JunoCam and the KAI-2020 Image Sensor

by  Michael DeLuca  - 06-27-2016 

Since its launch in August 2011, NASA’s Juno orbiter has travelled a long way – 2.8 billion kilometers (1.7 billion miles) or so – on its journey from Earth to Jupiter.  And after five years cruising through the inner solar system, its trip finally ends next week as the orbiter arrives at Jupiter on July 4.  

Juno’s scientific equipment was designed to help us better understand the beginnings of our solar system by revealing the origin and evolution of Jupiter.  Nine different instruments are on board to determine the amount of water in Jupiter's atmosphere, look deep into its atmosphere to measure composition, temperature, cloud motions and other properties, map Jupiter's magnetic and gravity fields to reveal the planet’s deep structure, and explore and study Jupiter's magnetosphere near the planet's poles.  And one of these instruments – JunoCam – will use a KAI-2020 image sensor to provide the first color pictures of Jupiter’s cloud tops from orbit.


Figure 1:  Juno Orbiter (NASA / JPL-Caltech)


Developed by Malin Space Science Systems, JunoCam’s hardware is based on the Mars Descent Imager (MARDI) that captured images as the Mars Science Laboratory descended to the surface of Mars.  But the imaging challenges for this mission are even more complicated – a highly elliptical, 11-day orbit will vary Juno’s distance from the Jupiter cloud tops from 2.7 million km to about 5,000 km, with the planet roughly filling the JunoCam field of view only at its closest approach.  In addition, the orbiter (and the camera) will be rotating at about 2 revolutions per minute, so that the sensor will be operated using Time Delay Integration to keep images from being blurred.

Even with these constraints, the imaging capabilities of JunoCam will be impressive.  The camera will capture data in four separate wavelength bands:  blue (420–520 nm), green (500–600 nm), and red (600–800 nm) for reconstruction of a color image; plus a band from 880–900 nm to image a narrow absorption of methane centered at 889 nm.  And the 3 km resolution available at closest approach (an order magnitude better than that available from the Voyager, Galileo, and Cassini probes) will enable viewing of small-scale structures in the atmosphere.


Figure 2:  Simulated view of the south pole of Jupiter as seen by JunoCam.  (NASA / JPL / MSSS via The Planetary Society).


As part of the Juno mission, NASA is partnering with the public on the operation of JunoCam.  Amateur astronomers can upload telescopic images and data of Jupiter to help identify – and vote on – the images to be captured by JunoCam.  And once captured, the raw data will be available for download, allowing anyone to process the images and upload finished files to the main JunoCam site.  This system was tested in 2013, when Juno’s trajectory brought it back to Earth for a gravity assist on its way to Jupiter – JunoCam used that flyby to capture images of Earth that are posted online.  But now it’s time for the main event.

So if you’ve ever wanted to take part in one of NASA’s missions to another planet, here’s your chance.  Because after five years of waiting, Jupiter is finally ready for its close-up.

Tags:CCD, CCD Image Sensor, Image Sensor, Industrial
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