Two robotic spacecraft are currently exploring asteroids up close: NASA's OSIRIS-REx is in orbit at asteroid Bennu and Japan's Hayabusa 2 is preparing to collect samples from asteroid Ryugu. Meanwhile, NASA's NEOWISE spacecraft, orbiting Earth, continues to improve on the most accurate survey of near-Earth objects every undertaken.
Images taken with Hayabusa 2's small monitor camera (CAM-H) during the Touchdown 1 Rehearsal 3 operation (TD1-R3). One image was captured every second from immediately after the spacecraft began to ascend on Oct. 25, 2018. Credit: JAXA)
The Hubble Space Telescope and ground-based radar observatories also contibute regularly to our understanding of asteroids. Several more missions, including NASA's Psyche and Lucy, missions are in development to keep exploring these small worlds. Scientists also use ground-based radar to explore nearby asteroids whenever possible.
- NASA's Galileo mission was the first spacecraft to fly past an asteroid. It flew past asteroid Gaspara in 1991 and Ida in 1993.
- NASA's Near-Earth Asteroid Rendezvous (NEAR-Shoemaker) mission studied asteroids Mathilde and Eros; and the Rosetta mission encountered Steins in 2008 and Lutetia in 2010. Deep Space 1 and Stardust both had close encounters with asteroids.
- In 2005, the Japanese spacecraft Hayabusa landed on the near-Earth asteroid Itokawa and attempted to collect samples. On June 3, 2010, Hayabusa successfully returned to Earth a small amount of asteroid dust now being studied by scientists.
- NASA's Dawn spacecraft, launched in 2007, orbited and explored asteroid Vesta for over a year. Once it left in September 2012, it headed towards dwarf planet Ceres, with a planned arrival of 2015. Vesta and Ceres are two of the largest surviving protoplanet bodies that almost became planets. By studying them with the same complement of instruments on board the same spacecraft, scientists will be able to compare and contrast the different evolutionary path each object took to help understand the early solar system overall.
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Why Is a NASA Spacecraft Currently Orbiting an Asteroid?
While much of planet Earth stays home to stop the spread of the coronavirus, the OSIRIS-REx spacecraft hovers 105 million miles away in the ultimate act of social distancing. The NASA spacecraft has been in orbit around the asteroid Bennu since 2018 with the goal of eventually grabbing a sample from its surface and returning that sample to Earth.
The sample grab is planned for August 2020, so in April, the team of scientists and engineers behind the OSIRIS-REx mission had a dress rehearsal of sorts. They practiced two of the four steps the spacecraft will have to perform to leave its orbit, approach the asteroid’s surface, and retrieve the sample before backing away.
First, they fired the spacecraft’s engines so that it left its safe orbit of 1 kilometer (or 0.6 miles) away. Then, while on its approach, they performed a checkpoint burn or a second engine firing.
That's when the spacecraft checks its location and adjusts its position so that its trajectory heads toward the planned sample retrieval site.
The spacecraft continued its approach, making it within about 75 meters (or 246 feet) of Bennu, but then backed away.
The whole smash-and-grab event will take only five seconds of actual contact between spacecraft and asteroid.
The team also practiced successfully deploying the spacecraft’s Touch-And-Go Sample Acquisition Mechanism—a fancy name for its arm, which will extend toward the asteroid’s surface to grab the sample.
The whole rehearsal took about four hours and was performed mostly by a team of scientists operating from home. (Talk about working remotely!) During it's close approach, the spacecraft took pictures.
You can check out the detailed images of the asteroid's surface on the mission website.
When the real sample grab happens in August, OSIRIS-REx will fire a charge of pressurized nitrogen. This blast is meant to stir up the surface so that the arm can collect a sample before the spacecraft backs off.
The whole smash-and-grab event will take only five seconds of actual contact between spacecraft and asteroid. The spacecraft is planned to eventually begin its two-and-a-half-year journey back to Earth in March, 2021.
Why are we orbiting an asteroid?
Asteroid Bennu is one of a subset of elite asteroids classified as PHAs, or potentially hazardous asteroids.
This means they cross Earth’s orbit and are large enough to cause significant damage should there be an impact. Bennu, specifically, is about a third of a mile across (or just shy of 500 meters.
) It has a “relatively high probability of impacting the Earth” one hundred or so years from now.
So learning about Bennu is most immediately an act of self interest—we want to know what it's made of to better understand the damage it could potentially do. Asteroids made of ice and porous rock, for example, are less dense than asteroids made of, say, iron. The ice-and-rock asteroid has less damage potential.
The OSIRIS-REx mission will help us answer deeper questions about how our solar system formed and how water—and thus, life as we know it—came to be on Earth.
Want to learn more about the effects of an asteroid impact? This simulation, created by scientists at Purdue, allows you to experiment with different asteroid sizes, densities, and impact angles to see just how much these factors matter in terms of eventual destruction.
Being able to study a sample from the asteroid up close will give us an idea of Bennu’s physical and chemical properties. While in orbit, OSIRIS-REx is also making detailed maps of the asteroid’s surface and monitoring its trajectory closely. All of this information together will help guide a plan toward mitigating any future impacts.
The OSIRIS-REx mission will also help us answer deeper questions about how our solar system formed and how water—and thus, life as we know it—came to be on Earth.
As we’ve discussed before, scientists still aren’t sure whether Earth’s water was brought here originally on a comet, an asteroid, or even during the same event that gave us the Moon.
Getting a detailed look at a sample of Bennu—in particular, its isotope budgets—will shed some light on whether the makeup of the asteroid is consistent with being Earth’s cosmic water source.
The unique level of detail to which we’ll get to know Bennu will also help us in all future asteroid studies. Of course, we’ve examined meteorites—cosmic debris that has fallen to Earth—but only after their trajectories have brought them across our path and through our atmosphere.
Since we don’t usually have the opportunity to examine an asteroid sample up close in the lab, we mostly study asteroids through ground- and space-based telescopes.
If all goes well, after 2023, we will have both an original sample and all of these other measurements for Bennu so we can see how they compare.
We can get an idea of how the conclusions we draw from those telescope-based measurements stack up to the real thing. Then, we can apply any adjustments to future studies of asteroids.
For other uses, see Aida (disambiguation).
AIDAMission typeDual asteroid probesOperatorEuropean Space Agency, NASAWebsiteAIDA study
Start of missionLaunch dateHera: 2024,DART: February 2022Rocket
- Hera: Ariane 6
- DART: Falcon 9
(65803) Didymos orbiterSpacecraft componentHeraOrbital insertionSeptember 2027(65803) Didymos impactorSpacecraft componentDARTImpact dateOctober 2022
The Asteroid Impact and Deflection Assessment (AIDA) mission is a proposed pair of space probes which will study and demonstrate the kinetic effects of crashing an impactor spacecraft into an asteroid moon. The mission is intended to test and validate impact models of whether a spacecraft could successfully deflect an asteroid on a collision course with Earth.
The original plan called for a European spacecraft, the Asteroid Impact Mission (AIM), to operate in synergy with a large NASA impactor called Double Asteroid Redirection Test (DART) and observe the immediate effects of the impact.
AIM was cancelled in 2016 when Germany was unable to fund its portion, and after some backlash within ESA, AIM was replaced in 2018 with a smaller spacecraft called Hera that will launch five years after DART to orbit and study the crater on the asteroid.
DART is currently planned to impact in 2022 in the small moon of asteroid 65803 Didymos, while Hera will arrive at Didymos in 2027, five years after DART's impact.
Initially, Hera's role was to be realized by a much larger spacecraft called Asteroid Impact Mission (AIM), that would have observed the plume, the crater, and the freshly exposed material to provide unique information for asteroid deflection, science and mining communities.
In December 2016 the European Space Agency cancelled the development of the AIM spacecraft after Germany decided to fund the ExoMars project only. Germany offered to cover only 35 million of the 60 million needed for the AIM portion to continue, and this was not enough to continue development.
 Had AIM been developed, its notional requirements in 2012 were: 
Space exploration in the 21st century by Anatoly Zak
- January 19: SpaceX conducts a successful launch abort test during the suborbital flight of the Falcon-9 rocket with an unpiloted Crew Dragon spacecraft.
- January 30: NASA's Spitzer infrared orbital telescope, SIRTF, is switched off permanently after 16 years of operation.
- February 9: An Atlas-5 rocket launches ESA's electrically powered Solar Orbiter to fly within 40 solar radii in a 150-day orbit following multiple flybys of Earth and Venus. (Originally planned for launch in 2015-2017)
April 30: Europe's BepiColombo spacecraft to fly 11,264 kilometers from Earth on its way to Mercury. (As of 2018. As of 2012, the Earth's flyby was planned on Aug. 14, 2016, then postponed in 2014.)
- May 5-8: Following its launch on the Chang Zheng-5B rocket, China's unpiloted prototype of the next-generation crew vehicle successfully performs its first test flight in the low Earth orbit, concluding with a soft landing of the Descent Vehicle in the Alashan Desert of Inner Mongolia on the Chinese territory.
- July 16: Europe's new-generation Ariane-6 rocket to make its maiden launch. (As of 2017)
- August 8: China to send the Huoxing-1 mission to Mars.
Oct. 16: Europe's BepiColombo spacecraft to make its first of two flybys of Venus (at a distance of 10,907 kilometers) on its way to Mercury. (As of 2012, the flyby of Venus was planned on Nov. 25, 2017, but it was postponed in 2014.)
- October-May 2021: The US-European Asteroid Impact and Deflection Assessment, AIDA, mission to launch ESA's Asteroid Impact Mission, AIM, spacecraft and NASA's Double Asteroid Redirection Test, DART, probe to a binary asteroid Didymos.
- India to launch the Aditya-L1 spacecraft into the L1 Langrage point in the Earth-Sun system to study Sun.
- NASA to send a rover to Mars.
Japan's Hayabusa-2 spacecraft to return to Earth with samples of a carbon reach asteroid. (As of an August 2010 budget proposal, approved in January 2012.)
China to launch a second add-on module for its Earth-orbiting space station. (As of end 2014) China to complete orbital assembly of a modular space station. (As of June 2013). China to launch a 20-ton manned space station into the Earth orbit with the Chang Zheng 5 rocket.
(An unofficial Nov. 2007 statement quoted by China Daily newspaper, by Long Lehao, one of the leading designers of the Chang Zheng 3A rocket. The date was officially denied, however in November 2012, another official Chinese statement promised “manned space station” in 2020.
Japan's new-generation H-3 rocket to fly its first test mission. (As of 2013)
China to launch a Mars rover. As of 2011. the launch was expected in 2022 but by 2016, the mission was apparently advanced to 2020-2021 to mark the 100-anniversary of the Chinese communist party.
South Korea to launch a lunar probe into a polar orbit around the Moon for a year-long mission. (As of 2017)
End of year: An Atlas rocket to launch a Dream Chaser space plane developed by Sierra Nevada corporation on its first mission to the ISS. (As of Feb. 8, 2018)
Unfulfilled in 2020:
January: NASA's Deep Impact probe to encounter a half-mile asteroid 2002 GT, which regularly crosses path with Earth. (As of December 2011).
Feb. 20-29: NASA's Atlas-5 rocket to launch the Europa orbiter, JEO, toward Jupiter. (As of February 2009, however cancelled before 2012.)
March 11-23: Europe's Ariane-5 ECA rocket to launch a Ganymede orbiter, JGO, toward Jupiter. (As of February 2009. Under consideration by ESA from March 2005 with a projected launch in 2016, In 2007-2008, Russia and Europe discussed a similar mission, known as Sokol-Laplas (Sokol-Laplace)).
Japan to launch Destiny+ mission.
The latest date for NASA to resume manned exploration of the Moon. (Set on Jan. 14, 2004, canceled on Feb. 1, 2010)
NASA to launch a formation-flying infrared interferometer to search for planets around other stars. (Delayed by the 2006 budget cut)
NASA's probe heading toward Neptune to flyby Jupiter. (A 2005 proposal within NASA Vision Mission)
Russia to launch a new-generation space station to replace ISS, into the polar orbit. (The statement of the Russian space agency head at the MAKS 2007 air and space show). Russia to launch a core module of the Earth-orbiting assembly complex for planetary spacecraft. (376)
The European Space Agency to launch the Tandem mission to Saturn, Titan and Enceladus, and possibly delivering a balloon into the atmosphere of Titan. (Later became known as Titan and Saturn System Mission, TSSM).
It competes with the Laplace mission, targeting Jupiter and Europa. (A 2007 proposal within Cosmic Vision study; the selection was originally expected in the Fall of 2008, but was delayed to the beginning of 2009.
The launch date was delayed from 2018.)