Why space matters and explaining imaging satellite operations, Part 2

Posted on by John Holst

In Part 1 of explaining imaging satellite operations, we assumed a low earth orbit (LEO) satellite is one of the better options for getting great “Earth-selfies” with a camera on board.  We also learned the range of LEOs is pretty big:  99 to 1200 miles.  But we also know closer is mainly better (see previous post to understand why), so naturally, why not choose the closest possible orbit of 99 miles?

The big problem is the atmosphere.  Again, Wikipedia tells us there are gasses between 50 and 313 miles from Earth’s surface.  These gasses tend to slow a satellite down (drag).  If a satellite experiences too much drag, it will eventually slow down too much.  A satellite that’s attempting to orbit between 50 to 313 miles will experience significant drag and slow down a lot.

Such drag is also called aerobraking (but only by those who need to feel important using big words).  If a satellite slows down too much, it will eventually be unable to complete an orbit, re-enter the atmosphere, and hit the Earth.  This can result in unpleasant consequences for those around the satellite’s impact point if the re-entry is unintended and uncontrolled (just ask the Aussies:  http://www.theaustralian.com.au/news/nasa-satellite-crashes-to-earth/story-e6frg6n6-1226145421345).

So, back to the question:  how close to the Earth’s surface can we get a satellite to orbit the Earth without encountering atmospheric drag?  And Wikipedia answers, “313 miles.”  Easy, right?  That’s not to say satellites can’t orbit the Earth using less than that number, but these would have to have to be considered disposable satellites.

Assuming the people running these camera sensors on the satellites want the best, most-detailed pictures, but don’t want the satellite to hit the Earth, then around 313 miles would be optimal for their satellite orbits.

But wait, there’s more…

2 thoughts on “Why space matters and explaining imaging satellite operations, Part 2”

  1. Pingback: Why Space Matters: GEO Satellite operations, Part 3–Revolution Earth | The Mad Spaceball
  2. Pingback: How Satellites Could Find Malaysian Flight MH370 - Defense News

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Published by John Holst

Ill-Defined Space is written by me, John Holst. ​If you’ve ever asked the following question, “What is this commercial space industry thing?” then welcome to my world. I will never have the answer to that question, but I do offer insights based on my industry experience and observations. I’ve tried defining, decrypting, deciphering, analyzing, and then translating the endless stream of the world’s space industry activities, policies, and press releases. I’ve experienced varying degrees of success in my attempts to do so. The upshot is that if you want thoughtful, occasionally useful, observations about the world’s space industry, then you may want to read my analyses. Boring, but potentially credibility-building information follows: I have a Master’s in Commercial Enterprise in Space through the Florida Institute of Technology. I was an undergrad at the University of Washington in Seattle, graduating from there with a degree in Journalism. My analysis of the space industry has been a definitive source for national lawmakers and departments, news outlets such as the Wall Street Journal, Financial Times, Bloomberg, and the San Francisco Chronicle, publications like National Geographic, and National Public Radio. It’s been published in The Space Report: The Authoritative Guide to Global Space Activity from 2014-2023 (here’s a link to a 1Q19 promo copy). You can also see my work in Quilty Analytic’s series of LEO Broadband Reports. ​ I’ve worked in the United States Air Force, Missile Defense Agency, Cobham, Space Dynamics Laboratory, the Space Foundation, and Quilty Analytics. I focused on space operations in the first few and conducted space industry research and analysis with the last two.