1. Lindley Johnson Program Executive NASA HQ 29 Sep 2010
Opportunities for Near Earth Object Exploration Future In-Space Operations Colloquium
Lindley Johnson
Program Executive
NASA HQ
29 Sep 2010

2. Terminology
“Near Earth Objects (NEOs)”- any small body (comet or asteroid) passing within 1.3 Astronomical Unit (AU) of the Sun
1 AU is the distance from Earth to Sun = ~ 150 million kilometers (km)
NEOs are predicted to pass within ~ 45 million km of Earth’s orbit
Population of:
Near Earth Asteroids (NEAs)
Near Earth Comets (NECs) – also called Earth Approaching Comets (EACs)
85 currently known
“Potentially Hazardous Objects (PHOs)” – small body that has potential risk of impacting the Earth at some point in the future
NEOs passing within 0.05 AU of Earth’s orbit
~ 8 million km = 20 times the distance to the Moon
Appears to be about 20% of all NEOs discovered
Human mission accessible objects are a subset of PHOs
Perhaps a reminder of terminology is in order. Astronomers have defined Near Earth Objects, or NEOs, as any small planetary body, those being comets or asteroids, whose orbits pass within 1.3 astronomical units of the Sun, with an astronomical unit being the mean distance of the Earth from the Sun over the course of its orbit, approximately 150 million kilometers. NEOs are therefore predicted to pass within 45 million kilometers of the Earth’s orbit – a large distance, but relatively close by Solar System standards. The population of these objects is often separated and referred to as either Near Earth Asteroids or Near Earth Comets, sometimes also called Earth Approaching Comets, of which 84 are currently known.
In actuality, the majority of these objects will pose no impact hazard to the Earth, so we are more intensely interested in a subset of them called the Potentially Hazardous Objects which do physically pose a risk of someday colliding with the Earth. These are objects whose orbits carry them within five hundredths of an AU of the Earth’s orbit. This is within about 8 million kilometers distance, or the equivalent of twenty times the distance to the Moon - truly very close by Solar System standards. However, it appears from our discoveries to date that about twenty percent of NEOs must be considered as potentially hazardous to the Earth.

3. Earth’s Cratered Past

4. Our “Big Buddy” Jupiter
Our “Big Brother “ Jupiter continually takes hits from relatively large objects, including two sighted this summer.
The impact of comet Shoemaker-Levy 9 in July 1994 brought both astronomical and media attention to the impact threat

5. “The Hard Rain” Fireball Data Points 2003 - 2005
U.S. early warning satellites detected a flash that indicated an energy release comparable to the Hiroshima burst. We see about 30 such bursts per year, but this one was one of the largest we have ever seen. The event was caused by the impact of a small asteroid, probably about 5-10 meters in diameter, on the earth's atmosphere.
--Statement of Brigadier General Simon P. Worden, Deputy Director for Operations, United States Strategic Command before
the House Science Committee Space and Aeronautics Subcommittee on Near-Earth Object Threat October 3, 2002
Fireball Data Points

6. Impact Frequencies and Consequences
Type of Event
Diameter of
Impact Object
Impact Energy(MT)
Average Impact
Interval (years)
High altitude break-up
< 30 m
<5
1 - 50
Tunguska-like event
> 30 m
>5
Regional event
> 140 m
~150
5,000
Large sub-global event
> 300 m
~2,000
25,000
Low global effect
> 600 m
~30,000
70,000
Medium global effect
> 1 km
>100K
1 million
High global effect
> 5 km
> 10M
6 million
Extinction-class Event
> 10 km
>100M
100 million

7. Effects of TUNGUSKA EVENT
June 1908 – 100 years ago

8. NEO Observation Program
US component to International Spaceguard Survey effort
Has provided 98% of new detections of NEOs
Began with NASA commitment to House Committee on Science in May, 1998
Averaged ~$4M/year R&A funding since 2002
Scientific Objective: Discover 90% of NEOs larger than 1 kilometer in size within 10 years (1998 – 2008)
NASA Authorization Act of 2005 provided additional direction (but no additional funding)
“…plan, develop, and implement a Near-Earth Object Survey program to detect, track, catalogue, and characterize the physical characteristics of near-Earth objects equal to or greater than 140 meters in diameter in order to assess the threat of such near-Earth objects to the Earth. It shall be the goal of the Survey program to achieve 90 percent completion of its near-Earth object catalogue within 15 years [by 2020].
An asteroid one kilometer in size, were it to collide with our planet at about twenty kilometers per second, would penetrate the atmosphere in less than ten seconds and cause catastrophic damage to any country and have long term effects with global consequences. It is for that reason the initial objective of our program was to discover at least ninety percent of these natural objects of one kilometer or larger within the ten year period from 1998 to The average annual budget of the program has been about four million US dollars. However, the US Congress has since provided NASA additional direction to investigate systems to extend the search down to objects of only 140 meters in size and attempt to achieve ninety percent completeness of this effort by the end of 2020.

9. NASA’s NEO Search Program (Current Systems)
Minor Planet Center (MPC)
IAU sanctioned
Int’l observation database
Initial orbit determination
NEO Program JPL
Program coordination
Precision orbit determination
Automated SENTRY
NEO-WISE
JPL
Sun-synch LEO
Catalina Sky
Survey
UofAZ
Arizona & Australia
Pan-STARRS
Uof HI
Haleakula, Maui
LINEAR
MIT/LL
Soccoro, NM
Since the program’s inception, NASA has funded several universities and space institutes to upgrade and operate existing one meter class telescopes to conduct the search. Of critical importance to the effort is also the Minor Planet Center of the Smithsonian Astrophysical Observatory, where automated systems process in near real-time observations produced by the search teams. and NASA’s NEO Program Office at the Jet Propulsion Laboratory, where precision orbits on the objects are produced and projected forward in time. Both these data processing and analysis centers utilize processes and procedures for NEO orbit determination and prediction that are sanctioned and monitored by the International Astronomical Union, and they produce data catalogues on small bodies in the Solar System that are utilized world-wide by the astronomical community. The web site links shown here for those two facilities will provide a wealth of information on our search efforts and what is known about NEOs.
At the peak of our early search efforts, we had five separate teams operating nine different telescopes . However, since 2008, only two of those original teams, LINEAR and Catalina, continue to operate because the remaining objects are simply too difficult to detect by the less capable systems. However, for the last two years we have also supported development efforts to bring two additional NEO search capabilities on-line, the USAF Panoramic Survey Telescope and Rapid Reporting System (Pan-STARRS), and the enhancement in processing of images returned from our recently launched Widefield Infrared Survey Explorer (WISE) in order to detect asteroids moving across its field of view, which we call NEOWISE.

10. Discovery Metrics Discovery Rate of >1km NEOs
This diagram depicts the number of one kilometer object discoveries by lunation, or lunar cycle – new moon to new moon, over the last ten years. The initial discovery rate increased for a few years as new search assets came online, but the rate leveled off in the 2001 through 2002 time period. That was the peak of discoveries of one kilometer size objects when we averaged seven to eight discoveries per month. However, as would be expected, after we had found a significant portion of the population the new discoveries get harder to make if no new capability was added. Therefore our discovery rate has tapered off. In the last year our average has dropped to only two per month, although there are still some peaks when the weather is good and skies clear in the American Southwest, where most of our search observatories are, but also some bad months due to weather or equipment problems. The observed drop off in discovery rate can be clearly seen in the graph, meaning we have now found the better part of the one kilometer population.

11. Discovery Metrics } 903* (85-95%) as of 9/27/10 *Includes 85 NECs
Estimated
Population
Goal
Achieved minimum goal
903*
(85-95%)
as of
9/27/10
*Includes
85 NECs
6393 smaller
objects also found
This plot assesses our progress toward obtaining our objective of finding 90% of the one kilometer sized NEOs. The estimated population is nine hundred forty to one thousand fifty objects, including Near Earth Comets (NECs), so 90% would be eight hundred fifty to nine hundred forty in round numbers. At of the end of 2008, the NEO search projects had found eight hundred forty eight NEOs estimated at one kilometer or larger, to include eighty some comets, and as of the end of this August we’ve found nine hundred and one. Although it appears we have done well to achieve our objective, we are auditing the numbers of asteroids and comets we now have in the catalog for their currency of data, and we continue to search for more objects. NASA intends to continue funding the NEO Observations Program through at least 2012.

12. Known Near Earth Asteriod Population
Start of
NASA NEO
Program
One reason we will continue to search is that even if the one kilometer population is completely known, there are still multitudes of unknown objects a few hundred meters in size that could do significant damage at the surface were they to impact the Earth. Population estimates predict these smaller but still dangerous objects may approach 100,000 in number. To date we have only found somewhat over six thousand.

13. Population of NEAs by Size, Brightness,
Impact Energy & Frequency (Harris 2006)
300,000
50 m
Numbers (powers of 10)
20,000
140 m
1,000
1 km

14. Known Near Earth Asteroid Population
85%
~40%
~8%
< 1%
<< 1%
One reason we will continue to search is that even if the one kilometer population is completely known, there are still multitudes of unknown objects a few hundred meters in size that could do significant damage at the surface were they to impact the Earth. Population estimates predict these smaller but still dangerous objects may approach 100,000 in number. To date we have only found somewhat over six thousand.

15. Recent Close Approaches
Two Small Asteroids Pass Close by Earth on September 8, 2010

16. Missions to NEOs Opportunities and Constraints

17. Encounters to Date YEAR MISSION OBJECT NEO FLYBY ORBITAL SAMPLE 1985
ISEE-3/ICE
C/Giacobini-Zinner X
1986
Vega 2
C/Halley
1991
Galileo
Gaspra
1993
Ida (& Dactyl
1997
NEAR
Mathilda
1999
Deep Space 1
Braille
2000
Eros
2001
C/Borrelly
2002
Stardust
AnneFrank
2004
C/Wild 2 X 
2005
Deep Impact
C/Tempel 1
Hayabusa
Itokawa X?
2008
Rosetta
Steins
2010
Lutetia

18. Near Earth Asteroid Rendezvous (NEAR)
First Discovery-class mission
Launched February 1996
Flyby Mathilde June 1997
Accidental Flyby Eros December 1998
Started Eros orbit February 2000
End of Mission February 2001
Touch down on Eros!

19. Deep Impact Discovery 8 mission Launched January 2005
Probe impacts Tempel 1 July 4th, 2005
Main spacecraft flies by
Begins EPOXI mission in 2007

20. Hayabusa (Muses-C) Japanese space agency mission Launched May 2003
Arrived Itokawa September 2005
Sample collection attempt Nov 2005
Started return April 2007
Sample Capsule returned June 2010

21. Comparing Asteroids (and Comet Nuclei)

22. Comparing Asteroids
Itokawa

23. The Future Encounters YEAR MISSION OBJECT NEO FLYBY ORBITAL SAMPLE
FUTURE ENCOUNTERS
2010
EPOXI
C/Hartley 2 X
2011
Stardust NExT
C/Tempel 1
Dawn
Vesta
2014
Rosetta
C/Churyumov-Gerasimenko
2015
Ceres
PROPOSED MISSIONS
OSIRIS-Rex
1999 RQ36
xPRM
Potential HSF Destinations
Marco Polo
Various
Don Quijote'
2003 SM84?

24. Exploration Precursor Robotic Missions (xPRM)
xPRM to be uniquely poised to provide critical Strategic Knowledge for Exploration for diverse set of destinations.
xPRM starting in this decade would enable Human Exploration in the next.
Analogous to robotic Surveyor landers ahead of Apollo human missions
Proposed scope uniquely focuses on HSF objectives while leveraging unique capabilities of partners.
No other program would fulfill this objective.
Fully consistent with current best estimate objectives for future HSF at NASA
CY 
2014
2015
2016
2017
2018
xPRP
NEO
Lunar Lander
Mars
MoOs
MOO1
MOO2
MOO3
MOO4
MOO5
xScouts
xS1 - NEO
xS2
xS3
xS4 24
NOTIONAL Point of Departure – Subject to Change

25. Why Missions to NEOs? Planetary Science Human Space Exploration
Material represents the most primitive building blocks of Solar System
Human Space Exploration
Early destinations for push out into Solar System
Unique Resources
For exploration of space and return to Earth
Planetary Defense
To design and test methods to deflect impactors

26. HSF NEO Mission Constraints
Preliminary outline of possible constraints for human mission success and safety:
Accessible with projected capability = < 7.5 (?) km/sec dV
Mission less than 180 (?) days round trip
Return entry velocity less than 12 km/sec
Greater than 50 meter sized object
Object in simple axis, slow rotation
Accessible by robotic precursor mission at least 3 years prior to crew launch

27. NEO Human-spaceflight Accessible Targets Study (NHATS) Preliminary Results

28. NEO Human spaceflight Accessible Targets Study (NHATS) Preliminary Results

29. Population of NEAs by Size, Brightness,
Impact Energy & Frequency (Harris 2006)
300,000
50 m
Numbers (powers of 10)
20,000
140 m
1,000
1 km
Need to find objects in this population

30. Population estimates
One-way Delta-v
Accessible range in semi-major axis
Accessible range in eccentricity
Accessible range in inclination
Estimated number of NEOs >30 m diameter*
3 km/s
0.789–1.201
<0.168
<5.77°
170
5 km/s
0.664–1.336
<0.251
<9.62°
710
*Based on NEO population studies of Bill Bottke, et al

31. “NEOStar” Concept
Spitzer
Kepler
“NEOStar” X ≈

34. Bottomline:
For finding Human Exploration targets, a telescope in a Venus-like orbit is the most technically viable option
~400 potential targets from 2 years of observing
For Planetary Defense (detection & tracking of all PHOs), an IR telescope in a Venus-like orbit speeds up the search by a decade