# Would measuring the Infrared radiation output of the sun be difficult, due to the output of other sources (Earth) interfering with the results?

If, hypothetically, there was to be an experiment that would look for solar activity induced increases in infrared radiation on the International Space Station, would the infrared radiation produced on Earth or from other sources (Cosmic Background Radiation) make the data hard to determine?

In fact the ESA observatory SOLAR has been monitoring the Sun activity from the ISS Columbus Laboratory since 2008. In particular the SOVIM science instrument is in charge to monitor the infrared radiation. Further infrared radiation sources can be handled provided they are well known.

• Why has this been downvoted? The SOLAR experiment does exactly what the question posits ('an experiment that would look for solar activity induced increases in infrared radiation'). – Hobbes Feb 17 '15 at 17:48
• +1. This is exactly the kind of instrument the OP asked about. – David Hammen Feb 19 '15 at 1:29

As a first approach:
total amount of power used on Earth: 150 TWh/year. Pretty much all of this ends up as heat, so it's a decent proxy for amount of IR produced.
total amount of solar energy received on Earth: 250 W/m$^2$ times 510 million km$^2$ is 1.275 EW, or 1.11 ZWh/y, or 2 million times as much.
So human production is only a factor if you want to measure to an accuracy of 0.05% or better.

• The 250 factor is the average produced on land, for something like this, you should consider all of the power, including that absorbed by the atmosphere. Still, this is a small effect. – PearsonArtPhoto Feb 17 '15 at 20:30
• The average power used on Earth is about 17.1 GW. The solar irradiance on the Earth is 127500 TW by your 250 number. I think you forgot to convert km^2 to m^2, which gives the factor another million times more power produced by the sun. – PearsonArtPhoto Feb 17 '15 at 20:34
• @PearsonArtPhoto No, I forgot to convert from instantaneous production to Wh/year. – Hobbes Feb 17 '15 at 20:49
• I knew there was no way that human produced heat was anywhere near as much as solar incidence. That looks better, although my gut tells me it still seems a bit high... – PearsonArtPhoto Feb 17 '15 at 20:51
• I recall the numbers being a little different from this. Human energy output is about 17TW in 2013, or about 0.2g per second. The solar energy incident on Earth is very nearly 1kg per second (actually about 1200 grams per second, with the figures you cite), a good easy figure to recall. So its a factor of about seven thousand. Still small, but much more appreciable than your numbers suggest. (Your answer's still a good one and accurate in its spirit BTW +1) – WetSavannaAnimal Feb 21 '15 at 8:26

The infrared coming from the Earth, or activities on the International Space Station, won't interfere with an instrument intended to observe infrared light produced by the Sun. The Sun's infrared output is primarily in wavelengths shorter than 1.75 microns. Thermal infrared is at wavelengths longer than 3 microns.

With regard to the CMBR, there's no overlap whatsoever between those long radio waves and the short near infrared produced by the Sun.

The James Webb Telescope will have instruments that look at wavelengths as long as 28.6 microns. That will require extensive cooling, but the Webb isn't intended as a solar observatory.