Space Probes

Pioneer 10 and 11 - 1972/97 - "Pioneer Project"

Image processing

Pioneer 10 and 11 were the first spacecraft to explore Jupiter and Saturn. They were designed as simple probes with a limited number of instruments.

As such, they didn't carry a camera in a conventional sense, but an Image Photo-Polarimeter. This device works by measuring the amount of light coming from a single point of space in two wavelengths (Red and Blue). These measurements were encoded on 64 levels (6 bits). Therefore, to produce a picture, that single point must move and scan the planet step by step and line by line.

This movement was connected with Pioneer's spin rate. A scan on each spin was converted into a 466 pixel long line, covering a 14º or 28º portion of sky, depending of the actual sample rate selected. We can consider this scan to be the equivalent of a line on a computer display.

Therefore, a raw Pioneer image can have a maximum of 466 horizontal pixels. The vertical dimensions of each image are not constrained. After reading a "line" the instrument could be repositioned to scan a small amount below or above the previous position. This was done as needed in order to scan the full disk of a planet from a distance or zones of interest when the spacecraft was closer.

In the case of Jupiter, at closest approach it took 30 minutes to scan a full image. This amount of time combined with spacecraft motion and the planet's rotation introduces severe distortions to the pictures.

The available images come in scanned format from printed paper or photographic sources. Where possible, I stacked several copies of the same image to reduce noise. Color RGB composites were generated from the separate red and blue data when available, with a synthetic green channel.

Image orientation, colors and proportions were corrected to get a more uniform gallery, but the original NASA geometric correction was maintained. This correction tried to reproduce the correct planet limb and overall shape, and didn't account for the positioning of the visible features within the disc. As such, the images show severe distortions.

Some cylindrical maps were produced from the semi-global Jupiter coverage provided by both spacecraft's encounters with Jupiter. Positions of features on the maps are only approximate, given the difficulty to correct all the geometrical distortions mentioned above in conjunction with the planet's rotation. For Saturn I've created mosaics by using parts of the best images available.

 

I've found some images in a "raw" format with no geometric correction. These are found as scanned prints or on a broadcast video of the Saturn encounter press conferences. When available, I'm displaying the raw image and the NASA corrected version.
Comparing both we can appreciate the amount of work NASA had in correcting the geometry, completing cropped ring edges, etc.

 

The images I was able to find are presented below, in the correct sequence. Image identification was based on the indicated distance to the planet or image code (if specifically indicated).

The source for the listing data is the Pioneer Odyssey book (Appendix 2) and Pioneer 11 Saturn Encounter Data, both by NASA. The Saturn encounter video is here.