Figure 3. A comparison of the size of the Chelyabinsk meteor to known objects. Source: https://3.bp.blogspot.com/-cfRY7Uvd6lI/W2sRYsdunEI/AAAAAAAAhVE/jUW1Y0w6zyQrjf5gq2wbQMLDfHiWPvB-wCLcBGAs/s1600/Chelyabinsk-Meteor-Size-Comparision.png fbclid=IwAR04lXNvuf0gdf206_O0lNSeqxYgO_xuxgndcQ21_CPTepYvM2nOrRml1co

As we have discussed, the Chelyabinsk meteor is the largest object we have witnessed enter Earth’s atmosphere in our lifetimes, giving us reason to learn from the event. Scientists came to the conclusion that some pieces of the original meteor were formed within the first four million years of the history of the solar system, adding size and pieces until the day it came into contact with another object which led the Chelyabinsk meteor to Earth.⁵ This allowed scientists to come to the conclusion that there are many more threats that could be close to our atmosphere that could do way more damage. Perhaps the most important is the planet needs to “wake up” when it comes to the possibility of objects entering the atmosphere. With the meteor being roughly the size of a six-story building, it went unnoticed for far too long as it entered our atmosphere.

This led NASA to develop a team dedicated to detecting these threats and using models created from the explosion of the meteor, it allows them to predict path’s, sizes, and possible damage of other objects.⁶ As they continued to research the event, scientists found that most of the damage from the meteor came from the air blasts of the debris, instead of the impact of the debris itself. For example, glass shards from exploding windows. Scientists should look into different compositions of windows to attempt to reduce this threat. Scientists utilized every ounce of information provided by this meteorite this also allowed them to confirm and tuning methods of predicting meteorite entry.

Predicting Entry of Meteors

Figure 4. Satellite images of the Chelyabinsk meteor. Source: https://www.researchgate.net/profile/Jekan_Thangavelautham/publication/318239696/figure/fig2/AS:513203981766657@1499368772570/Earth-Viewing-Satellite-Perspectives-and-ground-monitoring-of-the-Chelyabinsk-Meteor.png

The most important piece of information that scientists learned from the event is the possibility of something like this happening again is higher than we think, and something needs to be put in place for a catastrophe to be avoided. Scientists have learned patterns, compositions, and the history of meteors from the event, which gives viable information regarding other objects that could enter our atmosphere.

There are different types of methods used by scientists to determine the trajectory of meteors and some of the ones used for the Chelyabinsk meteor include radar observation, analyzing low-frequency sounds waves known as infrasound, optical data as well as data from geostationary satellites. All have their strengths and weaknesses.

Radar Observation Method

The first method is radar observation which provides measurements of the range and azimuth between a ground station and the meteor so giving the meteor’s position, and the Doppler shift in the returning signal can be used to estimate speed. Multiple observations can provide accurate estimates for meteor trajectory.⁷ Although, there are many regions not covered by radar and therefore no observations will be available for a meteor if it falls in such an area.⁷

Infrasound Method

Another approach is analyzing low-frequency sound waves (infrasound) produced by the passage of a meteor through the atmosphere. Data from infrasound stations can be used to estimate the meteor’s kinetic energy and by using multiple microphones and several stations, helps provide data on the meteors trajectory.⁷ Since stations can be and are spread out across the planet, there a greater chance to detect a meteor using infrasound than by radar.

There are still uncertainties about infrasound measurements, and the computed orbital elements will be more uncertain as well, particularly as it is hard to estimate the trajectory unless combining infrasound with a secondary source of data.⁷ Although, in many cases, this is not possible, which means the trajectory estimate will either be very inaccurate or entirely missing.⁷ Therefore, while infrasound is helpful there remain disadvantages to using infrasound.

Optical Data Method

The other approach is optical data which has been used for the Chelyabinsk meteor and this approach uses data from images or videos to estimate trajectory. If two or more cameras capture images of a meteor, than the camera positions and meteor azimuth and elevation within the images can be used to triangulate the meteor’s position.⁷ As with infrasound, the second set of measurements at a different time can be used to estimate the velocity. The optical data method was used by quite a few people because of the number of videos and images captured from bystanders during the Chelyabinsk event. This method is appealing because it doesn’t require specialized equipment and a number of source cameras can be used. Along with everyday use of cameras, there are numerous professional camera networks that are specifically designed to capture images of objects that enter the atmosphere.

Geostationary Satellite Method

Another method was used from geostationary satellites that typically generate images of Earth across multiple wavelengths, both in visible and infrared regions of the spectrum with a relatively frequent image capture time between 5 & 30 minutes.⁷ Each pixel within a satellite image is ‘geolocated’ so that it corresponds to a particular latitude and longitude on the Earth.⁷ This is useful when analyzing the land surface but problematic when examining features at high altitudes because the parallax effect means that geolocation for these features will be incorrect.⁷ The apparent position of the feature will be shifted relative to its actual position by an amount proportional to its altitude and the angle between it and the point directly below the satellite.⁷ Parallax correction tools exist for the use within meteorological analysis of satellite image that use an estimate of cloud height to correct for this shift and display the cloud at its correct location above the Earth.⁷

The trail of the meteor was visible from 3 of the Meteosat Second Generation (MSG) series of satellites.⁷ Two clear identifiable points on the trail were picked out in these images and used for determining the meteor’s position with the parallax correction method.⁷ This helped pinpoint the Chelyabinsk azimuth and slope as it moved through the atmosphere. By understanding the trajectories of meteorites we were able to further utilize this information to devise strategies to prevent and prepare for another potential meteor strike.

Future Prevention and Preparation

Figure 5. NASA’s Planetary Defence Goal to Detect NEO. Source: https://planetary.s3.amazonaws.com/assets/images/thumbnail/card-neo.jpg

After an Earth-shaking event such as the Chelyabinsk meteor strike the top priority has become how to prevent it from happening again. Events such as this and many others directly influenced the development of protocols, theories, and plans in order to monitor and handle situations dealing with near-Earth objects. NASA has been at the forefront of this critical system development. At roughly the same time as the Chelyabinsk meteor event, NASA’s near-earth object (NEO) observations program was growing in popularity due to the increased awareness of the risk of an asteroid impact.⁸ This NEO observations program focuses on locating asteroids 460 feet and larger that could potentially impact Earth and cause catastrophic damage. The intention behind this program is to locate the majority of asteroids early enough to permit deflection or at least allow preparations for impact mitigation.⁸

The Planetary Defense Coordination Office 

In early 2016 NASA established the Planetary Defense Coordination Office (PDCO) whose sole responsibility is to ensure early detection of potentially dangerous NEO. This is a very mild description of the PDCO their job is actually a lot more than just location NEO that poses a hazard of impacting Earth. They also are tasked with “Characterizing those objects to determine their orbit trajectory, size, shape, mass, composition, rational dynamics, and other parameters, so that experts can determine the severity of the potential impact event, warn of its timing and potential effects, and determine the means to mitigate the impact;”⁹ Furthermore they are also responsible for planning the appropriate action that would be necessary to deflect or disrupt NEO that is on a collision course with Earth and also implement this plan. If the NEO’s course cannot be altered they are also responsible to mitigate the effects of the collision and protect lives.⁹ The Planetary Defense Coordination Office plays a large role in keeping the Earth safe from near-earth objects by detecting the impending collision early enough better preparation can be conducted and possible deflection measures can be taken.

The National Near-Earth Object Preparedness Strategy and Action Plan

Even though we don’t hear much about asteroids and meteors colliding with Earth in the past couple years this doesn’t mean that advancement’s and protocols aren’t being developed. In June 2018 the National Science and Technology Council released a National Near-Earth Object Preparedness Strategy and Action Plan. This document depicted five main objectives for protecting Earth from NEO’s, this would hopefully increase accuracy, decrease uncertainty and allow for effective decision-making when NEO’s pose a threat to Earth.

In summary of the document, the first objective is to hopefully recruit any existing or planned telescope programs in hopes to improve detection and tracking through an increased volume and quality of data stream. The second objective is to improve modeling, prediction, and information integration across multiple agencies, this would potentially aid in locating if, when, and where an asteroid could strike and hopefully allow emergency service teams to be prepared for the impending collision. The third goal was a direct request to NASA to develop new ways to deflect asteroids on a collision course to Earth, specifically developing new technology for rapid response NEO reconnaissance missions; this would hopefully redirect asteroids from their impending collision course. The fourth objective is to bring together the world and create better cooperation between countries thus ensuring the safety of the planet as a whole. Finally, the last objective is directed to policymakers in the United States to develop an emergency protocol in case a large asteroid is going to strike Earth.¹⁰ Periodic advancements is needed to better prepare the world for impending asteroid strikes, this issue breaks the boundaries of nationality, religion, and culture, letting science do what is best for humanity as a whole.