There's a NASA spacecraft that gives us a view of the Moon we can never see from planet Earth.
Spacecraft offer us a unique perspective of the Universe, but they also offer a unique perspective of our own planet.
Only since the Space Age has humanity been able to see what it's like to observe our home world from space, to confirm what Earth looks like from different planets and moons of the Solar System
One such spacecraft, the Deep Space Climate Observatory, or DSCOVR, was launched in February 2015, and made headlines recently for its image of the October 14 2023 solar eclipse from space.
It captures amazing images of Earth and the Moon, including videos of Earth passing behind and in front of the Moon.
Moon passing in front of Earth, in pictures
On 11 February 2021 the Moon passed between DSCOVR and the Earth, and NASA's onboard EPIC (Earth Polychromatic Imaging Camera) instrument captured images of the event over a period of 3 hours.
You can see the event, showing the Moon passing in front of Earth, in the video below.
Let's take a look at what the spacecraft actually saw, frame by frame.
Images captured by DSCOVR show our bright blue planet Earth and its natural satellite, the Moon, slowing edging into view...
Then more of the lunar disc begins to emerge into the frame...
Before the entire lunar far side is in view, as the Moon passes between Earth and the spacecraft on its orbit around our planet.
And you may have noticed that the spacecraft has also captured Earth's rotation, as Australia emerges into full view and appears to drift across our planet's surface.
Pretty cool, eh?
Moon passing behind Earth
DSCOVR also captures images of the Moon passing behind Earth, as you can see in the video below.
Tidal locking and the Moon's orbit
There's a neat trick you can use to predict whether the Moon is about to pass in front of or behind Earth in DSCOVR's images and videos.
And it's because the same side of the Moon always faces Earth. The Moon is 'tidally locked' with Earth.
This means the Moon's orbit and its rotation are effectively synchronised, so that as it orbits our planet, its rate of rotation keeps the same side of the Moon in view.
That's why astronomers talk about the 'near side' – the side that always faces Earth – and the 'far side' – the side that always faces away from Earth.
Incidentally, astronomers never refer to it as the 'dark side of the Moon', because no such thing exists!
In DSCOVR's images and videos, if you see the Moon showing its near side, it's about to pass behind Earth, from the spacecraft's perspective.
If the Moon is showing its far side, it's about to pass in front of Earth.
DSCOVR's view
How can DSCOVR see Earth passing in front of the Moon? That must mean it's located beyond the Moon, right?
Yes, DSCOVR is located at a so-called Lagrange point, about 1 million miles from Earth,
Lagrange points are positions between Earth and the Sun where the gravitational pull of both bodies enables a spacecraft to exist in a stable equilibrium.
It's a 'neutral' gravity point between Earth and the Sun.
DSCOVR is located at Lagrange point L1. The James Webb Space Telescope, for example, is at Lagrange point L2, which is also about 1 million miles away, but at a different location.
L1 is key to DSCOVR's main science objective, which is monitoring the Sun, space weather and its effect on our planet.
The satellite won't be about for much longer, though, so enjoy its amazing images of the Moon and Earth while you can.
The Deep Space Climate Observatory (DSCOVR) satellite is expected to leave service in 2026.
See more videos and images at epic.gsfc.nasa.gov
