Something strange is killing off pixels at an alarming rate in the detectors of a multi-billion dollar space telescope scheduled to launch in 2014.
The problem is just the latest blow for NASA鈥檚 ultra-sensitive (JWST), which is expected to launch late and run over-budget.
JWST has a 6.5-metre mirror, which is nearly three times as wide as the mirror on the . The telescope could glimpse the universe鈥檚 first stars and galaxies.
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But in December of the University of Arizona in Tucson and colleagues found that roughly 2 per cent of pixels in a detector destined for JWST鈥檚 Near Infrared Camera (NIRCam) were transmitting signals although no light was hitting them. That鈥檚 four times as many 鈥渉ot pixels鈥� as there were when the detector was analysed in 2008.
The researchers later found that the problem affects four of the camera鈥檚 five long-wavelength detector arrays. 鈥淲e don鈥檛 know what is happening, and we don鈥檛 know if there鈥檚 a way to reverse it or slow it down,鈥� says Rieke, principal investigator for the NIRCam. 鈥淯ntil we understand the root cause, I think we鈥檙e all going to be quite nervous.鈥�
Latest setback
NASA allows no more than 5 per cent of a detector鈥檚 pixels to be hot by the end of the telescope鈥檚 five-year space mission. At this rate, the detectors may exceed this limit before the telescope even leaves the ground, says Rieke.
The pixel problem follows a series of setbacks for JWST. In November 2010, an independent review panel predicted that JWST is unlikely to launch before September 2015, more than a year later than planned, and will cost $1.5 billion more than expected.
NASA has set up a review board to analyse the detector problem and discuss solutions. 鈥淚t鈥檚 too early to speculate on what the root cause is or what we鈥檙e going to do to fix it,鈥� says JWST programme director Rick Howard. He says it may be a month or more before the expert board comes to a conclusion.
