If I can do this with Junocam's pictures, so can you

Nasa's Juno spacecraft downloaded its first images of Jupiter to Earth. Within days people around the world were putting their own spin on never-before seen views of the giant planet's polar regions.

People around the world - and not just scientists - are processing the first images from Nasa’s latest Jupiter mission. 

When the scientists in charge of the Juno mission sat down to decide what instruments should make the five year journey to the giant planet, a camera wasn’t on the list. Ultraviolet and infrared spectrometers? Check. Vector magnetometer? Check. Microwave radiometer? Check. Energetic particle detector? Check. Ka- and X-band translator? Check and check.

But no camera. Juno’s mission is to understand Jupiter’s atmosphere and magnetosphere. A visible spectrum camera just wouldn’t add much that scientists didn’t already know from previous Jupiter missions.

The Juno team decided to put a camera on it anyway - specifically for the public. One of the technical papers (DOI: 10.1007/s11214-014-0079-x) published for the scientific community put it this way:

…visible imaging is an important component of public engagement for any mission. So a visible camera, Junocam, was included primarily for education and public outreach…
— "Junocam: Juno’s Outreach Camera" Space Science Review

Yet Junocam is about more than just getting pretty pictures of Jupiter. Amateur astronomers and the general public are deeply integrated in the project. 

A team of amateur astronomers around the world are taking images of Jupiter from their backyard observatories. [Check out my interview with Filipino astrophotographer Christopher Go.] They produce more high quality images - 24 hours a day, 7 days a week - than the planetary science community could ever hope to get from their mountaintop observatories. Some of the amateurs post these images to the Junocam website. As Juno approaches Jupiter, the Junocam science team uses these images to pick targets for Junocam’s limited number of snapshots.

But it isn’t just up to the scientists. The public votes to decide which of the features in Jupiter’s cloud bands should be the highest priority. The scientists get the final say - it can’t be Great Red Spot all the time - but it is the public that decides what features are on the list.

Within days of Juno’s close approach the Junocam team posts the images to the camera’s website. Anyone can download the data and process the images themselves - and then repost their work to the Junocam site. The download includes five image files ranging from the original Junocam data to a basic processed color image.

My image (far left) is based on a series of processing steps from the Junocam team. The raw data downloaded from Juno is a stack of image stripes. The stripes must be converted into images for each of the red, green, and blue filters. These get combined into a final color image (far right) which has a yellowish cast to it.

The Experiment Data Record, or EDR, is an odd-looking image that seems to show the same picture over and over again. That’s because Juno spins in order to gather the scientific data from the other images. Junocam’s design lets it snap a picture each time Jupiter passes through its field of view.

The Reduced Data Records, or RDRs. use the raw data in the EDR to build images for each of Junocam’s filters. That produces three files for the red, green, and blue parts of the image. A fourth filter captures light at infrared wavelengths absorbed by methane in Jupiter’s clouds. The Junocam team keeps this data to support the science mission.

The final “map-projected” file combines the red, green, and blue files to create a color image. But the scientists don’t do anything to make this picture “pretty”. That’s what the public gets to do.

For my first attempt at processing a Junocam image I decided to skip the EDR and RDR files. Working with the raw data in the EDR is not like processing the pictures from your camera. You have to cut and splice the file to piece the three filter images together. That’s more than I wanted to do on a first take. Working with the RDR’s is a little easier with a little Photoshop magic, but call me lazy I decided to start with the map-projected file. 

Even then geometry makes things tricky. We are looking down at Jupiter from above the pole, which is the shortest distance from Junocam. The edge of the partial disc is Jupiter’s equator and the farthest distance from the spacecraft. The amount of light and the level of detail changes dramatically around the disc. 

It took me some trial and error to figure out how to get it done. I’m sure a Photoshop pro could do a better job done with less work. But after applying two dozen separate curve layers I got a picture that (in my opinion) looks pretty good.

If I can do this, then so can you. Take a look at the Junocam site. Pick a picture and see what you can do with it. Then share it with everyone else on team Junocam.