On June 11, 2008, the Gamma-ray Large Area Space Telescope (GLAST) lifted off aboard the last Delta II Heavy Launch Vehicle from Cape Canaveral, FL and reached low-Earth orbit shortly thereafter.
In the 10 years and one name change since that that day, what is now the Fermi Gamma-ray Space Telescope has used its main instrument, the Large Area Telescope (LAT) and its secondary instrument, the Gamma-ray Burst Monitor (GBM) to find hundreds of distant pulsars, watch gamma ray flashes in terrestrial lightning, study our own Sun as a gamma-ray source, help identify giant bubbles billowing out from the core of the Milky Way, discover that the neutron star at the heart of the Crab Nebula isn’t as calm as scientists used to think, and help confirm the origin of some cosmic rays.
It also had some interesting extracurricular adventures, like dodging a defunct Soviet spy satellite and using the entire Earth as its magnet while checking out a suspected excess of positrons impinging upon our globe from outer space (also discussed previously in this 2015 interview with KIPAC alum Justin Vandenbroucke). Another field it has had a role in is probing nearby dwarf satellite galaxies as repositories of self-annihilating dark matter, as was discussed in this 2015 KIPAC Research Highlight.
The discoveries haven’t stopped, either—August 17, 2017, nine years to the month after the start of science operations, Fermi saw the gamma-ray flash of two neutron stars colliding, precisely 1.7 seconds after the peak of the gravitational waves generated by this event rolled through the Laser Interferometer Gravitational-Wave Observatory (LIGO). In fact, some scientists consider this recent discovery as one of its most significant as it is the first time that the speed of gravity and that of light (i.e., any form of electromagnetic radiation) have been directly compared—and found to be the same to at least one part in 1016. Which has eliminated a vast swath of extensions of Einsteinian General Relativity, our current best working framework for gravity.
Along with discoveries, Fermi is making memories—some scientific, and some of a more personal nature. KIPAC members and some of their Fermi collaborators have had a big part in both, and came together to share memories about a decade (and more) of Fermi.
Development
Bill Atwood, Fermi co-creator: The whole deal started in May of 1992 when an odd mix of astrophysicists and experimental particle physicists came to together to design a “better” EGRET. This detector, launched as part of the Compton Gamma Ray Observatory in 1991, had given a glimpse of the gamma-ray sky few had anticipated: dramatic emissions from pulsars, AGNs flaring, gamma ray bursts, an all-pervading diffuse emission were all witnessed… just on and on. And so the appetite was whet for “more, please!” Contemporaneously, the developments in particle detector technology spurred on by the prospects of the SSC (Superconducting SuperCollider) had made previously exotic and expensive technologies such as silicon strip detectors and crystal scintillators viable for consideration in large-scale instruments.
The GLAST design intrinsically had an enormous field of view relative to other telescopes, similar to our own eyes, about 1/6 of an entire sphere, and an effective area almost 10X that of previous observatories. The combination led to almost a hundred-fold increase in light-gathering power. And it was mostly based on solid-state detector technology ideally suited for applications in an outer space environment.
KIPAC Staff Scientist Seth Digel: SLAC contributed fundamentally to the concept for the LAT, and crucial support from SLAC management helped it go forward. A great coordinated effort by people at SLAC helped pull it off, from project management, every kind of engineering: system, thermal, mechanical, electrical, plus beam testing, flight software, assembly, hardware testing, documentation, simulation, reconstruction, pipelines, data management, commanding, monitoring, to science analysis.
Preparing for launch
Jana Thayer, LAT Flight Software Manager: I remember going to the Apollo 11 exhibit with a bunch of other SLAC folks and NRL [Naval Research Laboratory] folks. As part of the exhibit, they did a re-enactment of the moon landing. During the landing, in fact, seconds from landing on the moon, there was an error (heavily dramatized in this re-enactment): "SOFTWARE ERROR!!!."
Neil Johnson [Deputy Principal Investigator of the Large Area Telescope; then at the NRL] was sitting behind me and gently patted me on the shoulder, whether to say "it's going to be ok," or "just think, in two weeks this could be you!” I'm not sure. But I remember that moment, in the dark of the theatre with the decades-old voices of astronauts ringing in my ears, feeling the weight of my responsibility and hoping that all the planning and testing and rehearsing of the software and the commanding meant that everything would go smoothly.
Launch
KIPAC Professor Emeritus Elliott Bloom: Since 1992 we had been planning, designing, searching for funding (thank you, DOE and NASA, and Astro and HEP agencies in France, Italy, Japan and Sweden), building the GLAST telescope, and getting it tested, joined to the spacecraft and tested again. Sixteen years of dedication and hard work for many; so, a lot was on the line as we watched our telescope disappear from view on a tower of flame...to the enthusiastic cheers of our Collaboration members around the globe (~ 400 strong). A few were actually at the Cape to watch the launch in person (hardy souls), after being disappointed by a series of launch holds during the Cocoa Beach Collaboration meeting during June 2-4. Most of us went home and watched anxiously via streaming video as the mighty bird lifted off in a wondrously successful launch.
Bill Atwood: ...The rocket lifted off just about noontime on June 11, 2008 (EDT). We all held our collective breath for the several minutes of rocket burn—no explosions! Cheers went up! Everything was looking great: the insertion into orbit and the separation. But we were reminded that the big “Whew!” would come when the solar panels unfurled and locked onto the Sun. And two hours into the mission they did.
Shantha Condamoor, Flight Software Test Engineer: Taking part in the launch of the Fermi instrument at Cape Canaveral, Florida in 2008 along with my daughters and witnessing the orbit via SLAC monitors was an exceptionally exhilarating experience. The subsequent day-to-day excitement following the launch at the SLAC ISOC control center while telemetry data continued to pour in and watching procedures executed remotely was equally thrilling. All in all, the entire experience of being part of the Fermi (GLAST as it used to called then) team prior to the launch was very memorable and remains to date one of my best experiences at SLAC.
Post-launch
Jana Thayer: To distinguish ourselves from the Flight Operations Team, who dressed in black slacks, white shirts, skinny black ties in a nod to the Apollo missions, the LAT flight operations crew also decided to adopt a dress code. We went casual with Hawaiian shirts. Our side of the control room was all flip-flops, leis, straw hats, and the finest Hawaiian steppin' out shirts Goddard has ever seen. We had buckets full of Swedish Fish, the official candy of early operations, and were so sugared up, we hardly needed any caffeine.
Bill Atwood: Of course the science team was all about, “Let’s turn it on!” But that’s not the way it goes. There was scheduled almost two weeks of spacecraft checkout, followed by a well-planned turn-on sequence for the LAT. So finally, at the end of June, GLAST saw its “first light.” By the end of the first few weeks we had replicated the EGRET sky. And then our first discovery! The pulsar CTA-1 was found in a blind search in gamma-rays by the NRL contingent. So it worked! And now it was time to rename the mission after Enrico Fermi: GLAST became Fermi-LAT.
Science and life
Nicola Omodei: I remember the first GRB detected by the LAT (080825C), the first short GRB (081024B), the first bright long GRB (080916C), the first bright short GRB (090510), and the brightest GRB ever detected (130427A), and how painful it is to write a catalog of GRBs….
KIPAC graduate student Alice Allafort: On March 7, 2011, as I was flare advocate, a bright flare was detected brighter than any source in the sky, for more than 10 hours. It puzzled some of us for a little bit, until we realized it was a solar flare, something we had not expected to see. It was the start of the solar cycle as seen by the Fermi-LAT.
KIPAC graduate student Christian Johnson: Attending the Fermi Summer School in Lewes, Delaware was a great experience—I learned a tremendous amount about how to perform Fermi analyses, and I got to see Fermi scientists in a context outside of Fermi conferences.
Stanford Provost Persis Drell: My favorite memory is the wonderful people that I met! I have a special soft spot for the Italian collaborators who were so wonderful to work with and so gracious in their hospitality.
KIPAC post-doctoral researcher Manuel Meyer: I remember the first time I visited SLAC in 2014 for my first collaboration meeting and an extended four-week stay to collaborate with the scientists involved in Fermi. This time had a lasting impact on me: the open and collaborative atmosphere that I experienced from Day One was striking. The positive spirit is what makes this collaboration so successful and unique.
KIPAC Director Emeritus Roger Blandford: I am proud to have been associated with such a brilliantly successful mission that is technically outstanding, felicitously managed and which has delivered so many great and unscripted discoveries. My fondest memory, with many contenders, has to be learning of its central role in identifying [neutron star collision] GW 170817, something I have dreamed of since the first binary pulsar was announced in 1974. I look forward to another decade of discovery, especially in collaboration with LIGO.
Right: Source localization on the sky from the INTEGRAL GRB satellite (light blue band), Fermi (the dark blue disk), LIGO alone (green ovals), and LIGO and VIRGO data combined (dark green oval). Notice that all sources identified the LIGO-Virgo area. A new source of light (located at the intersection of the tic marks) was identified inside the overlapping area by the Swope telecope (top image inset). The image below the inset is of the same area but 20.5 days before this event showing that this source was not present. (Credit: LIGO, Virgo, Fermi, Swope, DLT40.)
Seth Digel: It has almost been possible to take for granted that this six-foot box 350 miles up “just worked” from the start, and that the first science results came from in-orbit checkout data. And that the LAT has continued to just work essentially flawlessly, and the LAT collaboration alone has been publishing at a rate of one paper a week for the last 10 years. None of this happened without brilliance, commitment, and teamwork. I have had the privilege to work with the people here at SLAC who made the mission possible.
Elliott Bloom: All is well that ends well, and we have been rewarded many times over for our years of effort, now about 26 years for a few of us, and more than a generation of new astrophysicists and astronomers who have benefited from the science they have derived from this cutting-edge high-energy gamma-ray telescope. A five-year mission with a goal of 10 years, Fermi will actually continue beyond these 10 years that has yielded great discoveries, uncountable papers, and too many Ph.D. theses to shake a stick at. I am very proud to be associated with the Fermi mission and hope for years more of important work and discoveries using our boatload of data and more to come. Congratulations to all!
Bill Atwood: Now, a decade later, we’ve created a ten-year light curve of not just a single astronomical source of gamma rays but of the entire Universe revealing hundreds of new gamma ray pulsars, thousands of blazars, even high-energy cosmic ray electron spectra, and much, much, more….And the best part—it’s still is up there, taking data, essentially as good as when first launched. Yup! We’ve done a good thing!
For more images from the Fermi@10 celebration, see the SLAC Flickr page.
Related Reading
Perspectives on 10 Years of Discovery with Fermi
