National Environmental Satellite, Data and Information Service (NESDIS)



Understanding the Odd Shapes and Sizes of Satellites

Wednesday, March 2, 2016

Why do satellites look like that? Understanding the odd shapes and sizes of these precision machines!

JPSS-1 satellite preparing for calibration checks
The JPSS-1 satellite preparing for calibration checks in September, 2015. Credit: Ball Aerospace and Technologies Corp.

Despite orbiting Earth at speeds averaging 17,000 mph, satellites are far from the sleek, aerodynamic spacecraft we see in science fiction films.

On the contrary, these high-tech environmental observation machines tend to look more like flying refrigerators and phone booths, some the size of small buses— not exactly an image of speed. The key to their high flying routines is air, or a lack of it.

Artist conception of wind drag on a bike rider’s body
Up to 80 percent of the resistance a bike rider faces is caused by wind drag on the rider’s body. In space, satellites do not have to contend with as much resistance.

Air resistance, also known as "drag", is the resistance created by gases and particles moving around an object as it pushes through air.

Imagine riding your bike down a large hill. As you begin to pick up speed you start to feel the wind in your hair and air pushing against your chest. If you lean over the handlebars and tuck your head down, you suddenly begin to go faster, feeling less resistance.

This is because you are creating a more aerodynamic shape and reducing your aerodynamic profile, allowing you to knife through the thick air like the smooth, rounded edges of a race car.

In space, where NOAA satellites orbit, the atmosphere is so thin that there's virtually no air to contend with. When designing a satellite, scientists and engineers are much less concerned with how air will flow around the spacecraft. Rather, they are focused on designing an efficient, accurate and useful satellite that will provide critical Earth environment and space weather observations while also surviving the harsh conditions of launch and life in outer space.

JPSS-1 satellite undergoes solar array fit checks
The JPSS-1 satellite undergoes solar array fit checks during assembly and calibration. Credit: Ball Aerospace and Technologies Corp.

Satellites do encounter trace amounts of atmosphere, however, which produces drag and eventually slows them down.

For satellites in low orbits, like NOAA's POES and Suomi NPP and the Air Force's DMSP satellites, this slight atmospheric drag will result in orbital decay (the lowering of altitude) if not compensated. For some satellites, like Suomi NPP, this is done periodically using thruster-burn maneuvers called "orbital-station keeping." Other satellites, like the POES and DMSP satellites, do not have this capability and will inevitably experience orbital decay over time.

You may be thinking, "Then why did the NASA space shuttle have wings and a curved nose?" This is because the space shuttle was designed to re-enter Earth's atmosphere, where it would once again operate in thick air and come to a gliding landing, something satellites don't have to do.

GOES-R satellite being rotated prior to testing
The GOES-R satellite being rotated prior to testing. Credit: Lockheed Martin.

After launch, satellites rarely see Earth's surface again. Instead, once they are decommissioned, they are left to burn up upon re-entering the atmosphere or are placed much farther way, into something called a "graveyard" orbit.

While they may not look like sleek flying machines, NOAA satellites are capable of some pretty amazing things. Read about them here!