Cosmic TiVo to deliver images from the dawn of time
This week the worlds most reliable digital video recorders were delivered to NASA’s James Webb Space Telescope (JWST) team to vacuum up light in the most distant stars and galaxies emitted 13.5 billion years ago.
JWST will sit at the second Lagrange point (L2), approximately 1.5 million km from Earth, outside the orbit of the Moon, and use infrared to scan the distant stars and galaxies. Downloading information from the satellite, however, presented a problem as NASA can not continuously stream the data to its network of ground stations. To resolve this, scientists will bundle up the data on JWST on-board and grab the gathered data in four-hour windows every 12-hours. Data will be downloaded in 60Gb bursts from the recorder itself.
Chris Miller colleagues, from SEAKR Engineering in Centennial, Colorado, delivered a Solid State Recorder (SSR), a Cosmic TiVo-like device, to Northrop Grumman in Redondo Beach, California. ”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.
Challenges were met when building the SRR as memory chips are quite vulnerable to cosmic ray protons, which can flip the bits stored binary o’s to 1′s, and vice versa, as it tears through transistors. Using shielding and radiation hardened semiconductors the SRR also has some smart features built-in for error correction. ”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. While information sits in memory, errors can be fixed on playback or ahead.
Miller and his colleagues at SEAKR are quite confident with its engineering of the SSR, and does not see a need for a backup SSR unit on-board the JWST — and any problem it might suffer could fix itself. Hopefully that will be the case, as the telescope is far from the reach of astronaut hands to reach.