanks to the very
good observing conditions at the site, is to systematically search for
objects at low solar elongations (50-120 deg), especially Atens. The
program is also aimed at providing good astrometric follow-up of
discovered objects. At this moment the program may count on two weeks
of observation each month, bracketing the full moon. The principal
observers are: Andrea Boattini (IAS-Rome) and Andrea Di Paola and
Fernando Pedichini (Obs. of Rome), but several other Italian astronomers
are participating in the program. The ITANET project is now providing
upgrading of two other Schmidt instruments at Asiago (Padua) and Serra
la Nave (Catania) observatories. The three instruments will be fully
operational by mid-1998. Coordination of observations and archiving of
images will be performed at the IAS-Reparto Planetologia in Rome. It is
anticipated that, after the necessary initial tests, the ITANET network
will become a component of the Spaceguard System.
Since it began operations for NEO searching in 1989, the 0.9 meter
Spacewatch Telescope
operated by Tom Gehrels (University of Arizona)
and his team at Kitt Peak has been the leading instrument for discoveries of
near-Earth asteroids, delivering a large fraction of the NEAs found
in the kilometer size range as well as identifying objects of
unprecedented small size (ten meters and even lower). For the past
several years the Spacewatch team has been developing a new alt-az folded
prime focus telescope with an aperture of 1.8 meters, F/2.7, which was
also installed on Kitt Peak. The 1.8-m Spacewatch Telescope and building
will be inaugurated on June 7th.
A project currently being planned within the US is a spacecraft named
Clementine II. Clementine
I operated three years ago, completing a very
successful mission to the Moon, multispectral scans of much of the lunar
surface being obtained along with the tentative identification of polar
crater ice from radio data. Clementine I was then scheduled to be sent on
to the NEA (1620) Geographos, but an attitude control jet malfunction led to
mission abort.
Clementine II is now under study by the US Department of Defense, with the
likelihood of NASA involvement. As for the first mission, Gene Shoemaker is
chairing the science team. Whilst the precise mission has yet to be
finalized, it seems likely that after launch in late 1999 and a phase in
terrestrial orbit, and possibly lunar orbit, Clementine II will be sent on
to fly-by two NEAs [(4179) Toutatis and 1986 JK] in the year 2000. A
desired feature of the mission would be sending two small probes to impact
these asteroids to aid in investigations of their physical nature.
The Spaceguard Foundation is about to sign a contract with ESA for the
establishment of a Spaceguard Central Node (SCN) using ESA funds.
This is a pilot project, of 10 months duration, to be started at the
end of May 1997. The goal is to build, both from hardware and software
viewpoints, a facility able to connect and coordinate all observatories
involved in NEO research. The provisional structure of the SCN, which
will be located at the SGF Headquarters in Rome, is as follows:
The current WWW page of The Spaceguard Foundation will be upgraded
and will contain all information needed by SGF members and non-members
concerning SGF activity.
A tutorial section will address all the scientific issues related to
NEOs, from origin and dynamics, to physics and mineralogy, to impact
processes. This section is meant to provide background information to
newcomers and a forum for discussion on the social and political
aspects of the NEO researches. The section will also provide a
connection to the NEO Journal, a new scientific (electronic) journal
the establishment of which is under discussion with the Kluwer publishing
house; this journal would be completely devoted to NEO research.
Another section will eventually become the backbone of the
Spaceguard System. This section will contain access to the
Minor Planet
Center facilities, a "software tools" collection, an exhaustive archive
of CCD frames (and the software needed to manage it), and a bibliographic
section. The most important feature of this section, however, will be
the "situation room", where information will be inserted about
participating observatories, their observing schedules, opportunities
and suggestions. A continuously updated chart of "who is observing
what" will also be provided.
A last section will contain links to all centers, institutions and
people who are in any way connected to NEOs, in whatever scientific and
non-scientific discipline.
The cessation of all NEO astrometric tracking in the southern
hemisphere (see items 10, 11 and
12 below) has meant that there is a
special need for the development of a southern hemisphere NEO
observation site. Because of this The Spaceguard Foundation has made
one if its highest priorities the establishment of a new southern
hemisphere NEO observatory.
The proposed Spaceguard Southern Telescopes would consist of two large
instruments dedicated to NEO discovery, follow-up, and physical studies.
The smaller 4-meter telescope would be dedicated to the actual discovery
of NEOs, whereas the time on the larger 8-meter telescope would be
concentrated on follow-up astrometry, photometry, polarimetry, and
specroscopy. The Spaceguard Southern Telescopes would no less than
revolutionize the astronomical research on small bodies of the solar system.
The Spaceguard Foundation is currently looking for ways to
establish the telescopes on Gamsberg, Namibia. It is noted that the
United Nations Workshops on Basic Space Sciences held over the past few
years have passed resolutions calling for (i) A global network of small
telescopes for NEO search, tracking and other observations; and
(ii) The establishment of a major inter-African observatory and science park
in Namibia.
The Spaceguard Association of Japan (a private organization) was officially
founded on October 20, 1996, and it now has nearly 300 members including
professional scientists and members of the public. A regular scientific
meeting is held every alternate month, and public lectures are to be given
several times per year, beginning in August after IAU GA. In addition, an
information bulletin in published once every three monthes, and all suitable
NEO information is posted on the Spaceguard Japan WWW homepage
(http://www.crl.go.jp/ka/control/asteroid/SGFJ/), making this
information freely available to non-members.
There are two major projects for which funding is being sought. The first
of these is a pair of one-meter class ground-based telescopes to be located
in Japan. It appears that the Japanese government views this project
favorably, and we are hopeful that the budget will be approved next August.
These telescopes would be used both for NEO studies and for observations of
space debris.
The second project concerns a lunar-based NEO telescope. The NASDA (Japanese
national space agency) has plans to launch several lunar
missions beginning in 2003. The first mission is nearly totally defined. We
are discussing with NASDA the possibility of having the second mission
include a 30 cm NEO telescope as a site test instrument to the other main
instrument, with a launch in 2005. If this project were to go ahead, it
would be viewed as being a trial for a larger (one-meter class)
lunar-based NEO telescope in the future.
Japan is also involved in direct spacecraft investigations of NEOs. The
Muses-C spaceprobe is being built by ISAS (Institute of Space and
Astronautic Sciences) for launch on a M-5 rocket in 2002, the mission
entailing a rendezvous with the near-Earth asteroid (4660) Nereus, a
sample of that asteroid being returned to the Earth in 2006. ISAS is
collaborating with NASA on this program.
Spaceguard UK was established on 1 January 1997, with aims designed
to complement those of the Spaceguard Foundation, but with a distinct
national emphasis. Throughout 1996 the foundations of the
organisation were laid, making contacts and consulting with many of
the key players worldwide culminating in June with the presentation
of a paper on the NEO threat to the British government. The most
significant result was a major meeting of interested parties,
representatives of many scientific establishments and government
departments in November 1996. The meeting decided to establish a UK
NEO Working Group that will be meeting for the first time in July
1997. Spaceguard UK itself is a growing organisation. Dr Arthur C
Clarke and Dr Patrick Moore have both agreed to become Trustee
members, though the title will probably change due to the legal
implications of the term "trustee". Already there are over a dozen
Associate members, including Dr Duncan Steel, Professor Mark Bailey,
Professor Tony McDonnell, Dr Bill Napier, Dr Victor Clube, Dr Benny
Peiser and Dr Michael Martin-Smith. General membership stands at
nearly fifty, with two "corporate" members, "Meteor" magazine and the
Society for Popular Astronomy. We have a new government in the UK,
and a political campaign is planned for the late summer and autumn
with the aim of establishing a formal, government-sponsored NEO
programme. 1996 was a highly successful year, and 1997 promises much.
A consortium of astronomers from Argentina, Brazil and Uruguay are planning
the development of telescopes with aperture around one meter dedicated to
searching for, and tracking, NEOs. The likely site for the search
telescope is in western Argentina, with two follow-up telescopes in Brazil
and Uruguay. For information contact Gonzalo Tancredi
(gonzalo@fisica.edu.uy)
or see
http://www.fisica.edu.uy/PAGES/gonzalo/research.html
Not all components of these messages will be positive; we feel that the
The Spaceguard Foundation also has a responsibility to report on
developments which reflect negatively upon the general aim of the
foundation.
The program on NEO search and tracking in Australia, which was the only
such program in the southern hemisphere, terminated last December 31st
due to the cessation of funding. This was an important program largely
because it delivered astrometric observations of NEOs in regions of the
sky inaccessible from the north, this being especially significant for
newly-discovered NEOs moving south. For example, of 463 NEAs known at
the end of 1996, about 300 were large enough and had well-enough
defined orbits to allow some confidence of their telescopic recovery;
of those, 119 were observed astrometrically by the Australian team
(McNaught, Garradd, Steel) during 1996. In addition, the team has over
the years made many important precoveries of NEOs; for example, within
a week of the discovery of Comet Hale-Bopp in 1995 July, a faint image
of the comet was found on a U.K. Schmidt Telescope plate exposed in
1993 April, indicating that the comet was active whilst at a very large
heliocentric distance (and thus massive, as has proven to be the case),
and also that the comet was not a new comet in the Oort cloud sense,
instead having an orbital period of a few thousand years. The
termination of the Australian NEO program has meant that such searches
of old Schmidt plates are no longer carried out.
Various news media around the world reported in early April a
statement by an Australian government minister to the effect that the
government was looking at ways by which the program might be revived.
This announcement has misled many people in other nations working on
NEOs. At the time of writing in mid-May, the Australian government has
not been in contact with the team mentioned above in order to discuss
whether the program might be re-started; indeed, the press release was
issued when it was known that Steel and McNaught were out of the
country, and so unable to be contacted by the Australian media.
With the termination of the Australian NEO program, there is an added
need for other southern hemisphere observatories to fill the gap which
is left. Recently a question was asked in the New Zealand parliament
with regard to whether NZ is involved in observations of NEAs. The
answer given by the government minister was misleading, in that it was
said that the program which used to be operated at Mount John
University Observatory by Alan Gilmore and Pam Kilmartin (who is a
member of the Minor Planet Naming Committee) was "uncompetitive" since
it used photographic detection. In fact, with no other routine
southern hemisphere NEO tracking program in operation, there is no
competition. One could envision a situation whereby a NEA making a
close passage by the Earth and found by one of the US search programs
might be lost, whereas a single photographic detection from NZ might
secure its orbit. New Zealand, due to its latitude and longitude, and
the experience and expertise of Kilmartin and Gilmore, must be a member
of any international Spaceguard program. Further, we note that for a
small nation like New Zealand (population three million) there are few
ways in which the country can become a full member of any large space
program, except by providing ground-based services such as those
required for Spaceguard. Apart from the technological and scientific
benefits, we note that the involvement of such nations as participants in
space programs rather than merely as spectators must be inspirational and
motivational to their youth, leading to more able students directing
their studies towards engineering, technology, and science.
The following is provided without comment from The Spaceguard
Foundation (except to note that clearly we are, in general, unable to
agree with what is stated below between the quotation marks). We also
note that Gene Shoemaker, a member of the Board of Directors of The
Spaceguard Foundation, was the Chair of the NASA committee in question.
The issue of NEW SCIENTIST (London) dated 3 May 1997 contains a review
on pp.46-47 by John Casti of the Santa Fe Institute (New Mexico) of the
book "Cartographies of Danger: Mapping Hazards in America" by Mark
Monmonier (University of Chicago Press). Casti writes the following,
inter alia:
Maps of risk can also be dangerously misleading or erroneously
interpreted to serve a political agenda. A good example in the latter
category is NASA's 1993 map of ancient asteroid collisions, produced in
an effort to persuade Congress to part with $50 million to study a
high-tech defence against colliding asteroids. To convince Washington
to cough up the money for a network of satellites and early-warning
telescopes so that astronomers could catalogue such threatening objects
and forecast collisions with Earth, NASA tried to document the
magnitude of the threat with a map showing 130 terrestrial impact
craters.
What the map says is that asteroids, comets, and large meteorites have
struck the Earth many times over the past 2 billion years, with a clear
implication that they can strike again. So far, so good. In fact, the
map very likely understates the threat, since many such impacts have
probably occurred in the sea and in jungles, where evidence is hard to
come by.
What makes the NASA map absurd is not the impacts it shows, but the
implication that there is something that we can do to prevent an impact
in the future, should NASA's programme have detected an asteroid on a
collision course. Even with a Reagan-style Stars [sic] Wars defence
system, the likelihood of effectively destroying or diverting such a
bolide is negligible. Here, a valid hazard map was used to serve a
political agenda that cannot deliver what it claims.
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Last modified: June 3, 1997