APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

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APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by APOD Robot » Thu Apr 29, 2021 4:05 am

Image Apollo 17: The Crescent Earth

Explanation: Our fair planet sports a curved, sunlit crescent against the black backdrop of space in this stunning photograph. From the unfamiliar perspective, the Earth is small and, like a telescopic image of a distant planet, the entire horizon is completely within the field of view. Enjoyed by crews on board the International Space Station, only much closer views of the planet are possible from low Earth orbit. Orbiting the planet once every 90 minutes, a spectacle of clouds, oceans, and continents scrolls beneath them with the partial arc of the planet's edge in the distance. But this digitally restored image presents a view so far only achieved by 24 humans, Apollo astronauts who traveled to the Moon and back again between 1968 and 1972. The original photograph, AS17-152-23420, was taken by the homeward bound crew of Apollo 17, on December 17, 1972. For now it's the last picture of Earth from this planetary perspective taken by human hands.

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RocketRon

Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by RocketRon » Thu Apr 29, 2021 4:29 am

What a beautiful crescent view of a beautiful planet.

If only folks would look after it better .....

DL MARTIN

Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by DL MARTIN » Thu Apr 29, 2021 8:05 am

There's no free lunch!

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Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by wbeagle@optonline.net » Thu Apr 29, 2021 11:59 am

I've loved APOD for years, and check it every day for the beautiful photos and scientific explanations, keep up the good work.
One small comment on incorrect data in this explanation, though: There were 13 missions that made it to the vicinity of the Moon, with 12 landings. 24 men stood on the Moon, but since there were three men on each mission, 39 pairs of eyes saw this view, not 24.

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Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by orin stepanek » Thu Apr 29, 2021 12:18 pm

AS17-152-23420_Ord1024c.jpg

I've often wondered why we haven't taken the shuttle foe a trip around the moon! :?
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Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by Chris Peterson » Thu Apr 29, 2021 1:19 pm

orin stepanek wrote:
Thu Apr 29, 2021 12:18 pm
AS17-152-23420_Ord1024c.jpg


I've often wondered why we haven't taken the shuttle foe a trip around the moon! :?
The shuttle launch system couldn't get beyond low Earth orbit. Not enough propellant.
Chris

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Sa Ji Tario

Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by Sa Ji Tario » Thu Apr 29, 2021 1:21 pm

My understanding is that the lunar missions were Apollo 8, 10, 11, 12, 13, 14, 15, 16 and 17, nine in all. So it was only 27 sets of eyes that could see this view

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Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by Chris Peterson » Thu Apr 29, 2021 1:42 pm

wbeagle@optonline.net wrote:
Thu Apr 29, 2021 11:59 am
I've loved APOD for years, and check it every day for the beautiful photos and scientific explanations, keep up the good work.
One small comment on incorrect data in this explanation, though: There were 13 missions that made it to the vicinity of the Moon, with 12 landings. 24 men stood on the Moon, but since there were three men on each mission, 39 pairs of eyes saw this view, not 24.
Your numbers are highly inflated. I suggest you try itemizing the missions.
Chris

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Joe Geller

Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by Joe Geller » Thu Apr 29, 2021 2:00 pm

As Sa Ji Tario replied, there were 9 missions that went to the moon and therefore 27 pairs of eyes. Sa Ji Tario enumerated those missions.
6 landed on the moon, Apollo 8 was the first to circle the moon, Apollo 10 was a dress rehearsal and the lunar module went part way down only, Apollo 13 had trouble and had to swing around and return.

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Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by shaileshs » Thu Apr 29, 2021 2:19 pm

Background stars tooooooooooo faint to be seen (compared to bright light reflected from earth) I'm imagining .. ?

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Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by De58te » Thu Apr 29, 2021 2:33 pm

What I find interesting by this photo, besides the artistic beauty, is that it shows the exponential population growth. Back in 1972 you see no city night lights, but today photos from the Space Station would show the night side lit up by a spiderweb of city lights. This even though on December 17, 1972 you'd expect to have even extra Christmas lights everywhere adorning the streetlights. A few explanations could explain this. Apollo 17 could have been over the North Pole when they snapped the picture. They could have been over China or North Korea or some other non Christian country. Or the camera back in 1972 was not sensitive enough to capture the lights, just like no stars are visible.

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Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by Chris Peterson » Thu Apr 29, 2021 2:45 pm

De58te wrote:
Thu Apr 29, 2021 2:33 pm
What I find interesting by this photo, besides the artistic beauty, is that it shows the exponential population growth. Back in 1972 you see no city night lights, but today photos from the Space Station would show the night side lit up by a spiderweb of city lights. This even though on December 17, 1972 you'd expect to have even extra Christmas lights everywhere adorning the streetlights. A few explanations could explain this. Apollo 17 could have been over the North Pole when they snapped the picture. They could have been over China or North Korea or some other non Christian country. Or the camera back in 1972 was not sensitive enough to capture the lights, just like no stars are visible.
There would certainly have been city lights visible. Less than today, of course, but plenty all the same. This was shot on film- much less sensitive than modern electronic sensors. And even today, and image like this would probably be constructed from a stack of several exposures to extend the dynamic range (either externally, or increasingly, within the camera as part of the normal exposure process).
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Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by De58te » Thu Apr 29, 2021 2:47 pm

Sa Ji Tario wrote:
Thu Apr 29, 2021 1:21 pm
My understanding is that the lunar missions were Apollo 8, 10, 11, 12, 13, 14, 15, 16 and 17, nine in all. So it was only 27 sets of eyes that could see this view
Three astronauts made the journey from the Earth to the Moon twice: James Lovell (Apollo 8 and Apollo 13), John Young (Apollo 10 and Apollo 16) and Gene Cernan (Apollo 10 and Apollo 17). So that makes 24 people.

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Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by johnnydeep » Thu Apr 29, 2021 4:10 pm

De58te wrote:
Thu Apr 29, 2021 2:47 pm
Sa Ji Tario wrote:
Thu Apr 29, 2021 1:21 pm
My understanding is that the lunar missions were Apollo 8, 10, 11, 12, 13, 14, 15, 16 and 17, nine in all. So it was only 27 sets of eyes that could see this view
Three astronauts made the journey from the Earth to the Moon twice: James Lovell (Apollo 8 and Apollo 13), John Young (Apollo 10 and Apollo 16) and Gene Cernan (Apollo 10 and Apollo 17). So that makes 24 people.
Thanks! I was going to ask if anyone was on more than one mission. You preempted my question and skipped to the answer. :ssmile:
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Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by neufer » Thu Apr 29, 2021 4:18 pm

https://en.wikipedia.org/wiki/Michael_Collins_(astronaut) wrote:
<<Michael Collins (October 31, 1930 – April 28, 2021) was an American astronaut who flew the Apollo 11 command module Columbia around the Moon in 1969 while his crewmates, Neil Armstrong and Buzz Aldrin, made the first crewed landing on the surface. On April 28, 2021, Collins died from cancer in Naples, Florida at the age of 90.

During his day flying solo around the Moon, Collins never felt lonely. Although it has been said "not since Adam has any human known such solitude". In his autobiography he wrote "this venture has been structured for three men, and I consider my third to be as necessary as either of the other two". In the 48 minutes of each orbit when he was out of radio contact with the Earth while Columbia passed round the far side of the Moon, the feeling he reported was not fear or loneliness, but rather "awareness, anticipation, satisfaction, confidence, almost exultation".

One of Collins' first tasks was to identify the lunar module on the ground. To give Collins an idea where to look, Mission Control radioed that they believed the lunar module landed about four miles off target. Each time he passed over the suspected lunar landing site, he tried in vain to find the lunar module. On his first two orbits on the far side of the Moon, Collins performed maintenance activities such as dumping excess water produced by the fuel cells and preparing the cabin for Armstrong and Aldrin to return. Columbia orbited the Moon thirty times.

Just before he reached the far side on the third orbit, Mission Control informed Collins there was a problem with the temperature of the coolant. If it became too cold, parts of Columbia might freeze. Mission Control advised him to assume manual control and implement Environmental Control System Malfunction Procedure 17. Instead, Collins flicked the switch on the offending system from automatic to manual and back to automatic again, and carried on with normal housekeeping chores, while keeping an eye on the temperature. When Columbia came back around to the near side of the Moon again, he was able to report that the problem had been resolved. For the next couple of orbits, he described his time on the far side of the Moon as "relaxing". After Aldrin and Armstrong completed their EVA, Collins slept so he could be rested for the rendezvous. While the flight plan called for Eagle to meet up with Columbia, Collins was prepared for certain contingencies in which he would fly Columbia down to meet Eagle.

In a July 2009 interview with The Guardian, Collins said that he was very worried about Armstrong and Aldrin's safety. He was also concerned in the event of their deaths on the Moon, he would be forced to return to Earth alone and, as the mission's sole survivor, be regarded as "a marked man for life".>>
Art Neuendorffer

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Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by Spaceguy42@rogers.com » Thu Apr 29, 2021 4:41 pm

First off R.I.P. Mike Collins.

In captioned APOD you mentioned only 24 humans have had that view, when its actually 27. the Apollo 13 crew at least got the same view but had to abort the landing for obvious reasons. Just wanted to mention it for your files.

Love your site

Sa Ji Tario

Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by Sa Ji Tario » Thu Apr 29, 2021 5:11 pm

Thanks johnnydeep, I did not take that into account, by the way there were pairs of eyes that saw her more than once. Now, as long as the missions have not been done when the Moon was close to the new phase because the Earth would appear in the full phase

Sa Ji Tario

Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by Sa Ji Tario » Thu Apr 29, 2021 5:19 pm

Tanks De58te

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Re: APOD: Apollo 17: The Crescent Earth (2021 Apr 29)

Post by orin stepanek » Fri Apr 30, 2021 2:11 am

Chris Peterson wrote:
Thu Apr 29, 2021 1:19 pm
orin stepanek wrote:
Thu Apr 29, 2021 12:18 pm
AS17-152-23420_Ord1024c.jpg


I've often wondered why we haven't taken the shuttle foe a trip around the moon! :?
The shuttle launch system couldn't get beyond low Earth orbit. Not enough propellant.
Thanks! 8-)
Orin

Smile today; tomorrow's another day!