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 into low-power modes but need to continue sending telemetry data.

4. External shielding

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

The size of electronic components qualified for space usage is thus usually much larger than commercial/industrial ones.

Effects of radiation on spacecraft electronics

Even with all of these modifications to make electronics space-grade, they can still suffer in space from intense space radiation. A wide range of effects, known as Single Event Effects (SEE), can cause operational issues.

Ions in space radiation interacting with the chip components can flip the states of bits and cause memory errors.

A high-energy ion or proton passing through the inner transistor junctions can cause latchups, leading to short circuits.

Similarly, this high-energy particle radiation can also let electrons loose in a circuit, causing irreversible damage.

Memory losses, code execution sequences going haywire, latchups, etc. are all undesired events in a successful space mission. Some of these can only be overcome with a hard reset, while some cause permanent damage. Spacecraft electronics must be built with all these factors in mind.

Apart from the Phobos-Grunt incident, let’s have a look at space missions which act as a constant reminder of the harsh, unforgiving nature of space exploration. (This article was inspired by Emily's recent piece on sample collection.)

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.