Tag Archives: JPL

Near-Earth Object (NEO) Sky Surveys and Data Analysis are Refining our Understanding of the Risk of NEO Collisions with Earth

It seems that every week or two there is a news article about another small asteroid that soon will pass relatively close to the Earth. Most were detected while they were still approaching Earth. Some were first detected very shortly before or after their closest approach to Earth. That must have made the U.S. Planetary Defense Officer a bit nervous, but then, what could he do about it? (See my 21 January 2016 post, “Relax, the Planetary Defense Officer has the watch”).

While we currently can’t do anything to defend against NEOs, extensive worldwide programs are in place to identify and track NEOs and predict which NEOs may present a future hazard to the Earth. Here’s a brief overview of the following programs.

  • NASA Wide-field Infrared Survey Explorer (WISE)
  • International Astronomical Union’s (IAU’s) Minor Planet Center (MPC)
  • NASA’s Center for Near Earth Object Studies (CNEOS)
  • National Optical Astronomy Observatory (NOAO) NEO sky survey
  • University of Arizona Lunar and Planetary Laboratory

NASA’s Wide-field Infrared Survey Explorer (WISE)

WISE was an Earth orbiting infrared-wavelength astronomical space telescope with a 40 cm (16 in) diameter primary mirror. WISE operated from December 2009 to February 2011 and performed an “all-sky” astronomical imaging survey in the 3.4, 4.6, 12.0 and 22.0 μm wavelength bands. NASA’s home page for the WISE / NEOWISE mission is at the following link:


NEOWISE is the continuing NASA project to mine the WISE data set. An important data mining tool is the WISE Moving Object Processing System (WMOPS), which has been optimized to enable extraction of moving objects at lower signal-to-noise levels. A comet detection is shown in the following multiple images that have been combined to show the comet in four different positions relative to the fixed background stars.

Comet C/2013 A1 Siding Spring. Source: NASA/JPL-Caltech

To date, the NEOWISE data mining effort has resulted in the following:

  • Detection of ~158,000 asteroids at thermal infrared wavelengths, including ~700 near-Earth objects (NEOs) and ~34,000 new asteroids, 135 of which are NEOs.
  • Detection of more than 155 comets, including 21 new discoveries.
  • Determination of preliminary physical properties such as diameter and visible albedo for nearly all of these objects.
  • Estimation of the numbers, sizes, and orbital elements of NEOs, including potentially hazardous asteroids
  • Results have been published, enabling a range of other studies of the origins and evolution of the small bodies in our solar system.

The output from NEOWISE is delivered to NASA’s Planetary Data System (PDS), which NASA describes as follows:

“The PDS archives and distributes scientific data from NASA planetary missions, astronomical observations, and laboratory measurements. The PDS is sponsored by NASA’s Science Mission Directorate. Its purpose is to ensure the long-term usability of NASA data and to stimulate advanced research. All PDS data are publicly available and may be exported outside of United States under ‘Technology and Software Publicly Available’ (TSPA) classification.”

The link to the NASA Planetary Data System is here:


International Astronomical Union’s (IAU’s) Minor Planet Center (MPC)

The MPC describes itself as the “single worldwide location for receipt and distribution of positional measurements of minor planets, comets and other irregular natural satellites of the major planets. The MPC is responsible for the identification, designation and orbit computation for all of these objects.”

The MPC home page is here:


On this website, MPC lists the following 2017 summary statistics:

Source: MPC

The MPC website offers several short videos that explain the NEO hazard and the challenges of detecting these small objects and determining their orbital parameters with high precision. Key points made in the MPC videos include:

  • The Earth’s cross-section represents only 1/10,000th of the area of the near-Earth region. Earth is a relatively small target area for a NEO.
  • To determine if a NEO is a potential hazard, its orbital parameters must be established with a precision of greater than 1/100th of 1%.
  • There is a “zone of discoverability” (green area in the following diagram) that varies primarily by the size of the object and the aspect of its lighted side to observers on Earth. If an object is outside this rather small zone, then current sky survey instruments cannot detect the object. An example is the 15 February 2013 atmospheric blast that occurred near Chelyabinsk, Russia. This event was caused by a previously undetected NEO that approached Earth at a high relative velocity from the direction of the Sun and vaporized in the Earth’s atmosphere.

            Zone of discoverability (green area). Source: screenshot from MPC video “Asteroid Hazards, Part 2: The Challenge of Detection”

 NASA’s Center for Near Earth Object Studies (CNEOS)

CNEOS is NASA’s center for computing asteroid and comet orbits with high precision and estimating the probability of a future Earth impact. CNEOS is operated by the California Institute of Technology (Caltech) Jet Propulsion Laboratory (JPL) and supports NASA’s Planetary Defense Coordination Office.

The CNEOS home page is here:


CNEOS is the home of JPL’s Sentry and Scout programs:

  • The Sentryimpact monitoring system performs long-term analyses of possible future orbits of hazardous asteroids, searching for impact possibilities over the next century.
  • TheScout system monitors the IAU’s MPC database for new potential asteroid discoveries and computes the possible range of future motions even before these objects have been confirmed as discoveries.

The average distance between the Earth and the moon is about 238,855 miles (384,400 km), which equals 1 LD. On the CNEOS website, you can view data on NEO close approaches to Earth at the following link:


By adjusting the table settings and sorting by a specific column heading, you can create customized views of the close approach data. Just looking at data from the past year for NEOs that passed Earth within 1 LD yielded the following results:

  • 48 NEOs passed within 1 LD of Earth.
  • For these NEOs, object diameters were in the range from 1.8 to 83 meters (5.9 to 272 feet). The NEO that caused the 2013 Chelyabinsk blast was estimated to have a diameter of 10 to 20 meters (32.8 to 65.6 feet).
  • Their relative velocities were in the range from 4.02 to 23.97 km/s (8,992 to 53,620 mph). The NEO that caused the 2013 Chelyabinsk blast was estimated to have a relative velocity of 19.16 km/s (45,860 mph).
  • In the past year, the closest approach was by object 2017 GM, which had a “CA Distance Minimum” (3-signa estimate, measured from Earth center to NEO center) of 0.04 LD, or 15,376 km (9,554 miles). After subtracting Earth’s radius of 6,371 km (3,959 miles), object 2017 GM cleared the Earth’s surface by 9,005 km (5,595 miles).

Looking into the future, the CNEOS close approach data shows two objects that currently have values of “CA Distance Minimum” that are less than the radius of the Earth, indicating that impact is possible:

  • Object 2012 HG2: close approach date on 13 February 2047; modest size of 11 – 24 meters (36 – 79 feet); low relative velocity of 4.36 km/sec (9,753 mph)
  • Object 2010 RF12: close approach date of 6 September 2095; modest size of 6.4 – 14 meters (21 to 46 feet); modest relative velocity of 7.65 km/sec (17,112 mph)

So it looks like we have less than 30 years to refine the orbital data on object 2012 HG2, determine if it will impact Earth, and, if so, determine where the impact will occur and what mitigating actions can be taken. Hopefully, the U.S. Planetary Defense Officer is on top of this matter.

National Optical Astronomy Observatory (NOAO) NEO sky survey

On 30 August 2017, NOAO issued a press release summarizing the results of a survey of NEOs conducted using the Dark Energy Camera (DECam) on the 4 meter (157.5 inch) Blanco telescope at the Cerro Tololo Inter-American Observatory in northern Chile.

“Lori Allen, Director of the Kitt Peak National Observatory and the lead investigator on the study, explained, ‘There are around 3.5 million NEOs larger than 10 meters, a population ten times smaller than inferred in previous studies. About 90% of these NEOs are in the Chelyabinsk size range of 10-20 meters.’”

“David Trilling, the first author of the study,…explained…..‘If house-sized NEOs are responsible for Chelyabinsk-like events, our results seem to say that the average impact probability of a house-sized NEO is actually ten times greater than the average impact probability of a large NEO.’”

You can read the NOAO press release here:


You can read the draft paper, “The size distribution of Near Earth Objects larger than 10 meters,” (to be published in Astronomical Journal) here.


University of Arizona Lunar and Planetary Laboratory

In October 2017, astronomer Vishnu Reddy presented data on an intriguing NEO known as 2016 HO3, that is a “quasi-satellite” of Earth. The announcement is here:


As a “quasi-satellite,” 2016 HO3 is not gravitationally bound to Earth, but its solar orbit keeps 2016 HO3 in relatively close proximity to Earth, but in a slightly different orbital plane. As both bodies orbit the Sun, the motion of 2016 HO3 relative to the Earth gives the appearance that 2016 HO3 is in a distant halo orbit around Earth. The approximate geometry of this three body system is shown in the following diagram, with 2016 HO3’s solar orbit represented in red and the halo orbit as seen from Earth represented in yellow.

Source: www.EarthSky.org

You’ll find a video showing the dynamics of 2016 HO3’s halo orbit on the EarthSky website at the following link:


Observations of 2016 HO3 were made from the Large Binocular Telescope Observatory (LBTO), which is located on Mt. Graham in Arizona. You’ll find details on LBTO at the following link:


Key parameters for 2016 HO3 are: diameter: 100 meters (330 feet); distance from Earth: 38 to 100 LD; composition appears to be the same material as other asteroid NEOs. With its stable halo orbit, there is no risk that 2016 HO3 will collide with Earth.

For additional reading on NEO discovery:

Myhrvold, “Comparing NEO Search Telescopes,” Astronomical Society of the Pacific, April 2016


“I use simple physical principles to estimate basic performance metrics for the ground-based Large Synoptic Survey Telescope and three space-based instruments— Sentinel, NEOCam, and a Cubesat constellation.”


S.R. Chesley & P. Vereš, “Projected Near-Earth Object Discovery Performance of the Large Synoptic Survey Telescope,” JPL Publication 16-11, CNEOS, April 2017


“LSST is designed for rapid, wide-field, faint surveying of the night sky ….The baseline LSST survey approach is designed to make two visits to a given field in a given night, leading to two possible NEO detections per night. These nightly pairs must be linked across nights to derive orbits of moving objects…… Our simulations revealed that in 10 years LSST would catalog 60% of NEOs with absolute magnitude H < 22, which is a proxy for 140 m and larger objects.”



Relax, the Planetary Defense Officer has the Watch

On 7 January 2016, NASA formalized its ongoing program for detecting and tracking Near-Earth Objects (NEOs) by establishing the Planetary Defense Coordination Office (PDCO). You can read the NASA announcement at the following link:


PDCO is responsible for supervision of all NASA-funded projects to find and characterize asteroids and comets that pass near Earth’s orbit around the sun. PDCO also will take a leading role in coordinating interagency and intergovernmental efforts in response to any potential impact threats. Specific assigned responsibilities are:

  • Ensuring the early detection of potentially hazardous objects (PHOs), which are defined as asteroids and comets whose orbits are predicted to bring them within 0.05 Astronomical Units (AUs) of Earth (7.48 million km, 4.65 million miles); and of a size large enough to reach Earth’s surface – that is, greater than 30 to 50 meters (98.4 to 164.0 feet);
  • Tracking and characterizing PHOs and issuing warnings about potential impacts;
  • Providing timely and accurate communications about PHOs; and
  • Performing as a lead coordination node in U.S. Government planning for response to an actual impact threat.

As you can see in the following organization chart, PDCO is part of NASA’s Planetary Science Division, in the agency’s Science Mission Directorate in Washington D.C.  PDCO is led by Lindley Johnson, longtime NEO program executive, who now has the very impressive title of “Planetary Defense Officer”.

Planetary Defense Coordination OfficeSource: NASA PDCO

You can find out more at the PDCO website at the following link:


The PDCO includes the Near Earth Object (NEO) Observation Program, which was established in 1998 in response to a request from the House Committee on Science that NASA find at least 90% of 1 km (0.62 mile) and larger NEOs. That goal was achieved by end of 2010.

The NASA Authorization Act of 2005 increased the scope of NEO objectives by amending the National Aeronautics and Space Act of 1958 (“NASA Charter”) by adding the following new functional requirement:

 ‘‘The Congress declares that the general welfare and security of the United States require that the unique competence of the National Aeronautics and Space Administration be directed to detecting, tracking, cataloging, and characterizing near-Earth asteroids and comets in order to provide warning and mitigation of the potential hazard of such near-Earth objects to the Earth.’’

 This was further clarified by stating that NASA will:

“…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 (459 feet) 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 catalog within fifteen years (by 2020)”

The contractors supporting the NASA NEO Observation Program are Jet propulsion Laboratory (JPL), Massachusetts Institute of Technology (MIT) / Lincoln laboratory, Smithsonian Astrophysical Observatory, University Space Research Association, University of Arizona, and University of Hawaii / Institute of Astronomy.

Once detected, NEO orbits are precisely predicted and monitored by the Center for NEO Studies (CNEOS) at JPL. Their website is at the following link:


The catalog of known NEOs as of 3 November 2015 included 13,206 objects. NASA reports that new NEOs are being identified at a rate of about 1,500 per year. Roughly half of the known NEOs – about 6,800 – are objects larger than 140 meters (459 feet) in diameter. The estimated population of NEOs of this size is about 25,000. Current surveys are finding NEOs of this size at a rate of about 500 per year.  Recent encounters with NEOs include:

  • Asteroid 2015 TB145, the “Halloween Pumpkin”
    • Roughly spherical, about 610 meters (2,000 feet) in diameter
    • Detected 10 October 2015, approaching from the outer solar system, 21 days before closest approach
    • Closest approach occurred on 31 October 2015 at a distance of 310,000 miles (1.3 times the distance to the Moon) at a speed of about 78,000 miles an hour.
  • Asteroid airburst near Chelyabinsk, Russia
    • Airburst occurred 15 February 2013
    • Object estimated to be about 19 meters in diameter
    • Approached from the inner solar system; not detected before airburst
    • Peter Brown at the University of Western Ontario, estimated the energy of the Chelyabinsk airbust at 400 to 600 kilotons of TNT.  You can read this analysis in at the following link:


Another result of the NEO Observation Program is the following map of data gathered from 1994-2013 on small asteroids impacting Earth’s atmosphere and disintegrating to create very bright meteors, technically called “bolides” and commonly referred to as “fireballs”.  Sizes of orange dots (daytime impacts) and blue dots (nighttime impacts) are proportional to the optical radiated energy of impacts measured in billions of Joules (GJ) of energy, and show the location of impacts from objects about 1 meter (3 feet) to almost 20 meters (60 feet) in size.  You can see a rather uniform distribution of these fireballs over the surface of the Earth.

bolide_events_1994-2013 Source: NASA NEO Observation Program

In September 2014, the NASA Inspector General published the report, “NASA’s Efforts to Identify Near-Earth Objects and Mitigate Hazards,” which you can download for free at the following link:


Key findings were the following:

  • Even though the Program has discovered, categorized, and plotted the orbits of more than 11,000 NEOs since 1998, NASA will fall short of meeting the 2005 Authorization Act goal of finding 90 percent of NEOs larger than 140 meters (459 feet) in diameter by 2020.
  • ….we believe the Program would be more efficient, effective, and transparent were it organized and managed in accordance with standard NASA research program requirements

You will find an NEO Program update, including a reference to the new Planetary Defense Coordination Office, presented by Lindley Johnson on 8 November 2915 at the following link:


So, what will we see in the years ahead as technology is explored and techniques are developed to defend Earth against a significant NEO impact? There have been many movies that have tried to answer that question, but none offered a particularly good answer.

Asteroid movies 2Asteroid movies 1 Source: Google

In 1968, Star Trek explored this issue in Season 3, Episode 3, “The Paradise Syndrome”. Ancient aliens had left a planetary defense device to protect a primitive civilization against their equivalent of NEOs. Only the intervention of Capt. James T. Kirk restored the device to operation in time to deflect an incoming asteroid and save the indigenous civilization.

Star Trek - The Paradise Syndrome 1 Source: memory-alpha.wiki.comStar Trek - The Paradise Syndrome 2 Source: technovelgy.com

Our new Planetary Defense Officer has a comparable responsibility on Earth, but without the benefits of special effects.

In 2010, National Academies Press published, “Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies.” This report explores civil defense mitigation action and three basic defense techniques:

  • Slow push-pull methods
  • Kinetic impact methods
  • Nuclear methods

If you have a MyNAP account, you can download this report for free at the following link:


NAP Defending Planet Earth Source: NAP



The Bright Spots on Ceres Come into Focus

In my 20 March 2015 post, I discussed the Dawn spacecraft mission to the large asteroid Vesta and the dwarf planet Ceres, both of which are in the main asteroid belt between Mars and Jupiter. Dawn arrived in orbit around Ceres on 6 March 2015, at an initial altitude of 8,400 miles (13,518 kilometers). On approach and from this high altitude orbit, Dawn photographed two very bright spots on the surface of Ceres.

Ceres seen from Dawn  Source: NASA

After spending six months mapping the surface of Ceres and gradually descending to lower altitude orbits, Dawn currently is in a much lower “high-altitude mapping orbit” (HAMO) at 915 miles (1,470 kilometers) above the surface. Ceres’ diameter is about 587 miles (946 kilometers). Due to the low mass of this dwarf planet, Dawn’s orbital speed in the HAMO is only 400 mph (645 kph). The spacecraft completes one orbit in about 19 hours.

From its current vantage point in HAMO, Dawn has provided a much better view of the bright spots on Ceres. The following composite photo shows the bright spots at a resolution of 450 feet (140 meters) per pixel.

ceres-bright-spots-Sep2015,jpg  Source: NASA

The source of the bright spots has not yet been determined. We’ll get a more detailed view later in 2015, when the spacecraft descends to the “low altitude mapping orbit” (LAMO) at an altitude of 230 miles (370 kilometers).

You can keep up with the work of the Dawn project team at the following NASA / Jet Propulsion Lab website:


 9 December 2015 Update:

NASA’s Jet Propulsion Laboratory (JPL) released closeup photos of the bright spots, which appear to be globally distributed on Ceres. JPL scientists reported that Ceres has more than 130 bright areas, and most of them appear to be associated with impact craters.   There is evidence that the bright spots may be salt deposits left behind after a subterranean briny water-ice deposit was exposed by an impact and the  ice-water sublimated into space.  Here is a closeup, false-color photo of the Occator Crater, emphasizing the deposits of bright material on the crater floor.

Occator Crater - Ceres_JPL

You can read more on this subject on the JPL website at the following link:



Spitzer Space Telescope “Warm Mission” Continues

The Spitzer Space Telescope, an infrared space observatory, was launched on 8 August 2003 into an “earth-trailing” orbit around the Sun. It is one of four “Great Observatories” launched by NASA; the others being the Hubble Space Telescope, the Compton Gamma-ray Observatory; and the Chandra X-ray Observatory.

Spitzer_Telescope_Handbook013   Diagram source: NASA

The primary mirror is 85 cm in diameter, made of beryllium, and until May 2009, was cooled by liquid helium to 5.5 degrees K. With the on-board liquid helium supply exhausted, most of the instruments were no longer usable. However, the two shortest wavelength modules of the Infrared Science Archive (IRAC) camera remained operable at their original sensitivities. This allowed the mission team to continue with the “Spitzer Warm Mission”.

You can read about the design of the Spitzer Space Telescope at the following link:


An example of an image from the Spitzer Space Telescope is this view of Eta Carinae:

The tortured clouds of Eta Carinae  Photo source: NASA

You can see this and many other images from the Spitzer telescope, and related image data, at the following NASA / JPL / Caltech website: