# What was the temperature of the Apollo 11 moon landing zone?

It's soon 50 years from the Apollo 11 moon landing, so in honor of that event, I decided to post a question here.

I understand that moon has due to its long day and long night and also due to the lack of water very large temperature variations. For example, googling for "moon temperature" finds:

Daytime on one side of the moon lasts about 13 and a half days, followed by 13 and a half nights of darkness. When sunlight hits the moon's surface, the temperature can reach 260 degrees Fahrenheit (127 degrees Celsius). When the sun goes down, temperatures can dip to minus 280 F (minus 173 C)

What was the temperature of the moon landing zone in Apollo 11?

If the temperature differed from what we consider normal, how did the astronauts manage to survive in the prevailing temperature during walking on the moon surface?

• We consider it normal to have ambient air and a comfortable air temperature. But there is no air on the moon, only vaccuum without a temperature. So the moon boots should have a heat and cold resistant sole with good temperature isolation properties. – Uwe Jul 16 at 21:56
• @Uwe Right, but there is also thermal radiation. If you're walking on 127°C hot surface, it might feel as if there was a hot atmosphere surrounding you. – Everyday Astronaut Jul 17 at 6:34
• @EverydayAstronaut But the thermal radiation of the hot surface was blocked by the many layers of the EVA space suit worn. The astronauts did feel only the temperature of the liquid cooling undergarment worn under the suit. – Uwe Jul 17 at 8:32

Apollo 11 deployed the Early Apollo Lunar Surface Experiments Package (EASEP), a set of scientific instruments that measured various parameters on the moon and transmitted them back to the earth, this included temperature.

Here is a picture of Edwin Aldrin deploying the EASEP:

There is a Technical Memorandum from Bellcomm Titled: Lunar Surface Temperatures From Apollo 11 Data, that has this great chart detailing the temperature data from the instrument (as well as all the information you could ever want about the temperature instruments):

you can see that the temperature when they were landed (July 20-21st 1969, or 201-202 GMT) was between $$250^\circ K$$ and $$280^\circ K$$ or $$-23^\circ C$$ to $$7^\circ C$$.

The astronauts survived because of their Space Suits, which had environmental control equipment, as well as the Apollo Lunar Module (LM) which also had environmental control equipment as part of the life support system.

• That's a pretty tolerable temperature range to me, from a country where -23 degrees C is common... – juhist Jul 16 at 20:45
• @juhist I'm also surprised by the comfortable range. Moreover, keep in mind the matchless intensity of solar radiation on the Moon, as there is no atmosphere. I guess it heats up the spacesuits quite a bit. – Everyday Astronaut Jul 17 at 6:30
• Note that the lunar day (and temp cycle) is 28 Earth days. You can see the min and max over the entire cycle is -53 to +67C. The fact that the astronauts spent ~2/28th of a lunar day on the surface is like flying to Florida in July but only staying for two hours in the morning when it’s 74F out and claiming “oh that wasn’t so bad”. :-) – cms Jul 17 at 19:44

The landing time was selected to avoid the extreme temperatures. That's why there are huge shadows, the Sun's declination is low (I don't remember if it was early morning or late afternoon). During the 22 hours they were on the surface (Apollo 11, some others up to 4 Earth days IIRC) the lunar day didn't progress too much.