The theory of observations
So, first and most importantly, my work is observational, using the large infrared telescopes to measure details from the giant planets..computer modelling. While this sounds like I must spend a lot of time looking through telescopes,I actually spend my day in front of a computer, doing a whole variety of different things.,
OK... So, one step at a time, what does that mean?
Firstly, the InfraRed Telescope Facility (the IRTF) is a NASA based telescope, which looks at the infrared spectrum, the light that is just beyond the optical red in the rainbow, also known as heat. Unlike with the naked eye - which sees a wide range of different wavelenghts of light (the optical or visible spectrum), from red through to blue, this telescope can looks at a single very specific wavelength range that is far narrower. The telescope is based on the top of an extinct volcano on the Hawaiian Big Island. Because of the thin atmosphere and the surrounding ocean, the conditions there are some of the best in the world for observing, particularly in infrared. The disadvantages of working at an altitude of around 14000 feet include dizziness, headaches and a lack of concentration, but the advantages are a little more obvious...
A spectral image is an image taken with the telescope at a particular wavelength of light, usually either a wavelenght that show the planet particularly well, or the wavelenght that the rest of the data will be taken at. Because we look in the infrared, this means that the planets look different to the pictures we are used to from NASA. Another point to remember is that most of the pictures we see are taken from space. However, the details of the planets come out fairly clearly, despite this being a ground based telescope. However, as far as we are concerned, tthe image option on the telescope is only really there to help find and position the spectral slit on the planet so that you can start taking spectral data.
Spectral data is an alternative way of examining a planet. Rather than take a normal image, we use a spectrometer to split up the light. This means that we see less, because we use a slit to split the light, which cuts out all but a thin strip of what would be seen in an image. That's an annoying disadvantage, but the amount of information we gain is enormous - we can measure the winds, the temperature, the extent of cooling in the aurora.
Secondly, we look at a molecule called H3+. This is only found in large stable abundance in the upper atmosphere of the giant planets. This molecule is especially useful for us because when it is impacted with the particles in the surrounding space environment, it glows. We can look at a particular wavelength of the light, and while the H3+ glows really brightly at this wavelength, Jupiter itself is very dark, as the lower atmosphere absorbs all the light. This means that the aurora glows brightly compared with everything else.