AGI.com Blogs

Will "Spicey" Predict the End of the World?

By: Jason Ruggieri
 A couple of things… One, I’m a few months late on the “Spicey” jokes, and Melissa McCarthy kind of beat me to it. But I needed the literary device… this should be clear in just a moment. Two, click-bait titles are all the rage these days. I think we’re all accustomed to them. But I’ll take this opportunity to introduce you to Betteridge's law of headlines (if you’re not familiar). You’re welcome.  

Every so often you’ll read a headline like “Giant Asteroid to Give Earth a Very Close Shave.” While space is generally very big, there’s also lots of stuff out there. As gravity is apt to do, every so often it tugs one of these rocks across Earth’s path as it orbits the sun. The “Giant Asteroid” mentioned above is actually an object named 2012 TC4. According to Wikipedia, it’s “an Apollo near-Earth asteroid roughly 20 meters in diameter. On October 12, 2017 at 5:42 UT, the asteroid will pass 0.00033 AU (49,000 km; 31,000 mi) from Earth.” Twenty meters… not necessarily “Giant,” but you know, fake news. 

 

If you want to build scenarios in STK of these near earth asteroid events, you will need to use NASA SPICE files (now you get it…).  A SPICE (Spacecraft, Planet, Instrument, C-matrix--spacecraft attitude--, and Events) file contains binary data that defines the position and velocity of one or more celestial objects over large spans of time. Thankfully, there are a bunch of FAQs on the AGI website that will point you to where you can download SPICE files and how to use them in STK (What is a SPICE fileHow can I obtain STK-compatible SPICE files for comets, asteroids, and other small bodies?Creating a New Central Body from a SPICE File).  

Don’t miss the NASA JPL Center for Near Earth Object Studies. They have a great Close Approach website that allows you to query a database of objects and click links to download their ephemerides (SPICE files). 



Once you obtain SPICE data, there are a couple different ways to represent the asteroid object in STK. You can represent it as a Central Body and add it using STK’s Component Browser, or you can add it as a Satellite Object and utilize an ephemeris reader to read an ASCII SPICE file.  

To properly visualize the data and asteroid path in STK, you’ll want to set up your scenario and 3D Graphics view a bit differently. I find it helpful to add as many solar system Planet objects as required for proper reference. Additionally, for each of my 3D Graphics views, I like to increase the Max Visible Distance on the Properties - Advanced page to 1e+20 km to ensure the scenario objects and their orbits are drawn at long distances.  

Now you’re off and running and ready for analysis. 

As for the question posed in the headline: Will “Spicey” Predict the End of the World?  I say “maybe.” Probably not “Spicey,” but if an asteroid is projected to impact Earth in the not-so-distant future, I will guarantee there will be SPICE files to support the claim! 

Posted: 10/9/2017 12:42:36 PM


Tags