Cosmic TiVo to deliver images from the dawn of time

Paul Marks, senior technology correspondent

Artist's impression of the James Webb Space Telescope (Image: NASA)

One of the most reliable digital video recorders ever engineered was delivered to the team building NASA's James Webb Space Telescope (JWST) this week.

In the depths of space, 1.5 million kilometres from the Earth, the telescope will scan the heavens in the infrared, sucking in light the most distant stars and galaxies emitted 13.5 billion years ago. But that far from Earth, it cannot continuously stream data to NASA's network of ground stations. So to make sure scientists get to see the images harvested by the JWST's huge 6.5 metre mirror, the image data has to be stored on board until it can be downloaded to the ground stations of NASA's "deep space network" in a four-hour window once every 12 hours - and in 60 gigabyte bursts fired straight out of the recorder.

This week, Chris Miller and colleagues at SEAKR Engineering in Centennial, Colorado, delivered a deep-space-qualified solid state recorder (SSR) - a cosmic TiVo box if you like - to the firm building JWST, Northrop Grumman of Redondo Beach, California - which also makes the giant Global Hawk surveillance drone. "Operating like a digital video recorder, the SSR records all science data and engineering state-of-health telemetry for the observatory 24 hours a day, seven days a week," says Northrop Grumman in a statement.

Designing the SSR was a particular challenge because the memory chips at the heart of it are highly vulnerable to corruption by cosmic ray protons, which can bitflip stored binary zeroes to ones (and vice versa) as they tear through its transistors. Apart from using shielding and radiation hardened semiconductors, the SSR also uses ultra-smart error correction software to maintain data accuracy, says Miller.

"An Error Detection and Correction?code is appended to the science data when it is recorded and then recomputed and checked against the stored data upon playback of the data from memory," explains Miller. So errors can be fixed on either playback or beforehand - when the data is simply sitting in memory.

SEAKR is so confident in its engineering of the SSR it sees no need to have a backup SSR unit on board the JWST, saying there are no problems it could suffer that it can't fix itself. In the jargon, it's "single-point failure immune" Miller says.

We can only hope he's right. At 1.5 million kilometres from Earth, the telescope is too far away for any human service mission to reach.

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