Making the map

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The Sentinel Space Telescope in orbit around the sun. Image courtesy of Ball Aerospace.

The Sentinel Mission will provide a unique opportunity for the public to take ownership in a historic space mission that will protect Earth, while providing the necessary roadmap for future exploration.

Sentinel is a space-based infrared (IR) survey mission to discover and catalog 90 percent of the asteroids larger than 140 meters in Earth’s region of the solar system. The mission should also discover a significant number of smaller asteroids down to a diameter of 30 meters. Sentinel will be launched into a Venus-like orbit around the sun, which significantly improves the efficiency of asteroid discovery during its 6.5 year mission.

“The B612 Sentinel mission extends the emerging commercial spaceflight industry into deep space – a first that will pave the way for many other ventures. Mapping the presence of 1000′s of near earth objects will create a new scientific database and greatly enhance our stewardship of the planet.”

Dr. Scott Hubbard

B612 Foundation Program Architect

Mission Details

The spacecraft and instrument use high-heritage flight proven deep space systems, originally developed by NASA, to minimize technical and programmatic risks. These heritage missions include large space-based telescopes (Spitzer, Kepler), a large format camera made up of many individual detectors (Kepler), and a cryogenically cooled instrument (Spitzer). By detective and tracking nearly all of the Near Earth Objects greater than 50 meters in diameter, Sentinel will create a map of the solar system in Earth’s neighborhood enabling future robotic and manned exploration. The Sentinel data will also identify objects that are potentially hazardous to humans to provide an early warning to protect the Earth from impact.


- Most capable NEO detection system in operation

- 200 deg anti-sun Field of Regard, with a 2×5.5 deg Field of View at any point in time: scans 165 square degrees per hour looking for moving objects

- Precise pointing accuracy to sub-pixel resolution for imaging revisit, using the detector fine steering capability

- Designed for highly autonomous, reliable operation requiring only weekly ground contact

- Designed for 6.5 years of surveying operations. Actively cooled to 40K using a Ball Aerospace two-stage, closed-cycle Stirling-cycle cryocooler

- Ability to follow-up on objects of interest


- Provides highly specialized design specifically optimized for NEO detection and discovery

- NEO detection efficiency increased using IR-detector (5 to 10.4 microns). Venus-like orbit

- Provides an astrometric accuracy of 0.2-arcseconds for any detected NEOs (typical); NEO orbits determined in as few as two detections, with multiple visits to each region of the sky.

- On board detection processing reduces data downlink volume, minimizes contact requirements

- Provides a targeted follow-up observation capability, enabling time-critical revisit of high-priority targets

- Heritage draws lineage from great observatories and pioneering scientific missions: Kepler, Spitzer, Deep Impact

The Earth orbits the Sun among a swarm of asteroids whose orbits cross Earth’s orbit. These are not the asteroids that make up the asteroid belt between Mars and Jupiter, but rather the Near Earth Asteroids whose orbits take them much closer to the Sun, and who regularly approach the orbit of Earth.  These asteroids are remnants of the formation of our solar system, and range in size from pebbles to many miles across.

More than a million of these Near Earth Asteroids are larger than the asteroid that struck Tunguska in 1908, and about 1,000 times more powerful than the atomic bomb dropped on Hiroshima. That asteroid was only about 40 meter across (less than the length of an Olympic swimming pool), yet destroyed an area roughly the size of the San Francisco Bay area, destroying 80 million trees over 1000 square miles.

Currently there is no comprehensive dynamic map of our inner solar system showing the positions and trajectories of these asteroids that might threaten Earth.  The citizens of Earth are essentially flying around the Solar System with our eyes closed. Asteroids have struck Earth before, and they will again – unless we do something about it. The probability of a 100 Megaton impact somewhere on Earth each and every year is the same as the probability of an individual being killed in an automobile accident each year – about .01%.   These odds are small, yet few among us would drive around each day without wearing a seat belt.  What precautions are we taking with our planet?

We as a civilization have the capability to change the odds, and it is our mission to ensure that such impacts do not happen again.  Less than 1% of the over one million asteroids greater than 40 meters have been identified to date. B612 will discover the other 99% – or50 times more asteroids than have been found by all other telescopes combined.

Sentinel is a mission of mapping and discovery. Mapping the great unknown of the inner solar system is the first step in protecting the Earth from asteroid impacts and in opening up this next frontier.  By observing in infrared, Sentinel will discover more than 20,000 asteroids in just the first month of operation – more discoveries than all other telescopes combined have managed to discover in the last 30 years – and over 6.5 years will locate and follow the trajectories of more than 90% of asteroids larger than 140 meters.

The Sentinel Space Telescope will take about four years to build and test, with a scheduled launch in 2017-18, aboard a Falcon 9 rocket.  After 6.5 years of operation, Sentinel will discover about 500,000 NEAs.  Sentinel will compile the definitive catalog of NEAs, and within a few years nearly all NEAs known to humanity will have been discovered by Sentinel (more than 98% after 6.5 years).

As Sentinel orbits the Sun every 7 months, its field of view (looking away from the Sun) will sweep around the sky.  Sentinel will make repeated observations of the sky in infrared looking for objects that move: asteroids.  Sentinel will transmit the data on the locations of these asteroids back to Earth where the discoveries will be confirmed and the positions of the asteroids will be mathematically pieced together into orbits.

The work of the B612 Foundation and others over the past decade has shown that asteroid deflection is possible with current technology as long as the deflection is carried out decades before the impending impact.  The urgency in completing the mission arises because there could be an impact from an asteroid in the next few decades, when the task of deflecting them becomes extremely difficult, or almost impossible (depending on the size of the asteroid) using current technology. Why take this risk?

We are at the beginning of a new era in exploration where private organizations can now conduct grand and audacious space missions, previously only possible by governments – and at lower cost. Mapping the great unknown of the inner solar system is the first step to opening up this next frontier, as well as protecting Earth.

The B612 Foundation believes that humanity can harness the power of science and technology to protect the future of civilization on this planet, while extending our reach into the solar system.  Our view is that we are not passengers on Space Ship Earth – we are the Crew.

An important lesson we hope young people will be able to draw from Sentinel is that individuals and small private organizations can make a difference in the world.  Through the power of science and technology, humanity must eventually be able to change the evolution of the solar system.  The Sentinel mission may very well find an asteroid on a collision course with Earth (in fact it has a roughly 30 percent chance).  It is our belief that the people of the world will then unite in carrying out a deflection of that asteroid to prevent this future impact.   We hope that B612/Sentinel will be a source of inspiration to budding young scientists, engineers, and dreamers worldwide.

The Sentinel Space Telescope has been designed and will be built by the same expert team from Ball Aerospace that built the Kepler Space Telescope, Spitzer Space Telescope, Deep Impact Mission, and Hubble Space Telescope instrumentation.

Through a NASA Space Act Agreement, signed with the B612 Foundation on June 19, 2012, NASA will support the B612 Foundation Sentinel Mission in three critical areas: Use of NASA’s Deep Space Network for Communications, Navigation, and Tracking; Asteroid orbit calculation and threat assessment; NASA experts to support Sentinel Review Team. NASA also plans to appoint an independent science team to analyze the data provided by Sentinel and will conduct a comprehensive hazard analysis, making orbit determinations and threat assessments.

Read more about our Leadership team here.

Read more about our Sentinel Special Review Team here.

Data Operations Center

Sentinel will complete its survey of the inner solar system during its mission life of 6.5 years, with all systems designed for 10 years of operation. Data collected by the Sentinel Space Telescope will be transmitted first to the Sentinel Operations Center, located at the Laboratory for Atmospheric and Space Physics, Boulder, Colo., then distributed to education, research, scientific institutions and governments via NASA’s Minor Planet Center, Cambridge, Mass. As part of the B612 Foundation-NASA Space Act Agreement of June 2012, NASA JPL (NEO Center), Pasadena, Calif. will conduct a comprehensive hazard analysis, making orbit determinations and threat assessments.

The history of large telescopes is that many of them have been funded privately, so we hope to continue in that tradition.  The B612 Foundation plans to raise $450m over 12 years (or about $37m per year) to design, build, test, insure, and launch the Sentinel Space Telescope, build and operate the control center for the duration of the mission, carry out analysis of the observations, and deliver the data to the people of the world. This is substantially lower than the budget would be for a similar mission in the government sector, and comparable in cost to other philanthropic projects, including specialized medical research facilities, museums, performing arts centers, and academic buildings.

Q. The Sentinel Space Telescope will map the Inner Solar System.  How is such a map different from what is commonly thought of as a map?

Because the solar system is dynamic and subject to the laws of orbital mechanics, the individual pieces of territory (asteroids and planets) are continuously in motion.  A comprehensive map must therefore show not only where things are now, but also where they are going (think of the Marauder Map from Harry Potter, but much bigger, including a half million elements).   If the positions and velocities of asteroids are accurately enough measured, this also means that the locations of each of the asteroids can also be calculated for about 100 years. Sentinel will create such a comprehensive dynamic map of our inner solar.

Q. What role do maps play in exploration and why do we need such a map of the inner solar system?

Mapping the inner solar system is the first step to opening up the frontier and protecting the future of humanity on Earth.  Just as the US geological surveys and the mapping expedition of Lewis and Clark were instrumental in the development of the American frontier, the map of Near Earth Asteroids will be instrumental in pushing forward the frontier as humanity opens up the inner solar system.

The inner solar system is mostly uncharted territory as we have mapped the orbits of only about one percent (1%) of the Near Earth Asteroids larger than the one that struck Tunguska in 1908.  If we want to preserve life on Earth, and open up the inner solar system to scientific and economic endeavors, we need an accurate map of the locations and trajectories of asteroids.  We need to know which ones approach Earth and are therefore accessible, and which ones threaten Earth and therefore must be deflected.

Q. How much advance notice will we have of an impending impact with Earth?

The Sentinel Map will give Earth decades of advance notice of an impending impact so that deflection becomes relatively easy. There are several promising technologies including kinetic impactors, gravity tractors, and nuclear standoff explosions. The urgency in completing the map arises because there could be an impact in the next few decades, when the task of deflecting an asteroid becomes extremely difficult, to the point where it could become almost impossible (depending on the size of the asteroid) using current technology. Every year delayed in completing Sentinel increases our chances of having no available options.  Why take this risk?

Q. Where does the Sentinel Space Telescope need to be located for optimal mapping of asteroids?

The optimal location for tracking Near Earth Asteroids, and for creating the Sentinel Map, is from a location between the Earth and the Sun, from where a space telescope can scan Earth’s orbit while continuously looking away from the Sun.  The optimal wavelength to find asteroids is in the infrared, where asteroids stand out from the cold dark background.  This strategy has been analyzed and affirmed by both the National Academies report “Defending Planet Earth” and the NASA Advisory Council report on Planetary Defense.

Thus, we will launch the Sentinel space telescope into orbit around the Sun, near the orbit of Venus.  This has the advantage that at times Sentinel will be able to scan the opposite side of the Sun from Earth.  However, it also adds to the technical challenge in that the distance from Earth to the Sentinel Space Telescope will vary between 30-170 million miles. This is hundreds of thousands of times further than the Hubble Space Telescope, which was placed in orbit only 350 miles from Earth.

January 2013

  • Passed first major technical review
  • Prototype infrared detectors fabricated and in-test

June 2012

  • Technical leadership team among most experienced in world
  • Preliminary spacecraft and mission design complete
  • Firm fixed price proposal submitted by Ball Aerospace (enabled by early infrared detector work funded by B612)
  • Experienced Ball contractor team previously built Kepler Space Telescope, SpitzerSpace Telescope, Deep Impact Mission, Hubble Space Telescope instrumentation
  • NASA Space Act Agreement to provide communications, tracking, technical support


Click the image to view/print the Sentinel Data Sheet.

Defending Planet Earth – report of the National Academies on asteroid surveys and deflection

Report of the NASA Advisory Council on Planetary Defense

A Brief Note on the Economic History of Space Exploration in America, by Alexander MacDonald

Asteroid Threats: A Call for Global Response, Association of Space Explorers, October 2008

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