Comments on: Optimum space station/satellite orbits https://habitablezone.com/2017/04/12/optimum-space-stationsatellite-orbits/ Mon, 20 Apr 2026 21:56:17 -0700 hourly 1 http://wordpress.org/?v=3.3.1 By: TB https://habitablezone.com/2017/04/12/optimum-space-stationsatellite-orbits/#comment-38860 TB Fri, 14 Apr 2017 04:46:32 +0000 https://www.habitablezone.com/?p=63342#comment-38860 Apparently the only one using the Tundra Orbits right now is Sirius Satellite Radio. Apparently the only one using the Tundra Orbits right now is Sirius Satellite Radio.

]]> By: ER https://habitablezone.com/2017/04/12/optimum-space-stationsatellite-orbits/#comment-38858 ER Thu, 13 Apr 2017 20:31:01 +0000 https://www.habitablezone.com/?p=63342#comment-38858 Back when I used to work for an oil company, we used data from the HCCM bird which had a very clever orbital geometry. It was designed to fly at an altitude that it passed over every place on earth exactly 12 hours apart (except for extreme high latitudes, which its orbital inclination did not allow). This usually worked out to a late morning pass, and a late evening pass. The idea was that it would image the area beneath it in panchromatic (black and white, or albedo) in the daytime pass. This allowed us to determine how much solar energy the rocks were absorbing. That night, it would fly over the exact same location and image it again in the thermal infrared, which would give an indication how much those same rocks were radiating heat away into space. The orbital height and inclination were synchronized with earth's rotation in such a way that every single spot on earth covered by the satellite would be imaged twice a day, every day, at the same local solar time and insolation. The day and night brightness values were then plugged into an equation that would give us the thermal inertia of the rock. Thermal inertia is related to specific heat, it tells you how long it takes a substance to heat up and to cool off. Different types of rock may appear very similar, or the same rock may appear very differently, due to variations in surface weathering, such as desert varnish, but the thermal inertia is usually a pretty good indicator of what type rock it is. We felt this technique would allow us to distinguish what type of geology we were looking at, even if the outer millimeter or so were colored or weathered in a way that camouflaged its chemical or mineral reflectance and absorbance properties. It also was a measure that was not affected by how the surface of the rock was oriented to the sun's rays or the season of the year. Unfortunately, water has an extremely high specific heat, and even tiny variations in moisture at ground level played havoc with our readings. Still, I was always amazed that the orbital parameters of the satellite could be so cleverly manipulated to allow that kind of precise timing. Back when I used to work for an oil company, we used data from the HCCM bird which had a very clever orbital geometry. It was designed to fly at an altitude that it passed over every place on earth exactly 12 hours apart (except for extreme high latitudes, which its orbital inclination did not allow). This usually worked out to a late morning pass, and a late evening pass.

The idea was that it would image the area beneath it in panchromatic (black and white, or albedo) in the daytime pass.
This allowed us to determine how much solar energy the rocks were absorbing. That night, it would fly over the exact same location and image it again in the thermal infrared, which would give an indication how much those same rocks were radiating heat away into space. The orbital height and inclination were synchronized with earth’s rotation in such a way that every single spot on earth covered by the satellite would be imaged twice a day, every day, at the same local solar time and insolation.

The day and night brightness values were then plugged into an equation that would give us the thermal inertia of the rock. Thermal inertia is related to specific heat, it tells you how long it takes a substance to heat up and to cool off. Different types of rock may appear very similar, or the same rock may appear very differently, due to variations in surface weathering, such as desert varnish, but the thermal inertia is usually a pretty good indicator of what type rock it is. We felt this technique would allow us to distinguish what type of geology we were looking at, even if the outer millimeter or so were colored or weathered in a way that camouflaged its chemical or mineral reflectance and absorbance properties. It also was a measure that was not affected by how the surface of the rock was oriented to the sun’s rays or the season of the year.

Unfortunately, water has an extremely high specific heat, and even tiny variations in moisture at ground level played havoc with our readings. Still, I was always amazed that the orbital parameters of the satellite could be so cleverly manipulated to allow that kind of precise timing.

]]> By: hank https://habitablezone.com/2017/04/12/optimum-space-stationsatellite-orbits/#comment-38857 hank Thu, 13 Apr 2017 20:00:21 +0000 https://www.habitablezone.com/?p=63342#comment-38857 I suspect the "tundra orbit" is the high inclination orbits the Russians are forced to put their communications relay satellites in due to the fact that their country is located so far from the equator, but I guess I'm about to find out! 8) I suspect the “tundra orbit” is the high inclination orbits the Russians are forced to put their communications relay satellites in due to the fact that their country is located so far from the equator, but I guess I’m about to find out! 8)

]]> By: TB https://habitablezone.com/2017/04/12/optimum-space-stationsatellite-orbits/#comment-38854 TB Thu, 13 Apr 2017 18:00:18 +0000 https://www.habitablezone.com/?p=63342#comment-38854 I started typing this out, then realized about two paragraphs in that it was going to be a lot of work, so I dug <a href="https://space.stackexchange.com/questions/6585/orbital-altitudes-are-some-better-than-others-and-why" rel="nofollow">this link</a> up which should answer some of your questions on orbits. (I learned something too: I'd never heard of a "Tundra Orbit.") Short version: Low orbits decay quickly, but are easy to launch to. High orbits don't, but need more launch power and Van Allen belts come into it. The ISS orbit is sort of a compromise. It needs constant orbit boosts (see <a href="https://www.quora.com/How-does-the-International-Space-Station-maintain-its-orbit-and-what-propellant-does-it-use" rel="nofollow">this link</a>) to maintain it, particularly since the ISS has one big-ass drag issue. Willy Ley's famous space station had an orbit of around 1,000 miles, but that was published in 1958, which is the same year the Van Allen Belts were discovered. <img src="http://habitablezone.com/wp-content/uploads/2017/04/Willy_Ley_Space_Station.jpg" alt="Willy Ley Space Station" width="150"/> I started typing this out, then realized about two paragraphs in that it was going to be a lot of work, so I dug this link up which should answer some of your questions on orbits. (I learned something too: I’d never heard of a “Tundra Orbit.”)

Short version: Low orbits decay quickly, but are easy to launch to. High orbits don’t, but need more launch power and Van Allen belts come into it.

The ISS orbit is sort of a compromise. It needs constant orbit boosts (see this link) to maintain it, particularly since the ISS has one big-ass drag issue.

Willy Ley’s famous space station had an orbit of around 1,000 miles, but that was published in 1958, which is the same year the Van Allen Belts were discovered.

Willy Ley Space Station

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