| Dieter Hils |
I worked with Peter beginning in the early eighties until my early retirement in 2000. |
I first got to know Peter in the early 70's when i worked at JILA doing my PhD under the guidance of Steve Smith. One of my fellow graduate students and a friend, John Ward, was also working on his PhD project with Peter being his superviser. So it was easy for me to consult with Peter when a problem cropped up in the final stages of my experiment. As was usually the case his office door on the 9th floor was open and he welcomed me with a big smile.
After discussing my problem with him he made a suggestion which in the end proved to be successful and laid to rest my concerns.
Then it was in the early 80's after I returned to JILA working with Alan Gallagher as a postdoc when Peter and I met in the elevator and he asked me to come to his office. He described to me his idea how to detect Gravitational Waves from space which later on became known as project LISA. Peter andJim Faller were looking for somebody to investigate the numerous galactic background sources which could potentially drown out faint signals from far away extragalactic supermassive black hole binaries. I was then in the final weeks of my work with Alan and agreed to think about his offer for a few days. In the end I decided to accept and thus begun for me a very exciting collaboration with Peter in the years to come.
It is with great sadness when I learnt that Peter recently passed away. I will always remember him as a very kind person upon whose judgment one could absolutely rely on. |
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| Joseph A. Giaime |
Pete was my postdoc supervisor (together with Jim Faller) at JILA from early '95 to late '98. |
The group I worked with at JILA was led by fellows Pete Bender and Jim Faller and senior research associate Tuck Stebbins. I was fresh off a LIGO-related PhD, eager to help Pete's group develop seismic isolation for a far-off future LIGO that would have sensitivity down to nearly to the high end of LISA's expected band, 1 Hz. I think an earlier visiting fellow, Peter Saulson, may have catalyzed Pete's and Jim's foray into active seismic isolation for what would become Advanced LIGO. I was lucky for the chance to work with Pete; he was kind to all and generous with advice. His (and Jim's) decades of experience and acquired wisdom allowed him to cut through to the important issues affecting our instrument and its possible place in future GW detectors.
Our group included PhD students Dave Newell and Sam Richman. When I got there, an outermost active isolation stage supported a vacuum chamber that enclosed the inner two stages. Dave Newell's PhD work included designing and commissioning the outer two stages; it was written up here: http://dx.doi.org/10.1063/1.1148954 and worked wonderfully. The basic design had triangular stages, with tangential and vertical sensors and electromagnetic actuators at each corner. The sensors were JILA-built using LEDs and split diodes sensing the motion of a spherical lens embedded in a spring-supported test mass.
The next years led to our forming and contributing to a mini-collaboration, with eventual members JILA, Stanford, LSU, MIT/Caltech/LIGO, that would build a pre-prototype more likely to be accepted for LIGO use, giving up the 1 Hz for 10 Hz, and using commercial sensors and actuators. Sam Richman went to MIT as a postdoc, bringing the JILA expertise to a joint pre-prototype unit at MIT. It won an internal competition to become the basis of Advanced LIGO's isolation design.
The first internal seismic isolation (ISI) platforms were installed in 2008 at LIGO Livingston and Hanford as part of the "Enhanced LIGO" upgrade to hold the new DC readout. ISI platforms, two generations descended from the JILA design, now support almost all LIGO vacuum payloads and will likely serve (with improvements) in future upgrades. My hunch is that LIGO would have had a more difficult way forward had Pete's group not done its work in the late '90s.
Let's dream of the day when a LISA event, measured by one of Pete's inventions, continues its inspiral and is seen by LIGO (or its descendant), isolated from ground motion by another of his projects. |
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| Stefano Vitale |
I have been in the core team of the LISA project since 1995, and the principal investigator of LISA Pathfinder. |
I fell in love with LISA as soon as I heard about it, around 1994. Shortly after I had joined the project, in 1996, I met Pete, the person whose idea transformed the lives of many of us.
We sat next to each other on a bus at an event in Italy, likely the inauguration of Virgo, and immediately started discussing the technical details of LISA. We had an intense and pleasant conversation for over half an hour.
There, I not only discovered what a nice person Pete was but also realized what an extraordinary mind he had—a mix of profound knowledge in nearly all fields of physics, inflexible intellectual rigor, powerful creativity, and tireless thinking.
Over the following 35 years since that first meeting, I've had countless invaluable exchanges with him about crucial issues concerning LISA and LISA Pathfinder. He has been a priceless resource to me.
There are a handful of physicists from the generation before mine who have inspired my work throughout my career, and Pete is definitely one of them.
I sincerely think that LISA, when it flies around year 2035, should be called the Peter Bender Gravitational Wave Observatory
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| E. Sterl Phinney |
I joined LISA in 1997, and first met Pete in July 1998, at the second LISA symposium at Caltech, Pasadena CA. I was the beneficiary of much detailed advice from Pete
when Bill Folkner and I presented LISA first to the 2000 US Astronomy & Astrophysics Decadal Survey, and subsequently to the 2010 Decadal Survey. I met Pete at every LISA team meeting and LISA symposium while I served as Chair of the LISA Mission Definition Team (1997-2001), and as member of the LISA International Science team (2001-2011) and as co-chair of the LIST Sources and Data Analysis Working Group (2001-2011). When in 2004 NASA funded the Mission Concept Study of my proposed Big Bang Observer, the first and wisest thing I did as PI was to appoint Pete as a paid consultant! |
Many mission teams are subdivided into "technical leads", "science experts" and "political strategists". Pete was a one-man team for LISA (and space-based gravitational wave detection in general), with profound, well-thought out, and strongly-held opinions in all three of those areas. As the driving force in the early conception and design of LISA technologies, he of course had a deep understanding of physics of all the noise sources and technological trades. But in the service of propelling his technical vision for LISA, Pete also pioneered many of its science goals: already in 1990, Hils, Bender & Webbink understood the importance to LISA of the resolved and unresolved background of gravitational waves from white dwarf binaries and (shortly thereafter) AM CVn systems. In 1995, Hils and Bender published what I believe is the first prediction of the formation of EMRI's (extreme mass ratio in-spirals, of stellar mass compact objects spiralling into supermassive black holes) by 2-body scattering followed by gravitational radiation capture. This phenomenon is now one of LISA's three major science pillars, and a tremendously active area of research in both general relativity and stellar dynamics, recently made even more exciting by the discovery of QPE's, which are probably EMRIs interacting with an accretion disk.
Pete was a major contributor to the NASA Mission Concept Study for the Big Bang Observer (a gravitational wave interferometer of interferometers in the 0.1-1Hz range, capable of detecting and localizing to arcsec position every LIGO source ~a year before it enters the LIGO band, and the inflationary slow-roll background for r>0.001), producing a detailed analysis of 17 possible contributors to acceleration noise and mirror thermal noise. But he also argued passionately, and probably correctly, that the BBO goal was too ambitious, and that near-term reality should outweigh advertising potential in seeking further funding.
A successful LISA will be a great monument to Pete's vision, wisdom and persistence. Changes in the climate and water tables make even higher precision follow-ons to geodesy missions like GRACE increasingly important. Pete's legacy in that field too will only grow in importance. I just hope that mission teams can avoid design mistakes, which Pete would have promptly and forcefully corrected! He will be missed. |
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| Oliver Jennrich |
I first met Pete at the first ever LISA Symposium in 1996. A few years later in 1999, I worked as post-doc with him and Tuck Stebbins at JILA on LISA. Over the years, LISA connected us for more than a quarter of a century, through his time on the LISA International Science Team or meeting him in review panels. |
Pete and his late wife Bernice were one of the guests of the first ever dinner party my wife and I hosted during our time at JILA. In a sparsely furnished apartment with improvised seating and "table" and home-cooked (German style) food. |
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| Scott Pollack |
Pete was my graduate advisor, 2001 to 2005. |
I joined the CU physics department in the summer of 2000, working with Tuck Stebbins and his postdoc Oliver Jennrich on a tabletop interferometer demonstrating a phase measurement technique for LISA. As I later learned, this was just one of many of Pete’s conceptions. After Tuck took the role of LISA Project Scientist and left for Goddard, Pete became my graduate advisor. He held a wealth of information, always able to come up with answers to my questions, or jot down back-of-the-envelope calculations to help guide my research. I eventually had the office next to his, which allowed us to have daily conversations about supermassive black holes, binary stars, pulsars, LISA, GRACE, numerical simulations, and analytical techniques. I always walked away having learned something new or understanding something deeper.
I was awestruck by his remarkable recall. Any office visitor knew that he had columns of manila folders – he could always pluck the one he wanted without any sifting. Sometimes he moved large stacks out of the way, pulled a new stack from behind, split halfway down, and out came the exact paper. It was like a magic trick he’d perfected through the years. Similar too, his e-mail sorting. He relied on the old VAX machine and took down six digit numbers for each email he had yet to process – lists of numbers were in his notebook. He would go back and cross them out as he made replies. How did he know which number was to which email? How did he keep track of the old ones from pages ago that had yet to be crossed off? Attachments too, which occasionally I’d help him with – it speaks to his immense capacity to retain which series of numbers had which attachments, and to quickly type a number in and up came the email he wanted to show me.
Pete was always at JIRA. Over the course of five years, I don’t think there was a single day I came to the office that he wasn’t there – rain, snow, weekday, weekend, holiday, or not, Pete was always there. Only a few times I would arrive before him, on particularly snowy days. And it seemed like any hour of the day as well. He would take breaks for lunch in the basement, or for a jog at the gym, and dinner too. But then he’d be back again, door open, always available for another stimulating conversation. |
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| Scott Hughes |
I met Pete at conferences not too long after I finished my PhD (1998); we were members of the LISA International Science Team (LIST) from 2005-2011 and attended a lot of meetings together. |
The first time I really got to know Pete was when we were representatives for the "non-accelerator" physics community at the summer 2001 Snowmass workshop, high up in the Colorado mountains. After my talk, we spent a lot of time together talking about LISA astrophysics, waveform issues, and measurement. He invited me for a hike one day to continue our conversations. I had just turned 30, and figured if it was a hike this "old guy" had selected, then I surely would have no problem. The results were humbling. I vaguely remember at one point that he instructed me to sit in the shade catching my breath while he ran ahead to get some water for me.
That was my introduction to Pete's seemingly never-ending stamina and persistence. Over the years since then, I've accumulated quite a collection of "memo-form" emails from him on a huge range of topics where he wanted to make sure I got his very firm viewpoint. LISA meetings are going to have a big void without him. |
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| James Pryor Hauser |
Pete was my thesis advisor, 1970-1974. |
With a recent M.S. in Aero, Pete hired me in 1970 as a Fortran coder for his then current work on the Lunar Ranging Experiment. Pete made it clear that the work was not expected to lead to a Ph.D. thesis. However, as time went on, the work did evolve into a thesis (Aero 1974). I learned an enormous amount from Pete, and found that knowledge applied in many of the many engineering endeavors I have engaged in over the years. I will always be grateful for his patience and help seeing me through a Ph.D. He remains a role model to this day.
I had the good fortune of visiting with Pete a few weeks before he passed. I will cherish that time.
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| John Lewis Hall |
I met Pete Bender long ago (62 years!) while I was still a grad student at Carnegie Tech in Pittsburgh, and immediately decided I wanted to work for/with him. After my PhD work I was lucky to get an NRC Postdoc position with him at the original NBS in downtown Washington. Exciting new science ideas like lasers were fresh, as was the cold-war challenge of missile defense. Within the year 1961 the US decided to build a new top-level Research lab in the middle of the continent – to study possibly-relevant Atomic Physics processes. And so in 1962 JILA got set up in Boulder, originally in the old Armory building, just off the CU campus, with 10 scientists from the Washington NBS and two astrophysics researchers who were already at CU. The new JILA building was opened in 1965. And the laser story was just beginning! |
Pete had great curiosity and broad interests across many topics. He was friendly and approachable for anyone with ideas to share and a desire for discussion and exploration. He was an outstanding leader in understanding the key issues in these large-scale projects, such as LIGO, and especially his Space-based Gravitational Wave Laser Interferometer system, called “LISA.” He was basically the one person center of its technology discussions, how to organize the supporting labs in the US and Europe and, most critically, in attracting and stimulating powerful young scientific colleagues across the world.
My Personal Experiences & Remembrances
By mid August 1961 Lindy and I and our infant son were settled in a Maryland suburb of Washington, and Pete offered me, his fresh new postdoc, a range of activities. As an indication of Pete’s generosity, Pete offered the NBS’s only invitation over to me, to go to Bell Labs and hear their first-ever presentations about their lasers. This was a major and determining start of my whole career, and I can’t thank Pete enough for his sacrifice. There I was - one guy, and the youngest out of the ~200 professional US scientists - who (also) couldn’t wait to learn about this new advance, the Laser.
The most impactful consequence for me was to see and to adopt his role model, and mentally promise to boost some next young guy, when that time would come. I soon became a regular NBS employee. In less than a year we moved from Washington to Boulder with the group of 9 other families to start a new lab there. The expected future interaction between atomic physics and Astrophysics was even baked into our name: “The Joint Institute for Laboratory Astrophysics.” Now we just say “JILA”, although the laboratory research progress has been so excellent that some of us also think of JILA as meaning “The Joint Institute for Lasers and Atoms”.
In addition to applications in atomic physics experiments, JILA also housed a vigorous group interested in the art of Precision Measurement. Here the Speed of Light was a natural target scientifically, in addition to its coupling with our two parent organizations, the National Bureau of Standards and the CU Physics department, with its experience in Magnetic resonance, atomic collisions, and atmospheric physics. Starting with those “Stable” Lasers, the (un-ending) progress has by now led to a 10-million-fold advance, essentially in the hands of my former student, Jun Ye. His Atomic Clock with Strontium atoms would have an uncertainty well below 1 s, even across the age of the Universe!
Earlier, in the 1960’s it is true that Pete and two of his former Postdocs, Jim Faller and me, were always talking about schemes to measure the Speed of Light. One especially promising approach would measure the difference between two laser frequencies, and also the relationship between the two wavelengths. This would require a long, quiet and stable interferometer. In fact it was Pete himself who identified the best available horizontal indoor location for our vacuum system, an unused Gold Mine, called the Poorman’s Relief Mine. Only 20 minutes’ drive into the foothills west of Boulder, the mine was not too-wet and was already outfitted with electric power and lights. The JILA Shop guys did incredible things, drilling holes into the rock for our piers, establishing the 30 m vacuum tube (of 8 inch diameter) and building a solid concrete optical “table” for the laser setup. By April 26, 1968 our system was recording effectively the length of the 30 m path between the mirrors when, just past 8 am, a major seismic disturbance was detected and recorded. In fact it came from a deliberate 1.3 Mt blast detonated under the Nevada desert, under location U203i, within the National Test Site, about 70 miles West of Las Vegas. Another JILA colleague, Judah Levine, had been recruited into JILA by then and was normally doing geophysics research with the Poorman interferometer. These few minutes of data were highly interesting to certain officials from several government agencies. Of course we were all excited about this result, and the first conference for our announcement was an international one in Poland. So both East and West learned at the same time that clandestine tests would probably be noticed.
Another perpetual discussion topic in the Armory days was about shooting Jan’s laser pulses against the moon. Calculations indicated that this not too far into “crazy-land.” Jim suggested that corner-cube retro-reflectors would be a better target, rather than just the random lunar surface. Of course, getting into the schedule for such a NASA mission would take a long time, and lots of detailed planning. But also, in any case, there was no commercial source for optically perfect glass objects with 3 inclined surfaces to bounce the light back accurately in the direction of its source. Jim Faller, working with a master optician in Boulder did learn how to know how to grind and polish these surfaces. (That interesting guy, Bud Pearson, was the son of the master optician that made Albert Michelson’s famous experiments possible.) At this point Pete and Jim were in JILA, in Boulder and far away for easy influence on NASA’s program. So some other scientists and manager-types were brought into an expanded Lunar Laser Reflector program. The first such retro-mirror package was put on the moon’s surface by the Apollo 11 Astronauts on July 21, 1969, as a backup experiment, requiring little crew effort. AND Jim Faller’s team, using the Lick Observatory 3.1 m telescope got the first reflected laser returns on Aug 1, 1969. At present the earth-moon distance is accounted for within ~mm distances, by applying the multiple orbital, Relativity, Geophysics, earth-tidal, and atmospheric effects – many of these discussed first in the near-daily mini-seminars in the office and under the leadership of my wonderful friend and mentor, the late Dr Professor Peter L Bender, of JILA.
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| Sean McWilliams |
Coffee breaks and conference dinners |
I was taught the appropriate reverence for Pete as a grad student at UMD doing research at NASA. I met him at the 6th LISA Symposium and tried to sit near him at the conference dinner or find him at a coffee break at many meetings since. He was as generous with his time at LISA 6 as he was the last time I saw him. He knew I was a student those first few times and would quiz me on things that came up during talks, especially if he thought someone had gotten something wrong. I watched him interact with people, and he was the exact same person with everyone. At one dinner, he and I were at the end of the table and had a longer talk. I got to inpertinently ask him about things like being a teenager during WW2, and he told me a few different things about his life, like wrestling at Rutgers, where he claimed he only ever won if the other school had no one in his weight class. He was modest to his core. I hoped along with 1000 other people that the Universe would let him live as long as necessary to see his biggest idea come to life, but at least he knew it was well on its way. He'll be sorely missed. |
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| Tyson Littenberg |
An icon |
Pete was the first person I ever had dinner with at a conference whose name I was already familiar with from prior reading etc. and I was mesmerized. Over the years he reliably sent an email commenting on just about every LISA paper I ever submitted to a journal, even when I was just getting started in the field. Often because I neglected to reference his paper that did it first. Pete was always curious, constructive, and supportive, and has shaped countless careers that will carry his ideas forward. |
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| Ira Thorpe |
My entire scientific career is derived from one of Pete’s big ideas |
By the time I started working on the Laser Interferometer Space Antenna (LISA) as a graduate student in 2002, Pete had already been working on it for over three decades, longer than I had been alive. Much of his foundational work on LISA, which will observe elusive gravitational waves and use them to study the unseen universe, was being done while I was in elementary school. Pete’s work was ever-present during my early years working on LISA. No matter which aspect of the mission I was trying to learn about, my research would carry me to a paper by Pete. As I started to attend LISA conferences, I was able to meet him in person and discover that his scientific prowess was matched or even exceeded by his kindness. I quickly learned to treasure any opportunity I had to interact with Pete, be it a casual conversation or a detailed technical discussion. I am now two decades into my own LISA journey, currently serving as the NASA Project Scientist. The mission has recently made remarkable progress, and is on track to launch in the mid 2030s. I feel privileged to have known Pete and to have an opportunity to carry his vision for LISA closer to reality. |
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| Gregor MacGregor |
I worked with Peter when I was a student receptionist at JILA. |
I loved seeing Peter around, rain or shine, in the office and at the gym. He would say hi dropping by the front desk to check his mail like clockwork. I was surprised when I found out he was a good friend's grandpa. He was part of a great cast of characters that made JILA a special place. |
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| Dr. Tupper Hyde |
I worked with Peter on LISA 2002-2007. I was the NASA lead engineer for the mission when we entered Phase A around 2006 (and when we were un-Phase A'd the next year). Today, I continue to advocate for significant NASA participation in the LISA mission. Pete (and Tuck and Steve Merkowitz) taught me gravitational waves and how to measure them with spacecraft and lasers (and gold colored cubes flying freely through space with no disturbances!). |
The photo is of Peter is from May 20, 2005, in Friedrichshafen, Germany during a technical exchange meeting with the ESA LISA spacecraft study aerospace company. Pete always enjoyed any place work travel took him. I will miss listening to Pete’s stories after being dragged to eat Rijsttafel with him in Noordwijk; this happened multiple times!
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| Cindy Torres |
I was a custodian for several years in JILA and got to know him on the elevator, break-room breaks, and in the early mornings when it was just him and the custodial crew. |
When I was a custodian in JILA, I was a part of a crew of folks who made it our jobs to pay attention to the habits of people. Part of that job was to pay attention to Professor Bender and his habits in and around JILA. We knew he was going to be in JILA no matter how much snow fell or how much ice coated the sidewalks, so we'd make sure he had a safe path to work. We knew he'd be in his office early, so we'd clean his first. I loved his office - his rolodex, his flannel shirts hanging on the coat rack and the photos of him and his family in woodsy settings. He was on the 9th floor in the JILA tower and if I got lucky, we'd get to ride together on the elevator for a bit. He was quiet, soft spoken, but always kind enough to share his time if I had a question. One day I asked about his photo that hung in JILA - of him and some other scientists and the President (of the U.S., though I forget which one). I thought and said that that must have been quite an honor. He said in his humble way with a grin, Oh, that was just a little marketing. Professor Bender made a lasting impression on me. My condolences to his family, friends and colleagues. He will be missed. I took this photo of him one early morning. |
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| Robin "Tuck" Stebbins |
Multiple science collaborations over nearly 6 decades. |
I first met Pete at a colloquium on lunar laser ranging that he gave at Wesleyan University in November 1966. As a freshman working for Jim Faller, I was thermally testing optical material for retroreflector arrays. To my eternal surprise, Pete came to my wrestling match that evening, because, it turns out, he had been a collegiate wrestler as well. [This college freshman thought that Physics Department colloquium speakers did not routinely attend athletic events of students in the audience.] That connection was followed by associations through laser ranging to Surveyor VII, gravitational deflection of starlight under Henry Hill, laser ranging to the Apollo 11 retroreflector array, graduate school selection (JILA/University of Colorado), gravitational-wave detection in the Poorman Mine under Judah Levine, a doctoral thesis on solar oblateness under Henry Hill and Grant Athay, the conceptual design of LISA (again, at JILA), demonstration of active seismic isolation for LIGO, conceptual development of a sparsely-filled aperture telescope (LASII), U.S. LISA Project Scientist at Goddard Space Flight Center, and Senior Review Board on the GRACE Follow-On mission. Two weeks before his death, Pete gave me three tasks to follow up on: (1) recommendations for technology development for a LISA follow-on in the 2050s, (2) pressing the importance of a simplified gravitational reference sensor on a future earth gravity mapper, and (3) the value of particular orbital choices for that future mapper. |
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| neal lane |
I got to know and admire Peter during my visits to JILA as a visiting fellow in 1965-66 and1975-76. |
I met Peter when I visited JILA as a visiting fellow in 1965-66, and I had the opportunity to get to know him better on subsequent research visits. He was a brilliant physicist as others will attest. He was passionate about LISA. I recall learning about the possibility of observing gravitational waves from conversations with Peter. He was also a kind individual. Peter was the one who coaxed me to climb Long's Peak, and he made sure I made it all the up and back down again, without incident. He was a good friend and respected colleague. |
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| Daniel Packman |
In computer support at JILA I helped him with day to day tasks as well as some data analysis. |
Such a kind and gentle soul. I loved his excitement with the science as well as his ability to bring students into his gravitational well. |
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| Beth Kroger |
I was lucky to have worked with Pete during my time at JILA. |
As a non-scientist, Pete was inspirational to me with his passion and commitment to his work. Until recently, Pete was at JILA every day, including through the pandemic. He set a great example for all of us. As a founder of JILA he set a high standard and I'm proud to have worked with him as part of JILA's story. |
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