Why Do Satellites’ Orbits Look Like A Sinusoidal Wave On The World Map?

The International Space Station

If you’ve ever seen the footage of an artificial satellite’s orbit, this is what you would have seen:

The yellow lines depict the path of the International Space Station

From the image on the previous slide, it’s evident that the satellite has a wave-like orbit, but doesn’t it look a bit unusual for a satellite’s path around Earth?

It certainly doesn’t seem very efficient! The question is, do all artificial satellites, including the ISS, really have such wavy orbits when they circle Earth?

Why the ISS path appears like a wave on the map of the world?

ISS, just like any other artificial satellite, follows an (almost) circular path around Earth

The reason its orbit looks like a wave is because the orbit is 3-dimensional in nature

But when it’s projected on a 2-D Mercator map of the world, it flattens and appears distorted, so it looks like a sinusoidal wave.

ISS orbit around Earth

The International Space Station is a habitable artificial satellite that acts as a manned space station in low Earth orbit

It plays hosts to 5-6 astronauts at a time who conduct different kinds of scientific and technological research on-board

ISS orbit around Earth

Just like any other artificial satellite, the ISS also circles Earth in a predefined path, called an orbit

The ISS’ orbit is located at an altitude above Earth where it still experiences a strong gravitational pull from Earth

ISS orbit around Earth

Contrary to popular belief, it’s not ‘zero gravity’ up there

In fact, the ISS experiences as much as 90% of the gravity that we experience back here on Earth

It’s perpetually falling towards the Earth, but thanks to its huge orbital speed (17,200 mph/27,6000 kmph) and Earth’s rotundity, it never actually hits the surface

ISS orbit around Earth

One noteworthy thing about the ISS orbit is that it doesn’t coincide with Earth’s equator

Whenever we talk about a satellite revolving around the Earth, we generally tend to visualize its orbit coinciding with the equator, but in reality, the ISS orbit looks more like this:

ISS orbit around Earth

It’s evident from the picture on the previous slide that the ISS follows a circular path around the planet

Still, when the same path is represented on the world map, it undergoes a drastic change to look like this:

The Mercator Projection

The maps that we saw in schools when we were kids, the maps shown on TV…

basically (almost) every world map that we come across is wrong

The Mercator Projection

The maps that we saw in schools when we were kids, the maps shown on TV…

basically (almost) every world map that we come across is wrong

The Mercator Projection

There’s actually a good reason behind that

You see, our planet is a 3D object, whereas maps are always 2-dimensional

In order for us to see and visualize the boundaries of countries and large land masses on the face of the Earth, we need a way to project all that 3-dimensional stuff onto a 2-dimensional piece of paper. That’s exactly what a Mercator map does

A Mercator projection of the world

It nicely represents physical features and land masses of the world on a rectangular sheet of paper,

where latitudes and longitudes are straight lines that intersect perpendicularly and the shapes of countries are well-defined.

A Mercator projection of the world

However, apart from causing certain problems when it comes to the relative sizes of countries,

the Mercator projection also distorts the path of the ISS on the world map

Projecting the ISS orbit looks like a wave on a 2-D map

The ISS orbit looks way because its path is aligned with the equator of our planet on a 2-D world map (for our visual convenience)

The path of the ISS (and other artificial satellites) appears like a wave because it’s projected onto a 2-D screen, and not because artificial satellites follow a wavy path around Earth