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12Nov 2012

Nature News: After four years NOW we learn that NASA's premier gamma ray 'scope can't see highest energy stuff.

Nature News: After four years NOW we learn that NASA's premier gamma ray 'scope can't see highest energy stuff.

In 2008 NASA launched its Gamma-ray Large Area Space Telescope, or GLAST, since renamed the Fermi Gamma-ray Space Telescope. Gamma rays are given off copiously by very hot things, such as supernovae and accretion disks around black holes, nifty objects one and all if one is a high energy astrophysicist. The telescope has gotten good press ever since. No real signs of trouble. Yet, last week at a meeting of Fermi Observatory users in Monterey a NASA man reported to colleagues that fix is underway for a software problem that has, all these years, bollixed the instrument's ability to record gamma rays at the highest energy end of their spectrum.

   In other words, one of NASA's so-called Great Observatories isn't quite so great. It cannot now reach its built-in potential. It was doing gangbuster work on what it could see but it is missing some of the very best stuff. But such ability apparently had been in its performance specs from the start. The hottest things, the mind-blowingest emissions and their revelations, are not reaching the big orbiter's digital pixel recorder's memory.

    Veteran, hard-nosed space and astronomy reporter Ron Cowen has the story at Nature News. He's been a scoop machine for a long time - including years he spent at Science News and continuing now as a freelancer and frequent Nature correspondent. I find no sign any other agency has this so it's yet another Cowen excloo. With a fix, he reports, it will do a better job spotting annihilations among dark matter particles (if such things occur).

But here's a question. Cowen writes that this vision impairment is "long standing but little-publicized." Was it publicized at all? One finds one reference saying Fermi was a $700 million item. That's close enough to a billion to count as a load. To be sure, this is no scandal. But taxpayers and their representatives in Congress - those who follow space telescope news - did not have the full story if they'd thought all has been super-rosy in Fermi land and that the investment is paying off in full.

   Cowen merits kudos for having it now. His yarn also has some fascinating detail that few reporters are sufficiently savvy to tackle for fear of messing it up. One reads in this story just enough about how the detector works to get an idea of the machine's innards and data processing path. Gadgetry appreciators such as I are most grateful for the fine-grained reporting. But one wonders why it took so long for somebody to report it. Cowen after all writes that Fermi's team had from shortly after launch debated whether it was worth the time, away from doing the scintillating science the partly-blinded machine was returning, to try to write a software patch to get even more illuminating conclusions.

   One speculates that the Fermi team might have opted to get their telescope to vindicate its full, advance sales pitch sooner if somebody, even in specialty press, had spread this news a long time ago. A  Google Archive search produces no obvious instance like that. One doubts that any sort of cover-up is involved here. Most likely, if a reporter working on a feature story about the telescope had heard about this problem, the engineers in charge would have provided details.

   I put a few questions via email to Cowen. He replies that, as far as he knows, nobody in the Fermi community had previously mentioned to a reporter that the machine is not working quite right. He found out about it while researching a different story: on Fermi's examination of gamma rays from the Milky Way's core that might suggest dark matter annihilation. He was talking to a lot of people, he said. Eventually it just came up in conversation. That's the sort of bonus that occurs as a reporter really calls around and refuses to settle for what is openly offered by press release or other push from sources. The situation, he adds, has actually been in the public domain but with no fanfare: "reports with arcane titles." One example he offered is this one.

Grist for the Mill: NASA's Fermi Gamma-ray Telescope site.

- Charlie Petit




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