Happy 7th EIS-a-versary, everyone!

On Sat 28th October, 2006, somewhere in low Earth orbit, a small bit of wax on a satellite heated up and melted, right on cue, releasing a sprung aluminium door and illuminating the inside of a telescope with solar ultraviolet light. Astronomers call this moment “first light” – the first time that the telescope fulfils its purpose and takes an image of what it was always meant to. EIS’s first light image came through in real time, as we huddled around a laughably ancient (but very important) computer screen in the bowels of the mission control centre; but we couldn’t have asked for a better first glimpse.

EIS first light image
Left-hand X-ray image from HInode XRT shows the position of EIS’ slit and slot fields of view on the Sun when the EIS telescope door was opened. The trio of images on the right shows XRT, EIS transition region and EIS corona images seen with the slot. A small active region is seen near the bottom of the slit. Lower panel shows the spectrum taken from a single pixel along the dashed slit seen on the full-Sun XRT image.

The EIS spectrometer was pointed at a really lucky combination of the two most common sets of conditions on the Sun: a solar active region, where intense magnetic field pokes through the Sun’s surface; and the background ‘quiet Sun’, the Sun’s normal state in the absence of these strong fields. It gave our team the perfect demonstration that EIS was working well and revealing the ingredients, flows, heating and cooling of the million-degree solar atmosphere.

EIS was the last part of Hinode‘s three-instrument payload to go live. The months leading up to this were stressful for a lot of people concerned. Most recently, we’d been taking, reporting and checking measurements of all the instrument’s vital signs at every overhead satellite contact we could muster. Then, our instrument engineers from across the world would make sure it was all behaving normally, as they pain-stakingly brought EIS up from its boot state to the state in which we could start using it for scientific observations. Being involved in that work gave me a lot of respect for the guys who were there with us to commission the instrument, and I’d like in particular to thank Jason Tandy (EIS’s chief instrument engineer), Louisa Bradley, Charlie Brown, Clarence Korendyke, Hiro Hara, David Brooks and Matt Whillock for keeping a cool head and sense of humour throughout those often intense days.

The seven years since first light have brought observations, discoveries and questions that we didn’t imagine on that first day: EIS was designed to observe a largely uncharted part of the spectrum, to probe the vibrant corona and transition region of the Sun. In those seven years, there have also been huge advances in atomic data calculations, plasma theory and numerical simulations of the solar atmosphere from beneath the surface to the corona. The feedback between these different disciplines in solar science enriches the whole subject area; solar physics feels like it has moved on a lot between 2006 and 2013, with EIS playing a lead role in that evolution.

A lot of us who are involved with the Hinode project are now thinking about the seventh mission conference that’ll take place in the mountains of Japan’s Gifu prefecture in just two weeks.  I’m looking forward to a reunion with some of the people who were in that room when we got the first spectrum, of course, but also to find out what our unique instrument is continuing to bring to science at large. And I’m proud that EIS has made a powerful contribution to our understanding of our parent star and how that star affects its planets, of which our pale, blue dot is one.

Happy 7th EIS-a-versary, everyone!