Are there any resources that talk about what is a safe number of satellites for different altitudes and the effects of space pollution?
I have heard of the Kessler Syndrome, any suggestions that discuss this?
Generally as part of the permitting process you have to file an Orbital Debris Assessment Report that contains predictions for orbital lifetime, what will happen to the satellite at EOL, systems for putting the satellite in a safe orbit in case of in-service failure, launch failure etc, risk of collision with other orbital objects and so on.
The details differ depending what orbital regime. Things at ISS altitude (~400km) or below will deorbit very quickly (days to months). Terra Bella and other earth observation satellites are typically in slightly altitude, sun-synchronous, near-polar orbits. They will need to carry propellant to drop the vehicle down to a lower orbit when they are taken out of service, otherwise the orbital lifetime will be 5-50 years.
Geosynchronous satellites are basically going to be up there forever, so they are placed into a slightly lower (but still extremely high) parking orbit after their useful life ends. This keeps them out of the way of the active satellites, and the orbit there is so large that collisions are unlikely.
Finally, the US maintains radar tracking, and will notify operators if a collision is possible so they can make a maneuver. Generally a small adjustment, if performed ahead of time, is sufficient to reduce the probability of collision significantly.
The scary things are debris that are too small to track but large enough to cause damage, and situations where non-operational satellites conjuct.
Fun fact: if the conjunction probability is high enough, the Air Force will call you in the middle of the night.
Lots. It tracks radius squared, if not cubed. As altitude gets large (which you need for orbit anyway), you can fit a ton of small satellites safely.
I mean low earth orbit is at least as much space as we have on the surface, which is already pretty damn big.
Yeah, speeds and orbits and stuff change the game a bit, but i can't imagine even a few thousands of satellites cramping a space that large.
Which is when relative motion becomes a problem. The Empire State Building and the Trump Building are at approximately the same altitude (i.e. sea level) but you don't have to worry about them crashing into each other because their relative position doesn't change. In space everything is in relative motion which effectively costs you another dimension.
Then you no longer have "space" you just have "a line" and if two things are at the same point on the line, they eventually crash into each other.
The worst case would presumably be something large and heavy put into orbit around the equator at the same altitude and speed as geostationary orbit but going in the opposite direction.
But anyway space is very big and the probability of collisions is still low. Two geostationary satellites out of control would probably not collide, they will pass a few hundred of meters away in any direction. The big distance between them is mostly to avoid interference between the radio signals.
Tell me why you might think thats a bad idea?
https://en.wikipedia.org/wiki/Space_debris#Growth_mitigation
When a satellite nears the end of its life expectancy, US law requires that the remainder of the propellant be used to decelerate it so it disintegrates in the atmosphere over the ocean. Presumably European and Asian space agencies have similar rules. These rules didn't used to exist, and there's stuff that's been up for decades.
Yes, these objects are very far apart, but they are moving very fast, and there are surprisingly many of them. Operational satellites are extremely valuable, and if we anticipate anywhere close to a 1 in 1000 chance that one of these objects will collide with one of our satellites, we will burn some of the irreplaceable propellant to avoid it.
It's not an infinite amount of space, so without taking some precautions it would fill up over time, and it's undoubtedly easier and cheaper to avoid the problem altogether than it is to fix it once it becomes a problem.
"________ is huge, we don't have to worry about it!" is how we ended up with so much pollution on earth, so why make the same mistake in space?
See for example Figure 10 of: http://www.agi.com/downloads/resources/white-papers/20110808...
I've always wanted to get a group of people together at my college and build a CubeSat but when you say "I want to build a satellite" people think you are crazy.
We have the labs, the supplies, and the ability to expense anything we want but no one thinks it is possible.
It was one of the most rewarding things I did in college. We launched a cubesat and used it to capture images of the curvature of the Earth and measure the Earth's magnetic field. The work to build the cubesat was tough, but extremely rewarding.
Edit:
Check out http://www.nasa.gov/offices/education/programs/national/spac... and see if you can find a local Space Grant program. They'd more than likely be able to either get you the resources or point you in the right direction to get going.
We launched ours via a ballon which had the cubesats attached to it. We needed a micro-controller (even easier to find now) a camera and our sensors. All very obtainable. I think the most expensive thing was the magnetometers which ran $80 a pop.
[1] http://www.antipope.org/charlie/blog-static/2015/09/the-skys...
Kessler Syndrome can be brought under control with as few as five upper stage boosters brought out of orbit per year. Whether the political will exists to spend money to clean up our space mess is another issue entirely.