Hubble among 16 space telescopes to have major bug

26 Feb 2018

Image: MarcelClemens/Shutterstock

The discovery that 16 space telescopes, including Hubble, have a major technical flaw in their system raises questions about their research data.

The last thing you want to hear as a scientist is that the instruments you use on a regular basis to obtain precise data are not as accurate as you think.

That appears to be the case for many astronomers after an international team of researchers discovered what appears to be a systematic error in not one, but 16 different space telescopes, including the iconic Hubble Space Telescope.

According to The Register, the flag was raised after a team saw what looked like an error in the data from a Hawaii-based telescope. After taking a closer look, it saw that it might be experiencing a feedback error caused by the analogue-to-digital converters (ADCs), which convert what the telescopes see into digital data.

In a paper published to arXiv, the team detailed how the SuperNova Integral Field Spectrograph (SNIFS) error seemed to be down to the number of ‘1’ bits in the binary-coded output caused by crosstalk between pixels in the telescope’s electronic chain.

Based on the team’s calculations, this bug could mean the data is off by as much as 4.5 analogue-to-digital units (ADUs) per pixel, the unit by which astronomers can measure how many photons are contained within a pixel.

Worryingly, this error was found in 15 other telescopes, including: LRIS and DEIMOS on the Keck telescopes, WFC3-UVIS and STIS on Hubble, MegaCam on CFHT, GMOS on the Gemini telescopes, HSC on Subaru, and FORS on the European Space Agency’s (ESA) Very Large Telescope.

“A single ADU difference in the driver pixel value can correspond to a difference of up to 2.5 ADU in the mean of the residuals of the pixel read out two pixels afterwards,” the paper warned.

Patch released

The researchers have since published software online capable of detecting and correcting any errors in any of the affected telescopes, but added that hardware changes can also rectify any issues.

Speaking with The Register, astronomer Dr Brad Tucker from Mount Stromlo Observatory in Australia explained how damaging the issue would be for research.

“If you have a bright star, this will have less effect than a faint galaxy,” Tucker said.

“For those working on areas like supernova cosmology, getting a precision measurement is key to then measuring a distance to the supernova.”

Last week, Hubble was used to identify what appeared to be groundbreaking findings indicating that the rate of the expansion of the universe is considerably off when compared with previous estimates.

In this instance, the data was compared and found to be in line with the ESA’s Planck satellite, reducing the chance that the discrepancy in the values is a coincidence, to one in 5,000.

Colm Gorey was a senior journalist with Silicon Republic