Instrument FAQ

Instrument FAQ

What is SEE?

SEE is an acronym that stands for the Solar EUV Experiment. EUV is Extreme Ultraviolet, and is commonly used to refer to the very high-energy portion of the solar spectrum between 10 and 120 nm. SEE is a science instrument (one of 4) on board NASA’s TIMED spacecraft. SEE was built by a large team of people here at the Laboratory for Atmospheric and Space Physics which is part of the University of Colorado in Boulder.

How old is SEE?

The spacecraft was launched on December 7, 2001, and SEE began it’s normal observing sequence on January 22, 2002.

Can I see EUV from the sun?

No. Solar EUV is completely absorbed by Earth’s atmosphere. You should never look directly at the sun! (That’s our job.)

Why should we care about EUV?

EUV causes the atmosphere to heat up and increase drag on satellites. The sun has “weather” and can become quite stormy. Solar storms can produce a lot of X-rays and EUV, and are extremely powerful. It is common for these storms (sun-spots) to be larger than the earth. This is a concern for astronauts on-board NASA’s space shuttle and the space station during space walks, since they are not protected by earth’s atmosphere. EUV changes as the storm-like (sun-spot) activity of the sun changes. We want to be able to accurately measure the output of the sun, provide that information as soon as possible, and eventually predict what the sun is going to do.

What is SEE made of?

SEE has 4 major components, and two of them are science channels.
One is the EUV Grating Spectrograph (EGS) which makes spectral measurements of the solar EUV. The other science channel is the X-Ray Photometer System (XPS) which makes broader measurements at shorter wavelengths. The other 2 major components of SEE are a computer (microprocessor unit), and a pointing platform to steer the science channels towards the sun.

How often does SEE observe the Sun?

The SEE platform can only rotate in one axis, but SEE uses the spacecraft-drift to “move” the sun across another direction. These two things allow SEE to observe the sun (usually) once per orbit and there are about 14.8 orbits in one day. Each observation of the sun lasts about 3 minutes. Once each orbit, SEE “wakes-up” and collects science data.

How does SEE know when to look at the sun?

Basically, it doesn’t know when. We tell it when to look. A small team of CU undergraduate students and LASP professionals is responsible for determining the best times for SEE to look at the sun. We use planning tools (computer programs) to create a series of instructions (commands) for the computer inside SEE to perform. We usually send about 20 instructions each week. This is normal operations for SEE. We have a Science Operations Center dedicated to SEE here at LASP. The orbit of TIMED only allows a few ~10-minute periods each day when we are able to send commands to the spacecraft, and download the data.

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