<p>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 <code>arxiv.org</code> or <code>scholar.google.com</code> did not yield any conclusive or easy to interpret results.</p>
<ul>
<li>Mercury: <span class="math-container">$12\,121 {\rm W}/{\rm m}^2$</span> according to <a href="https://www.wolframalpha.com/input/?i=solar+irradiance+on+mecury" rel="nofollow noreferrer">Wolframalpha</a> which use the simple scaling. However, there are other sources, <a href="https://answers.yahoo.com/question/index?qid=20110523194228AA0FYvy" rel="nofollow noreferrer">one of which claiming to cite a reference handbook's value</a> of <span class="math-container">$9\,937 {\rm W}/{\rm m}^2$</span> which is a rather large deviation.</li>
<li>Venus: <span class="math-container">$2\,601.3 {\rm W}/{\rm m}^2$</span>, according to <a href="https://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html" rel="nofollow noreferrer">NASA's Venus fact sheet</a>, which is reasonable close to <span class="math-container">$2\,569 {\rm W}/{\rm m}^2$</span> according to <a href="https://www.wolframalpha.com/input/?i=solar++irradiance+venus" rel="nofollow noreferrer">Wolframalpha</a></li>
<li>Earth: <span class="math-container">$1\,361^{+1}_{-0} {\rm W}/{\rm m}^2$</span> according to <a href="https://en.wikipedia.org/wiki/Solar_constant" rel="nofollow noreferrer">Wikipedia on the solar constant</a></li>
<li>Mars: around <span class="math-container">$560.7 {\rm W}/{\rm m}^2$</span>, this is probably <a href="https://eos.org/research-spotlights/spacecraft-returns-its-first-data-on-martian-solar-irradiance" rel="nofollow noreferrer">measured more exactly</a></li>
<li>Jupiter: probably around <span class="math-container">$52.7 {\rm W}/{\rm m}^2$</span></li>
</ul>
<p>How accurate are the values? What are the error bars?</p>

CC BY-SA 4.0
2021-02-08T04:08:28.543Z
@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.
B--rian
CC BY-SA 4.0
2021-02-08T04:34:34.203Z
[Dawn](https://en.wikipedia.org/wiki/Dawn_(spacecraft)) and [Juno](https://en.wikipedia.org/wiki/Juno_(spacecraft)) 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](https://en.wikipedia.org/wiki/Parker_Solar_Probe) and ESA's [Solar Orbiter](https://en.wikipedia.org/wiki/Solar_Orbiter) will get pretty close to the Sun.
uhoh
CC BY-SA 4.0
2021-02-08T04:36:56.810Z
Rosetta got out past Jupiter's orbit as well, [but it hibernated](https://space.stackexchange.com/a/15376/12102) for 2.5 years when furthest from the Sun.
uhoh
CC BY-SA 4.0
2021-02-08T06:23:09.383Z
@uhoh Clever yet simple idea to use the spacecrafts' solar cell output as proxy.  Did you manage to find any publication with actual values?
B--rian
CC BY-SA 4.0
2021-02-08T06:31:23.733Z
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
CC BY-SA 4.0
2021-02-08T18:42:08.397Z
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.
planetmaker
CC BY-SA 4.0
2021-02-08T20:02:14.303Z
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)
planetmaker
<mars><jupiter><venus><mercury><modeling>
Measured values of the solar irradiance at other values than 1 AU?
B--rian
# Measured values of the solar irradiance at other values than 1 AU?

(Asked by: username_0 on 2021-02-07)

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](https://www.wolframalpha.com/input/?i=solar+irradiance+on+mecury) which use the simple scaling. However, there are other sources, [one of which claiming to cite a reference handbook's value](https://answers.yahoo.com/question/index?qid=20110523194228AA0FYvy) 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](https://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html), which is reasonable close to $2\,569 {\rm W}/{\rm m}^2$ according to [Wolframalpha](https://www.wolframalpha.com/input/?i=solar++irradiance+venus)
* Earth: $1\,361^{+1}\_{-0} {\rm W}/{\rm m}^2$ according to [Wikipedia on the solar constant](https://en.wikipedia.org/wiki/Solar_constant)
* Mars: around $560.7 {\rm W}/{\rm m}^2$, this is probably [measured more exactly](https://eos.org/research-spotlights/spacecraft-returns-its-first-data-on-martian-solar-irradiance)
* Jupiter: probably around $52.7 {\rm W}/{\rm m}^2$

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

**Tags:** mars, jupiter, venus, mercury, modeling
> **Comments:**
> **username_0**: @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.  
> **username_1**: [Dawn](https://en.wikipedia.org/wiki/Dawn_(spacecraft)) and [Juno](https://en.wikipedia.org/wiki/Juno_(spacecraft)) 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](https://en.wikipedia.org/wiki/Parker_Solar_Probe) and ESA's [Solar Orbiter](https://en.wikipedia.org/wiki/Solar_Orbiter) will get pretty close to the Sun.  
> **username_1**: Rosetta got out past Jupiter's orbit as well, [but it hibernated](https://space.stackexchange.com/a/15376/12102) for 2.5 years when furthest from the Sun.  
> **username_0**: @uhoh Clever yet simple idea to use the spacecrafts' solar cell output as proxy.  Did you manage to find any publication with actual values?  
> **username_1**: 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!  
> **username_2**: 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.  
> **username_2**: 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)  

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## 0 answers

