How COSMIC Works

Ever wonder why your Global Positioning System (GPS) device sometimes places you in the middle of a building, when you’re pretty sure you’re still on the street or sidewalk? Frustrating, yes, but the problem is not with the accuracy of the GPS network itself (the GPS satellites’ locations are known quite precisely). The problem comes from distortions in the GPS signal caused by the atmosphere around you. Temperature, pressure and humidity in the air — and even electrical variations in the upper atmosphere — all have a cumulative effect on the GPS signal by the time it reaches your location.

Turning vice into virtue, COSMIC is a groundbreaking joint project by the United States and Taiwan that listens to the distortion in the GPS signal and calculates information that can be used to improve weather forecasting, predict climate change and monitor the Earth’s changing magnetism.

Using a concept developed in the 1960s for the Mariner IV mission to Mars, and based on the success of a preliminary proof-of-concept experiment (Global Positioning System/Meteorology, or GPS/MET) in the late 1990s, the University Corporation for Atmospheric Research (UCAR) in Boulder, Colo., and Taiwan’s National Space Organization (NSPO) reached an agreement in 2001 to develop a more robust experimental program. While its official title is the Formosa Satellite Mission #3/Constellation Observing System for Meteorology, Ionosphere and Climate (FORMOSAT-3/COSMIC), it is generally referred to in the United States simply as COSMIC. The NSPO is providing 80 percent of the $100 million funding for the project, with UCAR and other American agencies providing the rest [source: Henson].

Perhaps more interesting than COSMIC’s name is what it’s proposing to do. Its five-year mission is to show that it doesn’t take a lot of resources to provide the kind of fundamental science needed to redefine meteorology and begin building the archive of accurate climatological data needed to improve existing climate models. This in turn will teach us a great deal about climate change.

Ultimately, the observations made by COSMIC could allow us to predict hurricanes, droughts, other major natural disasters and even thunderstorms much more accurately.

Next, let’s take a look at the different components that make up COSMIC.

COSMIC consists of a network of satellites, ground stations and data centers.

Satellites

Launched on April 14, 2006 on a single Minotaur rocket, the “constellation” of six cylindrically shaped COSMIC microsatellites took between one to two years to reach operational altitude and position [sources: COSMIC Web site, Fong]. Each satellite weighs around 110 pounds (70 kilograms) and measures about 46 inches (116 centimeters) wide and 7 inches (18 centimeters) high, and each one carries the same set of three instruments on board. We’ll cover those instruments and what they do a little bit later, but generally speaking, these satellites make detailed measurements across the atmosphere every day.

COSMIC satellites are in a polar orbit, meaning that during each trip around the planet they pass over both poles. Separated by 30 degrees of longitude and operating at about 500 miles (800 kilometers) above the planet, the satellites together are optimized to cover the entire surface of the Earth as often as possible [source: Anthes].

Because the mission approach is new and limited to six satellites, technical problems sometimes arise. At any one time, several of the satellites are experiencing low power or other technical issues, limiting their functionality and the number of observations the instruments on board can make. The projected life of the satellites is five years [source: Fong].

Ground Stations

Data transmitted from the satellites is collected by ground stations in Alaska, Virginia, Norway and Antarctica, with most of the downloading taking place in Alaska and Norway [source: Hunt]. These ground stations then relay the information to the data centers. The Multi-Mission Center (MMC) located in Taiwan controls the movement of the satellites themselves [source: Schreiner].

Data Centers

The data received by the ground stations is forwarded to the data centers in Taiwan and Boulder. In the United States, the data center is called the COSMIC Data Analysis and Archive Center (CDAAC), where a staff of 10 processes and distributes mission data to the scientific community.

But what data are actually collected, and how is this done? The next page explains just what’s on board each COSMIC satellite.

Before we explore the nuts and bolts of COSMIC, it helps to know a few details about the Earth’s atmosphere that most of us learned in school but may have forgotten. The atmosphere is not too different from a multi-layer birthday cake, with each layer sitting atop the next, except that inhaling air in the atmosphere won’t often give you a stomachache. Also, the dividing lines between atmospheric layers are not nearly as well-defined as layers of creamy chocolate frosting. The lowest level of the atmosphere is called the troposphere. It consists of the air that we breathe every day and is where most of the events we associate with weather take place. This layer goes from the ground up to around 6.2 miles (10 kilometers) above the Earth’s surface.

Above that sits the stratosphere, which stretches from approximately 6.2 to 20 miles (10 to 30 kilometers) above the Earth. Originally thought to be very stable, air warming or cooling in the stratosphere is now known to cause significant changes in weather patterns in the troposphere, making this area an extremely worthwhile subject to study [source: Yalda].

The last thing we need to know about is the ionosphere, which consists of the ionized, or charged, particles in the upper atmosphere starting around 50 miles (80 kilometers) above the Earth. Intense solar radiation at this altitude dislodges electrons from molecules in the air, electrifying the atmosphere [source: UCAR]. If you’ve seen the aurora borealis, you’ve seen the ionosphere in action.

Now that we have a better understanding of what COSMIC is looking at, let’s explore the instruments it uses to get the best view.

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