Double Asteroid Redirection Test (DART) Mission
The Double Asteroid Redirection Test (DART) mission is directed by NASA to the Johns Hopkins Applied Physics Laboratory (APL) with support from several NASA centers: the Jet Propulsion Laboratory (JPL), Goddard Space Flight Center (GSFC), Johnson Space Center (JSC), Glenn Research Center (GRC), and Langley Research Center (LaRC).
DART is a planetary defense-driven test of technologies for preventing an impact of Earth by a hazardous asteroid. DART will be the first demonstration of the kinetic impactor technique to change the motion of an asteroid in space. The DART mission is in Phase C, led by APL and managed under NASA’s Solar System Exploration Program at Marshall Space Flight Center for NASA’s Planetary Defense Coordination Office and the Science Mission Directorate’s Planetary Science Division at NASA Headquarters in Washington, DC.
Two different views of the DART spacecraft. The DRACO (Didymos Reconnaissance & Asteroid Camera for OpNav) imaging instrument is based on the LORRI high-resolution imager from New Horizons. The left view also shows the Radial Line Slot Array (RLSA) antenna with the ROSAs (Roll-Out Solar Arrays) rolled up. The view on the right shows a clearer view of the NEXT-C ion engine.
The binary near-Earth asteroid (65803) Didymos is the target for the DART demonstration. While the Didymos primary body is approximately 780 meters across, its secondary body (or “moonlet”) is about 160-meters in size, which is more typical of the size of asteroids that could pose the most likely significant threat to Earth. The Didymos binary is being intensely observed using telescopes on Earth to precisely measure its properties before DART arrives.
The DART spacecraft will achieve the kinetic impact deflection by deliberately crashing itself into the moonlet at a speed of approximately 6.6 km/s, with the aid of an onboard camera (named DRACO) and sophisticated autonomous navigation software. The collision will change the speed of the moonlet in its orbit around the main body by a fraction of one percent, but this will change the orbital period of the moonlet by several minutes – enough to be observed and measured using telescopes on Earth.
Once launched, DART will deploy Roll Out Solar Arrays (ROSA) to provide the solar power needed for DART’s electric propulsion system. The DART spacecraft will demonstrate the NASA Evolutionary Xenon Thruster – Commercial (NEXT-C)solar electric propulsion system as part of its in-space propulsion. NEXT-C is a next-generation system based on the Dawn spacecraft propulsion system, and was developed at NASA’s Glenn Research Center in Cleveland, Ohio. By utilizing electric propulsion, DART could benefit from significant flexibility to the mission timeline while demonstrating the next generation of ion engine technology, with applications to potential future NASA missions.
The DART spacecraft launch window begins November 24, 2021. DART will launch aboard a SpaceX Falcon 9 rocket from Vandenberg Air Force Base, California. After separation from the launch vehicle and over a year of cruise it will intercept Didymos’ moonlet in late September 2022, when the Didymos system is within 11 million kilometers of Earth, enabling observations by ground-based telescopes and planetary radar to measure the change in momentum imparted to the moonlet.
Schematic of the DART mission shows the impact on the moonlet of asteroid (65803) Didymos. Post-impact observations from Earth-based optical telescopes and planetary radar would, in turn, measure the change in the moonlet’s orbit about the parent body..
Credits: NASA/Johns Hopkins Applied Physics Lab
Is Earth Prepared for an incoming asteroid?
The chances of a large asteroid striking the Earth are remote, but because the consequences of such an impact are potentially catastrophic, NASA takes the possibility very seriously. To help counter the most likely potential threat, called Near-Earth Objects (NEO), the agency has released a 20-page multi-agency report outlining steps the US federal government needs to take over the next decade to respond to such an eventuality.
On February 15, 2013, an asteroid 20 m (66 ft) in diameter exploded over Chelyabinsk in Russia with a force of up to 30 times that of the first atomic bomb dropped on Hiroshima. Despite detonating at high altitude, the shockwave damaged buildings and thousands of people were injured by flying glass. That may seem nasty enough, but in 1908, another object 40 to 60 m (131 to 197 ft) wide blew up over Tunguska, Russia with a force of five to 10 megatons – flattening 2,000 km² (772 mi²) of forest.
What worries some space scientists and disaster relief planners is that these events aren’t anywhere near the top end of the scale. According to NASA, an asteroid 140 m (459 ft) in diameter would have an explosive force of 60 megatons if it hit the Earth. As to the upper limit, ask your local dinosaurs what the effect could be.
As part of a program to study the problem, in 2005 the US Congress instructed NASA to conduct a survey to find 90 percent of the NEOs that are at least in the 140-m range or larger. An NEO is an asteroid or comet that is on a trajectory that crosses the Earth’s orbit. Unfortunately, by 2017, the agency hasn’t been as successful as first hoped and will only find half the 140-m objects by 2033.
To help improve things, NASA, in coordination with the Office of Science and Technology Policy, the Federal Emergency Management Agency, and other federal agencies, has issued its report, “The National Near-Earth Object Preparedness Strategy and Action Plan.” Its purpose is to outline priorities to address over the next decade to best ensure an effective response to the threat posed by an asteroid impact is possible.
The plan will concentrate on five areas. These include:
- Enhancing the detection and tracking of NEOs, starting with the larger ones and then working down to the smaller. This will include radar and spectrographic analysis, development of new technologies and analysis techniques, and collaboration with other institutions.
- Improving the modeling of asteroids and their orbits to better predict the probability of an Earth impact, the site of the impact, the extent of the damage, and the options for preventing or mitigating the strike.
- Developing new technologies and techniques for deflecting NEOs if they are far enough away or to destroy them if deflection isn’t possible.
- Improve international cooperation in dealing with NEOs by building awareness of the threat, increased cooperation on observation infrastructure and modeling, and international planning on how to respond to a potential impact event.
- Developing emergency procedures and protocols for dealing with an asteroid strike if one occurs. This includes better communications, decision making, space-based evaluation, and mitigation plans.
“The nation already has significant scientific, technical and operation capabilities that are relevant to asteroid impact prevention,” says Lindley Johnson, NASA’s planetary defense officer. “Implementing the National Near-Earth Object Preparedness Strategy and Action Plan will greatly increase our nation’s readiness and work with international partners to effectively respond should a new potential asteroid impact be detected.”
Planetary Defense Coordination Office
Near-Earth objects (NEOs) are asteroids and comets that orbit the Sun like the planets, but their orbits can bring them into Earth’s neighborhood – within 30 million miles of Earth’s orbit. Planetary defense is “applied planetary science” to address the NEO impact hazard.
NASA established the Planetary Defense Coordination Office (PDCO) to manage its ongoing mission of planetary defense. The PDCO:
- Provides early detection of potentially hazardous objects (PHOs) – the subset of NEOs whose orbits predict they will come within 5 million miles of Earth’s orbit; and of a size large enough (30 to 50 meters) to cause significant damage on Earth;
- Tracks and characterizes PHOs and issues warnings of the possible effects of potential impacts;
- Studies strategies and technologies for mitigating PHO impacts; and
- Plays a lead role in coordinating U.S. government planning for response to an actual impact threat.
The PDCO sponsors projects through its Near-Earth Object (NEO) Observations Program that employ a variety of ground and space based telescopes to search for NEOs, determine their orbits, and measure their physical characteristics. The PDCO is studying possible space-based telescope missions optimized for NEO search and characterization that could accelerate the discovery of the currently undetected NEOs.
The PDCO is responsible for providing timely and accurate information to the government, the media, and the public on close approaches to Earth by potentially hazardous objects (PHOs) and any potential for impact. If any PHO is found to pose a significant chance of impacting Earth (greater than 1 percent over the next 50 years), the PDCO will provide notification messages for NASA to send to the Executive Office of the President, the U.S. Congress, and other government departments and agencies.
The PDCO sponsors studies of technologies and techniques for deflecting an asteroid off a predicted impact course with Earth. It is developing missions to demonstrate those technologies and determine their effectiveness in the event that these techniques must be utilized against a predicted asteroid impact threat.
The PDCO works with other government agencies to develop and update a National NEO Preparedness Strategy and Action Plan. The PDCO also provides expert input on the nature and effects of asteroid impacts to the Federal Emergency Management Agency (FEMA), so that adequate emergency response can be prepared in the event of a PHO impact that is not possible to avoid.