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NEO News - May 25, 1999

Forwarded from Dave Morrison:

NEO News (5/25/99): NASA NEO Search Program

Dear Friends and students of NEOs:

NASA, in collaboration with the US Air Force, is moving to implement a
search program to meet the objectives of the Spaceguard Survey, as set down
in the NASA Spaceguard reports of 1992 and 1995.  About a year ago I
reported on the testimony of NASA planetary exploration Theme Director Carl
Pilcher concerning the NASA commitment to the Spaceguard goal of
discovering 90% of NEAs (D > 1 km) within the next decade. NASA has been
working jointly with the US Air Force Space Command (AFSPC) and the
National Reconnaissance Office (NRO) of the US government to further
develop plans to meet this requirement.  At a May 11, 1999, meeting of the
Steering Group for the NASA NEO Program Office, additional details were
reported.

A presentation by Lt. Col. Lindley Johnson (AFSPC liaison officer to the
NRO) stated the joint agency search goal as "To the extent practicable, the
National Aeronautics and Space Administration, in coordination with the
Department of Defense and the space agencies of other countries, shall
identify and catalog within 10 years the orbital characteristics of all
comets and asteroids that are greater than 1 km in diameter and are in an
orbit around the Sun that crosses the orbit of the Earth."

In November 1998, the joint agency Partnership Council directed the NEO
Task Team to staff its recommendations through their respective
headquarters to include specific costs, schedule, and trade space of
options and their ability to meet the stated goal.  These studies concluded
that the NEO detection goal can be accomplished with current hardware and
funding, meeting the goal by the end of 2009.

The near-term actions to implement this goal are the expansion of the
Lincoln Lab (MIT) LINEAR program to use a second 1-m telescope in New
Mexico, so that LINEAR will operate 2 telescopes each at 18 nights/month.
An effort will also be made to extend operations of the NEAT (JPL) detector
on the 1-m USAF GEODSS telescope in Hawaii from 6 to 18 nights/month.
Farther in the future, the agencies will transition the NEAT search to a
1.2-m telescope at Hawaii, and the possibility will be investigated for
expanding the search to use additional AFSPC telescopes.  The general plan
in all these observing programs is for AFSPC to provide the telescopes and
NASA to support the operations associated with NEO searches.

A more detailed statement of the search strategy and requirements is
contained in a letter from NASA Administrator Daniel Goldin to General
Richard B. Meyers, Commander in Chief of the Space Command, dated April 6,
1999.  In part, Mr. Goldin wrote:  "Succinctly stated, the requirement is
to search 20,000 square degrees of sky each month and to detect all moving
objects in that search space to an apparent visual magnitude of 20.5.
Analysis, to date, on the characteristics of the small but significant
population of NEOs observed, indicate this depth in magnitude and monthly
sky coverage will enable us to inventory at least 90 percent of the entire
population of large NEOs (>1 km) within 10 years of the start of the
survey, a goal established by the congressional direction given us.

"Currently, there are two search projects that are funded by NASA but which
rely heavily on Air Force support.  We believe these projects together,
when they reach their full potential, will provide the primary means for
achieving the above goal.  The first is the Lincoln Near Earth Asteroid
Research (LINEAR) project, funded by NASA, but which uses both
state-of-the-art detector systems developed for the Air Force and two Air
Force telescopes at the Experimental Test Site (ETS) at Socorro, New
Mexico.  The second is the Near Earth Asteroid Tracking (NEAT) project
which is currently being supported on one of the operational Maui Ground
Electro-Optical Deep Space Surveillance telescopes.

"Cooperative discussions with the Air Force Space Command have led to the
identification of an Air Force Research Laboratory 1.2 meter telescope at
the Maui site for use by NEAT.  If the NEAT camera can be accommodated on
this telescope, it will enable the NEAT project to continue making an
important contribution to the search effort at the dimmer magnitudes, while
allowing the heavily used GEODSS telescope (now used part-time to support
NEAT) to be returned to full time space surveillance operations.

"We believe that the two LINEAR telescopes (one currently operating and a
second scheduled for future operation) at the ETS and the NEAT camera on
the 1.2m at Maui, if operated in close coordination, will be able to search
20,000 square degrees of sky per month for all NEOs brighter than magnitude
20.5. This year our funding for all phases of NEO survey work, including
discovery, follow-up, ground-based characterization, support of the Minor
Planet Center, and our new program office at the Jet Propulsion Laboratory
(JPL) in Pasadena, California, is $3.5M.  NASA is committed to sustaining a
vigorous search effort until the stated goal is reached.  We solicit your
continued support to these two projects so important to the success of the
NEO survey effort.

"We briefly note that our ground-based survey work on NEOs is but a small
part of NASA's total program of studying the comets and asteroids that
comprise the NEO population.  Space-based efforts include NASA's Near Earth
Asteroid Rendezvous (NEAR) mission, which will spend a year closely
studying the near-Earth asteroid Eros.  The Deep Space-1 spacecraft, an
exciting technology mission, will study the asteroid 1992 KD.  The recently
launched STARDUST spacecraft will return cometary dust samples to the Earth
in early 2006.  NASA has selected another mission, the Comet Nucleus Tour
(CONTOUR) mission, to investigate three diverse cometary nuclei.  In
addition, NASA is a partner on two non-US missions, the ROSETTA mission
which will perform a landing on a cometary nucleus and the Japanese MUSES-C
mission which will return a sample from a near Earth asteroid.  The data
returned from these missions on the physical and chemical nature of the
target bodies will be absolutely vital if we are presented with a future
need to modify the orbit of an Earth-threatening NEO."

The above statements by Lt. Col. Johnson and NASA Administrator Goldin
provide a clear and highly specific statement of the NASA and USAF goals
and their strategy for meeting these goals.  Probably the most difficult
task is to achieve NEA detection at V = 20.5 with the 1-m USAF telescopes,
which have previously been used for more rapid surveys that do not extend
this deep. To achieve the Spaceguard goals, the three NASA-AFSPC
telescopes, as well as others supported by NASA (such as Spacewatch,
LONEOS, and the Catalina Survey) will need to be coordinated to work
together as a team. LONEOS and Catalina are both still in their test
phases, and improvements are expected in each over the coming months. In
addition, if the anticipated discovery rate is achieved, it will be
necessary to enhance the follow-up capability on other telescopes,
primarily through international agreements.  In this coordinated search, it
will not be possible for the discovery telescopes to do their own
follow-up, a topic discussed extensively by NASA's Shoemaker Committee in
its 1995 report on the Spaceguard Survey.

Meanwhile, following is a snapshot of current discovery performance
prepared by Al Harris of JPL.  The values in the table are the numbers of
NEOs brighter than absolute magnitude 18.0 (i.e., D > 1 km) discovered in
successive 6-month periods.

NEA DISCOVERY SUMMARY (D > 1 km) JULY 97 THRU JUN* 99

Discoverer	97(2)	98(1)	98(2)	99(1)
------------------------------------------------------------------------
LINEAR		 2	10	26	 21
NEAT		 3	 5	 2	  0
Spacewatch	 1	 2	 1	  5
LONEOS		 0	 0	 4	  3
Catalina	 0	 0	 0  	  3
Other		 2	 2	 2	  2
------------------------------------------------------------------------
Total		 8	19	35	 34

* Scaled from actual discoveries Jan-Apr 1999.

We have so far discovered about 18% of the NEAs larger than 1 km.  The
current discovery rate is approximately 70/yr, dominated by the LINEAR
program (using one telescope). The current performance of the survey is
roughly a factor of 5 below that required to meet the Spaceguard goals
using the criteria that Harris has applied in the past.  In a recent
re-evaluation of these criteria, Harris now suggests that at this point in
the survey, we should be discovering about 500/year, or a factor of 7 more
than at present.  However, Harris also notes that there is considerable
uncertainly in this figure, and additional modeling would be useful.  He
will be speaking on this subject at the IMPACT workshop in Torino in June
1999.

The expansion of LINEAR to two telescopes and the increased performance
anticipated from NEAT could bring this system performance to within a
factor of 2-3 of that required if the 1-m telescopes can achieve detections
at magnitude 20.5.  Additional modeling of the total performance of these
instruments used in a coordinated manner will have to be done, as well as
actual experience to determine if performance at V = 20.5 is realized.
Clearly, however, we have made tremendous strides in the past year, and
NASA with its USAF partners has a goal to complete the survey (to 90%) by
2009.

	*	*	*	*	*	*	*

For your information, following is the membership of NASA's NEO Program
Office Steering Group (where IAU = International Astronomical Union):

Michael A'Hearn, President of the Solar System Division of the IAU
Andrea Carusi, President of the Spaceguard Foundation
Paula Cleggett, Deputy Associate Administrator, NASA Public Affairs Office
Timothy Ferris, University of California, author
Lindley Johnson, Lt. Col., US Air Force Space Command
David Morrison, President of the IAU Working Group on NEOs
Hans Rickman, Assistant Executive Secretary of the IAU
Irwin Shapiro, Director of the Harvard-Smithsonian Observatories

Also:

Donald Yeomans, NASA NEO Program Manager, JPL
Carl Pilcher, NASA Solar System Exploration Theme Director
Tom Morgan, NASA Planetary Astronomy Discipline Scientist

		*	*	*	*	*	*	*

In a separate news item, the Authorization Committee of the US House of
Representatives has passed a 3-year bill for NASA that authorizes
expenditure of up to $10.5M for NEO searches for each of the next three
fiscal years.  This represents an increase of $7M per year over the current
and anticipated NASA rate of expenditure for this purpose.  This
authorization is a clear statement of interest from Congress in pursuing
the Spaceguard Survey.  However, to actually be translated into additional
funds for NASA, this House authorization would have to be supported by
similar action in the Senate Authorization Committee, plus be voted by the
full House and Senate, plus be supported by the respective House and Senate
appropriation committees, plus be passed as an appropriation by both House
and Senate, plus be approved by the President.  Sorry folks, but that is
the process for appropriation of funds in the United States!

David Morrison

+++++++++++++++++++++++++++++++++++++++++++

David Morrison, NASA Ames Research Center
Tel 650 604 5094; Fax 650 604 1165
david.morrison@arc.nasa.gov or dmorrison@mail.arc.nasa.gov
website: http://space.arc.nasa.gov
website: http://astrobiology.arc.nasa.gov
website: http://impact.arc.nasa.gov

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