DART Mission
Ensuring Safety Of Our Planet
Double Asteroid Redirection Test (DART) is a NASA space mission of planetary defense against near-Earth objects (NEOs). Its purpose is to assess how much a spacecraft strike can deflect an asteroid using a transfer of momentum by striking the asteroid head on in turn slowing it down. Before learning about DART, let’s understand the meaning of an asteroid.
Asteroids are rocky materials that were left over from the formation of the solar system about 4.59 billion years ago. An asteroid may be regarded as a minor planet of the inner Solar System. They’re full of metals. Due to this, and based upon their composition the asteroids are classified into three categories — Chondrites, Stony and Metallic — written C, S, and M respectively. The asteroids are known to orbit around the Sun and follow a fixed path. Occasionally, they get deflected from their orbits. When they get deflected they pose threat to the planets. Our telescopes are roving 24x7 in search of these small objects.
Why do these asteroids get deflected from their fixed path?
Their orbits are fixed but sometimes their orbits get affected by the gravitation pull of planets like Jupiter and a very few times due to planets like Mars. These planets knock the asteroids out of the belt and throw them into all the possible directions.
Asteroids that passed at the starting of this year
This year is special in terms of observing and dealing with space. Right from the start of the year, we read in the newspapers about the asteroids that flew close to our planet. These include:
Asteroid 2021 YK is preferred to be known as a Near Earth Object (or NEO), i.e. it is an asteroid whose orbit is close to intersect Earth’s orbit.
Asteroid 2014 YE15 passed on 6 January 2022 within the distance range of 4.6 miles which is approximately 7.4 kms.
Asteroid 2020 AP1 is a 4m asteroid that passed on January 7 at a distance of 1.08 million miles.
Asteroid 2013 YD48 passed near the earth on Jan 11, 2022. It is regarded as a 105 m object that is even bigger than the Big Ben.
Asteroid 7482(1994 PC1) is two-and-half times the height of Empire State building.
Asteroids are not uncommon objects in the outer space. Asteroids with a 1 km diameter strike Earth every 500,000 years on average. Large collisions with 5 km objects — take place once every twenty million years. So we must know how to deal with these bodies.
Planetary Defence
Planetary defense include the capabilities required to detect and warn of potential asteroid or comet impacts with Earth, and then either prevent them or mitigate their possible effects. Near-Earth objects (NEOs) are asteroids and comets that orbit the Sun like the planets, and they can pass within about 30 million miles of Earth’s orbit. Planetary defense is “applied planetary science” to address the NEO impact hazard.
Types of asteroids on the basis of threat
Not all asteroids are dangerous for the earth. Only those that come in the vicinity of the earth are deemed dangerous. We can imagine the wrath they can bring along by citing the example of an asteroid that struck the earth and wiped out the entire existence of dinosaurs, and many other species. So not wasting any time, let’s study the threat levels associated with these asteroids. Asteroids can be classified as dangerous according to their respective size or diameter. These include:
- Threat level 1 — these asteroids have a diameter less than 10m.They’re not much dangerous. These enter a lot of times in the atmosphere of earth and gets ablaze.
- Threat level 2 — these asteroids are of diameter of 20–100m. They’re dangerous and can devastate an entire city.
- Threat level 3 — these asteroids are of diameter of 500m. They’ve a tremendous amount of energy which can be like combining the entire nuclear weapons of the entire world. These are expected once every 49000 years.
- Threat level 4 — these asteroids are of diameter of 2–3kms. When they penetrate the earth, most of the life on earth dies — oceans gets acidified, nuclear winter phenomenon is observed. It comes every 100 million years. Last time it struck earth and led to the mass killing of dinnausaurs when a 10 km wide asteroid had hit the Yucatan Peninsula. The Chicxulub crater is the mark the asteroid left behind. Its energy is beyond imagination; it’s equivalent to billion megaton of hydrogen bombs.
Note:An asteroid with diameter more than 150m that approaches earth is considered in the category of “hazardous” by NASA.
Methods to prevent asteroids from colliding with Earth
There is no way to completely shield our planet from the disastrous effects of the asteroids, but we surely can deflect some of them from their trajectories. Scientists have proposed certain methods or techniques to deflect these dangerous objects. Methods/techniques to save earth from such collisions include:
- Kinetic Impact — also called kick method — this method involves knocking off the asteroid from its course with the help of a heavy spacecraft. This method was used for the DART mission. It is the first method that has been successfully tested this year.
- Nuclear Explosion — This technique involves shredding the asteroid with the help of a nuclear weapon. It’s most preferably good for small asteroids.
- Painting — It is a unique technique, which will leave you awestruck. It involves painting the asteroid with white paint, spraying it on one end of the asteroid. Soon, Sun’s rays of light would be falling stronger on the more reflective side, and slowly the asteroid gets deflected from its path.
- Gravitational tractor technique — it is also an interesting technique, in which a heavy and large spacecraft flies alongside the object for many years, possibly 15–20 years. With the mutual gravity, the asteroid is deflected from its course and our planet is saved.
DART Mission
DART is a joint project between NASA and the Johns Hopkins Applied Physics Laboratory(APL). Several organisations are providing assistance to the mission. Even many nations are participants as International partners, such as the European Space Agency (ESA), Italian Space Agency(ASI), and Japan Aerospace Exploration Agency (JAXA).
DART is NASA’s first spacecraft mission developed to achieve planetary defense objectives.
DART carries both hydrazine propellant for spacecraft maneuvers and attitude control, and xenon to operate the ion propulsion technology demonstration engine.
DART collided with the 160-metre-wide asteroid Dimophos, which was orbiting a large asteroid Didymos, both of which were circling the sun, 11.2 million kilometers from our planet.
Didymos
The asteroid Didymos was discovered in 1996 by Joe Montani of the Spacewatch Project at the University of Arizona. The satellite Dimorphos was discovered on 20 November 2003, in photometric observations by Petr Pravec and colleagues at the Ondřejov Observatory in the Czech Republic. Dimorphos was detected through periodic dips in Didymos’s brightness due to mutual eclipses and occultations.
Result
The spacecraft struck the asteroid in the direction opposite to the asteroid’s motion. After observing the two bodies for the period of ten days, NASA announced that the trajectory of the smaller asteroid has been altered. Earlier, the orbit of Dimorphos around Didymos took 11 hours and 55 minutes. After studying the impact, it is found that an alteration of 32 minutes in the orbit has taken place which has been changed to 11 hours and 23 minutes.
DART spacecraft contains:
DRACO( Didymos Reconnaisance and Asteroid Camera for Optical Navigation) — it is a high resolution camera to observe the collision and its consequences.
LICIA Cube — a small CubeSat that piggybacked with DART and separated on 11 September 2022, 15 days before impact. It acquired images of the impact and ejecta as it drifted past the asteroid. Astronomers will now spend weeks and months observing the change in the brightness with the help of telescopes to study the altered orbital period.
Antenna — The DART spacecraft is the first spacecraft to use a new type of high-gain communication antenna, a Spiral Radial Line Slot Array (RLSA). The circularly-polarized antenna operates at the X-band NASA Deep Space Network (NASA DSN) frequencies.
GNC and Smart Navigation — GNC stands for guidance, navigation, and control (GNC). With its help, the DART team worked upon the algorithms called SMART Nav (Small-body Maneuvering Autonomous Real Time Navigation). It’s a different navigation system in a way that the optical navigation system identified and distinguished between the two bodies at Didymos and then, working in concert with the other GNC elements, directed the spacecraft toward the smaller body, Dimorphos.
Advanced Ion Propulsion — NEXT–C, an ion propulsion system developed by NASA Glenn Research Center and Aerojet Rocketdyne, gives improved performance, fuel efficiency, and operational flexibility compared to the ion propulsion systems flown on NASA’s previous planetary mission of Dawn and Deep Space 1.
Facts
- The Didymos system is not an Earth-crossing asteroid, so there is not even a single possibility that the deflection could create an impact hazard.
- The system is composed of two asteroids: the larger asteroid Didymos (diameter: 780 meters, 0.48 miles), and the smaller moonlet asteroid, Dimorphos (diameter: 160 meters, 525 feet), which orbits the larger asteroid.
- The timing of the DART impact in September 2022 was chosen to be when the distance between Earth and Didymos is minimized, to enable the highest quality telescopic observations.
Importance of mission
The mission has many advantages which are summarised below:
- Ensuring safety from the asteroids — Although it was a test mission but if in the future an asteroid approaches earth then we are ready with
- Mining rare earth metals (as these metals are hardly available on our planet eg., yttrium, niobium, rhodium, palladium, osmium, iridium, scandium).
Organisation that track asteroids
We can’t completely neglect outer space. So there are programmes that have been devised to search and gather information regarding these asteroids.
Asteroid Watch Dashboard
It tracks the asteroids and comets that have a possibility of approaching earth or even near the surface of our planet. It shows the date of closest approach, the diameter of the asteroid, and also the distance of the asteroid from earth.
This wonderful dashboard gives the complete picture of an asteroid or a comet in the form of physical day-to-day life objects like — one asteroid has been depicted by the size of a bus, another with a size of a car, the third with is shown in dimensions of a house and the next one as a size of a sky-scrapper.
Space guard Program
This program detects big asteroids, the ones that are more than 1km in size that cross earth’s orbit.
Space is not a safe place, and is full of objects that can pose threat to our planet. So long as the technological advancement is there we can ensure the safety of our planet. There are two challenges — first one is to gather information regarding these objects. The second one involves deflecting the path of their trajectories. The first challenge has been overcome by our advancing technologies especially our telescopes, while the stepping stone in dealing with the second challenge has been taken by the DART mission. This asteroid system is a perfect testing ground to check if intentionally crashing a spacecraft into an asteroid is an effective way to change its course, HERA mission of the ESA will be launched to Didymos in 2024 to study the assessment of the impact…….
