- The Washington Times - Thursday, July 18, 2002

The excitement surrounding the possibility of space travel to other planets and galaxies often overshadows some of the major developments orbiting Earth. Since the Russians launched Sputnik in 1957, satellites have played a major role in everything from meteorology to geography to accessing a television show to placing a phone call.

Goddard Space Flight Center project manager Doug Mclennan, who holds a doctorate in physics from Georgetown University, took some time to discuss the magic behind satellites and one of his department's latest endeavors, a mission known as Space Technology 5 or ST5.

How are satellites launched these days? They can be launched from the space shuttle, though shuttle flights mostly are reserved for manned flight, or they can be carried by an expendable launch vehicle or what we called a rocket when I was a child. This launch vehicle has enough energy to take you out of the atmosphere and into orbit.

Where are satellites launched from? We launch them from Cape Canaveral in Florida or from Vandenberg Air Force Base north of Los Angeles. The reason these launch sites are on the coasts is that it allows the launch to be over water for safety reasons. We also want to be close to the equator, because the closer to the equator, the more the spin of Earth gives an added kick.

How do satellites stay in orbit? There is no air, no wind resistance, so once you get it moving around the Earth, it has a tendency to remain there. For example, if I throw a baseball, ignoring wind resistance, it eventually will hit Earth due to gravity. The faster I throw it, the longer it will go before it hits Earth. If I could throw the ball fast enough so that the rate at which it falls is equal to the curve of Earth, it would stay in flight indefinitely. Therefore, if I stand in space and throw a baseball at seventeen thousand miles per hour, gravity pulls it down so that it follows the curvature of Earth, and the ball, or satellite, goes into orbit.

What is the ST5 project? We are miniaturizing satellites and reducing their mass from 1,000 pounds to less than 50 pounds these satellites are so small that we call them "nanosats." They allow us to look toward a new class of missions, where instead of only using one or two spacecraft, we can use one hundred to look at some phenomena, such as the disturbances caused by solar flares in the Earth's magnetic field and ionosphere. The region around Earth where this space weather takes place is the magnetosphere which is something that is not particularly well understood. Currently, the only information we have comes from single spacecraft orbiting and making measurements in a single location.

Why do you want to have more than one satellite in orbit doing these measurements at a time? The interesting thing about measuring the magnetic field is you have to measure it right where you are. If you want to get a mapping of how Earth responds to a solar flare, for example, you need to have a blanket of spacecraft mapping an entire area and the magnetic energy that is produced or disturbed.

What are some of the technologies that you are using to create the nanosats? We are looking at flying a lithium ion battery, the same type of battery used in a laptop or cell phone, and we also are in the process of developing a transponder, or space-to-Earth communications device, using cell-phone technology. Both of these technologies allow us to create a small satellite that works using low power.

Are you developing new technologies as well? One we are looking at is low-voltage digital logic circuitry. In laptops and cell phones, for example, they are looking at lower voltage digital chips to make them work longer on the battery. We are trying to make those low-voltage digital logic circuits space-qualified so they will survive the space radiation environment and instead of five volts work at half a volt.

Another technology in development is miniature louvers the size of a human hair that can be turned to let heat out or in. They are made out of silicon and are developed using processes similar to those used to make microcircuits.

What is the purpose of the louvers? The problem is, when an object is in orbit, you can't find shade from the sun, and because there is no atmosphere, you can't turn on a fan to move air over a surface to cool it. And then when the spacecraft moves into the shadow of Earth, away from the sun, it becomes very cold, so we need to design technologies that can work with all those constraints.

One thing we need to do is to develop miniature thermal coatings so we make the spacecraft run cooler when it is in the sun and then to conserve heat when the spacecraft's orbit is in Earth's shadow. The miniature louvers work by changing the surface of the satellite to either reflect the heat to stay cool or by closing to absorb the heat to retain it and stay warm.

What would be your dream project if any technology one could imagine were available? To do things to help man better understand his position in the universe. NASA has a series of satellites that are designed to better understand how Earth works. I think technologies that help man better understand where he sits in the big realm of things are important.

Write to Joseph Szadkowski, The Washington Times, 3600 New York Ave. NE, Washington, DC 20002; or send e-mail ([email protected]washingtontimes.com).

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