There’s been a lot of hand-wringing in recent years regarding space situational awareness (SSA). Almost every month another article appears, portending of the upcoming calamity in space–the point in which one rogue satellite or a chunk of debris hits another satellite or chunk of debris. These two chunks initiate a celestial version of pool. As in pool, one chunk will hit another chunk which speeds on to hit another chunk or cluster of chunks. The struck chunks fan out, hitting other chunks, and then those chunks hit even more chunks, and so on.
Invariably the hand-wringing prompts online conversations about whether this space-snooker-based scenario is realistically depicted in the movie “Gravity” (that Sandra, she floats so gracefully in space). Inevitably, a new round of blog posts use the computer-generated picture showing thousands of pixels surrounding the Earth–with each pixel representing one of the tens of thousands of objects, normally junk, orbiting the Earth.
The resulting picture from these conversations and blog posts is clear–the end is nigh, space-wise. Humanity has once again junked up another environment, and will soon reap what’s been sown. Unless we stop those smaller, less expensive satellites from messing it all up. Or something like that anyway.
According to some people, the number of objects (satellites, debris, rocket bodies, etc.) in orbit is reaching scary levels–tens of thousands–which is why they are verbally wringing their hands for public consumption. Is this a “chicken-littling” of space, or is there really something to worry about here? Is the blame for debris really so clear cut? Before getting to the answer, it’s probably useful to define SSA, particularly for readers new to the space arena.
There are many folks with specific definitions of SSA. The U.S. military is interested in the position, identification, and activities of objects orbiting the Earth which might potentially compromise the U.S. ability to defend itself or carry out global missions. The Europeans encompass some of the U.S. military SSA definition, but include discovering and identifying Near Earth Objects–things in space that might eventually literally have an impact on Earth if they get too close–and space weather.
For this post’s purposes, I will use my motorcycle and traffic survival skills to demonstrate SSA, but if you’re a car driver, you’ve been using aspects of SSA already.
When I first bought my motorcycle, I went through a motorcycle safety class (it’s a useful class–take it if you can). The class imparted one particular acronym that stays with me even now, 17 years later: SIPDE. Each word in the acronym suggests a way to survive on the road and hones great habits for motorcycle riding. S–Scan; I-Identify; P-Predict; D-Decide; E-Execute.
SIPDE reminds a rider to constantly use the tools at hand– eyes, brain, and motor skills-to make a rider aware of what’s happening close by, and then do something to keep the rider safe. Eyes scan for anything that may literally impact the rider. Once a rider’s eyes see something, the rider’s mind identifies it, internally racking and stacking the “threat.”
A rider then predicts what the object may do (a dog or child might run obliviously into the road, a self-righteous cyclist might blow through the stop sign from the left, a truck driver in the rear view mirror is on the phone and might not even see the rider). Once the prediction is made, the rider decides on a course of action, and then does it. This kind of cycle goes on if it’s ingrained in the rider, and it all will take place in seconds.
So, how do motorcycles and SIPDE have anything to do with space? Essentially the same actions help define SSA, except a satellite takes the place of the rider. The orbit is the “road” the satellite is on. The tools for scanning, instead of a rider’s eyes and brain, are networks radars and telescopes on Earth’s surface–although some nations have a few space-based SSA “eyes” too. The brains are the people and computers trying to make sense of what’s nearby in orbit (is an object at the same altitude, is it on a path to intersect with another satellite’s “road,” etc.).
These people and computers are also attempting to identify objects close to the satellite’s “road”–its orbit (is it the body of a rocket, is it small debris, is it a satellite that seems to be moving from it’s orbit). Once they figure out what an object is, then they must decide whether the object is a threat, and predict possible actions of the object. The people in this SSA network must then decide what to do and then do it. This may be as simple as notifying satellite owners about a possible collision, or just monitoring the same objects to see if anything changes.
But how bad is it really, out there? Exactly how many objects are orbiting the Earth? Again, is this a “chicken-littling” of space, or is there really something to worry about? Is the blame for debris really so clear cut?
The answer, as it always seems to be, is: it depends. That’s where I’ll end it today, but my next post should hopefully give some perspective.