Irradiation by gamma rays is one of the most crucial tests carried out on candidate spacecraft components, confirming their suitability for space. One of the leading facilities offering such testing, ESA’s cobalt-60 unit in the Netherlands, has received ISO accreditation, formally confirming its operational excellence.
Up to three tests can be run in parallel as if in a shooting gallery, behind 70 cm-thick walls (1.5 m -thick at the back). Once the 700 kg safety door has been closed, the cobalt-60 source rises into position to expose the delicate electronic parts to the gamma rays.
Gamma radiation from a Co-60 source is a standard method for simulating exposure to the effect of cosmic particles encountered in orbit.
The facility replicates the lifetime effects of cumulative radiation doses, with accelerated testing simulating years of exposure within just a few days.
Based in ESA’s ESTEC technical and engineering centre in Noordwijk, the facility has been awarded ISO 17025 accreditation – ‘General requirements for the competence of testing and calibration laboratories’, as prescribed by the International Organisation for Standardization (ISO) – from the Dutch Accreditation Council (RvA for short, from its initials in Dutch).
In practical terms, this means all the ESA projects and external customers using the facility can be sure its results have well-defined uncertainty margins, following testing and quality procedures that adhere strictly and transparently to international standards.
With space an ever-more international endeavour, different partner countries can apply these results with full confidence, knowing they are completely reproducible and repeatable.
“We were the first facility in ESA’s Product Assurance and Safety Department to apply for ISO 17025 accreditation,” said Raul Alarcon of ESA’s Quality Assurance section.
“The cobalt-60 facility was seen as a good starting point because we have many external customers, averaging a different project every week, and offer a single, well-focused service.”
The process was a lengthy one, with initial discussions back in 2007. The UK’s National Physical Laboratory played the crucial role of external advisor, coming up with ways of improving not just methods of testing but also their accompanying technical documentation.
“We were instructed that quality management came down to saying what we do, doing what we say – and being able to prove it,” explained Bob Nickson of the facility.
“For our own and our customers’ convenience we’ve moved as close to as possible to a paperless lab, based on the online collaborative Sharepoint documentation and content management system.
“That meant when the time came to submit our application to the RvA we were able to do so in electronic format, an innovative step much appreciated internally and by the RvA.”
All aspects of the facility’s activities were reviewed in a bid to provide customers with the lowest possible measurement uncertainties. To demonstrate this accuracy, the actual radiation field produced by the cobalt-60 source had to be meticulously mapped.
“This involved careful dosimeter measurement of about 2000 separate points,” said Michele Muschitiello of the facility.
“Other elements we investigated included our electronic equipment and the precision of our timing system. There are multiple factors that contribute to the uncertainty budget we have worked to minimise “
Accreditation lasts for four years at a time, subject to annual audits, but amounts to an ongoing commitment to maintain the highest quality standards, with any errors or problems swiftly logged as ‘non-conformances’ for immediate investigation and remedy.
“The changes have already increased our customer satisfaction,” concluded Raul. “We’re also summarising our lessons learned to guide other ESA labs planning their own accreditation.”
