<p>Occulations <em>of artificial probes</em> has been used to investigate the ionosphere of the moon. See, for example <a href="http://adsabs.harvard.edu/full/2008MSAIS..12...53P" rel="noreferrer">http://adsabs.harvard.edu/full/2008MSAIS..12...53P</a></p>

<p>In this technique, radio signals from the probe are monitored as the probe passes behind the moon. There is refraction from the lunar ionosphere, which can be detected indirectly, using a doppler method. This gives information on the (very thin) lunar atmosphere and the electron density in the lunar ionosphere.</p>

CC BY-SA 4.0
2020-03-25T13:47:09.760Z
2020-03-25T13:47:09.760Z
James K
<p>Yes, and lunar occultations have proved useful in several cases.</p>

<p><a href="https://ui.adsabs.harvard.edu/abs/1963Natur.197.1037H/abstract" rel="noreferrer">Hazard et al. 1963</a> used a lunar occultation to produce a high-resolution brightness profile of the now well-studied radio quasar 3C 273. <a href="https://ui.adsabs.harvard.edu/abs/1965MNRAS.129..199S/abstract" rel="noreferrer">Scheuer 1965</a> goes into a little bit of detail on general computations.</p>

<p>A slightly different tack was taken by <a href="https://academic.oup.com/mnras/article/450/3/2291/1058750" rel="noreferrer">Vedantham et al. 2015</a>. They were attempting to create interferometric maps of the cosmic 21 cm line signal using LOFAR. Unfortunately, they needed a calibration source to be able to measure this "global signal". The Moon, occulting portions of the field of view, provided a calibration source as they observed that patch of sky.</p>

CC BY-SA 4.0
2020-07-10T02:25:55.630Z
also see [this asnwer](https://astronomy.stackexchange.com/a/36708/7982) to *In the 1950's how were radio-astrometric positions with portable dishes so precise they could be assigned to their dim optical counterparts (Quasars)?*
uhoh
CC BY-SA 4.0
2020-03-25T14:03:38.823Z
2020-03-25T17:31:34.637Z
2020-03-25T17:31:34.637Z
HDE 226868
<p><a href="https://astronomy.stackexchange.com/a/35589/7982">This answer</a> to <em>Which kinds of astronomical observations most need to avoid the Moon being up?</em> mentions </p>

<blockquote>
  <p>For completeness - radio, mid-infrared and mm-wave observations are unaffected (unless the Moon is in the way!)</p>
</blockquote>

<p>The Moon is of course opaque to all wavelengths used in astronomy, from very low frequency radio waves to gamma rays. So if the moon eclipses a target radio signals will be blocked.</p>

<p>But are there any more subtle or non-obvious effects? For example if a target is very close to the Moon but not covered by it, would that affect an observation in any way? </p>

<p><strong>Question:</strong> Is this routinely avoided out of an abundance of caution? On the other hand, has a lunar occultation of a radio source ever be leveraged in some way for a specific measurement? </p>

<p>"Bonus points" for any anecdotes of strange results or confounding measurements in Radio Astronomy that turned out to be the result of not taking the position of the Moon in to consideration.</p>

CC BY-SA 4.0
2020-03-25T11:53:37.497Z
If you change this question to e.g. "Can the Moon interfere with radio astronomy measurements ?" or similar this might be OK.  As it stands it's an open ended "list" type question and those are typically closed.
StephenG - Help Ukraine
CC BY-SA 4.0
2020-03-25T12:01:23.140Z
@StephenG not exactly what you proposed, but I've made an edit. *Thanks!*
uhoh
<observational-astronomy><the-moon><radio-astronomy><history>
Has radio astronomy ever been done on objects that appear very close to the Moon? Is this avoided?
uhoh
# Has radio astronomy ever been done on objects that appear very close to the Moon? Is this avoided?

(Asked by: username_0 on 2020-03-25)

[This answer](https://astronomy.stackexchange.com/a/35589/7982) to *Which kinds of astronomical observations most need to avoid the Moon being up?* mentions

> For completeness - radio, mid-infrared and mm-wave observations are unaffected (unless the Moon is in the way!)

The Moon is of course opaque to all wavelengths used in astronomy, from very low frequency radio waves to gamma rays. So if the moon eclipses a target radio signals will be blocked.

But are there any more subtle or non-obvious effects? For example if a target is very close to the Moon but not covered by it, would that affect an observation in any way?

**Question:** Is this routinely avoided out of an abundance of caution? On the other hand, has a lunar occultation of a radio source ever be leveraged in some way for a specific measurement?

"Bonus points" for any anecdotes of strange results or confounding measurements in Radio Astronomy that turned out to be the result of not taking the position of the Moon in to consideration.

**Tags:** observational-astronomy, the-moon, radio-astronomy, history
> **Comments:**
> **username_1**: If you change this question to e.g. "Can the Moon interfere with radio astronomy measurements ?" or similar this might be OK.  As it stands it's an open ended "list" type question and those are typically closed.  
> **username_0**: @StephenG not exactly what you proposed, but I've made an edit. *Thanks!*  

---

## 2 answers

### Answer by username_3 on 2020-03-25. Score: 18

Yes, and lunar occultations have proved useful in several cases.

[Hazard et al. 1963](https://ui.adsabs.harvard.edu/abs/1963Natur.197.1037H/abstract) used a lunar occultation to produce a high-resolution brightness profile of the now well-studied radio quasar 3C 273. [Scheuer 1965](https://ui.adsabs.harvard.edu/abs/1965MNRAS.129..199S/abstract) goes into a little bit of detail on general computations.

A slightly different tack was taken by [Vedantham et al. 2015](https://academic.oup.com/mnras/article/450/3/2291/1058750). They were attempting to create interferometric maps of the cosmic 21 cm line signal using LOFAR. Unfortunately, they needed a calibration source to be able to measure this "global signal". The Moon, occulting portions of the field of view, provided a calibration source as they observed that patch of sky.

> **Comments:**
> **username_0**: also see [this asnwer](https://astronomy.stackexchange.com/a/36708/7982) to *In the 1950's how were radio-astrometric positions with portable dishes so precise they could be assigned to their dim optical counterparts (Quasars)?*  

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### Answer by username_2 on 2020-03-25. Score: 12

Occulations *of artificial probes* has been used to investigate the ionosphere of the moon. See, for example <http://adsabs.harvard.edu/full/2008MSAIS..12...53P>

In this technique, radio signals from the probe are monitored as the probe passes behind the moon. There is refraction from the lunar ionosphere, which can be detected indirectly, using a doppler method. This gives information on the (very thin) lunar atmosphere and the electron density in the lunar ionosphere.


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