Jupiter’s intense radiation called for a robust, armoured spacecraft
Approaching Jupiter more closely than any other spacecraft and surviving the fiercest planetary magnetic and radiation environment in the Solar System was always going to be a formidable challenge. Most of Juno’s electronics, including its RAD750 microprocessor, are composed of radiation-resistant tantalum, with wiring sheathed in a copper and stainless steel braid, all encased within the 10mm-thick walls of a cubeshaped titanium vault. Although not impenetrable, the vault reduces radiation damage by 800 times.
For extra robustness, Juno’s hardware was built bigger and external components – solar panels, cameras, sensors – received added protection, including 12mm-thick glass sheets. Ground-based electron tests showed the solar panels would lose 0-15 per cent of their output at Jupiter, so were built 10-15 per cent bigger. Over its lifetime, the spacecraft will endure the equivalent of 100 million dental X-rays.
“Juno is basically an armoured tank,” says principal investigator Scott Bolton. “Without its protective shield or radiation vault, Juno’s brain would get fried on the very first pass.”
Much of its 53.5-day orbit is spent beyond the worst radiation, but at perijove it dives quickly through the searing equatorial regions. “We thread a needle,” says Bolton. “By going over the poles, we’re able to drop down in a small gap between the atmosphere and these intense radiation belts.”
Just after having had its radiation vault fitted over its propulsion module, Juno is lifted on a rotation fixture at Lockheed Martin Space Systems, Denver in June 2010