China’s Chang’e-4 lander was the first
spacecraft to make a soft landing on the far
side of the moon back in 
January of 2019.
To mark its one year anniversary, the Chinese
Academy of Sciences released a trove of data
and photos of the rarely-seen 
side of the moon.
But aside from taking pretty pictures, what
has Chang’e-4 been doing up there?
Well, the first notable thing it’s done
is just survive for a year.
The original design life of the lander’s
rover, Yutu-2, was just 3 months.
That means the little six-wheeler has been up
there kicking moon dust
for four times longer than expected.
Not bad, considering the lander and rover were
modified spares
the China National Space Administration
had on hand in case the Chang’e-3 mission
was unsuccessful.
The longevity is also impressive 
when you remember
the challenges of working on the moon.
One full day-night cycle on the moon is about
29 and a half days, so that’s over 14 days
of continuous sunshine followed by more than
14 days of darkness.
When the long night comes, Chang’e-4 and
Yutu-2’s solar panels don’t generate enough
electricity to run its instruments and systems.
The crafts have to power down and hibernate
for almost two weeks, just staying alive thanks
to onboard radioisotopic heat sources.
Basically, a nuclear powered electric blanket.
Compare that long night to Mars, where rovers
have to deal with a full day-night cycle that’s
only about 40 minutes longer than a day on Earth.
But it’s not just the long, cold, lonely lunar
nights that threaten the mission.
High noon on the moon is also hot enough to
damage the rover, so it shuts down for about
six days at a time while the sun is directly
overhead, heat-blasting it.
That’s right: it takes a little nap in the
middle of the day.
I never thought I could relate to a spacecraft so much.
Sleeping as much as an average teenager is
part of what’s allowed the Yutu-2 rover
to survive as long as it has.
Yutu-1, the rover it’s almost identical
to, remember, short circuited and conked out
on just the second lunar day.
Meanwhile, Yutu-2 set a record for longevity
back in November, and is still going strong.
So don’t let anyone make you feel guilty
about needing a nap.
It’s called self-care.
The longer the rover and lander survive, the
longer both can perform experiments with the
suite of instruments they carry.
Yutu-2 has been studying the lunar regolith
as it rolls along with Lunar Penetrating Radar
that can see more than 100 meters down, and
a Visible and Near-infrared Imaging Spectrometer
that analyzes the mineral composition 
at the surface.
Data from these instruments have shown that
the Von Karman crater where Chang’e-4 touched
down has thicker regolith than the near side
of the moon, and the spectrometer has detected
minerals that appear to have come from the
mantle below the moon’s crust.
Continued study and analysis could lend insights
into how the moon evolved.
The lander itself is taking measurements of
radiation levels on the moon, and the same
instrument can be used to measure the amount
of water in the local lunar soil.
However the experiment I am most excited about
is the one that really takes advantage of
Chang’e-4’s unique location.
The lander’s Low Frequency Spectrometer
is made up of three 5 meter long antennae
that are observing low-frequency waves from
the sun, the lunar ionosphere, interplanetary
space, and galactic space.
It can do this in the relative radio quiet
on the far side of the moon, since the moon’s
body blocks the noisy signals we’re constantly
beaming off from Earth.
Unfortunately the antennae only deployed last
November,
so there’s just not enough data yet.
Maybe on Chang’e-4’s two-year anniversary,
after a lot more naps, it’ll have another
exciting update for us.
While Yutu-2 has set the record for longest
time driving on the moon, the record holder
for distance belongs to the soviet rover Lunokhod-2.
Thanks for watching, don’t forget to subscribe
and if you want to know more about the history
of Chang’e-4 check out my other video here.
I’ll see you next time on Seeker!
