Saturday, August 12, 2017

A Camera On the Moon

Jeran Campbell, who has a channel on YouTube and a website called "jeranism," has just released a video which asks a question that seems to be stuck in the minds of flat-Earthers: why doesn't NASA just land a video camera on the moon and provide a live feed of the Earth spinning? I'm not going to link to the video, and I didn't even watch the whole thing (and have no plans to) because I have ceased to take Jeran seriously.

However, the question is brought up often enough that I feel it is worth spending a little time to talk about why this is such an incredibly silly idea.

Let me start by repeating something that anyone even thinking about this should already have figured out: real-time video of the Earth has already been done. Not by NASA or any space agency, but by a private provider of satellite television service, Dish Network. Dish Network put a camera on one of its EchoStar satellites that fed 24-hour NTSC video of the Earth until the camera stopped functioning in 2012. The video was displayed on a channel called Dish Earth.

Does real-time footage from this camera still exist? Not that I've found. Why? Because it's really, really boring. as anyone who actually gave this any thought would expect. I've seen time-lapse footage, which is far more interesting. But, of course, advocates of the flat Earth just call it fake.

And that is the second point. Jeran even anticipates the accusation that flat-Earthers will just declare footage from a moon camera fake, and claims that there is a difference between photographs and live video footage. But, seriously, we saw two hours of live video from Apollo 11, and Jeran calls that fake, so why should a real-time camera from the moon be treated any differently?

More importantly, though, what would the purpose of such a mission be? To prove that the Earth is a sphere? To prove that men did really land on the moon? Do Jeran and his flat-Earth pals really think that the scientists at NASA are wringing their hands trying to figure out how to prove these most basic facts? This shows how far Jeran has sunk in search of things to make videos about.

Imaging the Earth is a worthwhile endeavor. That's why NASA and NOAA sent DSCOVR to orbit the sun to monitor the Earth. These images are not merely pretty pictures; they are taken in 10 different spectral bands and will be used to (as the EPIC website says) "measure ozone, aerosols, cloud reflectivity, cloud height, vegetation properties, and UV radiation estimates at Earth's surface."

EPIC is only one instrument among five aboard the craft. The fact that the pictures are also cool is just a bonus.

As are the stunning images from Japan's Himawari-8 geostationary satellite, also designed for climate research, along with Russia's Elektro-L-1. But what about a camera on the moon, sending high-definition video back to Earth, from the moon's constantly Earth-facing side? Wouldn't that have great scientific value?

Well, let's think about that. DSCOVR is orbiting the sun in the same orbital period as Earth, in roughly the same ellipsoid shape. Therefore, its aim and distance relative to the Earth are fixed, and we can see the Earth turn, albeit only as often as DISCOVR sends back images, about 10 single-band images per hour.

Hiwari-8 and Elektro-L-1 are geostationary satellites, which means that they will always aim at the same spot on Earth. More missions like these are planned by different space agencies, to provide, in time, full coverage of the planet.

Now let's consider a camera on the moon. The moon's orbit and rotation are locked together tidally with the Earth, and so, yes, the moon faces the Earth at all times. But, the moon does not stay in a fixed location, either with respect to a single point on Earth or with the location of the planet as a whole. The moon is traveling in the same direction as the Earth rotates, and so, over the course of a lunar month, it will drift around the planet as the Earth turns underneath it.

In addition, the moon's orbit is substantially elliptical, and so over the course of the month, the angular size of the Earth would vary by about 14%. Not very useful.

And remember, Jeran isn't talking about images; he's talking about real-time video. Himawari-8 can easily transmit a series of images (enough to produce one color composite, along with the other bands) every ten minutes because the equipment to receive the signal is always in its line of sight. The same was true of Dish Earth.

DSCOVR stores images and transmits them when it is able, over nearly a million miles of space.

But a camera on the moon, transmitting constant real-time video, would require a vast array of receivers to keep up. It's just not worth the time, trouble, and expense to maintain this infrastructure that serves no great scientific purpose.

But the Jerans of the world think that NASA needs to spend vast sums of money to prove what any thinking person can prove for him- or herself. That the Earth is a sphere, that people really did land on the moon, and that the notion of a flat-Earth is just so much hot air.