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For our readers who are worried about potential collision between any asteroid and our home planet earth, I would like to share some hopeful information, below: Double Asteroid Redirection Test (DART) is a planned space probe that will visit the double asteroid Didymos and demonstrate the kinetic effects of crashing an impactor spacecraft into an asteroid moon for planetary defense purposes. The mission is intended to test whether a spacecraft impact could successfully deflect an asteroid on a collision course with Earth. A demonstration of an asteroid deflection is a key test that NASA and other agencies wish to perform before the actual need of planetary defense is present. DART is a joint project between NASA and the Johns Hopkins Applied Physics Laboratory (APL), and it is being developed under the auspices of NASA’s Planetary Defense Coordination Office. The mission’s target is 65803 Didymos, a binary asteroid system in which one asteroid is orbited by a smaller one. The primary asteroid (Didymos A) is about 780 m (2,560 ft) in diameter; its small satellite Dimorphos (Didymos B) is about 160 m (520 ft) in diameter in an orbit about 1 km from the primary. DART will target the smaller asteroid, Dimorphos, in the video published on May 20, 2021, “NASA’s DART Spacecraft Hitting an Asteroid Headed by Earth at 6.6 kilometers per second simulation“, below: In the video published on Feb 4, 2020, “NASA’s Plan to Stop an Asteroid Headed for Earth“, below: In the video published on Nov 30, 2020, “These are the asteroids to worry about“, below: So, firstly and most importantly, let’s look for these asteroids first, do the surveys, build the telescope in space, to help better locate and understand the threat from the asteroids.  Once we’ve found the object/asteroid that may potentially be the threat, then we can focus everything we have on it and seriously think about ways to deflect it or evacuate from it. For more about DART (Double Asteroid Redirection Test), please refer to wikipedia page on the subject or read the excerpt from wikipedia, in italics, below: Double Asteroid Redirection Test (DART) is a planned space probe that will visit the double asteroid Didymos and demonstrate the kinetic effects of crashing an impactor spacecraft into an asteroid moon for planetary defense purposes. The mission is intended to test whether a spacecraft impact could successfully deflect an asteroid on a collision course with Earth. A demonstration of an asteroid deflection is a key test that NASA and other agencies wish to perform before the actual need of planetary defense is present. DART is a joint project between NASA and the Johns Hopkins Applied Physics Laboratory (APL), and it is being developed under the auspices of NASA’s Planetary Defense Coordination Office. In August 2018, NASA approved the project to start the final design and assembly phase. Background Originally, the European Space Agency (ESA) and NASA had independent plans for missions to test asteroid deflection strategies, and by 2015 they struck a collaboration called AIDA involving two separate spacecraft launches that work in synergy.^[5][6][7] Under the proposal, the European spacecraft, AIM, would have launched in December 2020, and DART in July 2021. AIM would have orbited the larger asteroid to study its composition and that of its moon. DART would then impact the asteroid’s moon in October 2022, during a close approach to Earth.^[6] AIM would have studied the asteroid’s strength, surface physical properties, and its internal structure, as well as measure the effect on the asteroid moon’s orbit around the larger asteroid. The AIM orbiter was cancelled, the full characterization of the asteroids will not be obtained, and the effects of the impact by DART will be monitored from ground-based telescopes and radar.^[8][7] In June 2017, NASA approved a move from concept development to the preliminary design phase,^[9] and in August 2018 NASA approved the project to start the final design and assembly phase.^[10] On 11 April 2019, NASA announced that a SpaceX Falcon 9 would be used to launch DART.^[11] It was originally planned for DART to be a secondary payload on a commercial launch to keep costs low, however a mission update presentation in November 2018 noted that the mission has a dedicated launch vehicle. Scientists estimate 25,000 large asteroids are in the Solar System, though to date, surveys have detected about 8000, therefore NASA officials think it is imperative to develop an effective plan should a near-Earth object threaten Earth.^[12] Mission DART is an impactor that hosts no scientific payload other than a Sun sensor, a star tracker, and a 20 cm aperture camera (Didymos Reconnaissance and Asteroid Camera for Optical navigation – DRACO) to support autonomous navigation to impact the small asteroid’s moon at its center. It is estimated that the impact of the 500 kg (1,100 lb)^[13] DART at 6.6 km/s (4.1 mi/s) ^[14][4] will produce a velocity change on the order of 0.4 mm/s, which leads to a small change in trajectory of the asteroid system, but over time, it leads to a large shift of path.^[15][6][16] Overall, DART is expected to alter the speed of Dimorphos (Didymos B) orbit by about half a millimeter per second, resulting in an orbital period change of perhaps 10 minutes.^[17] Over a span of millions of kilometers, the cumulative trajectory change would turn a collision with a genuinely Earth-bound asteroid or comet into a safe outcome.^[18] The actual velocity change and orbital shift will be measured a few years later by a small spacecraft called Hera that would do a detailed reconnaissance and assessment.^[19] Hera was approved in November 2019.^[20] DART spacecraft will use the NEXT ion thruster, a type of solar electric propulsion.^[8][21] It will be powered by 22 m² solar arrays to generate the ~3.5 kW needed to power the NASA Evolutionary Xenon Thruster–Commercial (NEXT-C) engine.^[1] The spacecraft’s solar arrays use a Roll Out Solar Array (ROSA) design, and this was tested on the International Space Station in June 2017 as part of Expedition 52, delivered to the station by the CRS-11 commercial cargo mission.^[22] The DART impactor is proposed to make flyby observations of other near-Earth asteroids such as 2001 CB₂₁ and 3361 Orpheus during its trajectory to 65803 Didymos.^[23][24][25] It will obtain some images in the visible spectrum. NASA’s first flight mission for planetary defense, the Double Asteroid Redirection Test (DART) seeks to test and validate a method to protect Earth in case of an asteroid impact threat. The DART mission aims to shift an asteroid’s orbit through kinetic impact – specifically, by smashing a spacecraft into the smaller member of the binary asteroid system Didymos. The Didymos asteroid system is comprised of Didymos and its small, orbiting moonlet, Dimorphos.  In 2022, DART will pummel into the latter, a boulder about 160 meters (525 feet) in diameter, and change its orbital period around Didymos by about 10 minutes.    Using ground-based telescope observations prior to and after impact, scientists will be able to compare Dimorphos’ path around Didymos to determine how much the orbit has changed.   Launching in 2021, the DART mission is designed to demonstrate a critical planetary defense capability. With less than a year until launch, DART is currently coming together at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland.  APL leads the DART mission for NASA, in the video published on March 2, 2021, “DART, NASA’s First Planetary Defense Test Mission“, below: Earth moves through a dangerous neighborhood. Astronomers estimate there are about 1,000 near-Earth asteroids larger than 1 kilometer—big enough to cause a global disaster. About 90 percent of them have been identified. Far less is known about smaller asteroids. All told, about 100 tons of extraterrestrial matter falls onto Earth every day, mostly in the form of harmless dust and an occasional meteorite. NASA’s Double Asteroid Redirection Test (DART) will be the first ever space mission to demonstrate asteroid deflection by kinetic impactor on a binary asteroid target: the smaller asteroid of Didymos, called Didymos B. Didymos is Greek for “twin.” DART is directed by NASA and undertaken by a team led by Johns Hopkins University Applied Physics Laboratory with support from NASA Goddard Space Flight Center, NASA Johnson Space Center, and the Jet Propulsion Laboratory. The Planetary Defense Coordination Office within NASA’s Science Mission Directorate is the lead for planetary defense activities and is sponsoring this mission. DART is planned to intercept the secondary member of the Near-Earth Asteroid Didymos binary system in October 2022, in the video published on Dec 17, 2018, “The Double Asteroid Redirection Test (DART): Hitting an Asteroid Head On“, below: Nancy Chabot, project scientist for the Double Asteroid Redirection Test (DART), discusses NASA’s first planetary defense mission. Scheduled to launch in 2021, DART will demonstrate asteroid deflection by a kinetic impactor, reaching its target, the Didymos binary asteroid system, in 2022, in the video published on July 17, 2019, “DART – The First Planetary Defense Mission“, below: In summary, objectives of DART’s first launch or mission in July of 2021:

• Redirect a moon of an asteroid
• Change the rotational period of an asteroid by about 73 seconds
• Figure out how much rotational period was changed from the ground level
• Measure how much the plume (upon collision with the asteroid) called ejecta. Need to measure how much the plume helped to push the moon along the way

The DART mission is a technology demonstrator for NASA, demonstrating:

• the first planetary defense technique
• the NEXT-C Ion Engine (NASA Evolutionary Xenon Thruster)
• Roll-Out Solar Arrays (solar cells on big blankets), providing power for the spacecraft
• SmartNav (to hit the asteroid)

Remember: NASA’s first planetary defense mission is scheduled to launch in July of 2021, from SpaceX’s Falcon 9.

Gathered, written, and posted by Windermere Sun-Susan Sun Nunamaker More about the community at www.WindermereSun.com Any comments, suggestions, concerns regarding this post will be welcomed at info.WindermereSun@gmail.com

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