# Measured values of the solar irradiance at other values than 1 AU?

It is straight forward to estimate the total solar irradiance of a planet using the Earth's solar constant, and scaling it according to the (mean) distance of the planets. But for which planets have measurements been made? A quick search of the usual suspects like arxiv.org or scholar.google.com did not yield any conclusive or easy to interpret results.

• Mercury: $$12\,121 {\rm W}/{\rm m}^2$$ according to Wolframalpha which use the simple scaling. However, there are other sources, one of which claiming to cite a reference handbook's value of $$9\,937 {\rm W}/{\rm m}^2$$ which is a rather large deviation.
• Venus: $$2\,601.3 {\rm W}/{\rm m}^2$$, according to NASA's Venus fact sheet, which is reasonable close to $$2\,569 {\rm W}/{\rm m}^2$$ according to Wolframalpha
• Earth: $$1\,361^{+1}_{-0} {\rm W}/{\rm m}^2$$ according to Wikipedia on the solar constant
• Mars: around $$560.7 {\rm W}/{\rm m}^2$$, this is probably measured more exactly
• Jupiter: probably around $$52.7 {\rm W}/{\rm m}^2$$

How accurate are the values? What are the error bars?

• @uhoh Thanks for the valuable feedback, I went for your suggestion. And no, the total solar irradiance does not have to be measured on the planets, I am after how it actually (not theoretically) depends from the distance of the sun. Feb 8 at 4:08
• Dawn and Juno were solar powered spacecraft that reached 3.95 and 6.46 AU and so their solar panel output telemetry could be considered as approximate measurements if it can be found. And of course Parker Solar Probe and ESA's Solar Orbiter will get pretty close to the Sun.
– uhoh
Feb 8 at 4:34
• Solar panel health and output would have been watched carefully in telemetry for any deviations from expected output as it is so mission-critical. I think you can ask about it separately in Space SE, I wouldn't be surprised if this is actually available somewhere!
– uhoh
Feb 8 at 6:31
• While I find the idea to utilize solar panels to obtain these data intriguing, I wonder what results you expect? The interplanetary space is empty enough that the only notable attenuation is the inverse-square law for the light - with the exception of a very few atomic or molecular lines where there might be slight absorption (mind that most of the solar spectrum here on Earth is interpreted as either in solar origin or Earth atmospheric origin, but not interplanetary influence). I know that for Rosetta analysis, its distance to the sun is used to assess insolation. Feb 8 at 18:42
• Anyhow, my search-foo did not provide me with any housekeeping data for the space craft and its power generation in particular - though I'm pretty sure they must be available somewhere. At least the science data should be freely available as the 1-year embargo time is over; I'm not sure that same policy goes for housekeeping data, too. But maybe it helps to ask ESA directly (I tried to find data for Rosetta as its mission covered a nice heliocentric distance range) Feb 8 at 20:02