I was listening to a hip-hop song, oh yeah I like hip hop, [How Low](https://www.youtube.com/watch?v=ox-lfowevqA), while I was thinking of satellites. 
How low can a satellite go to stay in orbit?


<div class="pull-right"><center><img src="https://steemitimages.com/DQmZbJVeRpPnoSpr7s1ZdAKG5KLPkahzfchjazUCgpugaNu/image.png" /><br/><em><sup><sup><a href="https://earthobservatory.nasa.gov/Features/WhyItMatters09/">The satellites of NASA’s Earth Observing System monitor daily events and long term changes. (NASA free image by Jenny Mottar)</a></sup></sup></em></center></div>


 A satellite is usually the word for that man-made equipment or machine that orbits the planet. But those are the artificial satellites. The moon, earth, etc. are natural satellites. The earth is the natural satellite of the sun; it orbits the sun. The other things in the solar system orbit the sun such the asteroids. comets, planets, etc.

The earth's moon is the natural satellite of the Earth; it orbits the earth.

<hr>



We need the artificial satellites in space for a lot of reasons. One of which is for communication such as phone calls, TVs and global positioning system (GPS), etc. 

<div class="pull-left"><center><img src="https://steemitimages.com/DQmUj6UdVNQ6PbphpKFf1LyQctSAjTNWtJGBSKRCsDTeU8k/GPS24golden.gif" /><br/><em><sup><sup><a href="https://commons.wikimedia.org/wiki/File:GPS24goldenSML.gif">By Paulsava (Own work) [CC BY-SA 4.0], via Wikimedia Commons: GPS constellation in medium earth orbit </a></sup></sup></em></center></div>

Currently, the GPS satellites alone has 31 satellites in orbit; this figure includes the decommissioned and those in reserve. For an excellent GPS sync, a total of 4 active satellites should be in available, and for the earth coverage a total of 24 active satellites.


If we look up above the sky appears all free and calm.

But according to the United Nations Office for Outer Space Affairs, UNOOSA [website](http://www.unoosa.org/oosa/osoindex/search-ng.jspx?lf_id=), a total of 8086 satellites was launched into outer space since 1957. With a total of 4788 currently orbiting in space. This amount is an increase of 3.3% from [last year's number](https://www.pixalytics.com/sats-orbiting-earth-2017/).


[James Yorder](https://www.digitaltrends.com/cool-tech/stuff-in-space-website/) was kind enough to make a 3D visualisation in real time of the various satellites, rocket bodies and debris currently floating around in the space. It is a delightful interactive website which you may like to check out [here](http://stuffin.space/). There are a bunch of information of each satellite too if you click on it such as altitude, velocity inclination, type, date of launch, etc.

So when next you look up the sky take a moment and take in the fact that there are thousands of human-made machines floating around in orbit.



<br>
What is an orbit and how does it occur?
<br>


The celestial body such as the plant has an area where the gravitational force can pull anything that is in proximity towards it.

But if an object can "escape" this region of gravitational force, it will not experience a continuous free fall.

Orbit is the outcome of a perfect balance between a planet's gravitational tug and the forward momentum of the body in space. The gravitational force is usually from the more prominent body in space such as a star or a planet.

The body manages to stay in orbit and move in circles as the tug-of-war between the forward momentum of the object and the gravity continues as seen in this image [here](http://www.qrg.northwestern.edu/projects/vss/docs/media/space-environment/tug-o-war.gif).


The two forces (inertia and gravity) has to be perfectly balanced for this orbit to be in place. If the forward momentum is too strong, the object will speed past the orbit, if too weak, the gravity will pull the object to the body exuding the gravitational pull.              


The gravitatational pull of earth can still be felt more than [238,855 miles](https://www.space.com/18145-how-far-is-the-moon.html) (384,000 km)  from earth. This distance is the closest approach (perigee) the moon's elliptical orbit from earth happens to be.

<div class="pull-left"><center><img src="https://steemitimages.com/DQmPzjjL2NoTTzW6KhthYjLFiE3FavFXP3ZNQ4tgsP3VABP/image.png" /><br/><em><sup><sup><a href="https://commons.wikimedia.org/wiki/File:GPS24goldenSML.gif">By Image of earth: Gringer. Scale orbits: Mike1024 [Public domain], via Wikimedia Commons: A scale diagram showing earth and various orbits above it</a></sup></sup></em></center></div>

 The orbit around the earth is in various categories which are dependent on the distance of the satellite from it. There are four broad categories of classification by altitude. These are the Low Earth Orbit (LEO) such as the orbit of the international space station (ISS). The LEO is also for monitoring the earth's surface and in military use for spying. The medium earth orbit (MEO) finds application in  GPS used in sat. navs. 

The Geosynchronous Orbit (GEO) such as the earth observatory, used mainly for communication purposes, e.g. satellite tv

The last is the High earth orbit (HEO) satellites. An example is the [Intersetllar Boundary Explorer](https://en.wikipedia.org/wiki/Interstellar_Boundary_Explorer) (IBEX) used by the NASA for scientific observation. It is the most suitable since its high orbit allows it to move out of the earth's  magnetosphere


| Name | Color |  Distance above earth(km) |
| -------- | -------- |  -------- | 
|Earth    | Blue/brown     | 0     |
Low Earth Orbit(LEO)    | Cyan area    | 160 to 2,000 |
| Medium Earth Orbit(MEO)     | Yellow area  |  2,000 to 34,780 | 
| International Space Station(ISS)   | Red dotted line   | 370    |
| Global Positioning System |Green dash-dot line  |20,230 | 
| Geostationary Orbit| Black dashed line| 35794  |
| High Earth Orbit|Not shown in drawing| above 35,794km|


So to answer the question, how low can you go to stay in orbit is 160km which is in the low earth orbit (LEO) region. If an object gets below 160km, it will experience an *orbital decay*, that is it will lose altitude due to the pull of gravity.

The LEO is an essential aspect of the space program since it is where the ISS is located. Also, all astronauts have to conduct their affairs at LEO except for the crew of the Apollo program between 1968 to 1972.


Now that I know this, all I require is a spaceship capable of catapulting me to a distance of 160km to hit that orbit and start orbiting the earth at a period of between 84 to 127 minutes. 

<hr>

<sup>**References**</sup>
* <sup>[Satellite](https://en.wikipedia.org/wiki/Satellite)</sup>
* <sup>[How many satellites are orbiting the Earth in 2017?](https://www.pixalytics.com/sats-orbiting-earth-2017/)</sup>
* <sup>[3D Visualization of Satelittes in Space](http://stuffin.space/)</sup>
* <sup>[How Far is the Moon](https://www.space.com/18145-how-far-is-the-moon.html)</sup>
* <sup>[Low Earth Orbit](https://en.wikipedia.org/wiki/Low_Earth_orbit)</sup>

<hr>

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