Scene by scene. I tell you and explain the incredible video of Perseverance landing on Mars
As promised, in the afternoon of Monday, February 22,
NASA began to release a high-resolution video of the most important and spectacular moments
of the descent of Perseverance to the Martian surface, which took place four days before.
The video, with an unprecedented quality for an interplanetary mission, shows the
last 11 km of the descent, capturing topical moments such as the opening of the parachute,
the ejection of the heat shield, the search for the ideal landing site, the descent at the tip of
the retrorocket and the shooting of the Skycrane that gently lower Perseverance on the ground.
This is the first ever high-definition video of atmospheric entry,
descent and landing on another world. Perseverance's predecessor Curiosity
recorded snippets of the final stages of its Mars landing in 2012 that resulted in a
short stop-motion video, and in 2005 the Cassini mission's Huygens lander beamed back images and
telemetry data from its chilly descent to Saturn's moon Titan that were later used to construct
remarkable visualizations. And there is, of course, no shortage of lunar landing footage from
the Apollo missions of yore. But never before has a spacecraft captured the entire sequence
of an otherworldly landing in such lush detail. More than mere eye candy, this data could prove
crucial for the design of future, more ambitious voyages to the Red Planet's surface, which is
considered to be one of the solar system's most technically challenging landing destinations.
Landing on Mars is not at all easy, and it is also for this reason that in previous missions
NASA focused only on the technical aspect of the descent,
without worrying about documenting the various stages with movies or photographs. During the
long years of preparation of the Perseverance mission - thanks to the improvement of digital
filming systems - NASA's top management thought that the time had come to develop solutions
to give emotions to the paying public (American taxpayers), as well as to have useful visual
information on the different phases of the descent.... and they did it by adapting cameras
already available on the market. The only priority was that the filming system did not
interfere in any way with the technical management of the rover landing... And the technicians really
did their best, assembling in economy a video recording system called "Entry, Descent, Landing"
consisting of five consumer cameras connected to a computer (based on Linux!), which encoded
the videos through the popular software FFmpeg. Two cameras were mounted on the outer shell of
the probe, to film the opening of the parachute. A third was placed on the bottom of the rover,
pointing downward to film the Martian surface. The fourth looks upward. Finally,
the fifth was mounted on the Skycrane to film the rover as it is lowered to the surface.
And the result was well above any expectation ... Despite some inconvenience due to high
stress during landing, the cameras have allowed to obtain a video with an unprecedented definition,
which gave moments of true emotion. The only weak point of the whole operation?
The fact that we were only able to enjoy this spectacle deferred and days later. Without the
pathos that would have been there with the live broadcast! The something was obviously impossible
to obtain because of the inevitable delay in receiving the signal due to the enormous distance
between Earth and Mars, and also because the signals from the rover can not be sent directly
to Earth, but must first be saved locally and then, when the alignment conditions allow it,
sent to the probe Trace Gas Orbiter, which in turn will transmit them to Earth.
In short, on our TV screens can never appear, not even in a distant future,
the flashing writing "Live from Mars"... There is the physical impossibility, as well as the
(momentary?) technological impossibility... Okay, but what exactly do you see in this
much vaunted video? Would it not be appropriate to make it a kind of review,
so that even those who only occasionally deal with space exploration can understand the meaning of
certain phases quite agitated? Obviously, yes, and that’s exactly what we’re about to do...
After a view of the control room of the Jet Propulsion Laboratory, understandably very quiet
and rather concerned, the film continues with the sudden opening of the parachute, which however
tenuous the martian atmosphere may be, will slow down the probe’s speed in the first part of the
descent. The NASA "filmmaker" shows us the scene in two versions: at real speed and slowed down.
At that moment Perseverance has been in the atmosphere for four minutes, is at an altitude of
about 11 km and is still traveling at a speed of 1500 km per hour. From the video we don't realize
it, but the parachute is huge, 21.5 meters in diameter, and the cables that secure it to the
descent module stretch almost 50 meters in length. The large umbrella opens quickly, and immediately
inflates without any wires getting tangled. The bright colors and patterns of the nylon dome are
important because they will help technicians study its orientation, determining which areas inflate
more or less. This film will be studied in depth over the next few years, also because of a curious
peculiarity... the need to create a brightly painted parachute with an asymmetrical design
stimulated the imagination of Ian Clark, an engineer with a passion for cryptography who was
assigned the task, and who seized the opportunity to hide a message encoded in binary numbers
in the shapes and colors of the parachute. Clark used the binary code to write
"Dare Mighty Things," a NASA motto taken from a speech by Theodore Roosevelt, and included
the GPS coordinates of the mission headquarters at the Jet Propulsion Laboratory in Pasadena,
Clark revealed the existence of the enigma in a televised conference organized the Monday
following Perseverance's landing, and to his great surprise, he had to take note of the fact
that just after six hours the solution had already been found. Some fans, in fact, immediately
noticed that the orange and white color scheme on the parachute looked intentional, and they arrived
at the result by using orange as the symbol for the digit one, and white as the symbol for zero.
"It only took space fans a few hours to solve the puzzle," Clark said,
"next time I'll have to be a little more creative. Sometimes even engineers can pull off a remarkable
sense of humor... Can't they? But OK, back to the description of the video!
Twenty seconds after the opening of the parachute, the heat shield,
which until then had protected Perseverance from the heat generated by friction with the
atmosphere, is ejected. And the camera, as if guided by a consummate filmmaker,
frames him as he fades downward, smaller and farther away... destined to crash on Martian soil.
"BE sure to join the Insane Curiosity Channel... Click on the bell,
you will help us to make products of ever higher quality!"
This is surely one of the most exciting and iconic sequences of the entire mission,
realized by the video camera placed in the lower part of Perseverance,
which is now at 9000 meters of altitude and is descending
at almost 600 km per hour. Without the shelter offered by the heat shield, the rover is exposed
for the first time to the Martian environment. Slower and slower by the parachute, Perseverance
continues to descend, and at this point starts a long shot in which we see the Martian surface
getting closer and closer, and where we can see more and more clearly the features of Jezero,
the large crater almost 50 km wide chosen as the point of arrival.
In the meantime, the radar is activated to calculate the height and another new
technology comes into play, the "Terrain Relative Navigation" that allows the rover to compare what
it sees with the camera with an on-board map to determine the optimal landing point.
After another 90 seconds, at a height of two kilometers, the parachute comes off
along with the backshell that still covered the top of the descent module.
And in the video the thing is clearly felt as the camera is shaken by the recoil
and immediately after the descent speed is almost halved, passing in two seconds from 320 to 170
km per hour: they are in fact turned on the retrorockets mounted on the descent module.
After another minute of controlled descent, the speed had dropped to a minimum of 0.8 meters
per second. At this point, there are only twelve seconds and about twenty meters to touchdown, and
it is time to start the "Skycrane" maneuver: the descent module remains almost suspended in the air
thanks to the thrust of the retrorockets, and gently lower the rover to the surface by means
of three cables about six meters long. Meanwhile, the rover activates its mobility system, locking
its legs and wheels in the landing position. her worried, the movie continues with the
sudden opening of the parachute, which as may be tenuous the Martian atmosphere, will
serve to slow the speed of the probe in the first part of the descent.
The video clearly shows how the whole operation takes place.
In a whirlwind of dust, in fact, the rover and the Skycrane film each other while one is engaged
in descending and the other in lowering ... A splendid cinematographic "double subjective"...
As soon as the rover detects that its wheels have touched the ground, it quickly cuts the cables
connecting it to the Skycrane, and this allows the latter, with a reversal of thrust of the engines,
to fly away at a safe distance, free to crash away from Perseverance.
A sequence from a science fiction movie, perhaps surpassed, in terms of beauty and
pathos, only by the historic take-off of the lunar module during the Apollo 17 mission.
The video then ends with the JPL control room exploding with enthusiasm for the perfect
execution of the maneuver. The end.
Practically every frame offers new information about the process of landing on Mars - for
instance, one of the springs used to eject the heat shield can be seen to have disconnected,
though it didn't affect the process. All the footage has been and no doubt will
continue to be scrutinized for other insights. In addition to these amazing landing videos,
in the days following the landing, Perseverance transmitted back to Earth
thousands of images taken by the cameras that are used by researchers to decide which path to follow
for their robot during its explorations. By piecing together some of these images,
mission managers have created a high-definition panoramic photograph that shows everything around
Perseverance in the Jezero area. On either side of the panorama, the back and front of the rover
are visible, with some distortion due to the lenses and the need to paste together images
from different angles to each other. NASA has also made a navigable version
of the new Martian panorama, which can be viewed via YouTube as a 360-degree video.
Perseverance is also a good listener: it is in fact equipped with several microphones to record
the impact on landing and especially to listen to the noise of rocks, wind, sand devils and wheels
moving on the surface. These sounds, that on Mars propagate differently for the different properties
of the atmosphere, will provide us humans an interactive experience, but above all will have
a high scientific value: those coming from the microphones on the SuperCam will provide, even at
a distance, data on mass, composition and hardness of the rock, useful to understand its origins.
A microphone remained on even during the rover's descent to the Martian surface,
but did not pick up any sound, while it was able to capture the audio below once it landed on Mars.
Dave Gruel, chief engineer of Perseverance's camera and microphone system,
explained, "What you hear for the duration of about 10 seconds is an actual wind gust
on the surface of Mars that was picked up by the microphone and sent back here to Earth."
It is the first time that a gust of wind is recorded directly and with this fidelity on Mars,
and it's incredible to think that this truly is wind blowing across another world...
A very subtle emotion, but that can be taken as a symbol of a mission that was conceived
not only as a scientific experiment,
but also as a romantic tribute to the spirit of exploration that is within each of us.
And what do you think, did you like the video or did you expect more?