Space grade electronics or How NASA’s Juno survives near Jupiter

Six space missions that reminded us space exploration is hard

Jatan Mehta
Mar 15, 2018 · 8 min read
Maneuvers to be performed by Phobos Grunt around Mars. Source: Wikipedia

Part A — Hardening electronics for space usage

Build to last

Electronic components used in spacecraft must be built to survive the harsh space environments and function reliably in it. The US Department of Defense mandates over 100 tests to ensure reliable operation under mechanical stress, wide temperature fluctuations and intense ionizing radiation. All space grade electronic components must be individually qualified as opposed to the sample testing common in commercial or industrial applications.

The Voyager spacecraft launched in 1977 is still functioning. Source: Wikipedia
A potted electrical transformer designed to be installed on a PCB for space usage. The surface formed by the potting compound is seen on the right. Source: Wikipedia

1. Potting

Launch time vibrations from the rocket can induce mechanical stress on the electronics and damage it. The process of potting involves filling the electronic assembly with a solid/gelatinous compound to resist shock and vibration.

2. Silicon on insulator

Chips for space usage are manufactured on an insulating substrate instead of a silicon one, allowing them to be more radiation resistant and fault tolerant.

3. RAM types

Static RAMs (SRAM) are preferred instead of Dynamic ones (DRAM) because they are less power hungry. This is crucial for when spacecraft go in low-power modes but need to continue sending telemetry.

4. External shielding

An external shield (like lead) around the electronic components reduces exposure to radiation, thereby increasing the mission’s life span. This is particularly useful in long-term missions like New Horizons which is currently en route to a Kuiper Belt Object.

Effects of radiation on spacecraft electronics

Despite the components tested to be space grade, things can still work unexpectedly in a space mission due to intense space radiation. A wide range of effects, categorized under the Single Event Effects (SEE), can cause operational issues.

  • A high energy ion or proton passing through inner transistor junctions can cause latchups, leading to short circuits.
  • Similarly, these high energy particles can also let electrons lose in a circuit causing irreversible damage.

Part B — Interesting cases of space grade electronics in various space missions

1. When you lose your star sensors

India’s first lunar orbiter Chandrayaan-1’s star sensor failed to work after a few months in lunar orbit. The extreme exposure to solar radiation combined with other factors caused the backup star sensor to fail too.

Chandrayaan-1 schematic showing the two star sensors. Source: Wikipedia

2. When you have six computers to complete one job

The Galileo spacecraft designed to orbit and study Jupiter had not one but six CPUs. Surviving in the radiation riddled Jovian (Jupiter’s) environment — which is orders of magnitude more intense than Earth’s — mandated that each major subsystem be controlled by its own CPU for fault tolerance. That way if one CPU dies, it only disables one major instrument.

Artist’s impression of NASA’s Galileo spacecraft flying past Jupiter’s volcanically active moon Io. Source: NASA. Note: In this impression, the high-gain antenna is shown fully deployed but it wasn’t during the mission.
Schematic of the Jovian magnetosphere encompassing its four Moons. Galileo spacecraft faced intense radiation on all close passes to Jupiter. Source: John Spencer

3. When solar flares damage your solar panels

En route to the asteroid Itokawa in 2003, the Japanese spacecraft Hayabusa was hit by one of the largest solar flares in recorded history. The flare damaged the solar panels thereby reducing their output. Not just that, the flare also took off one of the four ion engines of the spacecraft. The mission duration had to be reduced as a result.

JAXA’s Hayabusa spacecraft at Itokawa. Source: Planetary Society

4. Radiation hardening using RAD computers

One of the latest generations (in space grade terms) of radiation-hardened chips is the 32-bit RAD750 manufactured by BAE, based on the PowerPC 750 designed by IBM. It is designed to minimize losses even when facing extreme radiation from solar flares. Having a wider temperature range and 10x better performance than the previous generation RAD6000, the RAD750 has been used in over 150 space missions since its availability, including everyone’s favorite Mars rover Curiosity.

Curiosity rover selfie at Mount Sharp. Source: NASA

5. The case of Juno and Jupiter

Designed to study Jupiter’s poles and go closer to the planet than any spacecraft before it, Juno is faced with challenges. It turns out that using individually tested space grade components, one of the most radiation-hardened CPUs and making use of redundant components is still not enough to face the harsh environment near Jupiter, the planet with the largest magnetosphere in the solar system.

1 —Artist’s impression of Juno spacecraft with its large (and thick) solar panels. Source: NASA. 2 — Juno’s orbit gets it extremely close to Jupiter to achieve its science objectives, in the process exposing it to hazardous radiation belts. Source: Juno website
NASA JPL engineers installing the Juno Radiation Vault designed to protect its electronic components when in the intense Jovian environment. Source: NASA

“ Without its protective shield, or radiation vault, Juno’s brain would get fried on the very first pass near Jupiter”

- Scott Bolton, Juno’s Principal Investigator

Even then, Juno is expected to cease functioning later this year due to multiple close passes to Jupiter over its two-year mission span. A reminder that space is hard.

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Jatan Mehta

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Science officer @TeamIndus Moon mission • Space advocate, Astrophysics nerd and Open Source tech enthusiast •

TeamIndus Blog

Privately funded mission to land on the Moon in 2020