How the cameras on Voyager 1 took a portrait of solar system?
This is the “pale blue dot” image, a long distance photograph of a tiny, fragile Earth all alone in
the darkness of space, taken by the Voyager 1 spacecraft. Taken on February 14th, 1990,
it is one of the most iconic images in history. This image was taken as part of the Family
portrait series of the images of the solar system. Shortly after these images were taken the cameras
onboard the spacecraft were shut down for the last time. Today the Voyager is at a distance of
23.381 billion km (or 14.528 billion mi), making it the most distant man-made object from Earth.
But how did Voyager manage to take these images of the planets in our solar system?
Why were the cameras turned off? And what would we be able to see if they are turned back on today?
In this video we will talk about the cameras onboard the Voyager 1 spacecraft which took the
portrait of the solar system, and what would happen if we turn them back on.
Launched in 1977, Voyager 1 is a spacecraft that has been on an incredible journey. It
is now 6.4 billion kilometers (3.7 billion miles) from the center of the solar system,
and it has been able to look back at the home it left behind. It has flown past Jupiter,
Saturn, Uranus and Neptune, and it has been able to take some incredible images.
Voyager 1 is currently racing away toward the infinity of interstellar space,
and our entire solar system looks like a string of small colored dots clustered just to the right
of the constellation Orion. It is amazing to think about all that Voyager 1 has seen and accomplished
on its journey! A trail of 39 grayscale shots – with zoomed-in color insets of each planet,
assembled from another 21 color-filtered photos – makes up the famous solar system portrait.
Even though Voyager 1 was still approaching the solar system's border, where the protective
"bubble" of our Sun's solar wind gives way to interstellar space, the family portrait gives you
a feeling of the size of our neighborhood and that there is a great lot beyond it still to be found.
The spacecraft was about 6.4 billion kilometers (4 billion miles) from Earth when it took the photos,
and at that distance, even Jupiter appears as just a dot. Saturn's rings are barely visible,
and Uranus and Neptune are just blurry smears. Earth is an even tinier speck,
less than a pixel in the image. Yet despite its humble size, our world is still the most
beautiful object in the Voyager 1 family portrait. The pale blue crescent of our home planet stands
out against the blackness of space, a reminder of the fragility and preciousness of life.
Venus occupies only a fraction of a pixel, while Mercury is so near to the Sun that it
is undetectable in the Voyager 1 images. Mercury is the family member who always manages to sneak
behind someone taller just before the picture is taken. And Mars, like the person who blinks just
as the camera shoots, has lost its slender crescent in the glare of dispersed sunshine.
Pluto, which was still considered a planet at the time because we hadn't realized that dwarf
planets were a separate category of object to which the icy little world rightfully belongs,
also doesn't appear in the photo because it's too small and too dim to be visible.
Voyager 1 was designed and built here on Earth in the 70s. Despite being in space for
45 years as of 2022, the computers and systems onboard the spacecraft are still functioning.
The engineering of the spacecraft was beautiful and way ahead of its time, a perfect example of
that are the cameras onboard the voyager 1. It is no easy feat to take the images we are discussing
about today, in harsh environments of space. The Voyager 1 spacecraft has two cameras on board,
a wide-angle camera and a narrow-angle camera. The wide-angle camera is used to take grayscale
background photos, while the narrow-angle camera is used to take color photos of planets.
Each of the color photos of the planets actually consists of three photographs, which Voyager’s
narrow-angle camera snapped in rapid succession: one photo each with three different color filters
in violet, green, and blue. Voyager 1 started its panorama at the outer edge of the solar system and
worked its way inward, taking the grayscale background photos with its wide-angle camera
and photographing each planet in color with the narrow-angle camera as it came to them.
As a result, the Voyager 1 spacecraft has a unique set of images that provide an intimate look at
our solar system’s planets. The Voyager Imaging Science Subsystem (ISS) is a modified version of
the previous Mariner flights' slow scan vidicon camera systems. A high resolution Narrow Angle
(NA) camera and a lower resolution, more sensitive Wide Angle (WA) camera comprise the system.
The cameras are controlled by an imaging parameter table stored in one of the spacecraft's computers,
the Flight Data Subsystem. As Voyager 1 gets further from the sun, objects appear more faint,
so longer exposure times are used. Voyager 1 is also getting further from Earth,
so telecommunications capability at each encounter decreases.
The Voyager team had to program a sequence of commands in advance for the cameras, because
instructions from home took about 5.5 hours to reach Voyager 1’s radio antenna. For example, they
had to decide when and where to point the camera, which filter to use, and how long the exposure
should be. The exposures near Uranus and Neptune needed to be 15 seconds long with the narrow-angle
camera, while the exposures for the Sun only needed to be 1/5000th of a second long. Voyager
1 used a dark filter meant for photographing the wavelengths at which methane absorbs light. All
of these factors had to be considered in order to get clear, quality photos from Voyager 1. Cameras
with 800x800-14 m pixel resolution are installed at the end of Voyager's flexible scan platform.
Each frame needed 5,120,000 bits, which could be stored on a magnetic tape with a capacity of 536
million bits at 115,200 bps or relayed back to Deep Space Network receivers on Earth at 8400
or 14,400 bps. The tape backup was required to save images during occlusion (when a planet or
satellite obstructed the radio communication line) and was replayed at a lower data rate.
Even with all of the meticulous filtering and exposure time, the photographs of the
inner solar system are full with reflected beams and sunshine spots; Earth happens to be centered
in one of them in the color inset shot. That image, in particular, is a moving farewell
to mankind from our most distant creation; 34 minutes after the photographs were shot,
NASA engineers instructed Voyager 1 to turn off its cameras in order to conserve power for the
lengthy journey into the unknown. There isn't much to see in interstellar space, after all.
Regrettably the cameras onboard the Voyager spacecraft were disabled decades ago,
just after taking the last distanced image of the solar system. This is because the space
probe had traveled so far out into space that it no longer received enough light to function
as intended. After Voyager 1 took its last image (the "Solar System Family Portrait '' in 1990),
the cameras were turned off to save power and memory for the instruments expected to detect the
new charged particle environment of interstellar space. Both Voyagers' RTG "nuclear batteries''
are nearing the end of their lives. These spacecraft might be decommissioned at any moment,
and most likely within the next five years. More and more scientific experiments are being
shut off in order to preserve energy and extend their lives. Since then, the computer software
that operates the cameras has been overwritten to make room for additional scientific data.
Because it is becoming increasingly difficult to transmit data back to Earth, the ability to store
more data aboard the spacecraft for subsequent transmission is advantageous. Each spacecraft's
radioisotope thermoelectric generator produces 4 watts less each year. Due to dwindling electrical
power, the Voyager crew was forced to decide which instruments to keep running and which to
switch off. As part of power management, heaters and other spacecraft systems have been shut off
one by one. The Voyager team has decided to continue running the sensors that are most
likely to return critical data on the heliosphere and interstellar space – the fields and particle
experiments. Engineers intend to begin shutting down fields and particle physics equipment one
by one for Voyager 2 in 2020. Because Voyager 2 is now operating one more instrument than Voyager 1,
it will have to begin shutting off science equipment sooner. Engineers anticipate that
each spacecraft will continue to operate at least one scientific instrument until roughly 2025.
Even if science data is unlikely to be gathered after 2025,
engineering data may be returned for several years longer. Depending on how
much power the spacecraft still has to broadcast a signal back to Earth,
the two Voyager spacecraft might remain in the Deep Space Network's range until around 2036.
On top of this addressing our last question of what will happen if we turn on the cameras today?
Would we be able to see anything? The cameras onboard the Voyager 1 can be activated,
although it is not a priority for Voyager's Interstellar Mission. After taking its final
photograph (the "Solar System Family Portrait") in 1990, Voyager 1's cameras were shut off to
conserve power and memory for the equipment that would detect the new charged particle environment
of interstellar space. Mission controllers uninstalled the software that controls the camera
from both spacecraft. The computers on the ground that comprehend the programme and evaluate the
photographs no longer exist. The cameras and their heaters have also been subjected to the extreme
cold of our solar system for many years. Even if mission management rebuilt the computers on the
ground, reloaded the software onto the spacecraft, and turned the cameras back on, it is unclear if
they would operate. Furthermore, the Voyagers are currently in an extremely dark environment. While
the cameras could still view certain brighter stars and planets, amateur telescopes on Earth
can see these stars and planets far better. So the bottom line is, we might be able to turn the
cameras back on, but they wouldn’t be any useful. They might be damaged due to exposure to cold deep
space, and the cameras won’t do much good anyways as deep interstellar space is mostly black.