Jupiter, Juno, and Why Space Qualification Still Doesn’t Cut It
I have always been fascinated with space exploration. The endless possibilities of discovery captured my imagination as a kid. It wasn’t until I began working with space development that I could fully appreciate what goes into the development of a new space craft. Watching the Juno probe perform its Jupiter Orbit Insertion maneuver brought tears to my eyes and inspired me to learn more about the probe and Earth’s biggest neighbor.
There are many things which engineers at NASA, Space X, and at a semiconductor company like ADI must consider when developing products for use in space that anyone else wouldn’t have to worry about for earth-bound applications, most notably of which is radiation (of course unless you’re working on a nuclear power plant). Radiation can wreak havoc on any CMOS device, causing glitches and even damage beyond repair in many cases. We’ll cover these failure modes in a little bit.
For those with limited experience working in the space market, any device which is targeted to companies like NASA must adhere to a set of standards set by the Defense Logistics Agency (DLA). Among these specifications are different radiation tolerance levels which a “rad-hard” space qualified device must pass. This typically entails a standard level of radiation testing up to 100Krads.
While 100Krads may sound like a lot of radiation, even a standard “rad-hard” device as tested to DLA standards wouldn’t stand a chance around Jupiter. Jupiter has an enormous magnetic field, and it’s extremely strong. If we could see Jupiter’s magnetosphere from earth, it might look something like this. See Figure 1.
Jupiter’s Magnetosphere if it could be seen from earth; Photo Credit: NASA
Just like Earth’s, Jupiter’s magnetic field is distorted by the solar winds. The tail shown here extends all the way past Saturn’s orbit! This strong magnetic field traps solar wind particles, as well as those ejected by the volcanic moon Io, and flings them around the planet at ridiculous speeds. It’s these energetic particles that Juno’s electronics will need to worry about. The radiation levels seen around Jupiter can reach upwards of 20 million rads. To put that into perspective, that’s the equivalent of being blasted by 100 million dental x-rays at once! Juno’s orbit will thankfully keep it outside of the worst areas of radiation, but it still must punch through these zones in order to take the data it needs. In its closest approaches, Juno will be just about 3,100 miles (5,000 km) from Jupiter’s cloud tops.
With all of that radiation, even a space qualified device wouldn’t last long without extra shielding. Juno’s sensitive and most important electronics are housed inside a heavy titanium box to block as much radiation from reaching the inside.
Let’s take a look at a few aspects of radiation testing that any DLA space device must go through.