The Messenger No. 183 | 2021 - European Southern Observatory
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ESO Strategy for the 2020s
High-precision Astrometric Studies with SPHERE
VEGAS – Exploring the Outskirts and Intra-cluster Regions of Galaxies
The Messenger
No. 183 | 2021
ESO, the European Southern Observa- Contents
tory, is the foremost intergovernmental
astronomy organisation in Europe. It is The Organisation
supported by 16 Member States: Austria, Waelkens, C. et al. – ESO Strategy for the 2020s 3
Belgium, the Czech Republic, Denmark,
France, Finland, Germany, Ireland, Italy, Instrumentation
the Netherlands, Poland, Portugal, Spain, Maire, A.-L. et al. – High-precision Astrometric Studies in Direct Imaging
Sweden, Switzerland and the United with SPHERE 7
Kingdom, along with the host country of Maud, L. et al. – Enhancing ALMA’s Future Observing Capabilities 13
Chile and with Australia as a Strategic Boffin, H. M. J. et al. – FORS-Up: May the FORS Be With Us
Partner. ESO’s programme is focussed For Another 15 Years 18
on the design, construction and opera- Coccato, L. et al. – Colour Transformations for ESO Near-Infrared Imagers 20
tion of powerful ground-based observing
facilities. ESO operates three observato- Astronomical Science
ries in Chile: at La Silla, at P
aranal, site of Iodice, E. et al. – The VST Early-type GAlaxy Survey: Exploring the Outskirts
the Very Large Telescope, and at Llano and Intra-cluster Regions of Galaxies in the Low-surface brightness Regime 25
de Chajnantor. ESO is the European
partner in the Atacama Large Millimeter/ Astronomical News
submillimeter Array (ALMA). Currently Burtscher, L. et al. – Report on the ESO Workshop “Ground-based Thermal
ESO is engaged in the construction of the Infrared Astronomy — Past, Present and Future” 31
Extremely Large Telescope. Sbordone, L. et al. – Report on the ESO Workshop “20th Anniversary of
Science Exploration with UVES” 37
The Messenger is published, in hardcopy Solarz, A. – Fellows at ESO 41
and electronic form, four times a year. Koutoulaki, M. K. – External Fellows at ESO 42
ESO produces and distributes a wide Personnel Movements 43
variety of media connected to its activities.
For further information, including postal
subscription to The Messenger, contact
the ESO Department of Communication at:
ESO Headquarters
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85748 Garching bei München, Germany
Phone +498932006-0
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The Messenger
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Copy-editing: Peter Grimley
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Design, Production: Jutta Boxheimer
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Unless otherwise indicated, all images in
The Messenger are courtesy of ESO,
except authored contributions which are
courtesy of the respective authors.
© ESO 2021
ISSN 0722-6691 Front cover: This image, taken with the VST, depicts the nebula
NGC 3199, which contains the extremely hot and massive Wolf–Rayet
star HD 89358. The star generates incredibly intense stellar winds
and outflows that smash into and sweep up the surrounding material,
contributing to NGC 3199’s twisted and lopsided morphology.
2 The Messenger 183 | 2021
The Organisation DOI: 10.18727/0722-6691/5227
ESO Strategy for the 2020s
Christoffel Waelkens 1 –E
xploit the unique capabilities of the in particular for its ongoing flagship pro-
Willy Benz 2 VLT Interferometer (VLTI) ject — the construction of the ELT.
Xavier Barcons 3 –B
uild an Extremely Large Telescope on
a competitive timescale At its 150th meeting in June 2019, the ESO
–C
ontinue the successful partnership Council mandated its Strategy Working
1
Institute of Astronomy, KU Leuven, between ESO and its community Group (SWG) to review the 2004 strategy
Belgium and to propose to Council an updated
2
Physics Institute, University of Bern, The success with which ESO was able to document that will guide the organisation
Switzerland reach these goals has been remarkable. over the next decade. The SWG members
3
ESO A few indicators are worth mentioning: included Council delegates Amina Helmi,
Isobel Hook, René Michelsen, Martin
–T he efficient operation of its facilities Thomé, Christoffel Waelkens (Chair), and
The stability that stems from ESO’s inter- coupled with its engagement with the ex-officio members Willy Benz (Council
governmental status provides the Organi- community has allowed ESO to remain President), Denis Mourard (Scientific
sation with the remarkable ability to plan a world-wide reference in ground- Technical Committee Chair), and Xavier
its future years. During its almost 60 based astronomy, as evidenced by Barcons (Director General).
years of history, the commitment of ESO more than 1000 refereed papers pub-
Member States towards long-term plans lished every year using data obtained Following the Council mandate, the
has enabled the resourcing and success- at ESO’s facilities 2. SWG met twice in the following eight
ful development of world-class projects –A LMA construction was completed months and status reports were given to
on timescales of over a decade, projects and operations are now in full swing. Council and discussed in the Committee
that have resulted in ESO’s building and The ESO region is the most highly of Council (CoC) meetings of October
operating some of the most powerful and oversubscribed in regard to ALMA 2019 and March 2020. A report detailing
scientifically productive ground-based observing time, and astronomers from the findings of the SWG was presented
observatories in the world. the ESO region are first authors of at the Council meeting in June 2020 and
about 40% of all papers published with a first draft of the final document dis-
Planning is therefore an essential activity. ALMA data. cussed by the Committee of Council in
Defining the best plan is a challenge that –T he 2nd generation of VLT instruments October 2020. Hence, despite the diffi-
requires considering a hierarchy of ele- has been completed and is in very culties caused by the inability to meet in
ments that starts with the mission (why high demand by the scientific commu- person during most of 2020, Council
we exist), followed by the vision (what we nity, eager to use the new capabilities invested a significant amount of time in
want to be), the values (what we believe offered b. A rolling plan to keep the thorough discussions about the best way
in and how we will behave) and finally the instrument complement at Paranal to extend the strategy that led to the
strategy (what we want to achieve). competitive is in place and resourced successes of the past decade and a half.
in ESO’s long-term plan 3. Finally, the document outlining the strat-
The ESO mission was described in the –T he VLTI infrastructure overhaul has egy for 2021–2030 was met with unani-
Convention1 which entered into force in been completed and the 2nd genera- mous approval at the 155th meeting of
1962 and has been ratified by all Member tion of VLTI instruments delivered with Council in December 2020 and is pre-
States. In today’s wording, ESO’s mission here again a very high demand from sented below.
is twofold: building world-class astro- the community c.
nomical observatories on the ground and –E SO’s ELT, the largest of its kind, has In parallel, Council mandated the execu-
fostering cooperation in astronomy. The been in construction since 2015 d and tive to generate a draft proposal for a
current ESO vision was implicitly adopted is fully funded e, and the first science statement of ESO’s values, taking into
back in 2004 when Council approved the observations are planned for the second account both internal and external input.
previous version of the strategy, which half of the decade. A proposal is expected to be submitted
positioned ESO to deliver the Extremely – Instrument development in partnership to Council for approval in 2021.
Large Telescope (ELT) while keeping with institutions in the Member States
Paranal and the Atacama Large Millimeter/ has continued for the VLT and the VLTI, Finally, Council also expressed the need
submillimeter Array (ALMA) at the forefront. and the same model has been adopted to develop a collective look at the ESO
The ESO strategy a approved by Council for the ELT instruments, with the first- vision, i.e, what the organisation should
at its 104th meeting in December 2004 light instrument already well underway. become in the long term, beyond the clear
was formulated around the following goals: strategic milestones agreed. Discussions
Given these outstanding achievements on this topic have been deferred to a
– Retain European astronomical leadership in meeting the goals defined in its 2004 post-pandemic era, when the necessary
– Complete ALMA and start its efficient strategy, the ESO Council decided in face-to-face meetings can be resumed.
scientific exploitation 2019 to revisit this strategy and the asso-
– Maintain the world-leading position of ciated goals in order to keep up the The rest of this article is taken verbatim
the VLT, and deploy its 2nd generation organisation’s momentum and success from the corresponding sections of docu-
of instruments rate over the next decade (2021–2030), ment ESO/Cou-1911 conf. as approved
The Messenger 183 | 2021 3
The Organisation Waelkens, C. et al., ESO Strategy for the 2020s
unanimously by the ESO Council in At the core of this success lies arguably and is expected to continue doing so
December 2020. not just the mere increase in the number during the coming decade, as new
of Member States but also the model of cutting edge technologies enable the
cooperation that has been developed development of new generations of
Preamble over the years, which strongly involves telescopes and instrumentation,
the community within the Member States – ESO’s role in astronomical research
Astronomy, arguably the oldest science, in all new large developments. This trans- has been steadily increasing through-
is currently enjoying a golden age. Curiosity- parent bottom-up process has led to a out the history of the Organisation,
driven astronomy has led over the last culture of trust and consensus between relying on highly competent and dedi-
50 years to the development of innovative the Member States greatly facilitating cated staff and fruitful collaborations
technology that has not only led to a better discussions, decisions, and the definition with the community,
understanding of the structure and evolu- of common goals or vision. – the successful collaboration between
tion of our Universe and our place within the ESO Member States on science
it but also found its way in applications Emerging from these successes and this and technology has been of paramount
permeating our daily life. From enhanced culture of consensus is a common vision importance for ESO to become the
image and sophisticated signal process- of the role of ESO for the decades to undisputed world leader in ground-
ing to the development of extreme adap- come: The Organisation should strengthen based optical-infrared astronomy, and
tive optics and data science, astronomy its position as the world-leading organisa- that furthering international collabora-
has been at the very root of innovation in tion in ground-based astronomy enabling tion beyond ESO’s boundaries has
ideas and technology. And yet, this devel- the best opportunities for new discover- led to a unique astronomical facility in
opment process is only just beginning! ies. As such, it should consolidate its sub/mm astronomy,
The coming decades will see revolutionary position as a key actor on the world-wide – this constructive collaboration between
observatories coming online covering the scene of existing and future large astro- the ESO Member States should remain
sky at different wavelengths and based nomical facilities regardless of wave- the driving force ensuring that ESO can
on equally revolutionary technologies, length or messenger by fostering collabo- continue its mission for future genera-
many of which are still in development. ration and synergy. For the next decade, tions, with an open view on new mem-
completing successfully the ELT with its bers and collaborations,
When ESO was founded in 1962, its mis- original powerful suite of instruments is
sion was to “establish and operate an clearly a central element of strengthening adopts the following strategic milestones
astronomical observatory in the southern this leadership. for ESO during the decade 2021–2030:
hemisphere, equipped with powerful
instruments, with the aim of furthering and The strategic goals define ways consist- – Implement and operate the ELT as
organising collaboration in astronomy”. ent with values prevailing in the Organisa- the world-leading extremely large tele-
For Europe, it was a revolution starting tion to achieve the vision above, which scope, by
with five member countries and relatively itself derives from the mission statement. a. Enabling the delivery of the fully com-
modest means compared to current As the SWG embarked on its task, it was pleted ELT on a competitive timescale;
standards. Today, with sixteen Member realized that while ESO’s mission state- b. Ensuring that the telescope is
States, one strategic partner, and Chile ment is clearly defined in the Convention equipped with the state-of-the-art
as the long-standing and trusted host and its vision shared among the members instrumentation necessary to meet
state of the telescopes, ESO builds and of Council, its values needed to be more its overarching science goals;
operates the most powerful and innova- explicitly defined. A separate document c. Engaging fully with the community to
tive infrastructure in the world for obser- defining ESO’s values is being prepared ensure the best use of the telescope
vational astronomy from the surface of the by the Executive for later discussion and and its instruments;
Earth. This infrastructure edge provided eventual approval by Council. Notwith- d. Preparing an ELT archive consistent
by ESO to the European astronomy com- standing this document, the resolution with ESO-wide standards.
munity translates into a world-wide scien- below defines the strategic goals which
tific leadership in many areas of astron- will allow ESO to reach its vision and fulfil – Ensure that the current facilities remain
omy. Concurrently, ESO has also pushed its mission over the next decade. at the forefront of astronomical investi-
for increased collaboration in astronomy gations, by
by taking ownership of the European par- e. Ensuring, in partnership with the
ticipation in ALMA and becoming one Resolution community, that VLT, VLTI, ALMA
of its main Parties, and should continue (with ESO’s partners), including their
with hosting and operating the southern ESO Council, considering the report of its instrumentation, continue to be
array of CTA. Other examples include Strategic Working Group and recognising state-of-the-art;
ESO taking responsibility in coordinating that: f. A llowing flexibility to adapt to the
national publications towards the Euro- changing scientific landscape includ-
pean journal ‘Astronomy and Astrophysics’ – astronomy continuously delivers scien- ing multi-messenger astronomy and,
or developing science and technology tific discoveries of fundamental impor- accordingly, towards new modes of
joint programmes with ESA. tance and with a broad societal impact, operation;
4 The Messenger 183 | 2021
g. Considering the role of La Silla for the – Retaining ESO’s leadership role in Links
ESO community within this evolving astronomy, by 1
The text of the ESO Convention can be found in
landscape; m. Reinforcing ESO as a stand-alone the book Basic Texts Convention and Protocols:
h. Maintaining a high-quality archive organisation with its specific www.eso.org/public/products/books/book_0017/
and data-management tools for all domains of excellence, with empha- 2
The ESO Publication Statistics is derived from
ESO telescopes, including ELT. sis on efficient governance, while the Telescope Bibliography (telbib) database and
can be found here: http://telbib.eso.org/pubstats_
ensuring ESO remains agile enough overview.php
– Ensure that the Organisation is pre- for collaborations with other organi- 3
See, for example, the Paranal Instrumentation
pared for future projects when financial sations on a case by case basis; Programme Plan and 6 Monthly report of
projections so permit, by n. Outreaching effectively to the citizens September 2020, presented to the ESO Council
at its December 2020 meeting: https://www.eso.
i. Engaging with the community in eval- in the Member States and beyond to org/public/about-eso/committees/cou/cou-155th/
uating the evolving international share with them ESO’s discoveries, external/Cou-1912_162ndFC_PIP-6month_final.pdf
astronomical landscape and to milestones and plans for the future;
assess the emerging science cases, o. Coordinating distributed centres of
taking advantage of the time ahead expertise within the ESO community Notes
to have an open view on the nature (e.g. ARC nodes, VLTI centres of a
The ESO Council resolution on Scientific Strategy
of future projects; expertise), and exchanging expertise from 2004 can be found in The Messenger, 2005,
j. Maintaining some resources for con- and training through studentships 119, 2.
b
ducting feasibility studies of promis- and fellowships as well as scientific Until end of 2020 the number of refereed papers
that have used data from 2nd generation VLT instru
ing projects and of their associated meetings; ments are: MUSE (494), KMOS (83), X-shooter
technologies; p. Conducting a technology develop- (796) and SPHERE (223).
k. Developing a future-oriented ment programme which enables c
After the commissioning of GRAVITY and
human-resource policy consistent developing and operating current MATISSE, VLTI observing time requests reach
200–250 nights per semester, a clearly higher
with the long-term perspectives that and future facilities, in collaboration
request than prior to P95 when the infrastructure
ensures the availability of the needed with institutes and industry in the upgrade began (F. Patat, ESO Observing
expertise; Member States; Programmes Office).
l. Being ready to start the selection q. E xploiting the scientific synergies d
ESO Council confirmed the approval of the ELT
process for a new project, possibly in with other organisations (ESA, GW Programme at its December 2012 meeting and
authorised the start of Phase 1 of the ELT
collaboration, later in the decade, detectors, CTA, SKA) exploiting facili- construction at the December 2014 meeting.
and only when the financial perspec- ties in a multi-messenger astronomi- e
At its December 2020 meeting, the ESO Council
tive is clear. cal environment. committed the funding for the entire set of
activities included in building the ELT and bringing
it into operation.
Juan Carlos Muñoz-Mateos/ESO
This beautiful photograph of the glimmering arch of
the Milky Way as seen through a crystal ball, shining
with billions of stars and entwined patches of gas
and dust, offers an intriguing perspective on our
home galaxy. It was taken by ESO’s Photo Ambas-
sador Juan Carlos Muñoz-Mateos, who hopes to
“help others feel what it’s like to look at the night sky
from one of the darkest and most barren locations
on Earth” — the Atacama Desert, home of ESO’s
Paranal Observatory.
The Messenger 183 | 2021 5
Instrumentation
The dome of the VLT Survey Telescope (VST)
takes centre stage in this panorama, dominating
the foreground as it sits beneath the arc of the
Milky Way. Numerous nebulae can be seen dotted
along the arc of our galaxy. The remarkable glow
of one of the Milky Way’s satellites, the Large
P. Horálek/ESO
Magellanic Cloud, can be seen above the VLT Unit
Telescope. While the sky is typically dark in the
Atacama Desert, a faint and colourful airglow often
makes it brighter, especially over the horizon.
Instrumentation DOI: 10.18727/0722-6691/5228
High-precision Astrometric Studies in Direct Imaging
with SPHERE
Anne-Lise Maire 1, 2 Figure 1. SPHERE images
ESO/Lagrange/SPHERE consortium and ESO/NASA/ESA
at different epochs of the
Gaël Chauvin 3
giant exoplanet β Pictoris b
Arthur Vigan 4 (left) and of arch-like disc
Raffaele Gratton 5 features in the debris disc
Maud Langlois 6 of AU Microscopii (bottom).
High-precision relative
Julien H. Girard 7
astrometry is fundam ental
Matthew A. Kenworthy 8 to measuring the slow
Jörg-Uwe Pott 2 motions observed, from
Thomas Henning 2 south-west to north-east
for the planet and away
Pierre Kervella 9
December 2014 April 2016 from the star for the disc
Sylvestre Lacour 9 features. In the bottom
Emily L. Rickman 7 panel, the scale bar at the
Anthony Boccaletti 9 top of the picture indicates
the diameter of the orbit
Philippe Delorme 3
of the planet Neptune in
Michael R. Meyer 10 the Solar System.
Mathias Nowak 11
Sascha P. Quanz 12
Alice Zurlo 13
1
University of Liège, Belgium
2
Max-Planck-Institute For Astronomy, November 2016 September 2018
Heidelberg, Germany
3
Institute for Planetary sciences and
Astrophysics, Grenoble, France
4
Aix Marseille University, CNRS, CNES,
LAM, France
5
INAF–Astronomical Observatory of
Padua, Italy
6
Centre de Recherche Astrophysique
de Lyon, Saint Genis Laval, France
7
Space Telescope Science Institute,
Baltimore, USA 2010 Hubble
8
Leiden Observatory, Leiden, the
Netherlands
9
Paris Observatory, Meudon, France
10
University of Michigan, Ann Arbor, USA
11
University of Cambridge, UK
12
ETH, Zürich, Switzerland
13
Diego Portales University, Santiago, 2011 Hubble
Chile
Orbital monitoring of exoplanetary and
stellar systems is fundamental for analys-
ing their architecture, dynamical stability
and evolution, and mechanisms of for-
mation. Current high-contrast extreme- 2014 VLT/SPHERE
adaptive-optics imagers like the Spectro-
Polarimetric High-contrast Exoplanet
REsearch instrument (SPHERE), the only a small fraction (< 20%) of the orbit, implemented for SPHERE has facilitated
Gemini Planet Imager (GPI) and the leading to degeneracies and biases in high-precision studies by its users since
Subaru Coronagraphic Extreme Adaptive the orbital parameters. Precise and it began operating in 2014. As the preci-
Optics/Coronagraphic High Angular robust measurements of the position of sion of exoplanet-imaging instruments
Resolution Imaging Spectrograph com- the companions over time are critical, is now reaching milliarcseconds and is
bination (SCExAO+CHARIS) explore requiring good knowledge of the instru- expected to improve with forthcoming
the population of giant exoplanets and mental limitations and dedicated observ- facilities, we initiated a community effort,
brown dwarf and stellar companions ing strategies. The homogeneous dedi- triggered by the SPHERE experience, to
beyond typically 10 au, but they cover cated calibration strategy for astrometry share lessons learned for high-precision
The Messenger 183 | 2021 7
Instrumentation Maire, A.-L. et al., High-precision Astrometric Studies in Direct Imaging with SPHERE
astrometry in direct imaging. A homo- with planet formation within circumstellar analysis of companion-disc dynamical
geneous strategy would strongly benefit discs, and are similar to the Solar Sys- interactions will also help to clarify which
the Very Large Telescope (VLT) commu- tem’s configuration. Larger eccentricities disc features (for example, spiral arms,
nity, in synergy with VLT Interferometer might be connected to star-like formation rings, clumps) can be reliably associated
instruments like GRAVITY/GRAVITY+ and mechanisms; or they may indicate sub with companions. Another research
future instruments like the Enhanced sequent dynamical planet-planet interac- field that has recently emerged involves
Resolution Imager and Spectrograph tions in multiple planetary systems that monitoring the motion of disc features
(ERIS) and the MCAO-Assisted Visible could explain the broad eccentricity distri- to discriminate between different produc-
Imager and Spectrograph (MAVIS), bution of exoplanets detected with the tion mechanisms (Figure 1, bottom).
and in preparation for the exploitation radial velocity technique. Another valua- For instance, misaligned inner discs or
of the Extremely Large Telescope’s ble output of orbital fits are predictions of close-in companions have been proposed
(ELT’s) first instruments: the Multi-AO positions. This is important for optimising to explain shadows cast on the outer
Imaging CAmera for Deep Observations follow-up observations at longer wave- discs in various protoplanetary discs.
(MICADO), the High Angular Resolution lengths (lower angular resolution) or with
Monolithic Optical and Near-infrared slit/fibre spectrometry.
Integral field spectrograph (HARMONI), The problem of astrometric biases
and the Mid-infrared ELT Imager and There is a strong synergy between direct
Spectrograph (METIS). imaging, radial velocities and absolute The advent of the first dedicated
astrometry for orbital fits. Firstly, it can exoplanet imaging instruments (SPHERE,
constrain the masses of the companions, GPI, SCExAO+CHARIS; for example,
Motivation which is a fundamental step towards the Beuzit et al., 2019) has improved the pre-
calibration of models of the evolution of cision of relative astrometric measure-
High-precision relative astrometry in young giant planets, brown dwarfs, and ments of young substellar companions,
direct imaging is crucial for various sci- low-mass stars. For imaged companions, from about 10 milliarcseconds to about
ence cases, beyond determining the most mass measurements come from 1–2 milliarcseconds.
orbital parameters of exoplanets, brown evolutionary models, which suffer from
dwarf companions or multiple stellar sys- large theoretical uncertainties (for exam- Measurements with higher precision are
tems. For exoplanet surveys (Langlois et ple, clouds and molecular opacities for more sensitive to underestimated biases.
al., 2020), it is instrumental in testing the the atmosphere, initial entropy for the for- These can be caused by the use of dif
nature of the faint sources detected near mation). Secondly, it allows for the break- ferent methods for the data analysis and/
the targeted stars (Figure 1, top). The ing of degeneracies in the orbital param- or calibration, our limited knowledge of the
fields of view used are typically too small eters. Radial velocities are degenerate thermo-mechanical stability of the instru-
for absolute astrometry, so astrometry with the inclination (essential to constrain ments, and the use of different instruments
relative to the targeted star is used. Multi- the mass), but the degeneracy is lifted by (after upgrades, for example). Given the
ple-epoch monitoring enables one to test using imaging and absolute astrometry. long orbital periods of the imaged compan-
whether the candidate companions are For multiple-companion systems, direct ions compared to the lifetimes of instru-
comoving, with proper and parallactic imaging is valuable for breaking the degen- ments, maximising the measured orbital
motions similar to those of the host star, eracies with radial velocities or absolute arc is vital if we are to derive more robust
by rejecting contamination by stationary astrometry that are due to the unknown orbital constraints. Underestimated biases
(or slowly moving with the local field) orbital phases, although analysis of the may also affect co-motion tests of candi-
background or foreground sources. More dynamical stability may also be used. date companions and trigger follow-up
precise measurements allow for faster Thanks to the 24-year baseline between observations by mistake, wasting tele-
confirmations. This approach requires a Hipparcos and Gaia DR2, absolute scope time.
second observation, for example from astrometry can now detect massive sub-
archival data. One must be aware of the stellar companions at the separations Figure 2 illustrates the importance of
possibility that a candidate companion probed by direct imaging. Bridging these a good knowledge of the biases in co-
having significant proper motion might techniques will increase with Gaia and motion tests of candidate companions
mimic a physical companion with orbital the ELT to closer-in and/or planetary-mass using different instruments. For a star
motion (for example; Nielsen et al., 2017). companions, with the prospect of a com- with many candidate companions, the
Multiple-epoch monitoring remains the plete view of planetary and stellar systems. biases can be estimated by assuming
most reliable approach to confirming a that most of them are background con-
candidate companion, and ultimately Direct imaging offers a unique means to taminants. For a star with a single can
resolving its orbital motion to confirm that simultaneously analyse companions and didate companion, a new observation
it is gravitationally bound. their birth environment, the circumstellar is required to reach a conclusion.
discs. Determining the orbits of the com-
Constraining the orbital parameters panions provides insights into potential Figure 3 illustrates the importance of
of a companion provides clues to its for- dynamical interactions. Such systems a good knowledge of the biases in
mation and dynamical history. Orbits provide valuable benchmarks for planet orbital fits for the exoplanet HIP 65426 b
with small eccentricities are consistent formation and migration models. The (Chauvin et al., 2017; Cheetham et al.,
8 The Messenger 183 | 2021
7000 No correction Correction = 0.5°
Separation (mas)
6800 250
Differential dec. (mas)
6600 200
150
2010 2011 2012 2013 2014 2015
Position angle (deg)
154 100
153
50
152 SPHERE
NACO 0
151
2010 2011 2012 2013 2014 2015 150 100 50 0 –50 –100 150 100 50 0 –50 –100
Epoch Differential RA (mas) Differential RA (mas)
Figure 2. Tests for companionship of companion compared to the evolution for a stationary back- with many candidate companions (red data points)
candidates detected around stars with SPHERE and ground contaminant (black curve with grey areas). for two values of the assumed correction angle to
NACO showing the importance of a good knowledge The motion of the point source does not follow the the north. The black curves show the motion for a
of the biases in relative astrometry for the interpreta- stationary background track, suggesting a physical stationary background contaminant. If most candi-
tion. The left panel shows the temporal evolution of companion. However, underestimated systematic date companions are assumed to be stationary
the separation from the star (top) and position angle uncertainties could account for the discrepancies. background contaminants, a correction angle to the
relative to north (bottom, taken as positive from The right panel shows the differential declination as north is needed to make their motion compatible
north to east) for a single candidate companion a function of the differential right ascension for a star with the expected behaviour.
2019). Low eccentricities and a bimodal et al., 2020); 2) an accurate determination To analyse the astrometric data and
distribution of the time at periapsis are of the instrument overheads and metrol- derive the calibration, we developed a
favoured when combining data obtained ogy; and 3) regular observations of fields tool (Maire et al., 2016) that is included
in 2016–2017 from SPHERE and the in stellar clusters for the astrometric cali- in the SPHERE Data Centre1. The distortion
Nasmyth Adaptive Optics System/COudé bration (Figure 4; Maire et al., 2016). is mainly due to the optics in SPHERE and
Near-Infrared CAmera (NAOS-CONICA, is stable in time (see Table). It produces
or NACO), whereas the eccentricity is not We chose fields in stellar clusters as main differences in the horizontal and vertical
well constrained and can be high and astrometric calibrators because the large pixel scales which amount to 6 milli-
the periapsis is in the future when fitting number of stars available allows for pre- arcseconds at 1 arcsecond. The astro-
SPHERE data obtained in 2016–2018. cise measurements. They also allow for metric requirement is 5 milliarcseconds
These discrepant results point to under- measuring the distortion from the tele- (the goal being 1 milliarcsecond).
estimated systematic uncertainties scope optics. We selected cluster fields
between the SPHERE and NACO data. with positions measured precisely by the Figure 5 shows the temporal evolution
Hubble Space Telescope, which has a of the pixel scale and correction angle
good absolute calibration. We further to the north (Maire et al., in preparation).
SPHERE astrometric strategy selected fields with a bright star for adap- Except for pixel scale measurements
tive optics (AO) guiding (R < ~ 13.5 mag). obtained during commissioning, SPHERE
A homogeneous and regular astrometric Finally, we repeatedly observed two fields has demonstrated a remarkable astro-
calibration is crucial to minimising the to cover the whole year, 47 Tucanae and metric stability over five years. The stand-
biases and analysing the astrometric sta- NGC 3603. We chose 47 Tucanae as the ard deviation for the pixel scale measured
bility over time. Good astrometric stability reference field because the catalogue on 47 Tucanae is 0.004 milliarcseconds
eases co motion tests and orbital moni- provides the stellar proper motions (Bellini pixel –1 and for the correction angle to
toring of imaged companions. It relaxes et al., 2014). Langlois et al. (2020) com- the north 0.04 degrees. These variations
the need to take calibration data close to pared the relative astrometry for widely- translate into uncertainties at 1 arcsec-
the science observations and reduces separated and bright candidate compan- ond of 0.33 and 0.70 milliarcseconds,
the calibration overhead at the telescope. ions observed with SPHERE and present respectively, which is within the baseline
in the Gaia DR2 catalogue. The mean off- astrometric requirements. We plan to
The astrometric strategy for the SpHere set in separation is –2.8 ± 1.5 milliarcsec- release the measurements in the SPHERE
INfrared survey for Exoplanets (SHINE) onds (3.9 milliarcseconds RMS) and in Target Data Base 2.
was devised by the consortium before position angle is 0.06 ± 0.04 degrees
commissioning and was subsequently (0.11 degrees RMS). The RMS measures The pixel scale and correction angle
refined. It relies on: 1) an observing proce- agree well with the expected uncertain- to the north have also been monitored
dure to precisely determine the star’s ties in these quantities in SPHERE data. in the ESO monthly calibration plan.
location behind the coronagraph (Langlois The SHINE astrometric fields have been
The Messenger 183 | 2021 9
Instrumentation Maire, A.-L. et al., High-precision Astrometric Studies in Direct Imaging with SPHERE
1.0 1.0 1.0
SPHERE (2016–2017) + NaCo
SPHERE (2016–2018)
0.8 0.8 0.8
Arbitrary units
Arbitrary units
Arbitrary units
0.6 0.6 0.6
0.4 0.4 0.4
0.2 0.2 0.2
0.0 0.0 0.0
1000 2000 3000 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150
Period (years) Eccentricity Inclination (degrees)
1.0 1.0 1.0
0.8 0.8 0.8
Arbitrary units
Arbitrary units
Arbitrary units
0.6 0.6 0.6
0.4 0.4 0.4
0.2 0.2 0.2
0.0 0.0 0.0
0 50 100 150 0 50 100 150 0 1000 2000 3000 4000
Ω (degrees) ω (degrees) T0
observed without the coronagraph. We Figure 3. (Above) Dis
tributions of the orbital
analysed the data at the SPHERE Data
parameters of the
Centre to compute an astrometric table exoplanet HIP 65426 b
for the reduction of the open-time data. using two different sets
About 80% of the observations were not of relative astrometric
measurements. A good
suitable for deriving a good calibration.
knowledge of the biases
Work is ongoing with the ESO staff to is mandatory in order
improve the setup of their observations. to derive unbiased con-
straints. The panels
show the period, eccen-
The astrometric calibration of the SPHERE
tricity, inclination, longi-
images also requires measurement of the tude of the node, and
offset angle of the pupil in pupil-tracking argument and time at
mode. The pupil-tracking mode allows for periapsis, from left to
right and top to bottom.
subtracting the aberrations in the images
that are due to the telescope and the
instrument. We monitored this parameter
in 2014–2016 and showed that it is stable.
Work is ongoing to monitor it in the ESO
calibration plan.
In contrast, the astrometric calibration
for NACO was heterogeneous, irregular,
and mostly left to the observing teams.
NACO also underwent technical interven-
tions to commission new observing modes Figure 4. (Left) SPHERE
or fix issues, and was moved to another image of the 47 Tucanae
field used for the astro-
Unit Telescope of the VLT. This resulted metric calibration. The
in poor astrometric stability, making the field of view is ~ 11 arc
use of the data for high-precision relative seconds on one side.
10 The Messenger 183 | 202112.30 –1.5
12.28 –1.6
Correction angle to north (degrees)
Pixel scale (mas pixel –1)
12.26 –1.7
12.24 –1.8
12.22 NGC 6380 –1.9 NGC 6380
NGC 3603 NGC 3603
OrionB1–B4 OrionB1–B4
47 Tuc 47 Tuc
12.20 – 2.0
2014 2015 2016 2017 2018 2019 2020 2014 2015 2016 2017 2018 2019 2020
Epoch Epoch
Figure 5. Evolution of the pixel scale (left) and cor- and stellar companions next to stars. It in several systems, including systems
rection angle to the north (right) of SPHERE. A good
has been used for about 20 orbital stud- with a brown dwarf within the cavity of the
instrument stability is mandatory for high-precision
relative astrometry over time because it reduces ies, in combination with other imaging, debris disc. HR 2562 B could carve the
potential s ystematic uncertainties. Fewer measure- radial velocity, and/or absolute astrometric disc cavity, whereas another companion
ments are shown for the pixel scale because it measurements. may be needed around HD 206893. Disc
depends on the filter and coronagraph c onfiguration.
features were monitored, such as the
For the right panel, the dotted-dashed vertical line
indicates the epoch when the time reference issue The orbital analyses of the exoplanets arch-like features moving away from the
was solved (Maire et al., 2016). All previous measure- β Pictoris b (Lagrange et al., 2019) and star AU Microscopii. The current scenario
ments were corrected. The dashed horizontal line 51 Eridani b (Maire et al., 2019) are good involves dust produced by an unseen
shows the weighted mean of all the measurements.
examples of where biases between dif- parent body and expelled by the stellar
ferent instruments had to be dealt with. wind. The rotation of the spiral arms of
astrometry more difficult. The limitations β Pictoris b was monitored with NACO MWC 758 was shown to be compatible
encountered with NACO were taken and then SPHERE. It was recovered in with a planet-driven mechanism.
into account in the astrometric strategy September 2018 after conjunction with
of SPHERE. the star. The SPHERE data are now
probing the north-east part of the orbit, Future astrometric studies with direct
Required separation precision (mas) 5 (goal: 1) which was only covered by one NACO imaging facilities at ESO
Required position angle precision (deg) 0.2 measurement in 2003, and they favour
low eccentricities. 51 Eridani b was moni- Further monitoring of known compan-
tored for three years. Coupled with GPI ions and disc features will be important
Achieved precision calibration pixel
scale at 1″ (mas)
0.33 data, orbital curvature was detected in for refining their orbits and their formation
this system for the first time and the fit mechanisms, respectively. Moreover,
Achieved precision calibration
distortion at 1″ (mas)
0.2 suggests a high eccentricity (~ 0.3–0.6). Gaia is expected to detect a large number
Achieved precision calibration angle
A high eccentricity hints at dynamical of giant exoplanets. Young exoplanets
0.04 interactions that perturbed the orbit of detected from acceleration measurements
to north (deg)
Achieved precision calibration angle the planet, possibly by another as-yet- will be prime targets for imaging, to con-
0.06
pupil tracking (deg) undetected planet. firm and firmly constrain their orbits and
masses. This large sample of exoplanets
The orbital predictions were also used beyond a few au will allow for statistical
for GRAVITY observations to get spectra analyses of the distributions of eccentrici-
Highlights from SPHERE results at longer wavelengths and higher resolu- ties and relative inclinations to the stellar
tions (2.0–2.4 μm, R ~ 500) compared equatorial planes (for multiple-planet sys-
Thanks to the good astrometric preci- to SPHERE (1.0–2.3 μm, R ~ 50) and to tems and also mutual inclinations). Such
sion and stability of SPHERE, most get exquisite astrometry (~ 30 times more analyses will be crucial to understanding
users rely on the calibration derived by precise), confirming the robustness of their formation and evolution, and the
the instrument consortium. SPHERE has the SPHERE calibration plan. Companion- relation between planet and binary-star
enabled the discovery of 15 substellar disc dynamical interactions were studied formation mechanisms.
The Messenger 183 | 2021 11Instrumentation Maire, A.-L. et al., High-precision Astrometric Studies in Direct Imaging with SPHERE
The next step for exoplanet imaging will tion, parallel observations could be used de Paris/LESIA (Paris), and Observatoire de Lyon,
also supported by a grant from Labex OSUG@2020
be made with the ELT and its first three to check the astrometric consistency.
(Investissements d’avenir — ANR10 LABX56).
instruments: MICADO, HARMONI, and GRAVITY could be used to test/validate SPHERE is an instrument designed and built by a
METIS. They will access smaller planet- the absolute calibration of coronagraphic consortium consisting of IPAG (Grenoble, France),
star separations, down to 1 au, to detect instruments, thanks to the absolute cali- MPIA (Heidelberg, Germany), LAM (Marseille,
France), LESIA (Paris, France), Laboratoire Lagrange
predominantly giant exoplanets. Thanks bration provided by its internal metrology
(Nice, France), INAF–Osservatorio di Padova (Italy),
to the combination of increased angular system (Lacour et al., 2014). O bservatoire de Genève (Switzerland), ETH Zurich
resolution and larger collecting aperture, (Switzerland), NOVA (the Netherlands), ONERA
diffraction-limited ELT observations will We recently started an initiative between (France), and ASTRON (the Netherlands), in collabo-
ration with ESO. SPHERE was funded by ESO, with
at the same time access smaller angular the SPHERE team and the teams in charge
additional contributions from CNRS (France), MPIA
separations and achieve higher astrometric of the high-contrast imaging modes of (Germany), INAF (Italy), FINES (Switzerland), and
precision at angular separations acces forthcoming ESO exoplanet imaging facil- NOVA (the Netherlands). SPHERE received funding
sible to 8-metre-class imagers. MICADO ities at the VLT/I and ELT to share the from the European Commission Sixth and Seventh
Framework Programmes as part of the Optical Infra-
and HARMONI will be sensitive to young SPHERE experience and the lessons
red Coordination Network for Astronomy (OPTICON)
planets, whereas METIS will reach mature learned in the field of astrometric charac- under grant number RII3-Ct-2004-001566 for FP6
planets. Before the ELT, ERIS, GRAVITY+, terisation of exoplanets and discs. We (2004–2008), grant number 226604 for FP7 (2009–
and a potential SPHERE upgrade will be firmly believe that this offers the oppor 2012), and grant number 312430 for FP7 (2013–2016).
operational on the VLT/I. ERIS will be suit- tunity to federate our community: 1) to
able for imaging giant exoplanets around revisit past studies through archival data References
young stars, and more mature giant exo mining, 2) to push the calibration strategy
planets which are too faint for the SPHERE and performance of current instruments Bellini, A. et al. 2014, ApJ, 797, 115
Beuzit, J.-L. et al. 2019, A&A, 631, A155
AO system. GRAVITY+ will have better in operation, and 3) to share this exper-
Chauvin, G. et al. 2017, A&A, 605, L9
sensitivity than GRAVITY to access tise with consortia of forthcoming instru- Cheetham, A. et al. 2019, A&A, 622, A80
mature exoplanets. ments at the VLT/I and ELT to optimally Lacour, S. et al. 2014, A&A, 567, A75
prepare their scientific exploitation. We Lagrange, A.-M. et al. 2019, A&A, 621, L8
Langlois, M. et al. 2020, A&A, in press,
A joint and homogeneous strategy shared expect to prepare a workshop on this
arXiv:2103.03976
by the exoplanet imaging facilities at ESO topic in the future. Maire, A.-L. et al. 2016, Proc. SPIE, 9908, 990834
will enhance their use for high-precision Maire, A.-L. et al. 2019, A&A, 624, A118
astrometry, by minimising biases. The Nielsen, E. L. et al. 2017, AJ, 154, 218
successful calibration plan implemented Acknowledgements
for SPHERE could be applied and adapted A. L. Maire acknowledges financial support from the Links
to these instruments. If proposed by future European Research Council under the European
instrument consortia, interactions with Union’s Horizon 2020 research and innovation pro-
1
gram (Grant Agreement No. 819155). We thank The SPHERE Data Centre: https://sphere.osug.fr/
ESO would be valuable to check whether
Leonard Burtscher for useful comments. This work spip.php?article45&lang=en
such a calibration plan could be adopted. has made use of the SPHERE Data Centre, operated 2
The SPHERE Target Database: http://cesam.lam.fr/
As SPHERE is expected to be operational by OSUG/IPAG (Grenoble), PYTHEAS/LAM/CeSAM spheretools
during the first years of the ELT’s opera- (Marseille), OCA/Lagrange (Nice), Observatoire
ESO/Bohn et al.
This image, captured by the SPHERE instrument
on ESO’s Very Large Telescope, shows the star
TYC 8998-760-1 accompanied by two giant
exoplanets, TYC 8998-760-1b and TYC 8998-760-1c
(annotated with arrows). This is the first time astron-
omers have directly observed more than one planet
orbiting a star similar to the Sun.
12 The Messenger 183 | 2021Instrumentation DOI: 10.18727/0722-6691/5229
Enhancing ALMA’s Future Observing Capabilities
Luke Maud 1 We focus in particular on opening up Unfortunately, ALMA cannot simply test
Eric Villard 1, 2 high-frequency observing using ALMA’s a new observing mode on the telescope
Satoko Takahashi 2, 3 longest baselines, which offers the and thereafter open it directly to the com-
Yoshiharu Asaki 2, 3 highest possible angular resolution. munity. This is because all parts of the
Tim Bastian 4 observing chain involving the so-called
Paulo Cortes 2, 4 subsystems (Control software, Observing
Geoff Crew 5 Extension and optimisation of new Tool [OT], Scheduling, Quality Assurance
Ed Fomalont 2, 4 capabilities [QA], Pipeline, and Archive, to name just
Antonio Hales 2, 4 a few) must be up to the task. Before
Shun Ishii 2, 3 The global effort of adding new capa opening a new capability to the commu-
Lynn Matthews 5 bilities to ALMA is referred to as Exten- nity, ALMA must be able to demonstrate
Hugo Messias 2 sion and Optimisation of Capabilities the entire workflow: the correct creation
Hiroshi Nagai 6 (EOC). EOC was the natural progression of the observation files; successful, error-
Tsuyoshi Sawada 2, 3 after moving away from initial tests when free observations; data reduction — first
Gerald Schieven 7 ALMA was commissioned. During the using manual scripts and thereafter with
Masumi Shimojo 6 final years of construction and during the ALMA Pipeline; and finally data and
Baltasar Vila-Vilaro 2 Cycle 0 operations, almost ten years ago, product ingestion into the ALMA Archive
Andy Biggs 1 the development of new modes was such that it can be delivered to any Prin-
Dirk Petry 1 called Commissioning and Scientific Veri- cipal Investigator (PI) and used in any
Neil Phillips 1 fication (CSV). CSV was conducted to future Archive mining exercises.
Rosita Paladino 8 ensure that the capabilities offered were
fully operational and valid. Following this, The ObsMode process therefore follows
with ALMA as a fully operational tele- a yearly structure and is aligned with
1
ESO scope, testing as part of EOC activities ALMA observing cycles. For example,
2
Joint ALMA Observatory, Santiago, Chile has continued as an ALMA-wide effort the majority of work in 2021 began in
3
National Astronomical Observatory encompassing all partners1: the Joint October 2020 and will finish in October
of Japan, Santiago, Chile ALMA Observatory (JAO) in Chile and the 2021 (Figure 1). This system includes a
4
National Radio Astronomy Observatory, ALMA Regional Centres (ARCs) in East two-year lead time, such that any capabil-
Charlottesville, USA Asia, North America and Europe. In ity planned for release in Cycle 9 (due
5
MIT Haystack Observatory, Westford, Europe there are also contributions from to start in October 2022) must be fully
USA the ARC network (see Hatziminaoglou tested and verified in Cycle 7 a. Final tests
6
National Astronomical Observatory et al., 2015). The entire EOC effort, includ- during the first half of Cycle 8, before the
of Japan, Tokyo, Japan ing all coordination, planning and the Cycle 9 Call-for-Proposals (CfP) pre-
7
National Research Council of Canada intricate steps involved, is led by the JAO announcement is made, mark the final
Herzberg Astronomy & Astrophysics (see Takahashi et al., 2021). date to confirm the readiness of a capabil-
Programs, Victoria, Canada ity for scientific operations. The main con-
8
INAF–Institute of Radioastronomy, In this article we provide an overview of siderations throughout the year include:
Bologna, Italy EOC, and what features might be
expected in the coming cycles, with a – Proposed capabilities and priorities:
specific focus on pushing ALMA to A list is drawn up of capabilities aimed
With each observing cycle at the achieve the highest angular resolutions at science operations two years later.
Atacama Large Millimeter/submillimeter possible (a study involving significant input Given the ten years of ALMA operations,
Array (ALMA) new features and observ- from the European ARC). We also highlight there is a natural continuation from
ing modes are offered. Here we provide how the ALMA community benefits from previous years. ALMA management,
some background about how these each capability potentially offered. together with the science and operations
new capabilities are tested and then teams, arrange and discuss the priorities
made available to ALMA users. These with the ALMA Science Advisory Com-
activities help to drive the cutting-edge ALMA’s process for offering new mittee (ASAC), which confirms that
science conducted with ALMA and to capabilities these align with the community input b.
maintain ALMA’s position as the foremost – Initial capability plan: Plans are made
interferometric array operating at milli- Behind the scenes, the process that by the expert teams leading each
metre and submillimetre wavelengths. makes new capabilities possible is the capability. These must provide a tech-
ObsMode process (Takahashi et al., 2021), nical summary, identify the on-sky time
which is led and coordinated by the JAO. requirements, and detail each team
ObsMode Lead: Satoko Takahashi The intention of the ObsMode process is member’s role. Most importantly, the
ObsMode Technical Leads: Satoko Takahashi, to enable all observing modes that ALMA plans set the criteria for declaring a
Yoshiharu Asaki, Tim Bastian, Paulo Cortes, Geoff
Crew, Ed Fomalont, Antonio Hales, Shun Ishii, Lynn
was designed to support, as well as any particular capability as ready.
Matthews, Hiroshi Nagai, Tsuyoshi Sawada, Gerald additional ones identified since construc- – Test Observations: EOC observations
Schieven, Masumi Shimojo, Baltasar Vila-Vilaro tion began. are scheduled to have a minimal impact
The Messenger 183 | 2021 13Instrumentation Maud, L. et al., Enhancing ALMA’s Future Observing Capabilities
Figure 1. Simplified
schematic of the gen-
CfP pre-announcement
eral ObsMode timeline
Prioritisation process
focused around the
– Test plans year 2021 (Cycle 7 —
capabilities begins
– Continual meetings restarted because of the
Cycle with new
Assessment of
possible new
– Observations and data reduction pandemic), starting from
capabilities
– Technical reporting the identification of new
– Requirements to subsystems capabilities at the end
– Documentation CfP of the previous year and
leading up to the point
where they are planned
Deployment of offline and online software
for use in Cycle 9, two
features for new capabilities
years later. In reality the
EOC is a continual pro-
cess as there is an intrin-
ne
ne
ay
ay
ly
ly
ec
ec
g
g
g
p
p
ov
p
ov
ar
ar
b
b
n
n
ct
ct
ct
r
r
Ap
Ap
... ...
Au
Au
Au
Se
Se
Se
Fe
Fe
Ja
Ja
Ju
Ju
Ju
Ju
M
M
O
O
O
M
M
N
N
D
D
sic overlap of testing and
development between
2020 2021 — Cycle 7 2022 — Cycle 8 2023 the years.
on standard science observations, being fully detail and explain any newly discs. For extragalactic targets, parsec
conducted in small time windows or offered capabilities. scales could be resolved for sources
when science observations cannot take within 40 Mpc, offering unprecedented
place. Where possible, observations use details of galactic structures.
Scheduling Blocks (SBs) constructed Focusing on high frequencies and long
with the OT, however some tests baselines with band-to-band (B2B) What is B2B? Band-to-Band (B2B) is a
require custom command-line scripts phase-referencing technique in which
to operate ALMA in a manual mode. The European ARC is particularly the phase calibrator, interleaved between
– Data reduction and problem reporting: involved with EOC activities to offer high- the science target and used to correct for
Custom scripts are employed, using frequency observations (Bands 8, 9, and atmospheric variations (see, for example,
the Common Astronomy Software 10, > 385 GHz) using the most extended Asaki et al., 2020a), is actually observed
Applications package (CASA; McMullin, array configurations (C-8, C-9 and C-10, at a frequency lower than the observing
2007) reduction software with extra with maximal baselines of ~ 8.5, ~ 13.9 frequency of the science target. The
analysis and heuristics. Extra system- and ~ 16.2 kilometres, respectively). The-
level stability and data-validity checks oretically, the highest frequencies cou- Figure 2. Schematic of the main observing scheme
are also made. EOC teams aim to pro- pled with the longest-baseline array would employed for B2B test observations (Asaki et al.,
vide QA-like reduction workflows to achieve an angular resolution of 5 milli- 2020a). The instrumental band offsets are solved
enable an easier transition to science arcseconds. This translates to sub-au using the Differential Gain Calibration (DGC) blocks,
while the centre of the schematic shows the phase
operations. scales for sources within 200 parsecs referencing for the calibrator and target alternating
– Technical readiness: In September and and would provide the most detailed between low- and high-frequency bands. The time
October the EOC teams report their submillimetre picture of protoplanetary axis is not to scale.
findings and provide a technical report
to specific expert reviewers. These
Differential Gain Calibration block Differential Gain Calibration block
reports are used for a readiness assess-
ment to confirm whether the capability
meets the initial readiness criteria.
– Subsystem impact: Requirements are
created continually throughout the year B2B phase referencing block
for the subsystems involved. Although
developments are continual, a capability
tಿ t
can only be declared operational when
all subsystems integrate the required tswt
modifications. Examples of subsystem Observing time
changes are: (1) the addition of new OT
features that allow SBs to be generated,
and (2) modification of the QA2 process Low-frequency DGC source scan High-frequency DGC source scan
to provide the correct reduction path
(see, for example, Petry et al., 2020).
Low-frequency phase calibrator scan High-frequency science target source scan
– Documentation: Before the CfP is
issued, ALMA provides users with a
Proposer’s Guide 2 and a Technical High-frequency calibration scan (e.g., system temperature measurement, pointing)
Handbook 3. These documents must
14 The Messenger 183 | 2021You can also read
