It is very sad to hear of the passing of Jon Ables. Jon was well-known and highly respected by various sections of the scientific community, encompassing scientists and engineers from all age groups.

Jon Ables; Photo: © CSIRO

Perusal of Jon's publications provides some idea of the scope of his involvement across many fields, but it does not really reveal the significance of Jon's original thinking in the conception of these ideas. But those fortunate enough to have worked with Jon fully understand this.

In the radio astronomy area, Jon was widely known for his proposal for using Maximum Entropy Methods (MEM). His publication in 1974, titled "Maximum Entropy Spectral Analysis" has been extensively referenced in the literature of radio astronomy, medical imaging, crystallography, radar, various mathematical journals and many other application areas that rely on image coding, image reconstruction and image restoration. This paper has had a profound effect on the careers of many scientists.

Jon was an outstanding astronomer, especially in the early days of pulsar research. He proposed unique instrumentation methods, detailed designs and led some major discovery projects. This has led to the discovery of the first pulsar in another galaxy, theoretical explanation of pulsar broadening due to interstellar scattering, and theory of coherent diffraction in pulsar emission.

Jon was the inventor of many things. He was well-known for his design of the A4 digital audio processor chip, the development of the concept for a systolic array very-large-scale integrated (VLSI) cross-correlator chip that has served the ATNF extremely well, his Unified Clock Principle that influenced the design of the Compact Array, the Encoded Mask X-Ray Camera, the concept of the "distributed clock" now used in all ATNF telescopes and correlators and adopted by other observatories, and numerous other schemes in recent years related to medical diagnosis and monitoring. There are very few scientists that have the breadth of expertise that characterised Jon Ables. Jon had a sound background in science, a remarkable intellect and a single-mindedness that let him follow through on his hunches.

Jon Ables was the Director of the Parkes radio telescope from 1981 to 1989, and during that time led the support of the reception of data and images from the NASA Voyager 2 fly-by of the planets Uranus and Neptune, and the ESA Giotto space probe to Halley's comet. This period involved much negotiation with these two space agencies, and Jon's technical expertise was greatly appreciated by them. Under Jon's leadership, Parkes was extensively upgraded, incorporating many of his own concepts and design ideas. NASA and ESA felt assured that Parkes was under strong technical and managerial leadership and were confident that CSIRO would be a reliable partner for their important space missions.

Everyone looked forward to Jon's presentations. There would always be something new revealed, and in such an entertaining manner. We also looked forward to Jon's presence at social functions. He told entrancing stories, all part of his experiences, and his impeccable memory allowed him to tell every joke that he had ever heard. As a mentor for the younger staff, Jon was exceptional. We have all benefited greatly from Jon's skills. For many years, the offices and laboratories of the Signal & Imaging Technology Program were deliberately laid out so that Jon's favourite area was central. This was the meeting place for all to learn and all to have fun. It was a huge success; the pivot was Jon Ables.

Perspectives from Jon's most recent team (microwave cardiac sensing)

Jon was what some may refer to as an "old school" scientist, a scientist in the classical sense from basic theory, to generating a hypothesis and testing that hypothesis. His method of generating ideas seemed almost chaotic, and it may have appeared that he wasn't going towards any end goals, but those who worked with him know that he was the driving force behind the science of every project he worked on. Although it was sometimes difficult to see exactly what was happening, when his team had achieved its goal, you realised that he knew exactly what he was heading towards. Jon had a strong basis in the fundamentals of his physics, he had brilliant practical and engineering skills so that he could put the fundamentals into the real world, and as he put it, he had the sales skills that he had picked up in the Ozarks. He was one of the most well-rounded scientists in this or any other organisation. Many saw him as a mentor, he had the brilliant ability of being able to explain a concept to the layperson, yet at the same time, he was in circles that included Nobel laureates.

This breadth-of-skill set was what drew the young(er!) scientists to him. Jon has pretty much enhanced the career of everyone who has worked with him, up to this very day. Jon was also by no means a narrow man; he had many interests in music, talking often about his taste in blues and jazz as well as his love of the composer Philip Glass amongst others. Jon was also quite a handy cook as many who have tasted his food will tell you. He would often blend the tastes from his native Oklahoma with his love of Indian and Mauritian cuisines, and he loved eating Sushi. His plan after CSIRO (Jon had many plans!) was to drive a camper van around the outback, and he was in the process of converting his ute into a camper.

Ironically, Jon's passing away comes at a time when the CSIRO is celebrating its 80^th birthday, and the radio astronomy group its 60^th, which means that Jon was there for a good half of that time. His love of the organisation and CSIRO was such that early in his career he had turned down job offers from the NRAO, amongst others.

Jon's passion for radio astronomy meant he lost all sense of 9 to 5, and would turn up at the lab at all hours and most weekends.

In recent years, many of the younger scientists working around Jon referred to him as the oracle - any problem you had, he could usually come up with a novel way of solving it, or give you some insight to set you on the right path.

Colin Jacka and Geoff Poulton
(Colin.Jacka@csiro.au, Geoff.Poulton@csiro.au)