CCNet DIGEST, 15 January 1999

    Al Harris and David Morrison <>

    Steven N. Koppes <>

    Andrew Yee <>


    R. J. Whiteley & D.J. Tholen, UNIVERSITY OF HAWAII

    Andrew Yee <>



From Al Harris and David Morrison <>

15 January 1999

The Spaceguard Survey is the name given to the search for near-Earth
objects (NEOs, primarily asteroids) that could someday impact the
Earth. It focuses on surveying NEOs 1 km or larger in diameter, since
these NEOs are both the easiest to discover and track, and the ones
that dominate the impact hazard for us on Earth. The following
summarizes current progress, showing that the discovery rate is
accelerating rapidly, but we still need a factor of eight improvement
over the 1998 results to complete the Survey within a decade.


The goal of the Spaceguard Survey is to find 90% or more of the Near
Earth Asteroids (NEAs) within a decade. It is also a goal of NASA,
stated in the NASA Office of Space Science Strategic Plan, to
discover 90% of the NEAs within the next decade. This is a summary of
where we stand at the end of 1998 in this effort. We will try to make
further updates at 6-month intervals and post them on the NASA Impact
Hazard website.

For purposes of this discussion, NEAs with D > 1 km are equated to
asteroids with absolute H magnitude less than or equal to 18.0, with
perihelion distances less than 1.3 AU. There are approximately
1500-2000 NEAs estimated to exist that fit this definition. Other
definitions of NEAs (or ECAs, Earth-Crossing Asteroids, or PHAs,
Potentially Hazardous Asteroids) are more restrictive and also
require more detailed analysis of their orbits. The present
definition of an NEA, however, together with the estimate of
1500-2000 total NEAs, is sufficient to assess the current
performance of the survey.

Note that many of the NEAs discovered are smaller than 1 km (H >
18.0). Any survey system will discover more small asteroids than
large ones. But we will consider only asteroids larger than 1 km,
since these are the most dangerous, and the metric for success of the
survey is defined in terms of objects with D > 1 km.

The four most successful searches during the past 18 months have been
LINEAR (the Lincoln Laboratory NEA survey of the US Air Force), NEAT
(the NEA survey carried out jointly by JPL and the USAF), Spacewatch
(the search carried out for more than a decade at the University of
Arizona), and the new LONEOS (Lowell Observatory NEO Survey) program
that just started operation in the second half of 1998. Together
these four accounted for almost 90% of the discoveries. LINEAR has
dominated the growth, going from 0 to 2 to 10 to 26 NEAs (D > 1 km)
discovered in the last four 6-month periods.

The table below shows 62 NEAs larger than 1 km discovered in he 18
months from July 1997 through December 1998. This is an update of the
table posted previously, adding data for the second half of 1998.
Note one change in the previous numbers: LINEAR now gets credit for
only 10, rather than 12, discoveries H < 18.0, in the first half of
1998. As orbits and magnitudes are revised with further observations,
estimates of H values can become fainter (or brighter) than 18.0, and
computed perihelia values can become greater (or less) than 1.30 for
the same NEA, influencing the way these numbers are recorded. 
However, the relative stability of the numbers indicates that the
results are statistically valid. In addition to a new column for
98(2), we have added a new row, for LONEOS.


Discoverer 97(2) 98(1) 98(2) 98(1+2)
LINEAR 2 10 26 36
NEAT 3 5 2 7
Spacewatch 1 2 1 3
LONEOS 0 0 4 4
Other 2 2 2 4
Total 8 19 35 54

The average rate of discovery of large NEOs for 1998 was 54/yr or
almost 5/mo. The discovery rate in the second half of 1998 was
actually a factor of 5 greater than the same six-month period in

In a ten-year Spaceguard survey expected to detect 90% of the NEA
population with D > 1 km, we must discover just over 20% in the first
year, with the rate declining exponentially thereafter as greater
completion is reached and more of the objects found are
rediscoveries. Therefore, to achieve the stated Spaceguard goal of
finding 90% of the 1500-2000 NEAs in a decade, we need an increase by
about a factor of 8 over the 1998 average values.

The NEO discovery rate is accelerating due primarily to the
continuing success of LINEAR and now the recent addition of LONEOS.
If this trend continues, we should be within a factor of a few of the
Spaceguard capability by the end of 1999.

Alan Harris and David Morrison (15 Jan 1999)


David Morrison, NASA Ames Research Center
Tel 650 604 5094; Fax 650 604 1165 or


From Steven N. Koppes <>

January 13, 1999
For Immediate Release

Contact: Steve Koppes
         (773) 702-8366

University of Chicago/ARGOS satellite experiment to study space debris

Above the atmosphere bits and pieces of debris zip around the Earth at
tens of thousands of miles an hour. Some of these objects are natural
cosmic dust, produced by comets, meteoroid impacts or other natural
processes, while others are debris resulting from human activity in

These objects have caused varying levels of damage  to space shuttles,
satellites and the Hubble Space Telescope. And although detection
systems currently track the largest pieces of man-made debris, many
more particles are too small to track, ranging in size from pebbles or
sand grains down to particles that can only be seen with a microscope.

"Many of these particles are produced by collisions between larger
debris objects, and so information about these particles is important
for understanding the whole debris population in Earth orbit," said
Bruce McKibben, Senior Scientist at the University of Chicago's
Laboratory for Astrophysics and Space Research.

A Chicago instrument designed to provide data to help reach that
understanding will be launched Jan. 15 on the Advanced Research and
Global Observation Satellite (ARGOS) from Vandenberg Air Force Base in
southern California. ARGOS's scientific payload will include the
University's space dust experiment (SPADUS), which will measure the
mass, speed and trajectory of dust particles in low-Earth orbit, and
will allow scientists to determine whether they are particles left in
the wake of comets or man-made orbital debris.

"This is the first active experiment where you can separate these two
phenomena," said John Simpson, Chicago's Arthur Holly Compton
Distinguished Service Professor Emeritus. "We will be able to tell
whether the debris is uniformly distributed or in clouds around the
Earth, and even whether there's a ring around the Earth, like Saturn's,
but very weak. This is one of the discovery possibilities."

ARGOS, an unclassified U.S. Air Force satellite, will circle the Earth
for three years in a polar orbit at an altitude of 516 miles. This
altitude is near a region heavily used by commercial, scientific and
government spacecraft, where ground tracking of the larger objects
indicates a concentration of man-made debris. In addition to the
Chicago experiment, ARGOS will conduct high-temperature
superconductivity experiments,  upper atmospheric imaging and
environmental studies, and test electric propulsion methods.

Much of the current data regarding the quantity of debris particles in
low-Earth orbit was collected by NASA's Long Duration Exposure Facility
(LDEF) from 1984 to 1990. But LDEF could not distinguish between
natural and man-made debris and could not determine where or when in
its orbit an impact occurred. SPADUS will be able to do this by
measuring the time of impact and the particle trajectory and velocity
of debris with enough sensitivity to detect particles smaller than the
particles contained in a puff of cigarette smoke.

Man-made debris  in a circular orbit races about the Earth at speeds of
nearly 17,000 miles an hour. "This debris consists of everything from
rocket casings and dead satellites on down to the very small dust
particles that can result from the grinding down of these large objects
as they collide with each other and with dust particles already in
orbit," McKibben said.

Cometary debris, on the other hand, travels more than 25,000 miles an
hour. There is also a remote possibility that SPADUS will be able to
detect dust particles entering the solar system from interstellar space.
"They'll have even higher velocities," McKibben said. "Very small ones
have been detected by spacecraft in the outer solar system right now.
We might see them, but I wouldn't count on it."

SPADUS will be used to study the Leonid meteor shower next Nov. 17. The
Leonid meteor stream consists of the boiled off remains of Comet
Tempel-Tuttle and is usually fairly mild. But the shower was expected
to be far more intense in 1998 and possibly 1999, because last
February, the comet made its closest approach to the sun, which happens
once every 33 years.

Last year, satellite controllers changed the orientation of their
satellites to reduce surface area exposed to the cometary stream. "The
meteor shower was not as strong as some predictions in 1998, so maybe
this year we'll get the whole works," Simpson said.

Earth's orbital path will take it across other cometary streams as
well, said Anthony Tuzzolino, Senior Scientist at Chicago's Laboratory
for Astrophysics and Space Research. "There are 15 or 16 streams that
are possible candidates for detection based on how close we'll come to
them," he said. "There are a lot of things to look for."

Helping in the data analysis will be Herbert Gursky and his associates
at the Naval Research Laboratory in Washington, D.C. The NRL
contributed the instrument's mechanical design and construction of the
experiment housing. Similarly,  important contributions were made by
Lockheed Martin, which provided the digital electronics box, including
the microchips that make the sophisticated SPADUS measurements possible
in a package small enough for space flight.

H.N. Voss, then of Lockheed Martin and now a physics professor at
Taylor University in Upland, Ind., also led the effort to provide a
small radiation sensor system, known as the ADS as part of the digital
box. The ADS will monitor the radiation environment of the spacecraft,
and data analysis for will take place at Taylor University.

Instruments related to SPADUS are components on NASA's current Cassini
mission to Saturn and the Stardust mission to Comet Wild 2 (pronounced
"Vilt" 2). Similar Chicago-built dust instruments also flew aboard the
Russian Vega 1 and 2 spacecraft that visited Comet Halley in 1986.

Simpson and Tuzzolino built Cassini's High Rate Detector (HRD), part of
a larger instrument, the Cosmic Dust Analyzer from Germany, which will
collect and analyze dust particles found in interplanetary space and
those that form the major components of Saturn's rings.

On Dec. 31, 1998, the HRD was turned on for the first time since
Cassini's launch on Oct. 15, 1997, for three weeks of testing. The HRD,
which is working fine, will be turned on again in June to collect
several months of data as Cassini flies by Earth to gain
gravity-assisted momentum toward its destination.

Cassini will pass Earth at an altitude of 620 miles this summer.
"That's where the maximum of orbital debris is expected to be,"
Tuzzolino said. "The flyby will be a very exciting period." Tuzzolino
and Simpson, along with McKibben, also are providing the Dust Flux
Monitor instrument for Stardust, which is scheduled for launch Feb. 6.
The $2 million SPADUS instrument is funded by NASA, the Office of Naval
Research, the Naval Research Laboratory and Lockheed Martin.


Radio stations: The University of Chicago has an ISDN line.  Please call
for information. For more news from the University of Chicago, visit
our Web site at

Steve Koppes
University of Chicago News Office
5801 South Ellis Ave. Room 200
Chicago, IL 60637-1473
773-702-8324 (fax)


From Andrew Yee <>

University of Notre Dame
Physics Department
Phone: (219) 631-8297,8298


Prof. David Bennett
University of Notre Dame
(219) 631-8298

Prof. Sun Hong Rhie
University of Notre Dame
(219) 631-8297


AUSTIN, Texas -- Two international teams of astronomers from the United
States, Australia, Japan, and New Zealand have reported the first
observational result on extra-solar planets from a technique known as
gravitational microlensing. They have made use of the chance alignment
of two stars in the inner disk of our Galaxy to probe the vicinity of
the closer, "lens" star for planets. A slight variation in the
brightness of the lensing event is seen, which may be caused by a
planet with a mass between that of the Earth and Neptune at a distance
of about 2 astronomical units (AU).

In addition, the results rule out the possibility that this star has a
planet with a mass of 0.03% or more of the lens star's mass. Such a
planet cannot exist with a star-planet separation of about 1–4 AU
without causing additional variations in the brightness of the lensing
event that are not seen in the data. These results were reported by
Drs. Sun Hong Rhie and David Bennett of the University of Notre Dame at
the meeting of the American Astronomical Society here. "This event
shows that the microlensing technique is able put meaningful
constraints on planets of Neptune's mass, but our goal is to have
sensitivity to planets with masses as low as an Earth mass," says
Bennett. Rhie continues, "The microlensing technique is the only ground
based planet search technique that has been shown to be sensitive to

The observations were carried out by the MPS Collaboration on the 1.9m
(74") telescope at the Mt. Stromlo Observatory near Canberra, Australia
and by the MOA Collaboration on the 0.6m telescope at the Mt. John
Observatory in New Zealand. Drs. Rhie and Bennett are members of the
Microlensing Planet Search (MPS) collaboration, and the work was by MPS
in together with the Microlensing Observations in Astrophysics (MOA)
collaboration. MPS is a group of American and Australian astronomers,
while MOA is a group of astronomers from New Zealand and Japan.

The slight change in brightness that is observed is consistent with the
signal expected for a planet with a mass fraction of 0.002% and 0.01%
of the star's mass. The uncertainty is caused by the fact that the
observed brightness variation is not a great deal larger than the
measurement uncertainties, and because of this, the possible planetary
detection is not considered to be a definitive discovery. The lens star
has not been directly identified, but it is likely to be less massive
than the Sun. It is probably between 20% and 60% of a solar mass, and
this would put the mass of the possible planet at between an Earth mass
and a Neptune mass.

The event was discovered by the  MACHO Collaboration and announced via
email and the world wide web as MACHO-98-BLG-35 (i.e. the 35th
microlensing event discovered by MACHO toward the Galactic Bulge in
1998).This event reached a maximum magnification factor of about 80
which is about the highest magnification ever observed in a
gravitational microlensing event. The sensitivity of microlensing to
the presence of planets is substantially larger for high magnification
events like MACHO-98-BLG-35 than it is for events of more modest
magnification. This result from the MPS and MOA collaborations
represents the tightest observational constraint to date on extra-solar
planets at separations of 1-4 AU.

The gravitational microlensing planet search technique differs from
other planet search techniques in that it is most sensitive to planets
at a separation of 1-5 AU from their star. Extra-solar planet searches
using the radial velocity technique are sensitive to planets at these
separations, but they are not sensitive to planets below about 0.1% of
the stellar mass due to the intrinsic velocity variations of stellar
atmospheres. In contrast, the microlensing technique is sensitive to
planets down to much lower masses. For example, the MPS and MOA data
can rule out a planet with a mass of 0.01% of the star's mass for most
of the area between 1.5 and 3 AU separation from the star. Even greater
sensitivity can be expected in the future as more and larger telescopes
join the MPS collaboration.

The observation of a planetary signal in a gravitational microlensing
event requires frequent and sensitive observations of microlensing
events in progress, so it is advantageous to carry out these
observations from moderately large (1.5-2 m diameter) telescopes on
each of the temperate Southern Hemisphere continents. The result
reported here is based on observations taken from Australia and New
Zealand. Greater sensitivity and a possible confirmation of the
tentative low mass planet detection could have been achieved if this
event had been observed from South Africa. The MPS Project plans to
expand to include observations from both South Africa and Chile in the
near future, so future events may be observed with substantially better
sensitivity. With a global network of 2m class telescopes, it is
possible to mount an observing campaign that will be sensitive to
planets with masses as small as an Earth mass. The figure shown below
shows an example lightcurve for an Earth mass planet orbiting a star
of 0.3 solar masses.

Gravitational microlensing events occur when a faint or dark star
passes very close to the line of sight to a more distant, brighter
star. The light rays from the brighter star are bent by the
gravitational field of the closer, fainter star resulting in an
observable magnification of the more distant, brighter star. This is a
gravitational lensing effect, but separation of the multiple images of
the lensed star is too small to observe. This is the feature that
distinguishes microlensing from gravitational lensing on extra-galactic

The members of the MPS collaboration are Andrew Becker, David Bennett,
Chris Fragile, Bradley Johnson, Bruce Peterson, Jason Quinn, and Sun
Hong Rhie. Participating institutions include the University of Notre
Dame, the University of Washington, the Mt. Stromlo and Siding Springs
Observatory, and the University of Minnesota.

The MPS collaboration is funded by the National Science Foundation,
NASA's Origins Program, and by a Research Innovation Award from the
Research Corporation.

The members of the MOA collaboration are F. Abe, Ian Bond, B.S. Carter,
R.J.. Dodd, J.B. Hearnshaw, M. Honda, J. Jugaku, S. Kabe, P.M.
Kilmartin, B.S. Koribalski, K. Masuda, Y. Matsubara, Y. Muraki, T.
Nakamura, G.R. Nankivell, S. Noda, N.J. Rattenbury, M. Reid, N.J.
Rumsey, To. Saito, H. Sato, S. Sato, M. Sekiguchi, D.J. Sullivan, T.
Sumi, Y. Watase, T. Yanagisawa, P.C.M. Yock and M Yoshizawa. The
institutions participating in the MOA project are: Nagoya University,
the University of Auckland, the University of Canterbury, the Carter
National Observatory, the University of Tokyo, the Research Institute
of Civilization, the KEK Laboratory, Kyoto University, Victoria
University, the Tokyo Metropolitan College of Aeronautics, and the
National Astronomical Observatory of Japan.

[Image caption:] This
figure shows the lightcurve expected for a planet of 1 Earth mass
orbiting a star of 0.3 solar masses at a separation of about 2
astronomical units. The star must be at a favorable location in its
orbit for such a strong signal to be observed, however.

Relevant WWW links:

* Microlensing Planet Search or MPS Project:
* MOA Project:
* MACHO Project:
* PLANET Collaboration: (another group using microlensing to
  search for planets)


P. Pravec*), M. Wolf & L. Sarounova: Lightcurves of 26 near-Earth
asteroids. ICARUS, 1998, Vol.136, No.1, pp.124-153


We present the results of our photometric observations of 26
near-Earth asteroids (NEAs) in the range of absolute magnitudes
H = 13.6-20.0 (diameters approximately 0.4-8 km). The synodic
periods in the range 2.3-230 h were detected for 25 of them; 21
periods are new and in 4 cases we confirmed earlier determinations.
In 20 cases the synodic periods are interpreted as being the rotation
periods.. Among the 5 exceptions, in two cases there remains an
uncertainty whether the detected period is not half or twice that of
the rotation period, and in another two cases-(3691) 1982 FT and 1997
BR-there were found large deviations of the lightcurve points from
the mean curves that can be due to possible complex rotations of the
small, slowly rotating asteroids. Overall, the short period end (2.3-
3.3 h) of the spin rate distribution shows characteristics that are
consistent with the hypothesis of their ''rubble pile'' structure, as
noted by Harris (Lunar Planet. Sci. XXVII, 493-494); specifically,
there is a ''barrier'' against spins faster than 2.3 h and the
amplitudes of the fast rotating NEAs are smaller in comparison with
the other, longer period NEAs. In the group of slow rotators (P > 12
h), the suggested presence of objects in excited rotation states must
be confirmed by further observations using also different techniques.
This slow rotators group may be actually more abundant than our
results suggest (6 of 25 objects, i.e., 20-30%), since there is a
bias against low-amplitude slow rotators in the groundbased
photometric program. (C) 1998 Academic Press.


R. J. Whiteley*) & D.J. Tholen: A CCD search for Lagrangian asteroids
of the Earth-Sun system. ICARUS, 1998, Vol.136, No.1, pp.154-167


The L4 and L5 points of the Earth-Sun system were imaged using the
University of Hawaii 2.24-m telescope on 1994 May 5-7 and July 6-8
UT. We used a thinned Tektronix 2048 x 2048 CCD, subtending a field
7.5 arcmin on a side. Our objective in this search was to locate
sub-kilometer-sized asteroids orbiting near the libration point or,
failing this, to set a rough upper limit on the number density of
objects contained in such a population. Previous searches of these
areas have used various less sensitive photographic techniques, but
no asteroids have ever been discovered at the L4 or L5 points of the
Earth-Sun system. The limiting sensitivity of this search was R
similar to 22.8, corresponding to C-type asteroids similar to 350 m
in diameter or S-type asteroids similar to 175 m in diameter. No
objects were discovered in the approximately 0.35 square degrees
covered, leading to our crude estimate that the upper limit for the
number density of objects at or above our detection threshold is
approximately 3 objects per square degree. In this paper, we discuss
the various considerations governing our search strategy. We also
discuss the relevence of this search technique in looking for
near-Earth asteroids in general. Finally, in this paper we point out
areas of future theoretical work that can yield important information
on Earth's libration regions, and we discuss the outlook for using
large mosaic arrays in future asteroid searches of this nature. (C)
1998 Academic Press.


From Andrew Yee <>

A 36-page PDF version of the Stardust press kit (621KB) is available at .


From ABCNews.Online

New Analysis Finds Error in Computer Program

By Lee Bowman
Scripps Howard News Service

Jan. 14 — Federal researchers are backing away from a year-old study
that found suicide rates rose dramatically in the years following a
natural disaster.

The researchers from the Centers for Disease Control and Prevention
in Atlanta said they recently discovered an error in a computer
program that caused suicide deaths occurring in 1990 to be
double-counted in their study.

“After the error was corrected, a new analysis showed no significant
increase in suicide rates after natural disasters, either for all
types of disasters combined or for individual types of disasters,”
said the team, led by Dr. Etienne Krug, an epidemiologist with the
National Center for Injury Prevention and Control.

The original findings, published last February in The New England
Journal of Medicine, were widely reported. They showed suicide rates
in the year after an earthquake rising by as much as 62 percent and
by a third in the two years after a hurricane. The research was cited
as evidence that post-disaster mental health services should be

The study was the most sweeping look at suicide rates in disaster
zones ever done in the United States. The researchers traced suicides
in 377 counties where a disaster severe enough to warrant federal
relief struck between 1983 and 1989.

An Unusual Year for Disasters

The final year of the study was an unusual year for disasters, with
Hurricane Hugo hitting the Carolinas and the Loma Prieta earthquake
striking northern California within just a few weeks.

Although retracting their study in a letter to the journal, the team
noted that a second analysis of suicide rates in 70 counties affected
by two disasters did find an average  increase of almost 15 percent
in the two years following the second disaster compared with the
rates in the two years before the first event. That result was
obtained using a different computer program and still stands.

The researchers noted that much other research shows that victims of
severe disasters suffer many types of psychological distress, and
that despite the mistake, “it’s still clear there is a need for
mental health support among victims of severe disasters,” Krug said.

Copyright 1999 Scripps Howard News Service.

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    Louis Friedman <>

    Austen Atkinson <>


From Louis Friedman <>

A reply to Pete Worden and Jim Benson on the motivation for space

Col. Worden's and Jim Benson's juxtaposed comments in your CCN
newsletter today were interesting. Col. Worden noted that overriding
national interests will be required for human exploration in space,
while Mr. Benson said it is not for government at all, it'll have to
be done privately. On the latter point Col. Worden is exactly right --
it is ridiculous to suppose enough practical benefits for private
funding of exploration. There might be private funding of some gimmicks
(like the Mars Company lady and Japanese journalist who flew on Mir, or
like proposed tourist ideas) but that has nothing to do with science or
exploration and will probably be as useful as that Japanese journalist
trip. Exploration is ONLY going to happen with government support,
and like Col Worden says -- it will require  a real coming together of
motivations. Curiousity and adventure, national and international
achievement, may be such motivations -- and those may find a political
niche related to some of the historic military objectives, especially
in the new world of the new century. It is up to us to help develop
that rationale.

Louis Friedman


From Austen Atkinson <>

Benson is right of course. He is a man with enough guts and commercial
savvy to make the dream a reality. SpaceDev owns a raft of subsidiary
companies (including SIL in the UK) carefully selected to ensure that
the company could design, construct and launch their own spacecraft
(Near Earth Asteroid Prospector is the first). This is reality: a
company is going to space: rendezvous Nereus 2002.

No amount of political subsidy can create the perception shift that
Benson's talking about. If we can buy a piece of space on the stock
market, then it becomes real, a commodity. Exploitation might seem like
a dirty word, but if we want to get "out there" then the only realistic
way is to industrialise space.

Remember, governments are ephemeral, the real power brokers are
international corporations and conglomerates. They might not be
eternal, but their Chairmen generally enjoy longer periods in office
than any politician. They also have more power: the Senate can veto a
plan, few would argue with a C.E.O. who commands a workforce of several
million people. Benson would know about the impotence of politicians,
he advised Jimmy Carter on environment and energy.

I'm tired of hearing about irrelevant Earth-space interface projects.
We have the technology for interplanetary (I'm including small bodies
in that) travel. Let's do it before we all grow old and die talking
about it.

Austen Atkinson
Author & TV Producer

CCCMENU CCC for 1999