Sandy Antunes - DIY Instruments for Amateur Space: Inventing Utility for Your Spacecraft Once it Achieves Orbit

Sebastopol
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Ever wonder why astronomers loft telescopes higher and higher, to mountains and via balloons and satellites? We put telescopes up on mountains, launch balloons, send rockets into space and point them outward. The Earth observing (EO) folks take similar gear, fly it up high, then point it back to Earth.

Astronomers try to get our telescopes higher. Now, the main goal of a telescope is to use mirrors or lenses to essentially make a bigger eye. Its not that telescopes magnify; its that they gather more light. In short, they make faint stuff visible. Radio telescopes extend our eye because they look at wavelengths that our eyes cant pick up at all.

A small mirror has less light gathering than a bigger one, but up high, its less messed up by our atmosphere. From the ground, were looking through a mile high column of air: its like looking through a swimming pool, and the shifting air ruins our seeing.

Seeing is actually a technical term. We astronomers have a knack for naming things. For instance, the big array of radio telescopes we made is called the VLA, and that stands for Very Large Array. The big explosion that started the universe we all know as the Big Bang. We tend to be very straightforward and you can see why I often say that anyone can be an astronomer if he wants.

We put stuff up to get past the wet blanket we call our atmosphere. A smaller scope higher up will outperform a larger ground scope. Telescopes are on mountains to get above the atmosphere, and also to get above the weather, because our atmosphere has a lot of weather. We also want to isolate them from city light. All the lighting of modern civilization creates what we astronomers call light pollution.

Light pollution is that orange glow that you can see above Washington, DC every night instead of stars. It makes for a really pretty sunset but it makes for really lousy observing. If you put the scope higher up, you escape that.

For Earth observing, we dont want to escape the Earths atmosphere so much as a) observe it and b) get a bigger view. If you need to see out of a forest, youd climb a tree. To see the Earth, to see the top of the atmosphere, or to peer at different layers, you need to do flyovers. The best way to consistently fly over the Earth and survey it is via satellites. As a bonus, you can choose specific instruments with specific wavelength regions so you can examine specific layers of the atmosphere or look for specific phenomena on the Earths surface.

High altitude balloons are a way to go higher than a mountain, and you can get up cheaply and quickly. Some students in Spain actually lifted an ordinary digital camera 20 miles up and they did on a $100 budget. NASAs upcoming SuperPressure Balloon can lift 1,000 pounds for 100 days. Its the same concept: get things higher.

We have better visibility, less weather, longer nights, light you cant see from the ground, and a great field of view. Satellites (see ) provide the best of thesebut at a high cost. They get us higher and for a longer time, but they are a bit more expensive. And they do let us see X-rays and ultraviolet light, and give us vantage points from somewhere other than the Earth.

Figure 1. GOES image of Hurricane Katrina, image courtesy of NASA/NOAA

Given all this, we are still limited in what we can do. The ideal detector cannot exist, and youll always have to make tradeoffs between capability and bandwidth, between performance and cost, and between capturing a wide view and seeing the little details. Were here to help you design your instrument mission.