LIGO
ScientificCollaboration
Collaboration
Scientific
LIGO

LIGO MAGAZINE
issue 19 9/2021

GW200105 + GW200115
First Neutron Star - Black Hole Mergers p.6

LI

GO

In

di

a:

Search for young Supernova remnants in O3
ThContinuing continuous-wave science in a pandemic p.11

e

Pe

r fe

ct

Si

te

Science Summary Translations
Explaining our science to more people p.18... and Remembering A recibo: A Giant in Grav itational-Wave A stronomy p.21

Front cover

Rainbow Swirl by Carl Knox showing an artistic representation of a neutron star - black hole merger event.
Article on pp. 6-10.
Top inset: A NASA/ESA Hubble Space Telescope image of the supernova remnant Cassiopeia (Cas A). Article on pp. 11-12.
Bottom inset: Corey Gray and Sharron Yellowfly. Sharron Yellowfly translates LIGO-Virgo-KAGRA science summaries into
Blackfoot, and her son Corey Gray is an operator at LIGO Hanford. Article on pp. 18-20.
Bottom-left: The LIGO India site. Article on pp. 13-16.

Image credits
Photos and graphics appear courtesy of Caltech/MIT LIGO Laboratory and LIGO Scientific Collaboration unless otherwise noted.
Cover: Main image: Rainbow Swirl by Carl Knox, OzGrav / Swinburne University of Technology. Top inset: NASA, ESA, and the Hubble Heritage (STScI/
AURA)-ESA/Hubble Collaboration. Acknowledgement: Robert A. Fesen (Dartmouth College, USA) and James Long (ESA/Hubble). Bottom inset: Photo by
Corey Gray. Bottom-left: Photo by Tarun Souradeep (IISER Pune)
p. 3 Antimatter comic strip by Nutsinee Kijbunchoo.
pp. 6-7 Scientific visualization: T. Dietrich (Potsdam University and Max Planck Institute for Gravitational Physics), N. Fischer, S. Ossokine, H. Pfeiffer(Max Planck Institute for Gravitational Physics), T. Vu. Numerical-relativity simulation: S.V. Chaurasia (Stockholm University), T. Dietrich (Potsdam University and Max Planck Institute for Gravitational Physics).
p. 12 Cassiopia A: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgement: Robert A. Fesen (DartmouthCollege, USA) and James Long (ESA/Hubble).
pp. 13-16 Photos by Tarun Souradeep (IISER Pune).
p. 17 Photo of Prof. Dhiraj Bora by ITER (www.iter.org/newsline/96/1315). Photo of Dr. Srikumar Banerjee from IUCAA Archives.
pp. 18-20 Translations image by David Keitel (p. 18). Photo by Corey Gray (p. 19 & 20).
Screenshot from ligo.org (Credit LIGO/Virgo/KAGRA) with image by LIGO/Caltech/MIT/Robert Hurt (IPAC) (p. 19).
pp. 21-24 Starry sky and receiver platform photos from University of Central Florida (Courtesy: National Science Foundation) (pp. 21-22);
Damage to the telescope photo by Michelle Negron, National Science Foundation. (Courtesy: National Science Foundation) (p. 23);IEEE photo by Chris Amelung (CC By 2.0 https://creativecommons.org/licenses/by/2.0/deed.en) (p. 24).
p. 25 Photo by Grant David Meadors.
pp. 26-29 Photos by the authors.
p. 30 Virgo filter cavity photo by the Virgo Collaboration.
pp. 31 Image by Didier Verkindt including material adapted from an image by the SXS (Simulating eXtreme Spacetimes) Project and the music of Remo
Giazotto / Tomaso Albinoni.
pp. 32-33 Photos from the members of the 2021 LISA Canada Workshop Organising Committee (p. 32).
LISA image by University of Florida / Simon Barke (CC BY 4.0 https://creativecommons.org/licenses/by/4.0/) (p. 33).
p. 35 Photo by Georgia Mansell
Back cover: Illustrations by Paul Fulda.

2

Contents

4 Welcome5 News from the spokesperson – Foreword
6 The Observation of Two Neutron Star & Black Hole Mergers
11 Continuing Continuous Wave Science in a Pandemic
13 LIGO India - The Search for a Perfect Site
17 Remembering Prof. Dhiraj Bora and Dr. Srikumar Banerjee
18 Science Summaries: Explaing LIGO-Virgo-KAGRA Results to the Global Public
21 Remembering Arecibo - A Giant in Gravitational-Wave Astronomy
25 Work after LIGO: Solar Wind-swept to New Mexico
26 The LAAC Corner #4: Pandemic PhDs
30 Virgo Filter Cavity: On the Path to Frequency Dependent Squeezing for Observing Run 4
31 When Albinoni meets Virgo
32 Meanwhile in Space: The 2021 LISA Canada Workshop
34 We hear that…
35 The LIGO Magazine #19 – Masthead
36 How it works: LIGO Controls and Data System (CDS)

Antimatter3

Welcome to the 19th issue of the LIGO Magazine!

Welcome to the nineteenth issue of the LIGO Magazine! In this issue, we hear all about
the discovery of a new kind of gravitational-wave event with not one, but two neutronstar - black hole mergers observed in January 2020. Soichiro Morisaki, Rory Smith, and
Leo Tsukada tell us more, and we hear perspectives from around the community.
How do you choose a location for a gravitational-wave observatory? Tarun Souradeep
tells us the story of the LIGO India site selection in “LIGO India: The search for the perfectsite”. I’m sure we can look forward to many more updates in future LIGO Magazine issues
as the LIGO India Observatory progresses.
In “Continuing continuous wave science in a pandemic”, Lucy Strang is our guide to theworld of long-lasting (or continuous) gravitational waves and the hunt for these signals
from young supernova remnants.
Hannah Middleton
Editor-in-Chief

A key avenue for LIGO, Virgo, and KAGRA education and outreach efforts are the Science Summaries. Translating them into multiple languages is an important part of thisengagement. In “Explaining LIGO-Virgo-KAGRA results to the global public” David Keitel
and Isabel Cordero-Carrión tell us all about the Science Summary effort and the amazing
work of the volunteer translators from our collaborations.
In this issue’s LAAC Corner, we hear from five early career researchers on how the pandemic has affected them in “Pandemic PhDs”. And in our Life and Work after LIGO series
we catch up with Grant David Meadors on being “Solar wind-swept to New Mexico”.
In 2020, the research community was shocked by the demise of the Arecibo radio observatory. In “A giant in gravitational-wave astronomy”, our editors Sumeet Kulkarni andDeeksha Beniwal take us through the history of Arecibo, its contributions to gravitational-wave science, and we feature memories of Arecibo from members of the gravitationalwave community. Heading over to space-based gravitational-wave observatories, Jess
McIver updates us on the LISA community in Canada.
Finally, have you ever wondered how laser light produced by gravitational-wave observatories becomes the data that the LIGO-Virgo-KAGRA collaborations analyze? Find out

Anna Greenin this issues’ “How it works” on the back page!

Deputy Editor-in-Chief
As always, please send comments and suggestions for future issues tomagazine@ligo.org.
Hannah Middleton and Anna Green, for the Editors

4

News from the spokesperson
When I sit down to write these updates,

have suffered personal loss due to thetypically at the last possible minute, I’mpandemic. Please be kind to each otheralways struck by how much we have ac-

as we continue our work under this addi-

complished in the past 6 months. We havetional stress.

released 11 collaboration papers since
March 2021 reporting on searches for con-

We have a big year ahead of us. At least

tinuous waves, gravitational-wave back-

19 more papers are being written about

grounds, unmodeled bursts, and com-analysis and interpretation of the Observ-

pact binary mergers. We have extended

ing Run 3 (O3) data. Upgrades to the LIGO

our impact to look for lensing signatures

instruments and observatories are ongo-

and to place constraints on dark-pho-ing in preparation for Observing Run 4

ton dark matter using gravitational-wave(O4) scheduled to start in the second half

observations. Our paper on the neutron-of 2022. I am sure that it will bring many

star black-hole mergers GW200105 andmore exciting observational results.

Patrick Brady
LSC Spokesperson

GW200115, and the release of the GWTC2.1 catalog, were major scientific mile-

In parallel, we are examining the options

stones.

for post-O5 instrumental upgrades within
the existing LIGO observatories. A study

These superb observational results aregroup, chaired by Peter Fritschel, is lead-made possible by a broad-ranging re-ing this effort. The goal is to develop an

search program that addresses experi-

instrumental roadmap that will take us

mental, engineering, operational, andinto the next decade. Please contributeanalysis challenges with an eye on bothyour ideas to those discussions.

the short and long term. Our outreachprograms are also highly successful at

It has been two years since we could meetreaching people all around the world. It

in-person at a major collaboration meet-

is a privilege to work with such great col-ing; the last in-person meeting was inlaborators.

Warsaw in September 2019. As I look forward, I hope our next collaboration meet-

The impact of the COVID-19 pandemic

ing can be held in person in Baton Rougecontinues to be felt across our whole col-near LIGO Livingston. In the meantime,laboration. Many friends and colleagues

please contact me if you would like to dis-in the LIGO-Virgo-KAGRA collaboration

cuss any aspects of our collaboration.

5

Completing the trilogy: GW200105 and GW200115

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by Soichiro Morisaki, Rory Smith, and Leo Tsukada, with contributions from around the collaborationsI

n January 2020, a new type of gravitational-wave signal was seen for
the first time by the LIGO, Virgo, and
KAGRA collaborations. It was a neutron star merging with a black hole.
Before this observation, we had detected binary black hole (BBH) mergers and binary neutron star (BNS)
mergers, but not a confirmed neutron star - black hole (NSBH) merger.
The first NSBH observation was madeon 5th January 2020, and excitingly
it was quickly followed by another
NSBH during the following week on
the 15th January 2020! The observations are named GW200105 and
GW200115 for the dates they were observed (GWYYMMDD).

7

Completing the trilogy: GW200105 and GW200115
Soichiro Morisaki

Detecting the signals
At the time of GW200105, the LIGO Han-

is a postdoctoral researcherBlack holes can spin, and measuring theford detector was offline and only the LIGO

at the University of Wiscon-rate and orientation of the spins can help

Livingston detector observed a signal with

sin-Milwaukee. In his free

us piece together how the binaries area signal-to-noise ratio above the thresholdtime, he visits breweries

formed. There is a theoretical maximumof detection. GW200115, on the other hand,and enjoys some beers

spin of a black hole. We found the black

was seen by both LIGO Hanford and LIGO

and cheese curds.

hole spin for GW200105 could lie between

Livingston. For both events, the signal-to-

0 and as high as 30% of the maximum rota-

noise ratio recorded by the Virgo detector

Leo Tsukada

didn’t meet the detection threshold.

tion rate of black holes, while for GW200115,
the spin lies between 0 and 80% of theis a postdoctoral researcher

maximum rate. For GW200115, the black

When we make any detection, we estimate

at the Pennsylvania State

hole spin is likely to have a negative spin

how confident it is. We compute the statis-

University. He likes workout

projection. This means it is spinning in thetical significance of a detection by working

and hiking as well as enjoy-

opposite sense to orbital rotation of the bi-

out the possibility that noise could ran-

ing sci-fi movies on Netflix

nary system, which is quite unusual if it is

domly produce the same signal by chance.

on weekends.

the case. We do not have strong evidence

We consider GW200115 to be an astro-of neutron star spin because our measure-physical gravitational wave signal with

Rory Smith

very high confidence: we estimate that aments are not sensitive to it.

signal like GW200115 occurs due to ran-

is a lecturer in astrophysics

dom noise less than once in 100,000 years.

at Monash University, in

Why do we think we observed
neutron star-black hole binaries?

The statistical significance of GW200105

Melbourne Australia. In his

Based on the masses of the heavier objects

is more challenging to estimate due to it

free time, Rory likes to cook,in the binaries, we’re almost certain thatbeing a single-detector observation, but it

hike around the temperatethese are black holes: there’s really no otheralso clearly stands apart from all previously

rainforests in Victoria, andcompact object they could be. The masses

explore the awesome foodof the lighter objects in the binaries imply

seen noise effects. A signal like GW200105
would occur due to noise less than once inscene in Melbourne.

they are neutron stars, however in order todefinitively claim this, measuring masses isevery 2.8 years.

not enough. One could alternatively argue

NSBH mergers can, in principle, produce

What are the propertiesof the NSBHs?

light across the electromagnetic spectrum.

The heavier objects in GW200105 and“primordial black holes” that are speculated

Unfortunately, the direction of the sources

GW200115 have masses approximately 8.9

to have formed in the early Universe. We

in the sky could be measured only verytimes and 5.7 times the mass of our Sun,need a “smoking gun” that clearly charac-

imprecisely, to a sky localization between

respectively. They are both consistent withterizes the lighter objects as neutron stars.

2,400 and 29,000 times the size of the fullother black holes observed electromag-

In principle, there are two such characteris-

Moon. Together with the large distance of

netically and via gravitational waves.

tics that could be observed.

to the sources, this made observation of

The lighter objects have masses approxi-

The first is evidence of a neutron star “tid-electromagnetic counterparts unlikely, andmately 1.9 times and 1.5 times the mass

ally deforming”: stretching due to the grav-

none has been reported so far. Future ob-of our Sun, for GW200105 and GW200115

itational strain caused by the inspiral into

servations of NSBH mergers may produce

respectively. These masses are consistent

the black hole. This would slightly modify

observable light which could possiblywith known neutron stars and are well be-

the observed signal. The second is ob-

reveal the black hole “tidally disrupting”

low the maximum mass a neutron star canserving an electromagnetic counterpart,(tearing apart) the neutron star. This could

have. They are also consistent with gravita-

which could be caused by a neutron starprovide information about the extreme

tional wave observations of binary neutron

being “tidally disrupted” by the black hole:form of matter that makes up neutron stars.

star mergers like GW170817.

shredded apart due to extreme tidal forcesthat they are really light black holes such asaround 400 Mpc (cf. 40 Mpc for GW170817)

8

by Soichiro Morisaki, Rory Smith, and Leo Tsukada, with contributions from around the collaborations

before it has a chance to plunge into thedirectly compare our measurement to the-cluding how they’re made in the first place.

black hole. Neither of these characteristics

ory. There are two main formation scenar-

In other words, our work is far from done!

were observed. This is expected, though,ios that are consistent with the measured

given the relatively low signal to noise ra-merger rate. One of these starts with twotio, which makes tidal deformability diffi-

stars already orbiting each other. The stars

cult to measure, and the large distance tohave masses such that when they age, theyis an assistant professor at

the sources makes observing any possible

eventually explode in supernova explo-

the University of Potsdam

electromagnetic emission highly unlikely.

sions, one star leaving behind a black hole

(Germany) and Max Planck

Tim Dietrichand the other leaving a neutron star. This is

Fellow at the Albert Einstein

Without definitive evidence that we saw

called “isolated binary evolution”. The otherInstitute in Potsdam. In his

neutron stars, we instead check how consis-

possibility is that the neutron star and black

free time, he enjoys his fam-tent the masses are with known properties

holes form from separate stars in unrelated

ily time, watching Marvelof neutron stars. The masses are consistentsupernova explosions, and only afterwards(see above), so GW200105 and GW200115

find each other. This is called “dynamical

are suggestive that they came from the co-interaction” and can occur in dense stellar

While both the first gravitational-wave de-alescence of neutron stars with black holes.

environments such as young star clusters.

tection of binary black holes and binary

movies with his wife and playing football with his son.

Both GW200105 and GW200115 could haveneutron stars have been celebrated within

How often do neutron stars
and black holes merge?

formed through either scenario, and future

the entire astrophysical community, the firstobservations will be required to gain a bet-

detection of a mixed system went relatively

The two new discoveries allow us to di-ter handle on formation.

unnoticed. However, these observations

rectly estimate the NSBH merger rate forhave also been of central importance andthe first time. Currently, our ability to es-

finally complete the list of expected com-

timate this rate is limited by having only

NSBH perspectives

seen two events, as well as broad uncer-

pact binary sources. In fact, GW200105 and
GW200115 led to new scientific insights,

tainty on the population of NSBHs. We es-

Maya Fishbachtimate that there are between 12 and 242

for example a better understanding of themerger rates, and while we would have

NSBH mergers per cubic gigaparsec per

is an NHFP Einstein Postdoc-

wished for an event with an electromagnetic

year. This measure may not be especiallytoral Fellow at Northwesterncounterpart, the 'dark nature' of GW200105

intuitive, however a quick back of the en-

University. She enjoys bak-and GW200115 proved once more the im-velope calculation can tell us roughly how

ing bread, drinking boba,

portance of gravitational-wave astronomy.

many mergers there are in a given time pe-

and watching videos of cuteriod. For comparison, the binary neutron

animals.

Patricia Schmidt

star merger rate is roughly a factor of ten
higher, and there is about one binary neu-

is an assistant professor

tron star merger somewhere in the Uni-

My first reaction to the NSBH discoveries

in gravitational waves atverse every ten seconds or so. This means

was “We detected every type of merger!

the University of Birming-

that, somewhere in the Universe, NSBH

We’re done!” But after the celebration, it

ham, UK, where she works

mergers happen every few minutes.

can be disheartening to imagine that weon source modelling andwill never have another “first.” Fortunately,parameter inference with her

I’m confident that this isn't our last impor-group. When not working ontant discovery. Even after observing doz-

research, Patricia enjoys growing her own fruit and veg.

How did the NSBH binaries
form?

ens of BBH, a couple of BNS, and a couple
discovery

of

the

two

(poten-The merger rate is useful to figure out how

of NSBH, we’ve only sampled a tiny fractionThe

the systems may have formed. This is be-of the gravitational-wave universe. There’s

tially even three or four if we include

cause theoretical models of compact-bina-

just too much we still don’t understand

GW190426_152155 and GW190814) NSBH

ry formation predict merger rates, so we canabout black holes and neutron stars, in-binaries presents another milestone in the9Completing the trilogy: GW200105 and GW200115
Anna Puecher
still relatively young field of observational

black holes. This pair of NSBH mergers

is a PhD student at Nikhef

gravitational-wave astronomy. Their exis-(GW200105 and GW200115) therefore rep-and Utrecht University,

tence has been hypothesised for decades

resent the confirmation of these theoreti-

working on gravitational-

but promising electromagnetic candidates

cal predictions and the possibility of many

waves data analysis focused

kept being disproved. These gravitational-

future observations to come!

on binary neutron stars andwave observations provide the strongest

non-vanilla black holes. In

evidence for mixed compact binaries to

Leo Tsukada (author)

date. What we are lacking, however, is a

non-working time, Anna
loves hiking and reading.

measurement of tides demonstrating that

From the viewpoint of signal detection,

the lighter companions are indeed neu-

one of the challenges for these events

Gravitational waves give us an insighttron stars. Sensitivity upgrades are immi-

was the feature of single-detector ob-

into the most extreme events of thenent and with the community gearing up

servation. In these cases, the estimate

Universe, and allow us to test generalfor the third generation of gravitational-of the statistical significance is relatively

relativity

wave detectors, loud future observations

more uncertain compared to an observa-

There are different ways in which wewill allow us to determine their naturetion found by two or more detectors. For

can do this: we can look for deviations

much more affirmatively.

GW200105, in particular, the significancefrom the expected models, or measure

estimate changed a couple of times dur-the speed of gravitational waves; we

ing the re-analysis of a detection pipe-

can also look for phenomena that we

Simon Stevenson

instrong-field

conditions.

line and I had a mixed feeling about theknow are not present in general relativ-

is a postdoctoral researcher

confidence. To me, that was a psycho-

ity black holes, for example echoes, andworking on binary stellar

logically tough moment. I think we havemuch more. We are very excited thatevolution at Swinburne

got a lot of lessons to learn from these

now we also have NSBH mergers as a dif-

University of Technology,

events and it will be critically importantferent source of information, for these

Melbourne, Australia and is

to tackle the single-detector issues in fu-(and maybe new) ways to probe Ein-a member of the Australianture runs where there will be many morestein’s predictions.

Research Council Centre

similar events.

of Excellence for Gravitational Wave Discovery(OzGrav). He is a San Francisco 49ers fan and spends
much of his spare time playing video games.

Rory Smith (author)
Soichiro Morisaki (author)

I don’t think I can add much new about

While the estimated masses of the two

the scientific significance of the discover-

Astronomers first observed neutron stars

gravitational-wave sources are consistenties, so I’ll just give a brief personal per-and black holes in our Galaxy in the 1960s.

with NSBH binaries, we have not detected

spective as a member of the paper writ-

In the almost 60 years since, we’ve discov-any matter signatures of the lighter ob-

ing team. After 18 months, and what feels

ered dozens of neutron stars and blackjects in gravitational-wave or electromag-

like a thousand telecons, a million emails,

holes in binaries through observations of

netic observations. It leaves the possibil-

and an uncountable number of Slack andbinary pulsars, X-ray binaries and, recently,

ity that the lighter objects are light black

Mattermost messages, it’s wonderful togravitational waves.

holes. In either case, these events are ex-see our discoveries finally presented tociting: If the lighter objects are neutron

the world. It was a real privilege to be able

However, until now we had never seen astars, we detected NSBH binaries for the

to work so closely with many great people

neutron star and a black hole in a binary

first time. If the lighter objects are blackin the LVK, despite the anti-social hours of

together, despite observers hunting forholes, they may be primordial black holes

some of the telecons (Australia is a night-

them relentlessly, and theorists (like me!)formed in the early Universe. Detecting

mare to schedule with both the US and Eu-

predicting that they should be formed

the electromagnetic counterpart of NSBH

rope!). I look forward to all the new discov-from pairs of massive stars in a similar

merger is our next homework.

eries in Observing Run 4 and beyond!

way to binary neutron stars and binary
2021

10

Search for young supernova remnants in O3a6

Continuing Continuous
Wave Science ina Pandemic

am on Thursday. For a largepart of 2020, that was the only
marker I had that a whole week had
passed. The Australian response to the
COVID-19 pandemic was to close theborders and lock down any states withan outbreak. In Melbourne, this meantthat for most of 2020, there were four
reasons you were legally allowed to leave the house: essential work, medical
emergencies, essential supplies, andone hour of exercise per day. Months
and hours began to blur together as the
lockdown crept on. The passage of a
day was marked by my household drifting together to watch the daily press
conference on the case numbers. The
passage of a week was marked by the
first meeting I had, the weekly meetingwith the analysis team searching forcontinuous gravitational waves fromyoung supernova remnants.

Lucy Strang

but in retrospect, I wouldn’t trade the experience for the world.
Coordinating discussion across the team remained a challenge for the duration of the
project, but fortunately, human constraints
were our only challenge. A continuous gravitational-wave (CW) signal should be present
as a quiet, persistent signal in the data foris a PhD candidate at

the entire observing run. Unlike gravitation-

the University of Mel-al-wave astronomers interested in transientbourne with an interest

signals, CW astronomers don’t need to worry

in gravitational-wave

about binary coalescences not respecting aastronomy, signal process-9-5 working day. In fact, we can’t use the data

ing and other neutron-star

until the observing run is complete. Oncephysics. Outside of work,

the detector is off, the clock starts ticking as

they enjoy krav maga, boxing, and creative writ-

we race to complete our analyses before theing. They are currently based in Naarm, Melbourne

data is released to the public. It’s a short timeand acknowledge the Wurundjeri people as theframe, and one that is shrinking as we move

Traditional Owners of the land.

to shorter and shorter release schedules. The
data has to be calibrated and cleaned before
an analysis can start, and this process takes

Supernova remnants, like Cas. A (pic-longer every run. Every detector upgrade

tured p. 12), are the remains of mas-pushes us into new territory. As we increase

sive stars. When a star more than

the sensitivity, we find new sources of noiseeight times the mass of the sun burns

that were previously too quiet to detect. It’s athrough its fuel, it explodes in a su-

fair price to pay for greater sensitivity, but thepernova. The dense core of the starvital work of characterizing and controlling

collapses to a neutron star, and the in-

the noise takes time. It’s an essential and of-teraction of the explosion debris withten undervalued task that enables the science

the surrounding medium forms thewe do – but every tick of the clock counts.

intricate pattern of shocks that makeWe were a team of three, conveniently

supernova remnants so beautiful.

spread across three different time zones.

Once the data is cleaned, the challenge
becomes computing power. A CW signal

This came with some challenges. There isContinuous waves (CWs) are long-should be visible in the data for the entire

no meeting time that is friendly in Austra-

duration gravitational waves at arun, but the signal is expected to be much,lia, Europe and the U.S. – only times that“fairly constant” frequency – in themuch quieter than anything we’ve detected

are less unfriendly. My 6 AM meeting wascase of this search, a rotating, elliptic

before. The detection of GW150914 is often

at 10 PM in Europe. Somehow, we muddled

neutron star. What’s “fairly constant”?

compared to measuring the distance to thethrough. Throughout the project, I learnt so

In this case, the gravitational waves

nearest star (Proxima Centurai, approxi-

much more than I expected, both scientifi-

are emitted at twice the rotation fre-mately 4.2 light-years away) to an accuracy

cally and otherwise. I learnt how to collabo-

quency of the star, so it would typical-

around the width of a human hair. To detect

rate across continents and language gaps

ly take a couple of decades to shift bycontinuous waves, we need to be a million

and how valuable that kind of connection

one hertz. Continuous gravitationaltimes more sensitive. This would mean mea-

could be. It was difficult to appreciate it atwaves are much quieter than signals

suring the same distance to the accuracy

5:55 AM when preparing for the meeting,from compact binary coalescences.

around the width of a hydrogen atom.

11

by Lucy StrangThis is (or should be) unsurprising. The en-targeted supernova remnants each had analternative. In this scenario, we break theergy released during a compact binary co-

associated compact object, but no measured

observation time into small blocks andalescence ought to be much greater thanrotation frequency. All we have is a lower

analyse each block coherently before ty-

the energy available to a typical CW sourcebound on the age of the neutron star (im-ing them together. There are many ways

(for example, a rotating neutron star). To

plying an upper bound on the gravitational-

to tie the blocks together. By varying thehave any hope of detection, we have towave frequency). The possible frequency

way we analyse each block and how we tie

combine the data from the full observation

range for each target spans kilohertz. Eachthem together, we can develop different

run to try and boost the visibility of the sig-

frequency implies a range of possible spin-

analysis methods optimised to find differ-

nal enough to make a detection. So far, wedown rates to track how rapidly the star isent kinds of signals.

haven’t been lucky.

spinning down. Trying to do a maximally

The good news is that even a non-detec-

sensitive search across the full LIGO-Virgo

In the recent search for young supernova

band isn’t just impractical, it’s impossible.

remnants, we used three different, comple-

tion can contain interesting physics. A ro-mentary semi-coherent analyses to searchtating, elliptic neutron star should emit

Fortunately, there’s more than one way

for CWs. One was optimized for sensitivity;

CWs described by a simple sine wave at

to run a CW search. The most sensitive

another for flexibility, allowing for unusual

twice the rotation frequency of the star. An

searches are usually “coherent” searches.

signals; the last was optimized for a specificelliptic neutron star is one that needs three

Coherent searches compare the data to aphysical model.

dimensions to properly define the shape,

number of predefined signal models. This

much like a football. The more elliptic theis the most sensitive search that can be

Our search for supernova remnants inneutron star is, the louder the gravitational

done for a standard signal, but that sensi-

Observing Run 3 didn't find a CW detec-

waves should be. When choosing targets

tivity comes as a price: the computationaltion this time. But we were able to set

for a CW search, the goal is to pick targets

cost skyrockets if the observation time isan upper bound on how elliptical thesethat we expect to be very elliptic, close by,long or if the number of signal models

neutron stars could be. Next time, if we’reand in the most sensitive frequency bandrequired is very high, which it is for the

lucky, we’ll be sharing a new discovery

in the detector.

supernova remnant search.

instead. If we’re very lucky, we’ll be able

Neutron stars can be in binary systems or

When a coherent search is impractical, athen, we can at least meet via Zoom, evenisolated. For isolated neutron stars, the el-semi-coherent search is often the best

if it is at 6:00 AM.

to meet in the same time zone – but until

lipticity is left over from the supernova that2021

birthed the neutron star and diffuses overtime. This makes younger neutron stars
more promising targets – but, as usual,
there’s a catch. Younger neutron stars bothrotate and lose rotational energy more rapidly, so we now have to worry about thefrequency decreasing slowly as the star‘spins down’ (i.e. loses rotational energy).
Unfortunately, accounting for a decreasing frequency is computationally expensive. To make the search tractable, we needto either know what frequencies and spin
downs to search for or find new, clever ways
to search the data efficiently.
The search for CWs from young supernova
remnants required us to be clever. The fifteen
The supernova remnant Cassiopeia A (Cas A). This image was takenwith the NASA/ESA Hubble Space Telescope.

12Aundha Tehsil in Western India

LIGO India
The Search
for the
Perfect SiteT

he story1 of searching for asite for LIGO-India begins witha conversation I had in late 2011 with
Late Professor Govind Swarup, renowned Radio astronomer and theman behind the Giant Meter-wave Radio Telescope (GMRT) and Ooty Radio
Telescope (ORT) in India. Thumbing
through the project proposal document that I shared with him, he quizzed“What do you think is the most challenging aspect of the project?” Before I
could answer, he continued, “... you willtalk about all the technical challenges,
but your biggest challenge will be toidentify and acquire the large swath ofland. You will need to start working on
it right away!”

Members of the LIGO India team with the central station marker. Left to Right: Milind Goverdhan, DCSEM ;Sendhil Raja, RRCAT; Subroto Mukherjee, IPR; Author Tarun Souradeep, currently at IISER Pune.

Tarun Souradeep
currently chairs the Physics

by reserving some funds from its budget.

department at the Indian

The latter involved learning to coordinate

Institute of Science Educa-

within the limited resources and personnel

tion and Research (IISER),

available, on a very modest, but flexible,

Pune. He has built and led

budget and with a strong element of Indiana cosmology group on Cos-

‘jugaad’ (an Indian word that is now part ofmic Microwave backgroundthe Oxford English Dictionary) that makes(CMB) studies. He led the sole Indian group within

the story more exciting.

the international team of the Planck CMB space mission of the European Space Agency. He serves as theMy first visit to a candidate site was in mid-spokesperson for the LIGO-India mega-science proj-

September 2011, near Challakere, a town

ect and the member secretary, LIGO-India Scientificabout 200 kms from Bangalore with Bala

collaboration for the construction and operation ofIyer, Albert Lazzarini and Stan Whitcomb.

a gravitational-wave observatory on Indian soil.

We wanted to check if the facility could fit
and co-exist in a 11-thousand-acre span ofThis was remarkable foresight for the chal-sity Center for Astronomy and Astrophysics

land alongside a number of other institu-

lenging endeavor that was to unfold over

(IUCAA) in Pune, were identified for its ex-

tions. Our early lessons? First, get an idea

the next eight years. LIGO-India, at thatecution.

how far a distance of 4 kms appears on thetime, had no formal approval from the Gov-

flat ground. Second, understanding thaternment of India. It had been proposed in

The absence of a formal approval meanteven fairly arid and “desert-like” land in In-

2012 as a mega-science project to be jointly

there were no project funds at hand. Fur-dia hosts people and cultivation. And third,

funded by the Department of Atomic En-

ther, it also placed huge constraints on

our first taste of state bureaucracy, albeit inergy (DAE) and the Department of Scienceother resources and limited our ability tothis case a very positive one: from dealing

and Technology (DST) of India. Three leadformally deal with the state and district

with the paper-less office of the Principal

institutions: Institute for Plasma Researchmachinery. Enthusiastic support from theSecretary, right up to presenting our find-(IPR), Raja Ramanna Centre for Advanced

then Director and the Chair of the Govern-

ings to the Chief secretary (the topmost

Technology (RRCAT), and The Inter-Univer-ing Board of IUCAA helped with the former,

bureaucrat of the state administration)

1 A detailed site selection report is filed in the LIGO DCC (T1600181).

13

LIGO India: The Search for the Perfect Site

Panorama of the LIGO India site with site surveyors.

together with Directors of all the institu-

desert to the heartland of Madhya-Pradesh,kata), Sanjit Mitra (IUCAA). Managing thetions to whom the land had been allocated.

learning about fly-zones of military fighter

availability, schedule and travel was a fair

Although fairly promising, this reached ajets from bases, sharing cups of tea (andtask in itself, so was ensuring the safety ofdead end after a short seismic survey, sincesome times a ‘little’ more) with village chief-the equipment, and the immense time andcoexistence with the other campuses risked

tains; learning from the rich, vast and var-effort devoted to picking up and carrying

significant anthropogenic noise due theiried experience of co-passengers ranging

out the seismic data and terrain data anal-

planned activities.

from land related bureaucracy, geologi-

ysis by gravitational-wave expert, Rajesh

cal lessons, local cultivation, historical andNayak. By the end of November 2013, thisThe next year, 2012, was a total blur of many

mythological stories around various places.

extensive exercise led to a shortlist of four

visits across the country following up many,

All this was made possible by wholehearted

sites, two in the state of Madhya Pradesh

many leads. A key milestone was the timely

participation of team-members from otherand one each in Rajasthan and Maharash-induction of Sharad Gaonkar, a top-notch

institutions, RRCAT, TIFR-Mumbai, IISER

tra that all did well on the basic scientificseismologist, and then recently retired Se-

Kolkata, and the constant involvement at

requirements.

nior Deputy Director General of the Geolog-

a top-level liaison from LIGO USA lead byical survey of India. Sharad’s involvement

Stan Whitcomb and later Fred Raab. Also

The next task was to create a prioritizedlaunched a more informed search, starting

vital were the very helpful heads, academic

list. The key issues that emerged were: (i)with poring over seismic propensity maps

colleagues and other functionaries of aca-technical feasibility, time and cost of civilof a recent report of National Disaster Man-

demic institutions (ICTS, IISER Bhopal, IIT

construction; (ii) challenge posed by land

agement more knowledgeably, creating a

Jodhpur, Udaipur University) providing sup-acquisition and expected time of comple-

reasonable requirements document, estab-port and district/state level contacts.

tion, and (iii) long term aspects of efficient
operation of the gravitational-wave ob-lishing a protocol of following leads – first,

14

a round of online study with Google andPreliminary seismic studies at a shortlist

servatory. Each site scored well on certain

Bhuvan maps of the Indian Space Researchof promising sites were conducted withparameters, and not so well on others. We

Organization (ISRO), then a few exploratory

instruments borrowed from Geophysicist,

clearly needed more information to pro-site visits, discussions at district level orProf. Supriyo Mitra, IISER Kolkata, set up at

ceed further!

state levels as required and setting up avarious instances, by his student, Sharad,

short seismic study. The experience cameSendhil Raja and his team from RRCAT, Un-

To even address the first point, accurate

in all flavors, from the borders of the Tharnikrishnan (TIFR), Rajesh Nayak (IISER Kol-

topography was required beyond that pro-by Tarun Souradeep

vided publicly by Google, or Bhuvan. A

team over the next year or two. A lot oftake final decisions on important aspects

breakthrough here was the realization thatrather difficult-to-find information was alsoof the project. The inclusion of DCSEM as

the raw resolution of the data leading tomade available through the efforts of Shrianother lead institution brought into LIGO-

Bhuvan maps must be considerably higher,

Pandurang Pole, a very enthusiastic official

India much needed expertise, experiencegiven the specifications of the ISRO Carto-

from the Indian Administrative Service.

and considerable manpower to finalize theSat satellite. A friendly phone call betweensite selection, acquisition, and civil con-the Directors of IUCAA and Space Applica-

By Fall 2014, a formal site selection commit-

struction. The final recommendation of thetions Centre (SAC) of ISRO, allowed us totee set up by the DAE was tasked with mak-

LIGO-India site selection committee was ac-

soon get swaths of full resolution data thating the final recommendation of the prima-

cepted by the project boards and their find-allowed our team to create adequately de-ry and back-up sites for LIGO India. LIGO-US

ings were recorded in an extensive report intailed 2-D relief maps for each of the short-also pitched in with active participation in

Sept 2016. This was followed by the remark-listed sites. It was then possible to employ

these discussions and site visit, with the in-ably successful site acquisition, the feasibil-

the services of a top-notch engineering

volvement of Fred Asiri, an expert who had

ity of which was an important driving factor

consultancy firm to carry out a detailed

overseen LIGO site selection in the USA.

for final choice of the site.

site-feasibility study focusing on the civil

The LIGO-India site selection committee

construction of LIGO-India observatory.

was co-chaired by the Directors of RRCAT,The final LIGO-India site is in Aundha Tehsil,

To address the second point regarding

IUCAA, as well as involved experts of the

Hingoli district in the central Marathwada

the feasibility and ease of acquisition, an-

Directorate of Construction, Services andregion of Maharashtra state in Westernother consultant Prof. R. Gohad (retd. Col-

Estate Management (DCSEM) of DAE.

India. It is located 65 km from the city oflege of Engineering, Pune), with expertise

Nanded, with the nearest airport being 220

on land acquisition was hired at IUCAA. A

By February 2016, following the scientific

km away in Aurangabad. Unlike the otherthorough understanding of the applicablemilestone of the GW150914 discovery, we

sites which were indicated by leads, thisLand Act, its consequences for the feasibil-

had the momentous ‘in principle’ approvalsite was essentially ‘deduced’ through the

ity and expected timelines for the process

for LIGO-India by the Indian government.

use of remote sensing images. Seismologistof acquisition were worked out. Additional

The then Secretary of the DAE immedi-

Sharad Gaonkar had a gut instinct of pos-

information on sizes and facilities at theately took charge with a keen interest to

sible sites to the east of the Lonar crater. A

site, and neighboring towns and cities,

get things going, setting in place a formal

systematic scan and search of the area re-was put together by some members of the

project organization structure that could

vealed this promising site clearly standing

15

LIGO India: The Search for the Perfect Siteout due to the barren soil on the Hingoli
plateau. Befittingly, it was the Indian GW
guru, Sanjeev Dhurandhar, who went for
the first site visit along with Sharad, braving
really extreme summer temperatures. The
next visit was in much better weather in
November 2013, and it included members
from the LIGO US team.
The Hingoli plateau has a natural location
advantage as an isolated region, with lessinterference from industrial development
and the size of neighbouring settlements
being small. It is largely barren with scrubby
vegetation. The weather is very dry. Monsoon rains start from the month of June andend in September. For these few months,
the region transforms into being pretty
lush green compared to its usual barren
look. The Spring brings out a lovely bright
red bloom in the few small trees scatteredaround. Rain-fed agriculture is practiced onless than 10% of the area. The rest comprises
grazing land under the state government or
federal reserved forest. The region is a mixpot of two local cultures. The Marathwada
area was historically governed by the Nizamof Hyderabad and still retains quaint ties
with the Nizami values and culture, while
there is a healthy infusion of typical rural

Beautiful stone sculptures adorn the walls of this nearly one thousand-year old temple at
Aundha-Nagnath.

Maharashtra that is slowly taking over. The
Aundha tehsil also hosts the ancient Aundha-Nagnath temple that, besides being
an important pilgrimage site that attracts
about 100,000 visitors every year, is worth
a visit for its nice architecture and a taste of
local culture. Nanded city hosts the second
most significant sikh holy site –the Sri Huzur
Sahib Gurudwara. Also close to the LIGOIndia site is a geological marvel: the unique
Lonar crater lake formed by meteor impact.
About a 125 km drive away, it makes for an
excellent day outing. We look forward tohosting curious colleagues at Aundha soon!

2021

16

Spring blossoms at the LIGO India site.

With great sadness by the LIGO-India community

Remembering
Prof. Dhiraj Bora and Dr. Srikumar Banerjee
and the Director of the Heating and Current Drive (H&CD) Department during
2007-2013. He subsequently returned to
IPR as its Acting Director and served in thiscapacity till mid-2016. Prof. Bora will be remembered for his diverse contributions to
IPR and the LIGO-India project.

Dr Srikumar Banerjee, Chancellor of the Homi Bhabha Na-

tional Institute (HBNI), Former Chairman of
the Atomic Energy Commission (AEC), andSecretary of the Department of Atomic En-

I

Prof. Dhiraj Borat is with great sadness that we shareergy (DAE) passed away on May 23, 2021
after suffering a cardiac arrest. Dr. Baner-

Dr Srikumar Banerjee

jee had been associated with LIGO-India

The first formal proposal for the LIGO-

since its inception.

India project was made to the Mega Sci-news of the passing of Prof. Dhiraj Boraence Consortium of the Department ofon June 19, 2021. Prof. Bora contributed

Dr. Banerjee was born in Kolkata on

Atomic Energy and the Department of

towards the Technology Development

April 25, 1946. He was schooled at the

Science & Technology (DAE-DST) in its

and Capacity Building phase of the LIGO-

well-known

Government

meeting held in November 2012, that was

India project at the Institute for Plasma Re-

High School, passing out in 1962. Baner-co-chaired by Dr. Banerjee along with thesearch (IPR), Gandhinagar.

jee joined the Indian Institute of Tech-then Secretary of DST Dr. T. Ramasami.

nology (IIT) at Kharagpur for a degree

He has also served on the LIGO Oversight

BallygungeProf. Bora was an alumnus of the Physicalin Metallurgical Engineering, graduating

Committee from 2019 and was a member

Research Laboratory (PRL), Ahmedabad

with a B. Tech. in 1967. He then joined theof the Committee till his demise.

and was associated with the Plasma Phys-

Bhabha Atomic Research Center (BARC)

ics Programme right from its inception

as a Scientist. He was awarded his Ph.D. in

Dr. Banerjee is survived by his wife Ran-

during the early eighties, finally leading

1974 from IIT Kharagpur. Dr. Banerjee rosejana and his son Rajarshi. The LIGO-India

to the formation of IPR. After his work at

to become the Director of BARC in 2004.

Team offers them sincerest condolences

IPR on plasma heating and current drive

He left BARC in 2010 to become the Chair-and mourns the passing of one of its

systems, he worked at ITER Organization

man of the AEC in 2010, a post he retained

very senior mentors and well-wishers.

(France) as the Deputy Director Generaltill his retirement in 2012.
2021

17

Science Summaries

Explaining
LIGO-VirgoKAGRA results
to the global
publicS

ince the announcement of thefirst detection of gravitational
waves (GWs) shook the world in 2016,
LIGO and Virgo have been successfully “making waves” in the attention of
the global audience. Now also joinedby our KAGRA colleagues, our “LVK”
education and public outreach programmes cover the basics of our field(What is a GW? What is a black hole?
How does an interferometer work?),
but also the specific research we do in
the here and now: What are our actual
scientific journal papers about? A key
medium for this are our “Science Summaries” [1]. These short texts cover the
key points of each paper in a format
and style accessible to a wide audience, including students at all levels
and non-scientists around the world.
As a global collaboration, we are also
taking great efforts in translating thesesummaries to explain our science tomore people in their own languages.
For these translations, we draw on
our member scientists from across theglobe, and have so far published in a
total of 23 different languages.

Our record holder so far: GW190521 science summary in
17 different languages.

David Keitel
works at the Universityof the Balearic Islands inPalma de Mallorca, Spainon some of the “next firstdetections” that the LVK isgoing after: gravitational
waves from individual
spinning neutron stars andgravitationally lensed signals from compact binaries. In his free time, he likes to read or to explore thebeautiful nature and coast of his host island.

Isabel Cordero-Carrión
works in the Universityof Valencia, Spain on applied mathematics andastrophysics, with special
interest in the developmentof numerical methods forsolving partial differential
equations and performing numerical simulations ofastrophysical scenarios to extract their gravitationalradiation. She loves music and playing the flute inparticular, dancing flamenco and playing soccer
with her friends.

18

by David Keitel & Isabel Cordero-Carrión
Summaries in the online
and offline worlds
Summaries are usually between 2 and 4

ence around the globe, we need to bringamong their many other commitments. So

print pages long, including illustrations andour science to people in their own languag-

it is always worth checking back on ligo.

figures taken from the paper. They intro-

es. Our first science summaries were get-org as additional translations will often beduce the specific paper’s topic, very briefly

ting translated into Spanish since 2014, butposted later on.

explain the methods used, and focus on thethe effort has significantly picked up since

results and their impact. The reading level2016. By now for 22 different languages

And as a take-away message for readers

is somewhat higher than in newspaper sci-(beyond English) we have at least one sum-from other large international collabora-

ence stories, more similar to dedicated sci-mary translated and, as a record, the dis-

tions: you likely also have a big talent poolence magazines for enthusiastic lay readers.

covery of the exceptional event GW190521

available for doing outreach in general andWe reduce mathematical notation and tech-

was covered in 17 languages.

translations in specific; people just need tonical terms as much as possible, but we also

be motivated and organised! Writing andtry to teach the readers a few new concepts

These translations are a fully volunteer-driv-

translating outreach texts is also a great

and terms in each text, using glossaries anden effort: very few LVK members are paid foropportunity for scientists, especially early-

external links to explain in more depth.

outreach, so most translators are scientists

career researchers, to hone their writing

and students who do this in their free time.

skills. But foremost, what we realised is that

Behind the scenes, work on a summary

We try to have the English summaries readywhen telling the global public about what

usually starts some weeks or months be-early enough to give translators time before

we do, translations are a crucial ingredient

fore the paper becomes public. We (Da-a paper becomes public. We then send out

to improve global reach and to really bringvid and Isa) will identify someone closelya request to a translation volunteer email

our science to the people.

involved with the paper to draft the sum-

list, people self-organise to form pairs ofmary and two volunteers to review it,translators and proof-readers for each tar-checking that the explanations will makeget language, and often within a few days

sense to a broad audience. This is now also

the first completed translations come in.

integrated as a deliverable in our internal

Translators also often have a great eye forproject planning and editorial team roles

finding details that weren’t 100% clear infor each scientific paper.

the English version, sometimes leading toa scramble to update all versions of the

For the three observing runs since 2015, wesummary, but ensuring a higher-quality

have already written around a hundred pa-

output. For big discovery announcements,

pers [2] and summaries of these. The sum-

we then usually have several translations

maries are published online at ligo.org [1] andready to go live on “release day”, while foradvertised through social media. We also pro-other papers the schedule may be a bitvide attractively formatted PDF files for down-

slower since volunteers have to find timeload, which have traditionally proved very
popular at real-life outreach events. (Special
shout-out to Martin Hendry from the University of Glasgow for his tireless layouting work!)

Start of the online version of an example

Sharon Yellowfly, who translates into Blackfoot, with

science summary (GW190814 discovery).

her son Corey Gray, an operator at LIGO Hanford.

The summaries are also very useful as resources for starting research students, and sciencejournalists like to use them to get an overview
of new results, multiplying their impact.

Translations: improving
our global reach
Most of global science, and science communication, is conducted in English. But toreach the broadest and most diverse audi19

Science Summaries

by David Keitel & Isabel Cordero-Carrión

Volunteer perspectives
To highlight the enthusiasm that goes into

ing of course but seeing that an audience

the Collaboration. They cannot communica-

translating science summaries and theor some readers have understood some-te the deep technical aspects of the scientificpersonal motivations, here are quotes by

thing new thanks to your work is definitely

papers, but they highlight the beauty of thesome of our most active volunteers:

worth the effort.”)scientific results, they aim to bring out thepassion for our science.”)

Cristina Martí, under-

Hisaaki Shinkai, profes-

graduateatsor at Osaka Institute of

Sharon Yellowfly, trans-

University of the Balea-

Technology, translating

lating into Blackfootric Islands, translating…

into Japanese:[3,4]:

into Spanish:“Science Summaryは，“i s s s u u b u y a a b a n i s -“La traducción de resú-

手取り早く論文内容

daxin niixi LIGO’s gii

student

menes científicos brin-を理解するのに適しています．一般向

da la oportunidad de entender la ciencia a

けとはいうものの，内容は大学生向け

amustsk

todos, un objetivo imprescindible para con-でもあり，分野外の研究者にも役立つ

i_tu*dootstsiiya sigooxgaya nAbuutsbiiya

seguir una sociedad comprometida con laと思います．惜しむらくは，翻訳に名

spuu?ts nu?ganistsiitsiip ixgunadabii uut-

causa científica.”

乗り出てくれる院生がまだいないこと

sistabiitsip gii a~ku*banyuup giistuunnu-

into Catalan: “La traducció de resums cientí-です．いい勉強になるんだけどなあ．

un nitsidabiix. ayo?gwisxiniip myanistsii-

fics ofereix l’oportunitat d’entendre la ciència

私だけどんどん賢くなっちゃうよ”

xim_daan gii agitsuubuyaabanisduutsiibya

a tothom, un objectiu imprescindible per(“Science Summary is good for quickly under-

nitsidabibu~a?sin,aconseguir una societat compromesa amb lastanding the contents of a paper. Although it

nidumuu?dAximst nistunnaan, nugusiix gii

tasca científica.“

is intended for the general public, the content

istsgaabiists i_tu?dutstsiiw iesstuumskuutsp(“The translation of science summaries pro-is also suitable for undergrad students, and I

gii itstsiiya. okii Albert.”

vides the opportunity for everyone to under-

think it is also useful for researchers outside(“Translating LIGO's and Virgo's findings ofstand science, an essential goal to achieve a

the field. It is a pity that no graduate student

gravitational waves from black holes col-society committed to the scientific cause.”)has yet come forward to translate the article.

liding in space has been a life-affirming

It would be a good learning experience defi-

experience for me personally and a cul-

nitely. I'm getting smarter and smarter …”)

ture-affirming experience for the Blackfoot

Virgo's utu?gwiniimaxin
Abuduuxbiisii

o?bigimskAAsts

manii-bu~a?siniists,

Nicolas Arnaud, CNRS

people. To learn new ideas, concepts, andresearcher at Université

abstractions and then translate them into

Paris-Saclay and EGO,

Edoardo Milotti, pro-Blackfoot, creating neologisms, connects

translating into French:fessor at University ofme to my language, my people, and the“Communiquer sur nos

Trieste, translating intoscience that deals with energy and matter.

découvertes et, en par-Italian:Thank you, Albert.”)ticulier, les expliquer en“Science

Summaries

sono qualcosa di menofrançais, ma langue maternelle, est ma façon

References

de redonner ce que j'ai reçu. Une traduction

ma anche qualcosa diprend du temps bien sûr mais comprendrepiù degli articoli scientifici pubblicati dalla[1] https://www.ligo.org/science/outreach.php

que le public ou des lecteurs, ont découvert

Collaborazione. Non possono comunicare i[2] https://pnp.ligo.org/ppcomm/Papers.html

quelque chose de nouveau grâce à son tra-profondi aspetti tecnici degli articoli scientifi-[3] N. Greenfieldboyce 2019, NPR,

vail n'a pas de prix.”ci, ma spiegano la bellezza dei risultati scien-

https://www.npr.org/2019/03/31/706032203(“Communicating about our discoveriestifici, cercano di accendere la passione per la[4] M. Fore 2021, Symmetry Magazine,and, most importantly, explaining them

nostra scienza.”

https://www.symmetrymagazine.org/article/

in French, my mother tongue, is my way to(“The Science Summaries are both less andeinsteins-garden-translating-physics-in-

give back. Translating can be time-consum-

more than the scientific papers published byto-blackfoot
2021

20

Remembering Arecibo

A giant inGravitationalWave
AstronomyA

recibo Observatory is one of
the largest single-unit radio
and radar telescopes in the world. The
tragic demise of this facility on 10 August 2020 came as a huge shock to theresearch community around the world.
In this article, we briefly recap the success of Arecibo observatory and describe how it’s last hurrah might havebeen detecting low-frequency gravitational wave hums with NANOGrav. We
also hear testimonials from membersof the gravitational-wave community
who have benefited from visiting or
working with this telescope.

The starry sky above Arecibo Observatory in Puerto Rico.

Sumeet Kulkarni

the physics of re-entry and the composition

is a Ph.D. student studyingof the upper layers of the ionosphere were

population properties ofpoorly understood at the time. Around thecompact binary mergers at

same time, Professor William E. Gordon

the University of Mississip-

first conceived the idea of using incoher-pi. He pursues astrophotog-

ent scattering 1 to probe the ionosphere [2].

raphy in his spare time andThis idea progressed rapidly and became

when the night sky permits

the basis for the design of the Arecibo Iono-

it. Sumeet is also passionate about increasing publicspheric Observatory (AIO). With funding

engagement in science, through writing popularfrom ARPA and oversight from the US Air

science articles and hosting a local science cafe inForce and Cornell University, the construc-

Oxford, MS.

tion of this 1000ft (305m) diameter radio
Deeksha Beniwal

observatory, located in a sinkhole near Arecibo, Puerto Rico was completed in Novem-

The story of the Arecibo observatory start-

is a Ph.D. student at theed in the era of the space race. Following

University of Adelaide. Her

the successful flight of the world’s first ar-

research focuses on looking

While serving its primary objective of map-

tificial satellite (Sputnik) in 1957, the United-

for continuous gravitation-

ping the ionosphere, this multi-purpose

States Department of Defence quickly cameal wave signals from very

facility was also used by radio and radarto the realisation that the Soviet Unionhigh energy sources. Deek-

astronomers, for example, to accurately

sha enjoys going for walks,measure the orbital period of Mercury andhad advanced capability to rapidly exploit
military technology [1]. In an attempt todoing cross-stitch and cooking in her spare time.

organise competing American missile andber 1968 [2,5].

the Crab pulsar as well as discovering that
Venus rotates retrograde about once ev-

space projects and explore technologies

Among other anti-ballistic missile defence

ery 245 days [3]. Since the National Science

with potential military application, Presi-

projects, ARPA was exploring the idea ofFoundation took over the funding and man-dent Dwight D. Eisenhower authorised theidentifying nuclear warheads re-entering

agement oversight of AIO in 1969, the Are-

creation of the Advanced Research Projects

the Earth’s atmosphere by their unique sig-

cibo Observatory has been at the forefront

Agency (ARPA) in 1958.

nature in the ionosphere. However, bothof numerous groundbreaking discoveries.

1 This technique involves transmitting high-power radio waves to the ionosphere where the radar waves incoherently scatter off free electrons in the ionosphere.

The returned power can then be used to directly measure the electron density as well as the electron and ion temperatures and ion drift velocity.

21Remembering Arecibo

The receiver platform was suspended 150m above the dish. On 1st December 2020, several cables broke and the main telescope collapsed.

Among these include kick-starting the field

audible range, and hence can be converted

such as NANOGrav keep their eyes on anof observational gravitational-wave phys-

into audio. Being very short-duration, theyarray of Millisecond Pulsars (MSPs) spreadics! Arecibo observations were used in thesound like plucked notes of a violin.

throughout the galaxy. MSPs are compact
neutron stars: “objects with mass a little

discovery of the first-ever binary pulsar (akathe Hulse-Taylor binary) in 1974 [3]. Addi-

Low frequency gravitational waves, on theover one solar mass, squeezed into an area

tionally, the orbital period of the system wasother hand, sound more like the backgroundthe size of a city downtown, and spinningmeasured to decay over time. This was con-rumble in this spacetime symphony orches-

as fast as a kitchen blender”, as describedsistent with loss of energy from the systemtra. Such signals are expected to come fromby NANOGrav physicist Joe Simon. Beingin the form of gravitational waves, as pre-mergers of supermassive black holes. Thesepulsars, they emit pulses of radiation withdicted by Albert Einstein’s general theory of

gargantuan objects, with masses more thanextraordinary punctuality in the millisec-

relativity. As such, this discovery provided

a million times the mass of the Sun, emit

ond timescale, which NANOGrav has kept

the first indirect detection of gravitational

substantial gravitational-waves even whentrack of using Arecibo and the Green Bank

waves and was awarded the Nobel Prize ofthey’re well separated and revolving aroundtelescope. Each of the 45 pulsars acts like

Physics in 1993.

each other over a period of more than a year.

a probe for gravitational-wave detection,

This means that the signal frequency lies inwhich makes NANOGrav almost a galaxy-

Arecibo’s most recent contribution to thethe nanohertz (nHz) range, giving NANO-

sized detector!

field of gravitational-wave astrophysics has

Grav its name. Instead of detecting individ-

been in our search for low-frequency gravi-

ual mergers, the low-frequency spectrum isAssuming the center of mass of our Solartational-wave background using pulsar tim-

expected to be dominated by the collective

System, or ‘barycenter’, is a fixed reference

ing arrays, as a part of the North Americanbackground hum of a population of super-

point in the array of 45 pulsars, the time(s)Nanohertz Observatory for Gravitational

massive black hole pairs, or binaries; thinkat which these pulses arrive there with re-Waves (NANOGrav) collaboration.

of a hundred cellos drawing different notes

spect to each other can be accurately mea-

simultaneously, as opposed to the plucking

sured. One way in which this regularity canof a few lone violin strings. This is called thebe perturbed is by a passing gravitational

stochastic gravitational-wave background.

wave, which displaces the barycenter like a

NANOGrav and theGravitational Wave Background
Gravitational wave chirp signals seen by

22

floating duck. This leads to the pulses fromground-based detectors like aLIGO, aVirgo

In order to hear the gravitational-wave

the pulsars towards which we are displaced

and Kagra have frequencies in the human

background, Pulsar Timing Arrays (PTAs)

arriving sooner, and vice versa. These dis-by Sumeet Kulkarni & Deeksha Beniwal

Damage to the telescope at the Arecibo Observatory. Taken on 8th December 2020.

placements are extremely tiny, so to make a

ing arrays, there is still recorded data fromsomewhat unusual – during my studies,detection we need to observe and correlate

the legendary telescope that can contrib-

which helped me write a nice thesis. In 2009

the pulse arrival times from a set of pulsars

ute to NANOGrav’s next big data release.

I spent about ten days at the site to learn

spread across all angles and over a large pe-

It is only a matter of time before the right

how to observe with the telescope. A truly

riod of time. With enough data, we expect tochords are struck to reveal the gravitation-

wonderful time including a tour of the plat-

see a characteristic pattern of correlation in

al-wave background, and it would be a fit-

form I’ll always remember fondly.

the timing of two pulsars based on the angle

ting tribute if Arecibo was indeed listening

Benjamin Knispel, Max Planck Institute forthey form with respect to the barycenter.

to it in its last moments.

Gravitational Physics (Albert Einstein Insti-

This unique signature is known as known astute) Hannoverthe ‘Hellings and Downs curve’.
I would like to highlight Arecibo’s role inthe discovery of the Hulse-Taylor pulsar

world have published upper bounds on how

Memories of Arecibo from thegravitational-wave community

strong the gravitational-wave backgroundMy first attempt to visit Arecibo (12 yrs ago?)incontrovertible evidence for the reality of

could be whilst still escaping our detec-

was foiled when I and my friends excitedly

gravitational waves as well as for the exis-tion. In the latest results from NANOGrav, aarrived only to find it was closed for the day

tence of binary neutron stars. This proved

possible signal at low frequencies has been(a Tuesday, as I recall). Undeterred, I rented a

to be a precursor to the then envisioned but

revealed for the first time [6] and evidence

car and drove back on my own the next day

never before detected potential ground-is also seen by the Parkes PTA [7]. The na-

because I needed to see it. Such a magnifi-

based gravitational-wave detector source.

ture of the signal is uncertain and time willcent facility. I still have, and use, the travel

Both these aspects of this discovery weretell whether this is indeed the signature of

mug and grocery tote bag I purchased fromused in “political” advocacy for LIGO.

the gravitational-wave background. Future

their visitor center gift shop.

Beverly K. Berger, Stanford LIGO Groupobservations and combining data from theKim Burtnyk, LIGO Hanford Observatory

Over many years, PTA groups around the

PTAs might show increasing evidence for(PSR1913+16) whose orbital decay provided

I was lucky enough to spend the summer
As part of my PhD thesis I analysed PALFA

of 2013 at the Arecibo Observatory as anpulsar survey data taken by the Arecibo

REU student. I fell in love with both the tele-

While the sad demise of Arecibo is a big

telescope with Einstein@Home.. I was very

scope and pulsar astronomy; it was the be-blow to the entire community of pulsar tim-

lucky to discover two new pulsars – bothginning of a journey that eventually led methese correlations.

23Remembering Arecibo

by Sumeet Kulkarni & Deeksha Beniwal

IEEE sign at Arecibo observatory

References
to continuing pulsar timing array work as a

astronomer! I’m so grateful for the role that[1] M.A. Dennis, ‘Defense Advanced Research Projects

postdoctoral fellow. Long nights of observ-

Arecibo has played in my scientific life andAgency: United States government’, Encyclopedia

ing yielded exciting scientific results, which

for its remarkable contributions to pulsar

Britannica, 2019, https://www.britannica.com/topic/

convinced me that graduate school, and an

astronomy since that time, in particular for

Defense-Advanced-Research-Projects-Agency

eventual career in astronomy, was some-its vital importance to the NANOGrav proj-[2] D. Altschuler and C. Salter, ‘Early history of Arecibo

thing I could actually pursue. I'm heartbro-

ect over the past 16 years.

Observatory’, Physics Today, vol. 67, no. 6, pp. 11–12,

ken for all the staff, scientists, and students

Maura McLaughlin (NANOGrav), Eberly

DOI: 10.1063/PT.3.2402

in Puerto Rico enduring the loss of the tele-

Distinguished Professor, West Virginia Uni-

scope, and have hope that the observatory

versity.

at Arecibo Observatory, Hist. Geo Space. Sci., vol. 4, pp.

will be re-imagined and rebuilt.
Thankful Cromartie (NANOGrav), Einstein

I first went to Arecibo in 1972 as a first year

Postdoctoral Fellow, Cornell.

grad student, only a few years after pulsars
were discovered. My advisors and I were19-33, DOI: https://doi.org/10.5194/hgss-4-19-2013[4] National Science Foundation & Arecibo Observatory, ‘Legacy discoveries: Arecibo Observatory’,
https://www.naic.edu/ao/legacy-discoveries

In 1992, I was an undergraduate student atdoing a project that required maintenance

Penn State. I’d had no research experienceon a feed antenna, so it had to be lowered

and was not even sure I wanted to major infrom a boom hanging off one of the car-astronomy/physics or something else en-riage houses on the azimuth arm. To do thattirely when I approached Prof. Alex Wolszc-

some cables had to be disconnected and I[6] Z. Arzoumanian, et al. (NANOGrav), “The NANOGrav

zan to see if he had any research projects.

was elected to do that. As I was putting on

12.5 yr Data Set: Search for an Isotropic Stochastic

He did, and I was lucky enough to get to goa safety belt, my main advisor was saying,

Gravitational-wave Background”, Astrophysical Journal

to Arecibo that summer. I was completely“better that you go, Jim, since I’m wearing

Letters, vol 905, issue 2

awestruck by not only the telescope itself,

sandals.” So there I was hanging 500 feet[7] B. Goncharov, et al. (PPTA), “On the evidence for a

but by the welcoming and enthusiastic

above the dish. Little did I know what would

common-spectrum process in the search for the nano-community of scientists, engineers, andhappen 48 years later.

hertz gravitational wave background with the Parkes

staff at the telescope, and I decided thenJim Cordes (NANOGrav), George Feldstein

Pulsar Timing Array”, 2021, preprint: arXiv:2107.12112

and there that I was going to be a pulsar

Professor, Cornell
2021

24

[3] Mathews, J. D., ‘A short history of geophysical radar[5] C.M. Matthews, ‘The Arecibo Ionospheric Observatory’, CRS Report for Congress, 2/2012,https://fas.org/sgp/crs/misc/R40437.pdf

Life after LIGO

by Grant David Meadors

Solar
Wind-swept
to New Mexico
Grant David Meadors hiking up the hills of
Cerro Grande on the slopes of Valles Caldera.

As Jupiter & Saturn converged in my telescope eyepiece last year, long nights heralded abrighter future: I had finally becomea staff scientist in the Space Data Science group, high on the mesas of Los
Alamos National Laboratory. Now I
hope to help new discoveries emerge.
My journey started with summer internships at LIGO Hanford Observatory in 2005 and Caltech in 2007, throughmy PhD at the University of Michigan,and postdocs at AEI Hannover andOzGrav in Monash University. Characterizing instruments and analyzing
continuous waves around the globe
gave me pride. Too many colleagues
to name helped me to coalesce into
the astrophysicist who I am.

and oceans for most of the decade we’ve

VID publication. We hiked down the Rio

known each other. After first detection,

Grande and up Valles Caldera.

my sense of duty changed. We married. I
returned from adventure overseas.

Being in my third postdoc, options
seemed dim. Trying to simulate plasmas

When I left to study the solar wind here

made me miss the relative simplicity of

in February 2019, I said (for now) fare-gravity. I applied to the Space Data Sci-

well not only to tumbleweeds & tele-ence group, keen perhaps to bring LISA

cons, but to a community. I felt bothto Los Alamos. Once I joined, I began ex-

sacrifice and relief – to stop competing

perimenting with neural nets. Possibili-with my old friends.

ties are beginning to appear again, andso do responsibilities.

A NASA-funded space-weather project at
the Lab offered a bridge to a two-bodyThis planetary calamity has asked pa-

solution. Models of the Sun’s corona

tience of us all. Other crises demand ac-

could use statistical particle filteringtion. As a past LVC Ally, I now belong tofor solar wind predictions at satellites. I

local initiatives in justice, equity, diver-synthesized skills from my LIGO noise-sity, and inclusion, while acknowledg-

subtraction filtering and Bayesian infer-

ing the danger of assimilating into theence work and showcased the results at

dominant culture on this land that once

the American Geophysical Union. It was,belonged to the Tewa pueblo peoples.

Astronomy always enchanted me, as

at 2019’s close, the largest conference I’dWisely or not, researchers are respected.

physics revealed the stars. Wonder atever attended – and the last.

Our debt persists to future generations:the cosmos turned into self-reflection.

a cooler, calmer Earth, a kinder, humbler

Months measuring mirrors in the desert

As the pandemic swept this piny plateau,spurred the courage to trust in my own

I peeked out betwixt junipers every eve-truth: to come out as a gay man. In thening to finish the Messier galaxy catalog.

Understanding the universe is only theyear of the Big Dog, I met another scien-

Indoors, my Space Weather manuscript

beginning. We all leap into the unknown

tist who inspired me with his own clar-got published; I reviewed similar papers

with every theory and experiment. Life

ity. He & I were divided by mountains

and even pitched in an integral for a CO-transcends LIGO.

humanity.

2021

25

The LAAC Corner #4

Pandemic PhDs:
How the Pandemic has Affected Us
Graeme Ian McGhee
is a 2nd year PhD candidate at the Universityof Glasgow working inmirror coating development. Graeme began his
research in 2018 as partof his undergraduatew

e have now been living with
the COVID-19 pandemic forwell over a year, and know that it has
significantly affected everyone’s lives
in and out of work. We spoke to five of
our early career researchers to hear thenegative – and positive – effects of thepandemic for them both in the shorterand longer term.

to the experience of inhabiting exclusively
the same few rooms for most of the day
while the world stands still, and I did getlost in my own head at times. Initially, it was
hard to push through and get work done.
However, things have become much betteras the year has gone on, and I feel I have
now adapted to this new way of working
and socialising.

studies. He also has an avid fondness of honeyand camomile tea.

Q: Did lockdown have any positive im-

Leigh Smithpact on your progress?

Huy Tuong Cao

is a 1st year PhD stu-

Ultimately, I feel lockdown gave me a bit

is currently a postdoc

dent at the University

more control of my time management, andat the University of Ad-

of Glasgow working on

forced me to take that responsibility fully on

elaide, working on Ac-

black hole encounter

myself. I was also able to dedicate a bit more

tive Wavefront Control

burst events. She start-

time to taking college training courses thanupgrades for O4. Whened her candidature inusual. Networking over Zoom has been good

October 2020 duringin certain respects as well. I’ve got to “attend”

not working in the lab,
he enjoys being

the COVID-19 pandemic.

significantly more conferences than I otherwise would in normal times.

outdoors hiking and running.

Q: How have you found your PhD so far?
It has been a weird but rewarding experi-

Q: Did you develop any strategies for get-ence so far. It’s been 11 months since I

ting through lockdown?

started and I’ve not actually been on cam-

Setting myself a routine, trying to stick to

pus yet! Working from home took a while

the 9am-5pm, getting into the working

to adapt to, though my experience withmindset – and knowing when to switch off

my Master’s project really helped as a solid– really helped me. I’ve also been doing a lot

foundation to build upon. I’m enjoying myof plant keeping, playing my Switch, and wework and have gotten well into the swing

recently got a new addition to our house,of things now. Essentially the pandemic al-a dog, all of which has kept me happy andlowed me to have an extended reading pe-

entertained!

riod and firm up my knowledge.
Q: Have you felt supported by the col-26

Q: What impact has the pandemic hadlaboration and/or your institution in theon your wellbeing?

pandemic?

Adjusting to the lockdown was quite theMy supervisor has been very supportive.

challenge. I’m sure many of us can relate

The Glasgow data analysis group Zoom

by Graeme McGhee & Huy Tuong Cao

meetings have been great in integrating

Had it not succeeded, we would have given

Q: Do you have any tips for early career

me into the research group, and keeping

up and started looking for jobs back in the

researchers in a similar situation to you?

me up to date with what everyone else is

UK. That last attempt finally brought us toIf your plan gets delayed, make the mostworking on.

Australia, though at a much more expen-

out of that time! The delay allowed me tosive ticket price.

finish various projects that were 80% com-

Q: In the context of work is there any-

pleted, so I was able to get more publica-

thing you think won’t ever go “back to

I’m very grateful for the support that I got

tions out right at the start of my postdoc-

normal”?

during that time. UWA kindly helped with

toral career.

I think online conference integration/at-

moving costs, then provided me with a top-

tendance will probably become a lot more

up due to the lengthy visa and exemption

prevalent than before.

complications. The research group at UWA

Maya Kinley-Hanlon

also allowed me to start my job remotely,is a third-year Ph.D. stu-

part-time, a week after my viva. Thanks todent at the University

received his PhD frommy colleagues at Birmingham, I also foundof Glasgow where she

the University of Bir-another part-time research job there.

works on coating de-

Dr. Aaron Jones

mingham in 2020 forvelopment. Maya be-

his work on under-

Q: How was your experience working

standing impacts andremotely?

mitigation of wave-

The first few months were very hard. I nev-

gan her research with
Prof. Gregory Harry in
2014, joining LIGO in 2017.

front distortion in higher really solved the problem of time differ-precision interferometry. He now works asence. Initially, I was trying to follow Austra-

Q: Which special circumstances did you

a Postdoctoral Research Associate at The

lia time. I would wake up at 9 am Perth time

experience due to lockdown?

University of Western Australia.

(about 2 am in the UK), but then I wouldn’t

In March of 2020, when the pandemic was

go to sleep. I then tried to work with UK

just starting to go global, I became increas-

Q: How were your post-PhD plans affect-

time. But that was not suitable for any ofingly aware of how far away I was from myed by the pandemic?

the telecons. I ended up using an online

family and how hard it would be to reach

I got an offer to work at the University oftime tracking tool to ensure that I work an

them. Together with my advisor, we got theWestern Australia (UWA), but Covid-19

appropriate amount of hours and get suf-

paperwork in motion for me to work withbrought about lots of uncertainty, and theficient rest in between.

my undergraduate advisor from the Ameri-process of getting an exemption and visa

can University in case a stay in the U.S.

to come and work in Australia was very

I also found that virtual conferences are

occurred. On the evening of March 12th,

difficult. My fiance and I had to set hard

just not the same. I was excited to present

Trump shut the borders to the U.S and mydeadlines for ourselves regarding when weand get feedback on my work at confer-advisor messaged me that if I wanted to go

would have to give up pursuing my posi-

ences before, but in a virtual conference

home, it was time to book a flight. I packed

tion at UWA. We pushed this deadline backthere is a lack of networking and general

one carry-on bag and flew home. I expect-

twice. The last few months before moving

chit chat, which I think is very important.

ed to be in America for a couple of months,

to Australia, we were staying with our fam-

In a traditional conference, where you are

but have now been here for just under a

ily and it was progressively getting harder.

physically away, there is also less expecta-

year and a half.

Luckily, we got both of our exemptions andtion that you continue with local tasks, at-visas just days before our hard deadline,

tend group meetings, etc. That is however

Q: Do you think that lockdown delayed

but then had to rebook flights four times.

not the case for virtual conferences, and it

your thesis progress?

The third time, the flight was canceled on

is not only your supervisor’s expectation

There was some delay, but I did a lot of com-the day. We decided to give it one final try.

but also your own.

puter modelling, paper writing and started

27

The LAAC Corner #4: Pandemic PhDs

my thesis draft. When labs in Glasgow re-

Dr. Craig Cahillane

Japan. I ended up giving remote talks

opened, I was able to remotely take data,

is currently a post-

to LHO and the Australian National Uni-

and at times we have even been able to takedoc working at LIGO

versity (ANU). The Zoom talks for job ap-

more data than usual because of the time dif-Hanford

Observatory

plications over the last year really madeference. The most positive impact I have seen

(LHO). He received his

the whole process very formal. It was

through lockdown has been the strength of

PhD

California

much more difficult to learn about a re-the LIGO collaboration. The relationships be-

Institute of Technology

search group working culture throughtween labs allowed me to do what is best forin January 2021 for his

Zoom meetings.

my degree’s progress and my mental health.

work in calibration and controlling gravita-

fromtional wave detectors.
Q: How did lockdown affect your (men-

Q: What was thesis writing like?
My advisor, Alan Weinstein, came up total) wellbeing?

Q: What was your experience during

me back in November 1st last year andCalling the past year challenging feels

lockdown?

told me “Craig, I’m looking at your thesis

like an understatement. The pandemic,

The first lock-down at Caltech started inand I don’t see a lot there”. The only sec-

the fight for equality, the protests against

mid-March last year. At the time, I was ontion I had written for my thesis at thisinjustice, the election and violent presi-

the paper writing team for the Observing

point was some math required for analys-dential transition made it hard to focus

Run 3 detector sensitivity paper. I was lucky

ing data in the Observing Run detector

on my research. There were days when mythat the team was already remote, prepar-

paper. After that, I sat down and wrote

research paled in importance compared toing plots and writing for the paper. Not

continuously for two and a half months.

the needs and wellbeing of those aroundhaving an office or the usual access to co-

There were days that I collapsed after 4

me. But through everything, it also helped

workers made it hard to get anything done.

hours. Luckily Georgia forced me to go

keep me grounded. I am very thankful for

A few months into the pandemic, we com-

for a walk to keep me sane. I developed amy advisors throughout this year. I havepleted the paper, and I realised that I had toroutine, including an hour of doing some-felt supported in my desire to be home andgive up the interferometer modelling I wasthing active everyday, either walking or

close to loved ones. Being able to work indoing and buckle down to apply for jobs

some indoor bodyweight workout, which

the labs at American University has been aand write my thesis.

was very helpful.

I was living with my partner, Georgia,

The day that I finished defending my

Q: Did you feel more or less pressured toand housemates Gautam and Magnus

thesis, Georgia and I drove to a waterfall

produce results etc?

at Caltech in the first few months of thenear our place. It was an unforgettable

Generally speaking, the greatest pressure I feel

pandemic. Then in August 2020, Georgia

moment – the experience of being out inis the pressure I put on myself. This has stayed

had to move to work at Hanford. So we all

nature without the looming thesis in myrelatively the same throughout this year andpacked our belongings into a rental car

mind. There is that relief, but it also got

has kept me largely on track with my PhD.

and headed north to Richland, camping

me thinking about the next chapter of myalong the California coast to avoid contact

life. My PhD thesis had been my proxy. As

with many people.

soon as that was finished, all that was left

huge resource to stay productive.

Q: How did lockdown affect your work in
an international collaboration?

28

was one’s personal drive, and the quest to
Q: How was the job application processanswer what I would want to accomplish.

than anything else regarding the LIGO Col-during the pandemic?

It was a large paradigm shift that I’m stilllaboration specifically. The magic of confer-

Applying for a job during the pandemic

thinking over.

ences, in my experience, is being able towas definitely not easy. COVID led toconnect with people informally and I doa lot of my job application talks be-

Q: Do you feel like you have sufficient sup-not feel as though online conferences haveing cancelled, including ones at the Al-

port and supervision over the last year?

filled that gap.

bert Einstein Institute (Germany) and in

I was very lucky to have Georgia support-

I have missed in-person conferences moreby Graeme McGhee & Huy Tuong Cao

ing me, and the commissioners and scien-dering meals online and trying different

tists at Hanford were supportive and pro-things each day. It was long, but in thevided lots of guidance throughout my PhD.

end I got to see my family again, so that

The hardest part was worrying about mywas all good.

family. My mom was an essential worker.
Lots of her co-workers got COVID so I was

Q: What is working remotely from China

really worried about her contracting the

like? Does this affect your PhD progress

virus. She only took a few weeks off lastat all?

winter. My dad was in the most vulnerable

In a way, the work routine was similar toage group so we were worried about him

the lockdown in the US, but staying with

as well. Luckily, they all got vaccinated now

my family and not having to worry about

so we were able to visit them in the middle

the everyday things like food meant Iof summer this year.

could be really focused on my work. I had
to switch to performing simulations andcalculations. I certainly have got a lot of

Liu Tao

support from my advisor and colleagues:
did his undergraduate

we have weekly meetings on Zoom. This

study at the University

time was really productive: we have re-of Science and Technol-

cently published a paper based entirely

ogy of China in Anhuion the work we collaborated on remotely,

Province, China before

and another paper is now in its final stag-

starting his PhD Can-es. I’m pleased that these works were able

didature at the Univer-to progress during this difficult time. It issity of Florida, investigating the use of novel

still difficult to say how it would affect mybeam shapes to reduce coating thermal

PhD progress in the long term as I’ve justnoise in future gravitational-wave detectors.

started my second year. Hopefully, everything should be alright.

Q: How was your lockdown in the US andwhat led you to the decision to fly back

Q: What is your plan going ahead?

to China?

I will be flying back to Florida next week

I was completing the first year of my PhD(at time of interview) as the restrictions arewhen the pandemic hit and we went into

easing. Of course I will be missing my fam-

lockdown. I stayed with two flatmates,

ily, friends and the food here, but I’m also

but living abroad alone still brought

excited to get into the lab and get started

some worries. Despite that it was a goodon my experiments.

memory. However, at this point I had
been away abroad for more than a year

Q: Do you have any tips for anyone who

and I missed my friends and family inhas to work remotely in this ongoing

China. Travelling was getting harder, andlockdown?

I decided to head back to China, hop-I think the most important thing is to staying for restrictions not to last too long.

connected – engaging with others, wheth-

Upon arrival, I had to quarantine for aer they are your friends, family or your col-month. One good thing was the selection

leagues or supervisors. Those connectionsof food: I actually looked forward to or-really helped me through the last year.
2021

29

The Virgo filter cavity

On the path tofrequency
dependentsqueezing for
Observing Run 4

F

orty years after it was first proposed, the so-called squeezing technique, developed to reducethe impact of quantum vacuum fluctuations in gravitational wave detectors, is now routinely used during observation. Indeed, the squeezing was
one of the most notable successes ofObserving Run 3, bringing a remarkable reduction of the shot noise andan increase of the detection rate. But
for the next observing runs we want
to do more.

Installation of the input mirror suspension, composed by two pendulum stages sitting on a pre-isolator constituted by an inverted pendulum.

Eleonora Capocasa

dred Hz region as needed for our detectors.

is a researcher at APC lab in

At Virgo, substantial progress has been

Paris. She has also spent a

made in order to make the filter cavity

few years in Japan as partready for Observing Run 4.

of the KAGRA collaboration.
Besides fighting against
quantum noise, she likes

The installation ended in April 2021. It re-playing water polo andquired the building of several pieces ofinfrastructure and preparing several new

soaking in Japanese onsen.

optical and mechanical components: a 285

Yuefan Guo

m long vacuum pipe along the North arm,new clean rooms, two vacuum chambers

is a fourth year PhD student at

hosting the input and the end cavity sus-

Nikhef, Amsterdam, currently

pensions and two vacuum chambers host-working on the commissioning

ing the auxiliary optical benches neededof Virgo frequency dependent

In order to reduce the quantum noise also in

to inject the squeezed vacuum into the fil-squeezing. When she is not

the low frequency region, dominated by theter cavity, collect the reflected beams andworking, she enjoys baking,quantum radiation pressure, the squeezed

send them toward the interferometer.

playing board games andweekend trips around Italy.

vacuum will be first reflected by a FabryPerot cavity, the "filter cavity". This tech-

Since the cavity finesse has to be very highnique, usually known as “frequency depen-(about 11000), the longitudinal control is ini-

dent squeezing” will rotate the squeezing

tially acquired and kept using a green aux-

is a postdoc at the Universi-

ellipse differently for different frequencies

iliary beam (experiencing a much lower fi-

ty of Amsterdam, currently

before it enters the interferometer, allow-

nesse), and then moved to an infrared beamworking on commissioning

ing to reduce quantum noise in the wholeco-aligned with the squeezed vacuum.

at the Virgo site. In his free

Marco Vardaro

bandwidth. It has been experimentally dem-time he enjoys outdoor

onstrated in several prototypes, first in the

The cavity mirror suspensions, composed

MHz and kHz region and recently in the hun-of two pendulum stages sitting on a pre-activities: mountaineering, hiking, climbing andmountain biking.

30

History of Science

isolator constituted by an inverted pendu-

by Didier Verkindt

When Albinoni
meets Virgolum, were commissioned along with theirlocal controls in spring 2021. At the end

Didier Verkindt

of May 2021, we observed the first green
light transmitted by the cavity. On Juneis a CNRS physicist at

22nd, we achieved the first lock of the cav-

Laboratoire d’Annecy de

ity with the green beam, acting on the end

Physique des Particules

mirror. Then, the stability of the cavity was(LAPP). He has been work-

improved and now the cavity can keep theing on the Virgo experiment

lock for more than a day. Finally we weresince 1991, currently mainly
on detector characteriza-

able to align the bright infrared beam
(which is superposed with the squeezedtion, monitoring, calibration, and noise subtraction.

vacuum) into the cavity.

He loves astronomy and playing the piano.

In the 1930s, Remo Giazotto, a young
composer and musicologist, became fas-

The next steps will be to take measure-If you scratch a little at the layers of histo-

cinated by the life and oeuvre of Toma-ments of the optical losses, as we wantry, you sometimes come across surprises

so Albinoni, whose work had fallen into

to be sure that they are low enough notin science.

oblivion. Through his research Remo tried
to collect as much information on and as

to degrade these fragile squeezed states,
and to improve the cavity control system.

This story is of a musician, Remo Giazot-

many musical scores as he could find by

Then we should be able to measure fre-to, who is not well known, but came toAlbinoni. During the Second World War,quency dependent squeezing: one of thecompose a musical work known world-

intensive bombing ravaged the city ofimportant milestones of the Advanced

wide! The musician was the father ofDresden, especially the library where theVirgo + project.

Adalberto Giazotto1, an Italian physicist

archived manuscripts of Albinoni wereand one of the founders of the Advanced

stored. In 1945, our perseverant musi-

After forty years of squeezing develop-

Virgo gravitational wave observatory,

cologist went to search for manuscripts

ments, we are very excited to continue

which is now listening to the beautiful

in the ruins of the library of Dresden. He

playing with quantum mechanics and tomusic composed by binary neutron stars

found only ashes, but returned saying

produce frequency dependent squeez-

and binary black holes alongside the twothat he had found the start (a few firsting to push further the detectors’ sensi-

Advanced LIGO detectors.

measures at most) of an Adagio written

tivity for the next LIGO-Virgo-KAGRA observing runs.
2021

by Tomaso Albinoni. He stated that he
The story begins with Tomaso Albinoni,

had completed this score by writing theborn in Venice in 1671. He had great inter-missing notes himself.

est in music from an early age. His father
allowed him to learn the violin. However,

The full score was published in 1958 (byas the eldest son, he had to take on someRicordi). It acquired great success, to the

responsibilities in the family business atdelight of Remo Giazotto, who had finally

1 Adalberto Giazotto was born in 1940 in Genoa. Afterthe age of twenty. At the age of 38, whenmanaged to make the name of Albinoni

a physics degree from Sapienza University in Roma,his father passed away, Tomaso finallyknown around the world. We know to-

he started working in particle physics in the group

devoted himself fully to music. He was a

day that this composer and musicologistof Eduardo Amaldi. In the 1980’s, he worked with his

talented violinist and prolific composer,

had in fact found nothing in the library of

writing over 80 operas appreciated in

Dresden. He had composed entirely thistational wave detectors and finally proposed in 1989,

Venice, Munich and Dresden. After his

famous Adagio, which, even today, is of-with Alain Brillet’s group, the construction of the Virgo

death, many of his scores were preserved

ten attributed to Tomaso Albinoni.

Pisa group on the anti-seismic superattenuators withthe aim of opening low frequency window for gravi-interferometer for detecting gravitational waves.

in the Dresden library.
2021

31

Meanwhile in space ...

The 2021 LISA Canada workshop(nearly double the number of Canadian faculty who are members of the LIGO Scientific Collaboration). Up to this point, although
there was a strong Canadian presence inthe LISA Consortium, the coordination ofefforts between LISA PIs in Canada was infrequent. This team of twelve PIs organized
the 2021 LISA Canada workshop in part tocreate connections between these groups
and establish a robust new communication
network across Canada for LISA research.
In planning for the workshop, we realized
Members of the 2021 LISA Canada Workshop organising committee. From left to right: Daryl Haggard (McGill University),David Morrissey (TRIUMF), Djuna Croon (Durham University and formerly the UBC-TRIUMF LISA Consortium PI), Huan
Yang (University of Guelph & Perimeter Institute), John Ruan (Bishop’s University), Pasquale Bosso (University of Lethbridge),
Saeed Rastgoo (York University), Saurya Das (University of Lethbridge), Scott Oser (University of British Columbia), Will East
(Perimeter Institute for Theoretical Physics) and Jess McIver (see below).

Jess McIver
is Assistant Professor at
the University of British
Columbia. Jess has worked
in the field of gravitational
waves since she started anundergraduate research
project on LIGO detector
characterization at Syracuse University in 2007. Jessmoved to Vancouver, Canada from the U.S. in 2019,and enjoys the oceans, mountains, and trees of the
Pacific Northwest.

The LISA space mission will unlock a unique band of gravitational-wave observations, allowing
new insight into stellar remnants atvast distances, novel probes of fundamental physics and cosmology,
and tests of general relativity with unprecedented precision. The 2021 LISA
Canada workshop (https://meetings.
triumf.ca/event/220/), held virtually
April 27-29, 2021, helped to fuel thegrowing excitement of researchers in
Canada and around the world for LISA
and gravitational waves.

we had the opportunity to broaden ourgoals to explore how Canada could play asignificant role in enabling LISA to fly in the
mid-2030s. We planned to use the workshop to gauge the interest of Canadianphysicists and astronomers in LISA science.
As Canada has an active commercial spaceindustry with expertise relevant to LISA,
we also sought to investigate the interestof industrial companies in contributing to
the LISA mission.
To achieve these goals, we decided a key element of the program would be to provide
a comprehensive introductory overview of
LISA accessible to researchers of all career
stages, as well as attendees from industry.
To that end, we invited current leaders of
the LISA mission and the LISA Consortium
to give an overview of the LISA mission, itsscientific potential, and the current activities of LISA working groups. Public recordings of a subset of these talks are available
on YouTube1.

LISA science had already caught the attention of a diverse group of Canadian

The approach of giving researchers new toresearchers prior to this year. In late 2020,

LISA a path to entry attracted broad interest

about eight months into the pandemic, ain the workshop from around the world: 300

team of LISA group PIs in Canada realized

total participants from 33 countries regis-

we had a quorum of Canadians involved

tered, spanning six continents (maxing out

to the LISA Consortium: twelve PIs in total

our Zoom capacity). Over 150 participants

1 A list of publicly available 2021 LISA Canada workshop talks is on p.35!

32

by Jess McIver

joined live on Zoom for the introductorydemonstrating that the LISA mission has

overview talks. We also sought to make thethe potential to leverage interdisciplinary

Looking ahead: the future of
LISA research in Canada

workshop accessible to as many as possible

expertise across Canada and around the

In post-workshop survey results, Cana-in different time zones, likely suffering fromworld on a large scale.

dian researchers expressed interest in
future semi-annual LISA Canada meet-

Zoom fatigue during the height of the pan-Forging new connections between
LISA and Canadian potential

ings as well as collaboration on pro-consecutive days of talks and discussions,
lasting no more than three hours each day.

Participants from the European Space

Canadian respondents also identified

This structure (in topic and time) may serve

Agency (ESA) and the LISA Consortium

guidance from the LISA Consortium

as a useful model for future virtual scientificalso discussed opportunities for Canada

and funding for student and postdoc-

workshops as well as engaging scientists

to contribute hardware to the LISA mission

toral trainees as the resources mostfrom different fields around the world in an

during the workshop. A key outcome fromneeded to effectively contribute to LISA

exciting emerging topic.

the closeout discussion was the establish-

science. We hope that the 2021 LISA

ment of a line of communication between

Canada workshop sparked interest andthe workshop organizers, ESA, and the Ca-

enthusiasm that will establish a critical

By the numbers:
an emerging LISA researchcommunity in Canada

nadian Space Agency (CSA) to identify po-

mass for LISA research in Canada in thetential overlap between the LISA mission

long term.

At the time of the LISA Canada 2021 work-

Workshop attendees also identified com-

To learn more, you can read our execu-

shop, 25 Canadian researchers, including 12

puting infrastructure (hardware and soft-

tive summary of the 2021 LISA Canada

at the faculty-level across nine Canadian in-ware) as a potential contribution to theworkshop and its outcomes on the work-

stitutions, were active members of the LISALISA mission where Canada has consider-shop website:

Consortium.

able experience and expertise.

https://meetings.triumf.ca/event/220/

demic. We scheduled the program for threeposals to fund LISA-related research.

needs and Canadian industrial expertise.

A total of 108 Canadian researchers regis-

2021

tered for the LISA Canada 2021 workshop,from 30 different Canadian institutions. In
a post-workshop survey, 100% of Canadian
respondents who were not already members of the LISA Consortium indicated theywould like to join.
Canadian researchers who participated in
the LISA Canada 2021 workshop currently
work in wide array of disciplines, including gravitational-wave astronomy withground-based detectors such as LIGO
and Virgo; cosmology; extreme stellar
environments and stellar history; galaxy
formation; modeling sources of gravitational radiation; tests of general relativity
and theoretical explorations of extreme
spacetime; particle physics and tests ofdark matter; and experimental subatomic
physics, among others. Workshop organizers noticed similar trends in current disci-“LISA will be able to detect the reverberations of cataclysmic events in the early universe,
not unlike the echo from a booming Hayley Wickenheiser slapshot.” - David Morrissey,
Research Scientist, TRIUMF

pline for registrants from other countries,

33

We hear that ...
Career UpdatesAwards

New LSC positions

Sharan Banagiri has finished his Ph.D at theChristopher Berry recently received the Gen-

Stefan Ballmer has been elected as the Elec-

University of Minnesota and is now working aseral Relativity and Gravitation Young Scientist

ted Member of the LSC Management Team.

a postdoc at CIERA at Northwestern University.

Prize from the International Union of Pure andApplied Physics (IUPAP), awarded by the In-

Patrick Brady has been re-elected as Spokes-

Craig Cahillane earned his PhD in Physics fromternational Society on General Relativity andperson of the LSC.

Caltech (thesis: LIGO-P1800022), and is now a

Gravitation.
Marco Cavaglia has been re-elected as co-

Postdoctoral Scholar in Physics at Caltech, stationed at LIGO Hanford Observatory.

Sylvia Biscoveanu has been awarded thechair of the LSC-Virgo Burst Working Group.

2021 Barrett Prize for astrophysics at MIT.
Tim Dietrich has been appointed Max Planck

Vuk Mandic has been re-elected as co-chair ofFellow at the Max Planck Institute for Gravita-

Alessandra Buonanno has been electedtional Physics (Albert Einstein Institute)member of the US National Academy of Sci-

https://www.aei.mpg.de/666244/tim-dietrich-ences and elected member of the Leopoldina

Jessica Steinlechner has been elected as chair

appointed-max-planck-fellow?c=26160

https://www.aei.mpg.de/691072/alessandra-of the Optics Working Group.

the LSC-Virgo Stochastic Working Group.

buonanno-elected-member-of-the-us-nationGrant David Meadors is now a staff scientist

al-academy-of-sciences?c=26160

in the Space Data Science group at Los Alamos

ht tps: //w w w. aei.mpg.de/687527/Prof_-

National Laboratory.

Buonanno - ele c te d - memb er- of-the -Other News

Leopoldina?c=26160
The oral history of Stephen C. McGuire, Sou-

Kentaro Mogushi has graduated from Missouri S&T with a thesis on detector char-

Tim Dietrich has been awarded the Heinz

thern University Endowed Professor of Physics

acterization, entitled "Improving the data

Maier-Leibnitz Prize

Emeritus, has been featured in the AIP History

quality in gravitational-wave detectors by

https://www.aei.mpg.de/660938/heinz-maier-

Newsletter Volume 53 (2021), Number 1. P. 19.

mitigating transient noise artifacts." He hasleibnitz-prize-for-tim-dietrich?c=26160.

https://www.aip.org/history-programs/history-newsletternow moved back to Japan to start a job in a
pharmaceutical company.

Colm Talbot was recently awarded the 2021
Charlene Heisler Prize of the The Astronomi-

The five year anniversary of the LISA Path-

The Australian National University has promot-

cal Society of Australia, for the most outstand-finder mission was celebrated with a series

ed Professor Susan Scott and Professor David

ing PhD thesis in astronomy or a closely relat-of short video clips, which can be viewed at

McClelland to its highest academic level ofed field, accepted by an Australian university.

https://www.lisamission.org/news/latest-

Distinguished Professor.

https://asa.astronomy.org.au/prizes_and-news/lisa-pathfinder-space-saga

grants/prizes-awards/charlene-heisler-prize/
Sidd Soni has graduated from Louisiana State

2021

University with his PhD focused on detector char-Marina Trad Nery (AEI Hannover) won theacterization. He will be a postdoc at MIT next.

2020 GWIC-Braccini Thesis Prize for her PhD
thesis “Laser Power Stabilization via Radiation

Colm Talbot, Postdoctoral Scholar at Caltech

Pressure”

LIGO Lab, will be moving to MIT as a Kavli Postdoctoral Fellow in September.

Professor Bernard Schutz has been elected
as Fellow of the Royal Society.

John Zweizig, Staff Scientist at LIGO Labora-

h t t p s : // w w w. a e i . m p g . d e /69753 0/ b e r-

tory Caltech (for the past ~25 years) will retire innard-schutz-elected-fellow-of-the-royal-

October 2021, at which point he will continue tosociety?c=26160

contribute to LIGO as a part-time consultant.

34

The LIGO Magazine
Publicly available 2021 LISA
Canada workshop talks (from p.32)

LIGO is funded by the National Science Foundation and operated by the California Institute of Technology and
Massachusetts Institute of Technology. This material is based upon work supported, in part, by the National Science Foundation. Any opinions, findings, and conclusions or recommendations expressed in this material arethose of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Workshop Introduction(Jess McIver):https://youtu.be/P_dUYB-EgT8

The authors gratefully acknowledge the support of the United States National Science Foundation (NSF) for the construction and operation of the LIGO Laboratory and Advanced LIGO as well as the Science and Technology Facilities
Council (STFC) of the United Kingdom, the Max-Planck-Society (MPS), and the State of Niedersachsen/Germany forsupport of the construction of Advanced LIGO and construction and operation of the GEO600 detector. Additional
support for Advanced LIGO was provided by the Australian Research Council. The authors gratefully acknowledge
the Italian Istituto Nazionale di Fisica Nucleare (INFN), the French Centre National de la Recherche Scientifique (CNRS)
and the Netherlands Organization for Scientific Research, for the construction and operation of the Virgo detector
and the creation and support of the EGO consortium. The authors also gratefully acknowledge research support fromthese agencies as well as by the Council of Scientific and Industrial Research of India, the Department of Science andTechnology, India, the Science & Engineering Research Board (SERB), India, the Ministry of Human Resource Development, India, the Spanish Agencia Estatal de Investigación, the Vicepresidència i Conselleria d’Innovació, Recerca i
Turisme and the Conselleria d’Educació i Universitat del Govern de les Illes Balears, the Conselleria d’Innovació, Universitats, Ciència i Societat Digital de la Generalitat Valenciana and the CERCA Programme Generalitat de Catalunya,
Spain, the National Science Centre of Poland and the Foundation for Polish Science (FNP), the Swiss National Science
Foundation (SNSF), the Russian Foundation for Basic Research, the Russian Science Foundation, the European
Commission, the European Regional Development Funds (ERDF), the Royal Society, the Scottish Funding Council,
the Scottish Universities Physics Alliance, the Hungarian Scientific Research Fund (OTKA), the French Lyon Instituteof Origins (LIO), the Belgian Fonds de la Recherche Scientifique (FRS-FNRS), Actions de Recherche Concertes (ARC)and Fonds Wetenschappelijk Onderzoek Vlaanderen (FWO), Belgium, the Paris Île-de-France Region, the National
Research, Development and Innovation Office Hungary (NKFIH), the National Research Foundation of Korea, theNatural Science and Engineering Research Council Canada, Canadian Foundation for Innovation (CFI), the Brazilian
Ministry of Science, Technology, and Innovations, the International Center for Theoretical Physics South American
Institute for Fundamental Research (ICTP-SAIFR), the Research Grants Council of Hong Kong, the National Natural
Science Foundation of China (NSFC), the Leverhulme Trust, the Research Corporation, the Ministry of Science andTechnology (MOST), Taiwan, the United States Department of Energy, and the Kavli Foundation. The authors gratefully
acknowledge the support of the NSF, STFC, INFN and CNRS for provision of computational resources.

LISA Science Overview(Kelly Holley-Bockelmann):
https://www.youtube.com/watch?v=VrIi6Tpx3Y
LISA Detector Overview(William Weber): https://www.youtube.com/
watch?v=fb0vpAwde6g
LISA Astrophysics Working Group(Shane Larson): https://www.youtube.com/
watch?v=DVaPbXUmC2Q
LISA Data Challenge Working Group(Nikolaos Karnesis): https://www.youtube.com/
watch?v=BaBkQ8snODs

Online ISSN: 2169-4443
World Wide Web URL: https://www.ligo.org/magazine
Publisher: LIGO Scientific Collaboration, Pasadena, CA, USA
LIGO DCC: LIGO-P2100332
Contact: magazine@ligo.org
Editor-in-Chief: Hannah Middleton • Deputy Editor-in-Chief: Anna GreenLISA Parallel Session A(Observations/Instrumentation):
https://www.youtube.com/
watch?v=PlrbfloGF44
LISA Parallel Session B(Theory): https://www.youtube.com/
watch?v=TPsowHIayhk

Editors: Kendall Ackley, Deeksha Beniwal, Laura Cadonati, Andreas Freise, Tobin Fricke, Paul Fulda, Gabriela
González, Amber Strunk Henry, Nutsinee Kijbunchoo, Sumeet Kulkarni, Mike Landry, Sean Leavey, Susanne Milde,
Brian O‘Reilly, Sascha Rieger

Design & production: Milde Marketing International Science Communication + formgeber
Printed by GS Druck und Medien GmbH Potsdam
Supported by the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI),
and the California Institute for Technology (Caltech)

The LIGO Magazine is printed on certified sustainable paper.

LISA Consortium Overview(Nelson Christensen): https://www.youtube.
com/watch?v=90gQ_3mUfLILISA Canada Workshop Discussion
Summary and Closeout:
https://youtu.be/i-zsUtCKch4"Keita Kawabe checks the beam centering and optic angle
on the VOPO platform - the heart of the squeezer - at LIGO
Hanford. We've made some modifications to the platformto accommodate paths to and from the new 300m filter
cavity. This particular optic he's holding the card in frontof is on the path between the squeezer and filter cavity, so
it's crucial there is minimal loss." - Georgia Mansell.

35

How it works: LIGO Controls and Data System (CDS)
LIGO uses laser light to search for gravitational waves, but how does the laser light get turned into
data that gets analyzed? Let’s follow the signal path from the detection photodiode to find out…
Laser light hits thephotodiode, creating ananalog electrical signalthat passes out of themain lab area to the
CDS electronics room.

The signal passes
through an anti-aliasing(A.A.) filter whichremoves frequencies toohigh for the analog-todigital converters (ADC).

The signal is digitized by
an ADC in the CDS inputoutput (IO) chassis. The digital
signal is sent over PCIe bus tothe computer.

The signal is read by the
Input/Output Processor (IOP) at
64kHz, where it can be routed to
instrument actuators and written
to shared memory. The User
Process reads/writes a downsampled signal at 16kHz from/tothe IOP.

The calibrated signal is sent
to the Data Acquisition System(DAQ), where it is combined withall the other CDS signals. The
signals are sent to the control
room by the Network Data Server(NDS) and written as frames by
the frame writer.

The frame files aresent to the site’s LIGO Data
Analysis System (LDAS),
which in turn sends to theCaltech LDAS and then on
to the LIGO-Virgo-Kagra
collaboration members foranalysis.
2021

36

by Dave Barker, illustrations by Paul Fulda

DCC number P2100332 https://dcc.ligo.org/P2100332

In the User Process
the digital signal isamplified and filtered to
produce the calibrated
gravitational wave signal.