On March 2, 1972, Pioneer 10, was launched by NASA on top of an Atlas-Centaur rocket (AC-27 / Atlas 3C no. 5007C / Centaur D-1A) to study Jupiter, the largest planet in our solar system, and its environment.

The mission’s primary goal was to fly by Jupiter and study its atmosphere, magnetosphere, and radiation belts. Pioneer 10 was the first spacecraft to visit Jupiter and provided scientists with the first up-close look at the gas giant and its four largest moons, Io, Europa, Ganymede, and Callisto.

March 2 story of what happened this day in Science, Technology, Astronomy, and Space Exploration history.

Pioneer 10

Pioneer 10 was NASA’s first mission to the outer planets. The mission was a spectacular success. Originally designed for a 21-month mission to fly by Jupiter, Pioneer 10 lasted more than 30 years.

The space probe sent its last signal to Earth in January 2003 from a distance of 7.6 billion miles (12.23 billion kilometers).

Pioneer 10 launch
The launch of Pioneer 10 on March 2, 1972, on top of an Atlas-Centaur rocket (AC-27 / Atlas 3C no. 5007C / Centaur D-1A). Pioneer 10 was the first spacecraft to travel through the asteroid belt, and the first spacecraft to make direct observations and obtain close-up images of Jupiter. Image source: NASA

Pioneer 10’s firsts

The spacecraft notched a series of firsts unmatched by any other robotic spacecraft to date.

Pioneer 10 (and 11) were carrying a 1-pixel (0.000001 megapixels) camera!

NASA’s Pioneer 10 and 11 spacecraft were equipped with a camera that had a resolution of 0.000001 megapixels. The camera captured images by scanning a single pixel over the target body as the spacecraft spun continuously in one direction and slewed in the other. Thus, producing a single image required a significant amount of time, during which the spacecraft and the target body would shift position, leading to distortions in the final image.

The reason why Pioneers carrying such a basic imager is – the planning and payload selection for both missions took place in the 1960s, and they were launched in the early 1970s, at a time when the focus was on conducting fields and particle experiments, which were considered more scientifically significant than visual imaging. The limited mass and power of the spacecraft meant that they had to prioritize their science objectives accordingly.

Even if the engineers wanted to make imaging the primary mission, they did not have the resources or technology available to do so, unlike the Voyager spacecraft, which launched later.

It’s taken for granted today, but for the first few decades of space exploration, the simple prospect of how to capture images remotely and return them to Earth (or even of translating digital image data into something a human could see) was a quite an engineering challenge.

Pioneer space probes’ cameras (the “imaging photopolarimeter”) are made up of a handful of photo-diodes (sensitive to different wavelengths) connected to an optical system with a very narrow field of view of just 0.03 degrees across.

The probes were spin-stabilized with a rotation of 4.8 rpm so they would scan a full 360-degree strip of the local sky every 12.5 seconds. The probes could adjust their orientation to move where that strip scanned or it could just let it naturally sweep across objects as it moved through space and in that way take pictures of larger objects by collecting essentially hundreds of single-pixel images and collecting them into a mosaic.

The later Viking probes (Viking 1 and 2) used similar imagers but had movable mirrors to scan where they pointed to be able to take images of the Martian terrain without having to move the probes (which were just stationary landers).

These types of imagers had many advantages at the time as they were all solid-state and very robust while having reliable response characteristics.

Ultimately, Pioneer 10 and 11 did their best to maximize their scientific return given the limitations they faced.

Photograph of Jupiter by Pioneer 10 spacecraft
Photograph of Jupiter by Pioneer 10 spacecraft at a range of 2,584,000 km (1,605,623 miles). Photo: NASA Ames Research Center Photo Library.

Sources

M. Özgür Nevres
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