Final week, we noticed the primary pictures from NASA’s $10B James Webb Area Telescope. The images are gorgeous and characterize an unimaginable achievement. The images are sharper and extra detailed than these from the Hubble Area Telescope. They will even unlock key info for researchers working exhausting to know the universe’s origins, how stars and galaxies kind, and if there are planets on the market that may help life. The pictures are spectacular, and the telescope’s know-how is extraordinarily refined, so it might be shocking to study that they are being saved aboard the house telescope on a comparatively paltry 68GB SSD. The exhausting drive can maintain a couple of day’s price of Webb pictures.
IEEE Spectrum experiences Webb generates about 57GB of information every day. As compared, Hubble generates about 1 to 2GB of every day knowledge. Webb reserves 3 p.c of its 68GB SSD for engineering and telemetry knowledge. Scientific knowledge that Webb collects throughout its mission will even should be saved on board, because the telescope does not keep fixed communication with Earth. Nonetheless, earlier than the drive fills, which takes about 24 hours, Webb will beam knowledge again to Earth throughout a pair of four-hour contact home windows every day.
Knowledge transmission is a essential element of the Webb mission and has been fastidiously studied and deliberate for many years. The telescope is about 1.5 million km (932,000 mi) from Earth at Lagrange level L2. That is an extended solution to ship knowledge. Webb is the primary mission to make use of Ka-band frequencies to ship its comparatively excessive quantity of information. Particularly, IEEE Spectrum notes that the JWST is transmitting knowledge on a 25.9GHz channel at as much as 28Mb/second (0.0035GB/sec). That works out to about 12.6GB per hour.
Ka-band frequencies can transmit extra knowledge than both X-band (7-11.2GHz) or S-band (2-4GHz). These bands are typical selections for distant spacecraft. Given Webb’s excessive quantity of information, these bands weren’t a viable possibility. Additional, per Carl Hansen, a flight techniques engineer on the Area Telescope Science Institute (STScI), a comparable X-band antenna would have been giant sufficient that it might have hampered Webb’s potential to seize sharp pictures.
Though major knowledge is transmitted utilizing a Ka-band, Webb consists of two S-band channels. A 2.09GHz uplink transmits statement schedules to the telescope at about 16Kb/s. A second 2.27GHz S-band has a 40kb/s downlink that transmits engineering knowledge, together with operational standing and system well being.
At L2, Webb is topic to excessive temperatures of round -223° C (-370° F) and important radiation. The SSD needed to undergo intensive testing, in fact. Even nonetheless, after a decade, the SSD’s capability will likely be lowered to round 60GB on account of radiation and common put on and tear. NASA expects Webb to carry out at the very least 20 years, double its unique mission plan. Nonetheless, at what level will SSD deterioration turn out to be an impediment?