investigators per country. Ireland and the United Kingdom have no identified
contributions to the instrument or the ground segment but contribute to
scientific activities. None have co-investigators. Note that people identified
as contractors, observers or associates, in the Consortium database are not
included as active members of the X-IFU Consortium.

##  9 Communication and outreach

The X-IFU internal communication is managed through various tools, such as the
Document Management System CapLinked, Teamwork for action management, and
Formsite for online forms and surveys. The external communication is achieved
through a dedicated web site222http://x-ifu.irap.omp.eu, which is the gate for
accessing X-IFU related resources, e.g. response files. The web site is
providing access to outreach material and links to the social media, e.g. a
YouTube channel dedicated to X-IFU in which movies explaining X-IFU are
available in several languages. Outreach activities are coordinated with the
Athena community office[88]. The Consortium database, more than 300 entries,
is managed through Python, interfacing with the web site (where the various
bodies of the Consortium are listed).

##  10 X-IFU and its environmental footprint

As shown above, the X-IFU is a rather complex instrument, involving very
advanced technologies, large resources, and a large number of partners spread
all across the world. X-IFU is being developed right at the time when it is
becoming very clear that without an immediate and drastic reduction of our
emissions (by at least 50% by 2030), across all sectors, the objective of
limiting global warming to 1.5 degrees will not be reached. X-IFU is also
developed when the need for building new large scientific infrastructures
having major environmental impacts is being debated within the community[89],
this very same community that should lead by example [90]. In this context, a
life cycle assessment (LCA) of X-IFU is being performed to evaluate the global
footprint of developing X-IFU along its complete life cycle. The LCA will
identify the contribution of all life cycle phases (from cradle to grave) to
several environmental impacts, including global warming (in particular CO2
emissions), waste, water consumption, raw materials consumption, human health,
and biodiversity. The idea is simply to identify hot spots and take corrective
actions whenever possible, while not jeopardizing the ultimate success of the
project. X-IFU has already committed to reduce significantly its global travel
footprint[91], starting even in the pre-covid era, but the LCA will enable us
to go one step further by identifying those actions in our daily activities
that can lead to substantial reductions of our impact, such as switching off
test equipments over night, and sharing resources and infrastructures wherever
possible. At the time of this writing, the assessment has not yet been
completed, but the data have been collected from all sub-systems making up the
X-IFU. There has been enthusiastic support for the tedious data collection,
which is now extrapolated when partial and properly modeled with a dedicated
LCA software. There is great hope that the quality of the assessment will
enable clear guidelines to be formulated for building the X-IFU, while
lowering its environmental impact.

##  11 From the SRR onward

The discovery of an unanticipated cost increase of Athena by the ESA executive
now imposes us the challenge of a design-to-cost exercise to bring the cost of
Athena within an envelope affordable by the ESA science program ($\sim 1.3$
G€). This exercise should preserve the flagship capabilities of the Athena
mission. The X-IFU team, including its international partners, has the
expertise and is committed to enter this exercise in a pro-active way,
focusing first on the way to simplify the cooling chain. Let alone for feeling
accountable for the tax-payer money already spent, the scientific and
technical expertise developed over the years should not be wasted, and will be
a critical input of the design-to-cost exercise, which will start from the
X-IFU design presented at the SRR.

The extent by which X-IFU will change will also depend on the changes applying
to the overall telescope and spacecraft, which are under ESA responsibility. A
close collaboration between ESA and the instrument teams will be required for
Athena to retain the capability to reach most, if not all, the scientific
objectives spelled out for the Hot and Energetic Universe, and whose
priorities have been repeated constantly since its original formulation in
2013.

##  12 Conclusions

X-IFU entered its system requirement review with a consolidated design and
performance budgets understood. As an indication of the extent of the work
done for the SRR, the data pack produced by the team consisted of over 100
documents and of more than 5000 pages. This paper aimed at summarizing this
documentation, providing a reference point for the upcoming design-to-cost
exercise. We, as a team, will use all our knowledge for X-IFU to maintain
flagship capabilities in spatially resolved high resolution X-ray
spectroscopy, as to enable most of the original X-IFU related scientific
objectives of the Athena mission to be retained.

##  13 Acknowledgments

This paper is based on the documentation assembled by the CNES project team
and the Consortium partners for the X-IFU System Requirement Review, which has
started at the end of June, albeit with reduced objectives (the review will be
completed in September 2022). DB wishes to thank the CNES Project and Support
teams for continuing the preparation of the SRR data pack, during the
disruptive and unfortunate events that happened to Athena, which could have
led to the termination of X-IFU. There is no doubt that their efforts will be
rewarded in the upcoming design-to-cost exercise. DB would also like to
express his gratitude to the CNES Management (Philippe Baptiste, President),
Lionel Suchet (Chief Operating Officer), Caroline Laurent (Director of orbital
systems and applications), Philippe Lier (Deputy-Director of orbital systems
and applications), the French ESA SPC delegation (Olivier La Marle and
Juliette Lambin) for their unfailing support to X-IFU. This support was
instrumental in preserving an X-IFU on the new Athena mission and will remain
precious in the upcoming phase of the reformulation of the mission. Special
thanks to all the SPC delegations which supported the objective of keeping a
flagship X-ray observatory in the ESA Science Program. DB is also thankful to
Gilles Bergametti (President of the CNES Comité des Programmes Scientifiques,
CPS), Athena Coustenis (President of the CNES Comité d’évaluation de la
recherche et de l’exploration spatiale, CERES) and Pierre-Olivier Petrucci
(President of the Programme National des Hautes Energies) for their support
and for providing the feedback from the French scientific community at large.
The French contribution to X-IFU is funded by CNES, CNRS and CEA. This work
has been also supported by ASI (Italian Space Agency) through the Contract
2019-27-HH.0, and by the ESA (European Space Agency) Core Technology Program
(CTP) Contract No. 4000114932/15/NL/BW and the AREMBES - ESA CTP
No.4000116655/16/NL/BW. This publication is part of grant RTI2018-096686-B-C21
funded by MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making
Europe”. This publication is part of grant RTI2018-096686-B-C21 and
PID2020-115325GB-C31 funded by MCIN/AEI/10.13039/501100011033.

We wish to thank an anonymous referee for a very careful reading of our
manuscript, and for providing helpful comments.

##  14 Declarations

There is no conflict of interest.

## References

  * [1] Nandra, K., Barret, D., Barcons, X., Fabian, A., den Herder, J.-W., Piro, L., Watson, M., Adami, C., Aird, J., Afonso, J. M., Alexander, D., Argiroffi, C., Amati, L., Arnaud, M., Atteia, J.-L., Audard, M., Badenes, C., Ballet, J., Ballo, L., Bamba, A., Bhardwaj, A., Stefano Battistelli, E., Becker, W., De Becker, M., Behar, E., Bianchi, S., Biffi, V., Bîrzan, L., Bocchino, F., Bogdanov, S., Boirin, L., Boller, T., Borgani, S., Borm, K., Bouché, N., Bourdin, H., Bower, R., Braito, V., Branchini, E., Branduardi-Raymont, G., Bregman, J., Brenneman, L., Brightman, M., Brüggen, M., Buchner, J., Bulbul, E., Brusa, M., Bursa, M., Caccianiga, A., Cackett, E., Campana, S., Cappelluti, N., Cappi, M., Carrera, F., Ceballos, M., Christensen, F., Chu, Y.-H., Churazov, E., Clerc, N., Corbel, S., Corral, A., Comastri, A., Costantini, E., Croston, J., Dadina, M., D’Ai, A., Decourchelle, A., Della Ceca, R., Dennerl, K., Dolag, K., Done, C., Dovciak, M., Drake, J., Eckert, D., Edge, A., Ettori, S., Ezoe, Y., Feigelson, E., Fender, R., Feruglio, C., Finoguenov, A., Fiore, F., Galeazzi, M., Gallagher, S., Gandhi, P., Gaspari, M., Gastaldello, F., Georgakakis, A., Georgantopoulos, I., Gilfanov, M., Gitti, M., Gladstone, R., Goosmann, R., Gosset, E., Grosso, N., Guedel, M., Guerrero, M., Haberl, F., Hardcastle, M., Heinz, S., Alonso Herrero, A., Hervé, A., Holmstrom, M., Iwasawa, K., Jonker, P., Kaastra, J., Kara, E., Karas, V., Kastner, J., King, A., Kosenko, D., Koutroumpa, D., Kraft, R., Kreykenbohm, I., Lallement, R., Lanzuisi, G., Lee, J., Lemoine-Goumard, M., Lobban, A., Lodato, G., Lovisari, L., Lotti, S., McCharthy, I., McNamara, B., Maggio, A., Maiolino, R., De Marco, B., de Martino, D., Mateos, S., Matt, G., Maughan, B., Mazzotta, P., Mendez, M., Merloni, A., Micela, G., Miceli, M., Mignani, R., Miller, J., Miniutti, G., Molendi, S., Montez, R., Moretti, A., Motch, C., Nazé, Y., Nevalainen, J., Nicastro, F., Nulsen, P., Ohashi, T., O’Brien, P., Osborne, J., Oskinova, L., Pacaud, F., Paerels, F., Page, M., Papadakis, I., Pareschi, G., Petre, R., Petrucci, P.-O., Piconcelli, E., Pillitteri, I., Pinto, C., de Plaa, J., Pointecouteau, E., Ponman, T., Ponti, G., Porquet, D., Pounds, K., Pratt, G., Predehl, P., Proga, D., Psaltis, D., Rafferty, D., Ramos-Ceja, M., Ranalli, P., Rasia, E., Rau, A., Rauw, G., Rea, N., Read, A., Reeves, J., Reiprich, T., Renaud, M., Reynolds, C., Risaliti, G., Rodriguez, J., Rodriguez Hidalgo, P., Roncarelli, M., Rosario, D., Rossetti, M., Rozanska, A., Rovilos, E., Salvaterra, R., Salvato, M., Di Salvo, T., Sanders, J., Sanz-Forcada, J., Schawinski, K., Schaye, J., Schwope, A., Sciortino, S., Severgnini, P., Shankar, F., Sijacki, D., Sim, S., Schmid, C., Smith, R., Steiner, A., Stelzer, B., Stewart, G., Strohmayer, T., Strüder, L., Sun, M., Takei, Y., Tatischeff, V., Tiengo, A., Tombesi, F., Trinchieri, G., Tsuru, T. G., Ud-Doula, A., Ursino, E., Valencic, L., Vanzella, E., Vaughan, S., Vignali, C., Vink, J., Vito, F., Volonteri, M., Wang, D., Webb, N., Willingale, R., Wilms, J., Wise, M., Worrall, D., Young, A., Zampieri, L., In’t Zand, J., Zane, S., Zezas, A., Zhang, Y., and Zhuravleva, I., “The Hot and Energetic Universe: A White Paper presenting the science theme motivating the Athena+ mission,” arXiv e-prints , arXiv:1306.2307 (June 2013).
  * [2] Barret, D., Nandra, K., Barcons, X., Fabian, A., den Herder, J. W., Piro, L., Watson, M., Aird, J., Branduardi-Raymont, G., Cappi, M., Carrera, F., Comastri, A., Costantini, E., Croston, J., Decourchelle, A., Done, C., Dovciak, M., Ettori, S., Finoguenov, A., Georgakakis, A., Jonker, P., Kaastra, J., Matt, G., Motch, C., O’Brien, P., Pareschi, G., Pointecouteau, E., Pratt, G., Rauw, G., Reiprich, T., Sanders, J., Sciortino, S., Willingale, R., and Wilms, J., “Athena+: The first Deep Universe X-ray Observatory,” in [SF2A-2013: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics ], Cambresy, L., Martins, F., Nuss, E., and Palacios, A., eds., 447–453 (Nov. 2013).
  * [3] Barcons, X., Nandra, K., Barret, D., den Herder, J. W., Fabian, A. C., Piro, L., Watson, M. G., and the Athena Team, “Athena: the X-ray observatory to study the hot and energetic Universe,” in [Journal of Physics Conference Series ], Journal of Physics Conference Series 610, 012008 (May 2015).
  * [4] Barcons, X., Barret, D., Decourchelle, A., den Herder, J. W., Fabian, A. C., Matsumoto, H., Lumb, D., Nandra, K., Piro, L., Smith, R. K., and Willingale, R., “Athena: ESA’s X-ray observatory for the late 2020s,” Astronomische Nachrichten 338, 153–158 (Mar. 2017).
  * [5] Barret, D., Decourchelle, A., Fabian, A., Guainazzi, M., Nandra, K., Smith, R., and den Herder, J.-W., “The Athena space X-ray observatory and the astrophysics of hot plasma,” Astronomische Nachrichten 341, 224–235 (Feb. 2020).
  * [6] Pointecouteau, E., Reiprich, T. H., Adami, C., Arnaud, M., Biffi, V., Borgani, S., Borm, K., Bourdin, H., Brueggen, M., Bulbul, E., Clerc, N., Croston, J. H., Dolag, K., Ettori, S., Finoguenov, A., Kaastra, J., Lovisari, L., Maughan, B., Mazzotta, P., Pacaud, F., de Plaa, J., Pratt, G. W., Ramos-Ceja, M., Rasia, E., Sanders, J., Zhang, Y. Y., Allen, S., Boehringer, H., Brunetti, G., Elbaz, D., Fassbender, R., Hoekstra, H., Hildebrandt, H., Lamer, G., Marrone, D., Mohr, J., Molendi, S., Nevalainen, J., Ohashi, T., Ota, N., Pierre, M., Romer, K., Schindler, S., Schrabback, T., Schwope, A., Smith, R., Springel, V., and von der Linden, A., “The Hot and Energetic Universe: The evolution of galaxy groups and clusters,” arXiv e-prints , arXiv:1306.2319 (June 2013).
  * [7] Ettori, S., Pratt, G. W., de Plaa, J., Eckert, D., Nevalainen, J., Battistelli, E. S., Borgani, S., Croston, J. H., Finoguenov, A., Kaastra, J., Gaspari, M., Gastaldello, F., Gitti, M., Molendi, S., Pointecouteau, E., Ponman, T. J., Reiprich, T. H., Roncarelli, M., Rossetti, M., Sanders, J. S., Sun, M., Trinchieri, G., Vazza, F., Arnaud, M., Böringher, H., Brighenti, F., Dahle, H., De Grandi, S., Mohr, J. J., Moretti, A., and Schindler, S., “The Hot and Energetic Universe: The astrophysics of galaxy groups and clusters,” arXiv e-prints , arXiv:1306.2322 (June 2013).
  * [8] Croston, J. H., Sanders, J. S., Heinz, S., Hardcastle, M. J., Zhuravleva, I., Bîrzan, L., Bower, R. G., Brüggen, M., Churazov, E., Edge, A. C., Ettori, S., Fabian, A. C., Finoguenov, A., Kaastra, J., Gaspari, M., Gitti, M., Nulsen, P. E. J., McNamara, B. R., Pointecouteau, E., Ponman, T. J., Pratt, G. W., Rafferty, D. A., Reiprich, T. H., Sijacki, D., Worrall, D. M., Kraft, R. P., McCarthy, I., and Wise, M., “The Hot and Energetic Universe: AGN feedback in galaxy clusters and groups,” arXiv e-prints , arXiv:1306.2323 (June 2013).
  * [9] Kaastra, J., Finoguenov, A., Nicastro, F., Branchini, E., Schaye, J., Cappelluti, N., Nevalainen, J., Barcons, X., Bregman, J., Croston, J., Dolag, K., Ettori, S., Galeazzi, M., Ohashi, T., Piro, L., Pointecouteau, E., Pratt, G., Reiprich, T., Roncarelli, M., Sanders, J., Takei, Y., and Ursino, E., “The Hot and Energetic Universe: The missing baryons and the warm-hot intergalactic medium,” arXiv e-prints , arXiv:1306.2324 (June 2013).
  * [10] Aird, J., Comastri, A., Brusa, M., Cappelluti, N., Moretti, A., Vanzella, E., Volonteri, M., Alexander, D., Afonso, J. M., Fiore, F., Georgantopoulos, I., Iwasawa, K., Merloni, A., Nandra, K., Salvaterra, R., Salvato, M., Severgnini, P., Schawinski, K., Shankar, F., Vignali, C., and Vito, F., “The Hot and Energetic Universe: The formation and growth of the earliest supermassive black holes,” arXiv e-prints , arXiv:1306.2325 (June 2013).
  * [11] Georgakakis, A., Carrera, F., Lanzuisi, G., Brightman, M., Buchner, J., Aird, J., Page, M., Cappi, M., Afonso, J., Alonso-Herrero, A., Ballo, L., Barcons, X., Ceballos, M. T., Comastri, A., Georgantopoulos, I., Mateos, S., Nandra, K., Rosario, D., Salvato, M., Schawinski, K., Severgnini, P., and Vignali, C., “The Hot and Energetic Universe: Understanding the build-up of supermassive black holes and galaxies at the heyday of the Universe,” arXiv e-prints , arXiv:1306.2328 (June 2013).
  * [12] Cappi, M., Done, C., Behar, E., Bianchi, S., Braito, V., Costantini, E., Dadina, M., Feruglio, C., Fiore, F., Gallagher, S., Gandhi, P., Grosso, N., Kaastra, J., King, A., Lobban, A., Maiolino, R., Piconcelli, E., Ponti, G., Porquet, D., Pounds, K., Proga, D., Ranalli, P., Reeves, J., Risaliti, G., Rodriguez Hidalgo, P., Rovilos, E., Sim, S., Stewart, G., Tombesi, F., Tsuru, T. G., Vaughan, S., Wang, D., and Worrall, D., “The Hot and Energetic Universe: Astrophysics of feedback in local AGN,” arXiv e-prints , arXiv:1306.2330 (June 2013).
  * [13] Dovciak, M., Matt, G., Bianchi, S., Boller, T., Brenneman, L., Bursa, M., D’Ai, A., di Salvo, T., de Marco, B., Goosmann, R., Karas, V., Iwasawa, K., Kara, E., Miller, J., Miniutti, G., Papadakis, I., Petrucci, P.-O., Ponti, G., Porquet, D., Reynolds, C., Risaliti, G., Rozanska, A., Zampieri, L., Zezas, A., and Young, A., “The Hot and Energetic Universe: The close environments of supermassive black holes,” arXiv e-prints , arXiv:1306.2331 (June 2013).
  * [14] Branduardi-Raymont, G., Sciortino, S., Dennerl, K., Güdel, M., Holmstrom, M., Koutroumpa, D., Maggio, A., Micela, G., Pillitteri, I., Sanz-Forcada, J., Read, A., Bhardwaj, A., Ezoe, Y., and Gladstone, R., “The Hot and Energetic Universe: Solar system and exoplanets,” arXiv e-prints , arXiv:1306.2332 (June 2013).
  * [15] Sciortino, S., Rauw, G., Audard, M., Argiroffi, C., Chu, Y. H., De Becker, M., Drake, J., Feigelson, E., Gosset, E., Grosso, N., Güdel, M., Guerrero, M., Hervé, A., Kastner, J., Montez, R., Nazé, Y., Oskinova, L., Stelzer, B., and ud-Doula, A., “The Hot and Energetic Universe: Star formation and evolution,” arXiv e-prints , arXiv:1306.2333 (June 2013).
  * [16] Motch, C., Wilms, J., Barret, D., Becker, W., Bogdanov, S., Boirin, L., Corbel, S., Cackett, E., Campana, S., de Martino, D., Haberl, F., in’t Zand, J., Méndez, M., Mignani, R., Miller, J., Orio, M., Psaltis, D., Rea, N., Rodriguez, J., Rozanska, A., Schwope, A., Steiner, A., Webb, N., Zampieri, L., and Zane, S., “The Hot and Energetic Universe: End points of stellar evolution,” arXiv e-prints , arXiv:1306.2334 (June 2013).
  * [17] Decourchelle, A., Costantini, E., Badenes, C., Ballet, J., Bamba, A., Bocchino, F., Kaastra, J., Kosenko, D., Lallement, R., Lee, J., Lemoine-Goumard, M., Miceli, M., Paerels, F., Petre, R., Pinto, C., Plucinsky, P., Renaud, M., Sasaki, M., Smith, R., Tatischeff, V., Tiengo, A., Valencic, L., Vink, J., Wang, D., and Wilms, J., “The Hot and Energetic Universe: The astrophysics of supernova remnants and the interstellar medium,” arXiv e-prints , arXiv:1306.2335 (June 2013).
  * [18] Jonker, P., O’Brien, P., Amati, L., Atteia, J.-L., Campana, S., Evans, P., Fender, R., Kouveliotou, C., Lodato, G., Osborne, J., Piro, L., Rau, A., Tanvir, N., and Willingale, R., “The Hot and Energetic Universe: Luminous extragalactic transients,” arXiv e-prints , arXiv:1306.2336 (June 2013).
  * [19] Cucchetti, E., Pointecouteau, E., Peille, P., Clerc, N., Rasia, E., Biffi, V., Borgani, S., Tornatore, L., Dolag, K., Roncarelli, M., Gaspari, M., Ettori, S., Bulbul, E., Dauser, T., Wilms, J., Pajot, F., and Barret, D., “Athena X-IFU synthetic observations of galaxy clusters to probe the chemical enrichment of the Universe,” Astronomy and Astrophysics 620, A173 (Dec. 2018).
  * [20] Barret, D., Lam Trong, T., den Herder, J.-W., Piro, L., Cappi, M., Houvelin, J., Kelley, R., Mas-Hesse, J. M., Mitsuda, K., Paltani, S., Rauw, G., Rozanska, A., Wilms, J., Bandler, S., Barbera, M., Barcons, X., Bozzo, E., Ceballos, M. T., Charles, I., Costantini, E., Decourchelle, A., den Hartog, R., Duband, L., Duval, J.-M., Fiore, F., Gatti, F., Goldwurm, A., Jackson, B., Jonker, P., Kilbourne, C., Macculi, C., Mendez, M., Molendi, S., Orleanski, P., Pajot, F., Pointecouteau, E., Porter, F., Pratt, G. W., Prêle, D., Ravera, L., Sato, K., Schaye, J., Shinozaki, K., Thibert, T., Valenziano, L., Valette, V., Vink, J., Webb, N., Wise, M., Yamasaki, N., Douchin, F., Mesnager, J.-M., Pontet, B., Pradines, A., Branduardi-Raymont, G., Bulbul, E., Dadina, M., Ettori, S., Finoguenov, A., Fukazawa, Y., Janiuk, A., Kaastra, J., Mazzotta, P., Miller, J., Miniutti, G., Naze, Y., Nicastro, F., Scioritino, S., Simonescu, A., Torrejon, J. M., Frezouls, B., Geoffray, H., Peille, P., Aicardi, C., André, J., Daniel, C., Clénet, A., Etcheverry, C., Gloaguen, E., Hervet, G., Jolly, A., Ledot, A., Paillet, I., Schmisser, R., Vella, B., Damery, J.-C., Boyce, K., Dipirro, M., Lotti, S., Schwander, D., Smith, S., Van Leeuwen, B.-J., van Weers, H., Clerc, N., Cobo, B., Dauser, T., Kirsch, C., Cucchetti, E., Eckart, M., Ferrando, P., and Natalucci, L., “The ATHENA X-ray Integral Field Unit (X-IFU),” in [Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 10699, 106991G (July 2018).
  * [21] Nicastro, F., Kaastra, J., Krongold, Y., Borgani, S., Branchini, E., Cen, R., Dadina, M., Danforth, C. W., Elvis, M., Fiore, F., Gupta, A., Mathur, S., Mayya, D., Paerels, F., Piro, L., Rosa-Gonzalez, D., Schaye, J., Shull, J. M., Torres-Zafra, J., Wijers, N., and Zappacosta, L., “Observations of the missing baryons in the warm-hot intergalactic medium,” Nature 558, 406–409 (June 2018).
  * [22] Reeves, J. N., Braito, V., Nardini, E., Hamann, F., Chartas, G., Lobban, A. P., O’Brien, P. T., and Turner, T. J., “Resolving the X-Ray Obscuration in a Low-flux Observation of the Quasar PDS 456,” Astrophysical Journal 867, 38 (Nov. 2018).
  * [23] Miller, J. M., Raymond, J., Fabian, A. C., Gallo, E., Kaastra, J., Kallman, T., King, A. L., Proga, D., Reynolds, C. S., and Zoghbi, A., “The Accretion Disk Wind in the Black Hole GRS 1915+105,” Astrophysical Journal Letters 821, L9 (Apr. 2016).
  * [24] Guainazzi, M. and Tashiro, M. S., “The Hot Universe with XRISM and Athena,” in [Perseus in Sicily: From Black Hole to Cluster Outskirts ], Asada, K., de Gouveia Dal Pino, E., Giroletti, M., Nagai, H., and Nemmen, R., eds., 342, 29–36 (Jan. 2020).
  * [25] Barret, D., den Herder, J. W., Piro, L., Ravera, L., Den Hartog, R., Macculi, C., Barcons, X., Page, M., Paltani, S., Rauw, G., Wilms, J., Ceballos, M., Duband, L., Gottardi, L., Lotti, S., de Plaa, J., Pointecouteau, E., Schmid, C., Akamatsu, H., Bagliani, D., Bandler, S., Barbera, M., Bastia, P., Biasotti, M., Branco, M., Camon, A., Cara, C., Cobo, B., Colasanti, L., Costa-Kramer, J. L., Corcione, L., Doriese, W., Duval, J. M., Fabrega, L., Gatti, F., de Gerone, M., Guttridge, P., Kelley, R., Kilbourne, C., van der Kuur, J., Mineo, T., Mitsuda, K., Natalucci, L., Ohashi, T., Peille, P., Perinati, E., Pigot, C., Pizzigoni, G., Pobes, C., Porter, F., Renotte, E., Sauvageot, J. L., Sciortino, S., Torrioli, G., Valenziano, L., Willingale, D., de Vries, C., and van Weers, H., “The Hot and Energetic Universe: The X-ray Integral Field Unit (X-IFU) for Athena+,” arXiv e-prints , arXiv:1308.6784 (Aug. 2013).
  * [26] Ravera, L., Barret, D., den Herder, J. W., Piro, L., Clédassou, R., Pointecouteau, E., Peille, P., Pajot, F., Arnaud, M., Pigot, C., Duband, L., Cara, C., den Hartog, R. H., Gottardi, L., Akamatsu, H., van der Kuur, J., van Weers, H. J., de Plaa, J., Macculi, C., Lotti, S., Torrioli, G., Gatti, F., Valenziano, L., Barbera, M., Barcons, X., Ceballos, M. T., Fàbrega, L., Mas-Hesse, J. M., Page, M. J., Guttridge, P. R., Willingale, R., Paltani, S., Genolet, L., Bozzo, E., Rauw, G., Renotte, E., Wilms, J., and Schmid, C., “The X-ray Integral Field Unit (X-IFU) for Athena,” in [Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray ], Takahashi, T., den Herder, J.-W. A., and Bautz, M., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 9144, 91442L (July 2014).
  * [27] Barret, D., Lam Trong, T., den Herder, J.-W., Piro, L., Barcons, X., Huovelin, J., Kelley, R., Mas-Hesse, J. M., Mitsuda, K., Paltani, S., Rauw, G., RoŻanska, A., Wilms, J., Barbera, M., Bozzo, E., Ceballos, M. T., Charles, I., Decourchelle, A., den Hartog, R., Duval, J.-M., Fiore, F., Gatti, F., Goldwurm, A., Jackson, B., Jonker, P., Kilbourne, C., Macculi, C., Mendez, M., Molendi, S., Orleanski, P., Pajot, F., Pointecouteau, E., Porter, F., Pratt, G. W., Prêle, D., Ravera, L., Renotte, E., Schaye, J., Shinozaki, K., Valenziano, L., Vink, J., Webb, N., Yamasaki, N., Delcelier-Douchin, F., Le Du, M., Mesnager, J.-M., Pradines, A., Branduardi-Raymont, G., Dadina, M., Finoguenov, A., Fukazawa, Y., Janiuk, A., Miller, J., Nazé, Y., Nicastro, F., Sciortino, S., Torrejon, J. M., Geoffray, H., Hernandez, I., Luno, L., Peille, P., André, J., Daniel, C., Etcheverry, C., Gloaguen, E., Hassin, J., Hervet, G., Maussang, I., Moueza, J., Paillet, A., Vella, B., Campos Garrido, G., Damery, J.-C., Panem, C., Panh, J., Bandler, S., Biffi, J.-M., Boyce, K., Clénet, A., DiPirro, M., Jamotton, P., Lotti, S., Schwander, D., Smith, S., van Leeuwen, B.-J., van Weers, H., Brand, T., Cobo, B., Dauser, T., de Plaa, J., and Cucchetti, E., “The Athena X-ray Integral Field Unit (X-IFU),” in [Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Takahashi, T., and Bautz, M., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 9905, 99052F (July 2016).
  * [28] Barret, D., Lam Trong, T., den Herder, J.-W., Piro, L., Cappi, M., Houvelin, J., Kelley, R., Mas-Hesse, J. M., Mitsuda, K., Paltani, S., Rauw, G., Rozanska, A., Wilms, J., Bandler, S., Barbera, M., Barcons, X., Bozzo, E., Ceballos, M. T., Charles, I., Costantini, E., Decourchelle, A., den Hartog, R., Duband, L., Duval, J.-M., Fiore, F., Gatti, F., Goldwurm, A., Jackson, B., Jonker, P., Kilbourne, C., Macculi, C., Mendez, M., Molendi, S., Orleanski, P., Pajot, F., Pointecouteau, E., Porter, F., Pratt, G. W., Prêle, D., Ravera, L., Sato, K., Schaye, J., Shinozaki, K., Thibert, T., Valenziano, L., Valette, V., Vink, J., Webb, N., Wise, M., Yamasaki, N., Douchin, F., Mesnager, J.-M., Pontet, B., Pradines, A., Branduardi-Raymont, G., Bulbul, E., Dadina, M., Ettori, S., Finoguenov, A., Fukazawa, Y., Janiuk, A., Kaastra, J., Mazzotta, P., Miller, J., Miniutti, G., Naze, Y., Nicastro, F., Scioritino, S., Simonescu, A., Torrejon, J. M., Frezouls, B., Geoffray, H., Peille, P., Aicardi, C., André, J., Daniel, C., Clénet, A., Etcheverry, C., Gloaguen, E., Hervet, G., Jolly, A., Ledot, A., Paillet, I., Schmisser, R., Vella, B., Damery, J.-C., Boyce, K., Dipirro, M., Lotti, S., Schwander, D., Smith, S., Van Leeuwen, B.-J., van Weers, H., Clerc, N., Cobo, B., Dauser, T., Kirsch, C., Cucchetti, E., Eckart, M., Ferrando, P., and Natalucci, L., “The ATHENA X-ray Integral Field Unit (X-IFU),” in [Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 10699, 106991G (July 2018).
  * [29] Pajot, F., Barret, D., Lam-Trong, T., den Herder, J. W., Piro, L., Cappi, M., Huovelin, J., Kelley, R., Mas-Hesse, J. M., Mitsuda, K., Paltani, S., Rauw, G., Rozanska, A., Wilms, J., Barbera, M., Douchin, F., Geoffray, H., den Hartog, R., Kilbourne, C., Le Du, M., Macculi, C., Mesnager, J. M., and Peille, P., “The Athena X-ray Integral Field Unit (X-IFU),” Journal of Low Temperature Physics 193, 901–907 (Dec. 2018).
  * [30] Smith, S. J., Adams, J. S., Bandler, S. R., Betancourt-Martinez, G. L., Chervenak, J. A., Chiao, M. P., Eckart, M. E., Finkbeiner, F. M., Kelley, R. L., Kilbourne, C. A., Miniussi, A. R., Porter, F. S., Sadleir, J. E., Sakai, K., Wakeham, N. A., Wassell, E. J., Yoon, W., Bennett, D. A., Doriese, W. B., Fowler, J. W., Hilton, G. C., Morgan, K. M., Pappas, C. G., Reintsema, C. N., Swetz, D. S., Ullom, J. N., Irwin, K. D., Akamatsu, H., Gottardi, L., den Hartog, R., Jackson, B. D., van der Kuur, J., Barret, D., and Peille, P., “Transition-edge sensor pixel parameter design of the microcalorimeter array for the x-ray integral field unit on Athena,” in [Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Takahashi, T., and Bautz, M., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 9905, 99052H (July 2016).
  * [31] Smith, S. J., Adams, J. S., Bandler, S. R., Beaumont, S., Chervenak, J. A., Denison, E. V., Doriese, W. B., Durkin, M., Finkbeiner, F. M., Fowler, J. W., Hilton, G. C., Hummatov, R., Irwin, K. D., Kelley, R. L., Kilbourne, C. A., Leutenegger, M. A., Miniussi, A. R., Porter, F. S., Reintsema, C. D., Sadleir, J. E., Sakai, K., Swetz, D. S., Ullom, J. N., Vale, L. R., Wakeham, N. A., Wassell, E. J., and Witthoeft, M. C., “Performance of a Broad-Band, High-Resolution, Transition-Edge Sensor Spectrometer for X-ray Astrophysics,” IEEE Transactions on Applied Superconductivity 31, 3061918 (Aug. 2021).
  * [32] Welty, R. P. and Martinis, J. M., “Two-stage integrated SQUID amplifier with series array output,” IEEE Transactions on Applied Superconductivity 3, 2605–2608 (Mar. 1993).
  * [33] Kiviranta, M., Gronberg, L., Puranen, T., van der Kuur, J., Beev, N., Salonen, J., Hazra, D., and Korpela, S., “Two-Stage SQUID Amplifier for the Frequency Multiplexed Readout of the X-IFU X-Ray Camera,” IEEE Transactions on Applied Superconductivity 31, 3060356 (Aug. 2021).
  * [34] Doriese, W. B., Morgan, K. M., Bennett, D. A., Denison, E. V., Fitzgerald, C. P., Fowler, J. W., Gard, J. D., Hays-Wehle, J. P., Hilton, G. C., Irwin, K. D., Joe, Y. I., Mates, J. A. B., O’Neil, G. C., Reintsema, C. D., Robbins, N. O., Schmidt, D. R., Swetz, D. S., Tatsuno, H., Vale, L. R., and Ullom, J. N., “Developments in Time-Division Multiplexing of X-ray Transition-Edge Sensors,” Journal of Low Temperature Physics 184, 389–395 (July 2016).
  * [35] Doriese, W. B., Bandler, S. R., Chaudhuri, S., Dawson, C. S., Denison, E. V., Duff, S. M., Durkin, M., FitzGerald, C. T., Fowler, J. W., Gard, J. D., Hilton, G. C., Irwin, K. D., Joe, Y. I., Morgan, K. M., O’Neil, G. C., Pappas, C. G., Reintsema, C. D., Rudman, D. A., Smith, S. J., Stevens, R. W., Swetz, D. S., Szypryt, P., Ullom, J. N., Vale, L. R., Weber, J. C., and Young, B. A., “Optimization of Time- and Code-Division-Multiplexed Readout for Athena X-IFU,” IEEE Transactions on Applied Superconductivity 29, 2905577 (Aug. 2019).
  * [36] Durkin, M., Adams, J. S., Bandler, S. R., Chervenak, J. A., Denison, E. V., Doriese, W. B., Duff, S. M., Finkbeiner, F. M., Fowler, J. W., Gard, J. D., Hilton, G. C., Hummatov, R., Irwin, K. D., Joe, Y. I., Kelley, R. L., Kilbourne, C. A., Miniussi, A. R., Morgan, K. M., O’Neil, G. C., Pappas, C. G., Porter, F. S., Reintsema, C. D., Rudman, D. A., Sakai, K., Smith, S. J., Stevens, R. W., Swetz, D. S., Szypryt, P., Ullom, J. N., Vale, L. R., and Wakeham, N., “Mitigation of Finite Bandwidth Effects in Time-Division-Multiplexed SQUID Readout of TES Arrays,” IEEE Transactions on Applied Superconductivity 31, 3065279 (Aug. 2021).
  * [37] Vaccaro, D., Akamatsu, H., Gottardi, L., van der Kuur, J., Nagayoshi, K., Taralli, E., de Wit, M., Bruijn, M. P., van der Linden, A. J., van Leeuwen, B.-J., van der Hulst, P., Ravensberg, K., de Vries, C. P., Kiviranta, M., Gao, J.-R., and den Herder, J.-W. A., “Frequency domain multiplexing readout for large arrays of transition-edge sensors,” arXiv e-prints , arXiv:2208.12604 (Aug. 2022).
  * [38] Akamatsu, H., Gottardi, L., van der Kuur, J., de Vries, C. P., Bruijn, M. P., Chervenak, J. A., Kiviranta, M., van den Linden, A. J., Jackson, B. D., Miniussi, A., Ravensberg, K., Sakai, K., Smith, S. J., and Wakeham, N., “Progress in the Development of Frequency-Domain Multiplexing for the X-ray Integral Field Unit on Board the Athena Mission,” Journal of Low Temperature Physics 199, 737–744 (Jan. 2020).
  * [39] Akamatsu, H., Vaccaro, D., Gottardi, L., van der Kuur, J., de Vries, C. P., Kiviranta, M., Ravensberg, K., D’Andrea, M., Taralli, E., de Wit, M., Bruijn, M. P., van der Hulst, P., den Hartog, R. H., van Leeuwen, B. J., van der Linden, A. J., McCalden, A. J., Nagayoshi, K., Nieuwenhuizen, A. C. T., Ridder, M. L., Visser, S., van Winden, P., Gao, J. R., Hoogeveen, R. W. M., Jackson, B. D., and den Herder, J. W. A., “Demonstration of MHz frequency domain multiplexing readout of 37 transition edge sensors for high-resolution x-ray imaging spectrometers,” Applied Physics Letters 119, 182601 (Nov. 2021).
  * [40] Irwin, K. D. and Hilton, G. C., “Transition-Edge Sensors,” in [Cryogenic Particle Detection ], Enss, C., ed., 99, 63 (2005).
  * [41] Durkin, M., Adams, J. S., Bandler, S. R., Chervenak, J. A., Chaudhuri, S., Dawson, C. S., Denison, E. V., Doriese, W. B., Duff, S. M., Finkbeiner, F. M., FitzGerald, C. T., Fowler, J. W., Gard, J. D., Hilton, G. C., Irwin, K. D., Joe, Y. I., Kelley, R. L., Kilbourne, C. A., Miniussi, A. R., Morgan, K. M., O’Neil, G. C., Pappas, C. G., Porter, F. S., Reintsema, C. D., Rudman, D. A., Sakai, K., Smith, S. J., Stevens, R. W., Swetz, D. S., Szypryt, P., Ullom, J. N., Vale, L. R., Wakeham, N. A., Weber, J. C., and Young, B. A., “Demonstration of Athena X-IFU Compatible 40-Row Time-Division-Multiplexed Readout,” IEEE Transactions on Applied Superconductivity 29, 2904472 (Aug. 2019).
  * [42] Lotti, S., D’Andrea, M., Molendi, S., Macculi, C., Minervini, G., Fioretti, V., Laurenza, M., Jacquey, C., and Piro, L., “Review of the Particle Background of the Athena X-IFU Instrument,” Astrophysical Journal 909, 111 (Mar. 2021).
  * [43] Macculi, C., Argan, A., D’Andrea, M., Lotti, S., Laurenza, M., Piro, L., Biasotti, M., Corsini, D., Gatti, F., Torrioli, G., Fiorini, M., Molendi, S., Uslenghi, M., Mineo, T., Bulgarelli, A., Fioretti, V., and Cavazzuti, E., “The Cryogenic AntiCoincidence detector for ATHENA X-IFU: a program overview,” in [Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Takahashi, T., and Bautz, M., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 9905, 99052K (July 2016).
  * [44] Macculi, C., Argan, A., Brienza, D., D’Andrea, M., Lotti, S., Minervini, G., Piro, L., Biasotti, M., Ferrari Barusso, L., Gatti, F., Rigano, M., Chiarello, F., Torrioli, G., Fiorini, M., Uslenghi, M., Cavazzuti, E., Puccetti, S., and Volpe, A., “The cryogenic anticoincidence detector for ATHENA X-IFU: advancement in the project,” in [Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series ], Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 11444, 114444A (Dec. 2020).
  * [45] Macculi, C., Argan, A., Brienza, D., D’Andrea, M., Lotti, S., Minervini, G., Piro, L., Biasotti, M., Ferrari Barusso, L., Gatti, F., Rigano, M., Torrioli, G., Fiorini, M., Molendi, S., Uslenghi, M., Cavazzuti, E., and Volpe, A., “The Cryogenic AntiCoincidence Detector for ATHENA X-IFU: The Project Status,” Journal of Low Temperature Physics 199, 416–424 (Jan. 2020).
  * [46] D’Andrea, M., Macculi, C., Torrioli, G., Argan, A., Brienza, D., Lotti, S., Minervini, G., Piro, L., Biasotti, M., Ferrari Barusso, L., Gatti, F., Rigano, M., Volpe, A., and Battistelli, E. S., “The Demonstration Model of the ATHENA X-IFU Cryogenic AntiCoincidence Detector,” Journal of Low Temperature Physics 199, 65–72 (Apr. 2020).
  * [47] D’Andrea, M., Ravensberg, K., Argan, A., Brienza, D., Lotti, S., Macculi, C., Minervini, G., Piro, L., Torrioli, G., Chiarello, F., Ferrari Barusso, L., Biasotti, M., Gallucci, G., Gatti, F., Rigano, M., Akamatsu, H., Dercksen, J., Gottardi, L., de Groote, F., den Hartog, R., den Herder, J. W., Hoogeveen, R., Jackson, B., McCalden, A., Rosman, S., Taralli, E., Vaccaro, D., de Wit, M., Chervenak, J., Smith, S., and Wakeham, N., “ATHENA X-IFU Demonstration Model: First Joint Operation of the Main TES Array and its Cryogenic AntiCoincidence Detector (CryoAC),” Journal of Low Temperature Physics (July 2022).
  * [48] Prêle, D., Chen, S., Coleiro, A., Varniere, P., Peille, P., Ravera, L., and Kirsch, C., “Warm front end electronic modelization for the X-IFU ATHENA readout chain simulation,” in [Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series ], Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 11444, 114443U (Dec. 2020).
  * [49] Ravera, L., Gumuchian, P., Clénet, A., Bertrand, B., Murat, D., Oziol, C., Camus, T., Pointecouteau, E., and Barret, D., “First results of the ATHENA/X-IFU digital readout electronics prototype,” in [Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 10699, 106994V (July 2018).
  * [50] Peille, P., Ceballos, M. T., Cobo, B., Wilms, J., Bandler, S., Smith, S. J., Dauser, T., Brand, T., den Hartog, R., de Plaa, J., Barret, D., den Herder, J.-W., Piro, L., Barcons, X., and Pointecouteau, E., “Performance assessment of different pulse reconstruction algorithms for the ATHENA X-ray Integral Field Unit,” in [Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Takahashi, T., and Bautz, M., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 9905, 99055W (July 2016).
  * [51] Cobo, B., Ceballos, M. T., Peille, P., Mesnager, J.-M., Wilms, J., Dauser, T., Kirsch, C., Pinsard, F., Cara, C., Gros, M., Ravera, L., Bandler, S., Porter, F., Kilbourne, C., and Sakai, K., “ATHENA X-ray Integral Field Unit on-board event processor: analysis of performance of two triggering algorithms,” in [Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 10699, 106994S (July 2018).
  * [52] Cobo, B., Cardiel, N., Ceballos, M. T., and Peille, P., “Pulse processing in TES detectors: comparative of different short filter methods based on optimal filtering: case study for Athena X-IFU,” in [Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series ], Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 11444, 1144496 (Dec. 2020).
  * [53] Vega-Ferrero, J., Ceballos, M. T., Cobo, B., Carrera, F. J., García, P., and Puyol-Gruart, J., “Event Detection and Reconstruction Using Neural Networks in TES Devices: a Case Study for Athena/X-IFU,” Publications of the Astronomical Society of the Pacific 134, 024504 (Feb. 2022).
  * [54] Jackson, B. D., van Weers, H., van der Kuur, J., den Hartog, R., Akamatsu, H., Argan, A., Bandler, S. R., Barbera, M., Barret, D., Bruijn, M. P., Chervenak, J. A., Dercksen, J., Gatti, F., Gottardi, L., Haas, D., den Herder, J. W., Kilbourne, C. A., Kiviranta, M., Lam-Trong, T., van Leeuwen, B. J., Macculi, C., Piro, L., and Smith, S. J., “The focal plane assembly for the Athena X-ray Integral Field Unit instrument,” in [Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Takahashi, T., and Bautz, M., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 9905, 99052I (July 2016).
  * [55] Duband, L., Charles, I., and Duval, J. M., “Coolers development for the ATHENA X-IFU cryogenic chain,” in [Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray ], Takahashi, T., den Herder, J.-W. A., and Bautz, M., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 9144, 91445W (July 2014).
  * [56] Duband, L., Charles, I., Duval, J.-M., Ercolani, E., Gully, P., Luchier, N., Prouve, T., and Thibault, P., “Space cryogenics at CEA-SBT,” in [Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series ], Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 10566, 105660A (Nov. 2017).
  * [57] Barbera, M., Collura, A., Gatti, F., Lo Cicero, U., Macculi, C., Piro, L., Renotte, E., and Sciortino, S., “Baseline design of the thermal blocking filters for the X-IFU detector on board ATHENA,” in [Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray ], Takahashi, T., den Herder, J.-W. A., and Bautz, M., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 9144, 91445U (July 2014).
  * [58] Barbera, M., Argan, A., Bozzo, E., Branduardi-Raymont, G., Ciaravella, A., Collura, A., Cuttaia, F., Gatti, F., Jimenez Escobar, A., Lo Cicero, U., Lotti, S., Macculi, C., Mineo, T., Nuzzo, F., Paltani, S., Parodi, G., Piro, L., Rauw, G., Sciortino, L., Sciortino, S., and Villa, F., “Thermal Filters for the ATHENA X-IFU: Ongoing Activities Toward the Conceptual Design,” Journal of Low Temperature Physics 184, 706–711 (Aug. 2016).
  * [59] Sciortino, L., Lo Cicero, U., Magnano, E., Píš, I., and Barbera, M., “Surface investigation and aluminum oxide estimation on test filters for the ATHENA X-IFU and WFI detectors,” in [Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Takahashi, T., and Bautz, M., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 9905, 990566 (July 2016).
  * [60] Barbera, M., Lo Cicero, U., Sciortino, L., Parodi, G., D’Anca, F., Giglio, P., Ferruggia Bonura, S., Nuzzo, F., Jimenez Escobar, A., Ciaravella, A., Collura, A., Varisco, S., and Samain, V., “Preliminary Mechanical Characterization of Thermal Filters for the X-IFU Instrument on Athena,” Journal of Low Temperature Physics 193, 793–798 (Dec. 2018).
  * [61] Barbera, M., Lo Cicero, U., Sciortino, L., D’Anca, F., Lo Cicero, G., Parodi, G., Sciortino, S., Rauw, G., Branduardi-Raymont, G., Varisco, S., Ferruggia Bonura, S., Collura, A., Candia, R., Di Cicca, G., Giglio, P., Buttacavoli, A., Cuttaia, F., Villa, F., Cappi, M., Lam Trong, T., Mesnager, J.-M., Peille, P., den Hartog, R., den Herder, J. W., Jackson, B., Barret, D., and Piro, L., “ATHENA X-IFU thermal filters development status toward the end of the instrument phase-A,” in [Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 10699, 106991R (July 2018).
  * [62] Lo Cicero, U., Lo Cicero, G., Puccio, E., Montinaro, N., Gulli, D., Todaro, M., Calandra, E., Törmä, P., Cuttaia, F., Villa, F., Ferruggia Bonura, S., Lullo, G., Collura, A., D’Anca, F., Sciortino, L., Varisco, S., Jackson, B., van Leeuwen, B.-J., Gloaguen, E., and Barbera, M., “Radio frequency shielding of thin aluminized plastic filters investigated for the ATHENA X-IFU detector,” in [Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 10699, 106994R (July 2018).
  * [63] Sciortino, L., Lo Cicero, U., Ferruggia Bonura, S., D’Anca, F., Buttacavoli, A., Puccio, E., and Barbera, M., “Thermal modelling of the ATHENA X-IFU filters,” in [Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 10699, 1069950 (July 2018).
  * [64] Sciortino, L., Lo Cicero, U., Ferruggia Bonura, S., Magnano, E., Nannarone, S., Koshmak, K., and Barbera, M., “A Temperature-Dependent X-Ray Absorption Characterization of Test Filters for the ATHENA Mission X-IFU Instrument,” Journal of Low Temperature Physics 193, 799–804 (Dec. 2018).
  * [65] Puccio, E., Todaro, M., Lo Cicero, U., Sciortino, L., Laurent, P., Ferrando, P., Giglia, A., Nannarone, S., and Barbera, M., “Synchrotron x-ray transmission measurements and modeling of filters investigated for Athena,” Journal of Astronomical Telescopes, Instruments, and Systems 6, 038003 (July 2020).
  * [66] Bozzo, E., Barbera, M., Genolet, L., Paltani, S., Sordet, M., Branduardi-Raymont, G., Rauw, G., Sciortino, S., Barret, D., and Den Herder, J. W., “The Filter Wheel and Filters development for the X-IFU instrument on-board Athena,” arXiv e-prints , arXiv:1609.03776 (Sept. 2016).
  * [67] de Vries, C. P., Fioretti, V., den Herder, J. W., Schyns, E., and Pinto, S. D., “Simulating modulated x-ray calibration sources for future x-ray missions using GEANT4,” in [Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 10699, 1069965 (July 2018).
  * [68] den Hartog, R., Barret, D., Gottardi, L., den Herder, J. W., Jackson, B., de Korte, P., van der Kuur, J., van Leeuwen, B. J., van Loon, D., Nieuwenhuizen, A., and Ravera, L., “Requirements for the detectors and read-out of ATHENA X-IFU,” in [Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray ], Takahashi, T., den Herder, J.-W. A., and Bautz, M., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 9144, 91445Q (July 2014).
  * [69] Peille, P., den Hartog, R., Macculi, C., Barbera, M., Lotti, S., Cucchetti, E., Kirsch, C., Dauser, T., Wilms, J., Bandler, S. R., Smith, S. J., Jackson, B., Geoffray, H., Mesnager, J.-M., Pajot, F., Barret, D., Lam-Trong, T., den Herder, J.-W., and Piro, L., “The performance of the ATHENA X-ray Integral Field Unit,” in [Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 10699, 106994K (July 2018).
  * [70] Ettori, S., Pratt, G. W., de Plaa, J., Eckert, D., Nevalainen, J., Battistelli, E. S., Borgani, S., Croston, J. H., Finoguenov, A., Kaastra, J., Gaspari, M., Gastaldello, F., Gitti, M., Molendi, S., Pointecouteau, E., Ponman, T. J., Reiprich, T. H., Roncarelli, M., Rossetti, M., Sanders, J. S., Sun, M., Trinchieri, G., Vazza, F., Arnaud, M., Böringher, H., Brighenti, F., Dahle, H., De Grandi, S., Mohr, J. J., Moretti, A., and Schindler, S., “The Hot and Energetic Universe: The astrophysics of galaxy groups and clusters,” arXiv e-prints , arXiv:1306.2322 (June 2013).
  * [71] Porter, F. S., Chiao, M. P., Eckart, M. E., Fujimoto, R., Ishisaki, Y., Kelley, R. L., Kilbourne, C. A., Leutenegger, M. A., McCammon, D., Mitsuda, K., Sawada, M., Szymkowiak, A. E., Takei, Y., Tashiro, M., Tsujimoto, M., Watanabe, T., and Yamada, S., “Temporal Gain Correction for X-ray Calorimeter Spectrometers,” Journal of Low Temperature Physics 184, 498–504 (July 2016).
  * [72] Cucchetti, E., Eckart, M. E., Peille, P., de Vries, C., Pajot, F., Pointecouteau, E., Leutenegger, M., Kilbourne, C. A., and Porter, F. S., “Energy scale calibration and drift correction of the X-IFU,” in [Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 10699, 106994M (July 2018).
  * [73] Kirsch, C., Lorenz, M., Peille, P., Dauser, T., Ceballos, M. T., Cobo, B., Merino-Alonso, P. E., Cucchetti, E., Smith, S. Â. J., Gottardi, L., Hartog, R. H. d., Miniussi, A., Durkin, M., Prêle, D., and Wilms, J., “The Athena X-IFU Instrument Simulator xifusim,” Journal of Low Temperature Physics (Mar. 2022).
  * [74] Brand, T., Wilms, J., Dauser, T., Peille, P., Cobo, B., Ceballos, M., den Hartog, R. A., Kaastra, J. S., O’Brien, P., Barcons, X., Piro, L., den Herder, J. W. A., and Barret, D., “Observing the WHIM with Athena,” in [Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Takahashi, T., and Bautz, M., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 9905, 99055F (July 2016).
  * [75] Walsh, S., McBreen, S., Martin-Carrillo, A., Dauser, T., Wijers, N., Wilms, J., Schaye, J., and Barret, D., “Detection capabilities of the Athena X-IFU for the warm-hot intergalactic medium using gamma-ray burst X-ray afterglows,” Astronomy and Astrophysics 642, A24 (Oct. 2020).
  * [76] Kammoun, E. S., Barret, D., Peille, P., Willingale, R., Dauser, T., Wilms, J., Guainazzi, M., and Miller, J. M., “The defocused observations of bright sources with Athena/X-IFU,” arXiv e-prints , arXiv:2205.01126 (May 2022).
  * [77] Peille, P., Dauser, T., Kirsch, C., den Hartog, R., Cucchetti, E., Wilms, J., Barret, D., den Herder, J. W., and Piro, L., “The Performance of the Athena X-ray Integral Field Unit at Very High Count Rates,” Journal of Low Temperature Physics 193, 940–948 (Dec. 2018).
  * [78] Dauser, T., Falkner, S., Lorenz, M., Kirsch, C., Peille, P., Cucchetti, E., Schmid, C., Brand, T., Oertel, M., Smith, R., and Wilms, J., “SIXTE: a generic X-ray instrument simulation toolkit,” Astronomy and Astrophysics 630, A66 (Sept. 2019).
  * [79] Jaubert, J. and Debout, V., “in 11th International Workshop on Planning and Scheduling for Space Conference Proceedings,” in [IWPSS ], Berkeley, ed. (July 2019).
  * [80] Prouvé, T., Duval, J. M., Charles, I., Yamasaki, N. Y., Mitsuda, K., Nakagawa, T., Shinozaki, K., Tokoku, C., Yamamoto, R., Minami, Y., Le Du, M., Andre, J., Daniel, C., and Linder, M., “ATHENA X-IFU 300 K-50 mK cryochain test results,” Cryogenics 112, 103144 (Dec. 2020).
  * [81] Shinozaki, K., Tokoku, C., Yamamoto, R., Minami, Y., Yamasaki, N. Y., Mitsuda, K., Nakagawa, T., Duval, J. M., Prouvé, T., Charles, I., Du, M. L., Andre, J., Daniel, C., Linder, M., Tsunematsu, S., Kanao, K., Otsuka, K., and Narasaki, K., “Cooling performance of Joule Thomson coolers in 300 K -50 mK cryochain demonstration for ATHENA X-IFU,” in [Materials Science and Engineering Conference Series ], Materials Science and Engineering Conference Series 502, 012069 (Apr. 2019).
  * [82] Betancourt-Martinez, G., Pajot, F., Beaumont, S., Roudil, G., Adams, J., Akamatsu, H., Bandler, S., Bertrand, B., Bruijn, M., Castellani, F., Cucchetti, E., Doriese, W., Dupieux, M., Geoffray, H., Gottardi, L., Jackson, B., van der Kuur, J., Kiviranta, M., Miniussi, A., Peille, P., Ravensberg, K., Ravera, L., Reintsema, C., Sakai, K., Smith, S., Wakeham, N., van Weers, H., Wernicke, D., and Witthoeft, M., “A test platform for the detection and readout chain for the Athena X-IFU,” arXiv e-prints , arXiv:2107.03412 (July 2021).
  * [83] Cucchetti, E., Pajot, F., Pointecouteau, E., Peille, P., Betancourt-Martinez, G., Smith, S. J., Barbera, M., Eckart, M. E., Bandler, S. R., Kilbourne, C. A., Cappi, M., and Barret, D., “Testing the X-IFU calibration requirements: an example for quantum efficiency and energy resolution,” in [Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray ], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds., Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series 10699, 106994O (July 2018).
  * [84] Barret, D. and Cappi, M., “Inferring black hole spins and probing accretion/ejection flows in AGNs with the Athena X-ray Integral Field Unit,” Astronomy and Astrophysics 628, A5 (Aug. 2019).
  * [85] Eckart, M. E., Adams, J. S., Boyce, K. R., Brown, G. V., Chiao, M. P., Fujimoto, R., Haas, D. A., den Herder, J.-W. A., Hoshino, A., Ishisaki, Y., Kilbourne, C. A., Kitamoto, S., Leutenegger, M. A., McCammon, D., Mitsuda, K., Porter, F. S., Sato, K., Sawada, M., Seta, H., Sneiderman, G. A., Szymkowiak, A. E., Takei, Y., Tashiro, M. S., Tsujimoto, M., de Vries, C. P., Watanabe, T., Yamada, S., and Yamasaki, N. Y., “Ground calibration of the Astro-H (Hitomi) soft x-ray spectrometer,” Journal of Astronomical Telescopes, Instruments, and Systems 4(2), 1 – 22 (2018).
  * [86] Levine, M. A., Marrs, R. E., Henderson, J. R., Knapp, D. A., and Schneider, M. B., “The Electron Beam Ion Trap: A New Instrument for Atomic Physics Measurements,” Physica Scripta Volume T 22, 157–163 (Jan. 1988).
  * [87] Leutenegger, M. A., Eckart, M. E., Moseley, S. J., Rohrbach, S. O., Black, J. K., Chiao, M. P., Kelley, R. L., Kilbourne, C. A., and Porter, F. S., “Simple, compact, high-resolution monochromatic x-ray source for characterization of x-ray calorimeter arrays,” Review of Scientific Instruments 91, 083110 (Aug. 2020).
  * [88] Martínez-Núñez, S., Carrera, F. J., Ceballos, M. T., Castillo, S., Barret, D., Rau, A., and Bozzo, E., “The Athena Community Office,” in [XIV.0 Scientific Meeting (virtual) of the Spanish Astronomical Society ], 232 (July 2020).
  * [89] Knödlseder, J., Brau-Nogué, S., Coriat, M., Garnier, P., Hughes, A., Martin, P., and Tibaldo, L., “Estimate of the carbon footprint of astronomical research infrastructures,” Nature Astronomy 6, 503–513 (Mar. 2022).
  * [90] Burtscher, L., Balaguer-Núñez, L., D’Orazi, V., Barret, D., Beuchert, T., Dil, E., Janiuk, A., Mingo, B., and Poggio, E., “Astronomy organizations should lead in our battle against the climate crisis,” Nature Astronomy 6, 764–764 (June 2022).
  * [91] Barret, D., “Estimating, monitoring and minimizing the travel footprint associated with the development of the Athena X-ray Integral Field Unit,” Experimental Astronomy 49, 183–216 (June 2020).


# Piercing the Veil: Designs to Support Information Literacy on Social
Platforms

Jan Wolff<EMAIL_ADDRESS>Human-Computer Interaction Group,
Leibniz University HannoverAppelstraße 9AHannoverLower SaxonyGermany30167 and

(2021)

###### Abstract.

In this position paper we approach problems concerning critical digital and
information literacy with ideas to provide more digestible explanations of
abstract concepts through interface design. In particular, we focus on social
media platforms where we see the possibility of counteracting the spread of
misinformation by providing users with more proficiency through our
approaches. We argue that the omnipresent trend to abstract away and hide
information from users via UI/UX design opposes their ability to self-learn.
This leads us to propose a different framework in which we unify elegant and
simple interfaces with nudges that promote a look behind the curtain. Such
designs serve to foster a deeper understanding of employed technologies and
aim to increase the critical assessment of content encountered on social
platforms. Furthermore, we consider users with an intermediary skill level to
be largely ignored in current approaches, as they are given no tools to
broaden their knowledge without consultation of expert material. The resulting
stagnation is exemplified by the tactics of misinformation campaigns, which
exploit the ensuing lack of information literacy and critical thinking. We
propose an approach to design that sufficiently emancipates users in both
aspects by promoting a look behind the abstraction of UI/UX so that an
autonomous learning process is given the chance to occur. Furthermore, we name
ideas for future research within this area that take our considerations into
account.

learnable interfaces, critical thinking, computer literacy, social media

††copyright: acmcopyright††journalyear: 2021††conference: CHI’21 Workshop on
Technologies to Support Critical Thinking in an Age of Misinformation; May 09,
2021; Melbourne, AU††ccs: Social and professional topics Computing
literacy††ccs: Human-centered computing Information visualization††ccs: Human-
centered computing User centered design

##  1\. Introduction

The surge of misinformation campaigns and conspiracy theories during the
COVID-19 pandemic are, in part, symptomatic of a severe lack of critical
digital literacy in parts of the online population. We want to propose the
argument that this represents just a very visible tip of the iceberg. Ever
since home computing became ubiquitous, the main target of interface design
has been to initially make computers, then the internet, and by proxy a vast
amount of information easily digestible. Yet, as became apparent in the debate
on the term digital native, mere exposure to digital systems does not imply a
deep understanding of the technology at hand (Bennett et al., 2008).
Nevertheless, especially since the widespread introduction of smartphones and
social media, computer usage and interconnectedness is on a stable path to
become globally ubiquitous. In 2018 for the first time more than half of the
global population were using the internet in a continuously rising trend
(Union, 2018). But this development is not accompanied by a simultaneous in-
depth education on digital systems. As a matter of fact, it is mainly driven
by the introduction of systems that keep their internals hidden. In part to
explicitly avoid a critical examination.

One visible manifestation of the problems posed by this fact is found in
online spaces where users are provided with a seemingly endless influx of
information that is highly personalized (Covington et al., 2016). Within the
context of the attention economy (Davenport and Beck, 2001) this serves to
increase the time spent lingering on each platform in order to maximize
exposure to advertisements. A negative side-effect arises due to the relative
ease with which content can be shared and one’s own material can be
circulated. The lack of information about each platforms’ inner workings
therefore runs the risk of leading users to draw wrong conclusions about why
content recommendation systems expose them to certain media pieces (Bucher,
2017). Unknowingly, users are subjected to highly sensationalized content that
leads to longer interaction with the platform. The ease of sharing, discussing
and creating media pieces encourages one’s own tendency to sensationalize, as
such content is rewarded by being recommended to a larger audience. There are
indications that these mechanisms play a substantial role when it comes to
problems with radicalization on online platforms through reinforcement of
fringe opinions within communities (Thompson and Warzel, 2021). The
personalization of presented content further causes the formation of filter
bubbles (Pariser, 2011), which present an overly skewed view of the global
community, leading to incorrect assumptions about the prevalence and shared
agreement of expressed opinions.

###  1.1. Problem Statement

With these previous assumptions in mind, we see the problem of lacking
critical media literacy to be twofold. For one, rewarding sensationalized news
and opinion pieces disincentives unopinionated factual statements, which then
leads to a lack of fact checking as it solely reinforces and strengthens
previously held viewpoints. But secondly, users are given nearly no agency to
assess and explore different opinions once they are part of a filter bubble.
One of the few places where exposure to other segregated communities might
occur is in globally trending topics, where—once again—sensationalized content
is rewarded by being exposed to a larger set of people. Such circumstances are
hardly beneficial for healthy and factual discussion, because the most visible
opinions are strongly influenced by the prevalent sentiments found in their
respective communities and express often incompatible viewpoints. This serves
to create environments in which factual evidence is given lesser weight than
non-factual content, as it is surrounded by other highly charged statements if
it is expressed by another social group.

This area is often neglected when it comes to solving the problem of fake
news. We see a chance in giving users more agency about exploring opinions and
giving more visibility to the factors that contribute to their selection of
content. As a first step, we address the increasing opaqueness of user
interfaces found on social media platforms. For this reason we explore
examples of designs that—while user-friendly—prevent any engagement with the
layers below them.

##  2\. Addressing Social Platforms

Certainly the design of commercial social platforms is based most strongly on
economic incentives. Some of the problems thus stem from recommender systems,
which present users with content that is vast in scale, high in velocity111As
one of the five V’s of big data, velocity refers to the rate at which new
content is created. and automatically selected to cause long periods of
interaction with the platform. Visible indications explaining the reasoning
behind recommendations are often missing, which is especially concerning given
that a main factor for pre-selecting content is the user’s predicted
interaction with it. Thus, unbeknownst to users, they are presented with
controversial information in order to elicit interaction with the content
(Bucher et al., 2017). As this property is not communicated by designs, users
who are missing this insight have been found to assume that they are simply
presented a balanced selection of the content they are subscribed to (Rader et
al., 2018).

Similarly, grasping the scale of a platform’s user base is not always possible
within the bounds of the platform itself. Taking Twitter as an example, only
few tools are provided that allow gaining an awareness of how representative
one’s selection of connected profiles is in relation to the platform’s general
population. The only methods available at the time of writing are a global
search, the list of trending topics, and an indicator on each profile page
showing the list of mutual followers. However, getting any meaningful large-
scale information using only these tools is impossible, simply due to the
required amount of manual work. Furthermore, knowing about the existence of
certain peer groups is a prerequisite for searching them, inverting the
directionality that should be provided.

When looking beyond social media, other user interfaces show similar
tendencies when analysed. For example, an ongoing trend in desktop interfaces
is to be increasingly less verbose about processes that are performed. This
poses the risk of leading users to take several aspects presented by the GUI
as uncontrollable. Thus, while simplifying the initial process of learning how
to interact with such systems, any mental models and experiences are strictly
coerced into the set of tasks provided by the UI. No elements indicate that
deeper knowledge could be acquired, possibly engendering a mental state
similar to the Dunning-Kruger effect (Mahmood, 2016; Gibbs et al., 2017), as
it is impossible to perform an offhand assessment of one’s own expertise. This
bears the risk of contributing to factors that make users more susceptible to
misinformation campaigns, especially concerning the content encountered on
social platforms. Yet, other aspects of digital systems can be affected as
well. For example, assumptions made about privacy, security, or malware.

###  2.1. Related Work

Previous works exist in which methods for increasing awareness towards the
underlying data, algorithms, and applications have been explored. Common
methodologies either give more context to the content found on different
platforms or directly support a deeper understanding of the technological and
societal mechanisms at play.

####  2.1.1. Opinion Space

This work by Faridani et al. (Faridani et al., 2010) addresses the problem of
assessing the prevalence and relationship of opinions. In their design,
answers to a primary question are visually laid out in a two-dimensional space
based on participants’ responses in a supplementary 5-question opinion
profile. Through a principal component analysis the 5-dimensional answer space
is projected onto a two-dimensional plane. Additionally, comments with a high
rating stand out visually, guiding users towards them, while an overview of
the diversity in opinions is maintained. In a user study, the interface has
been found to increase dwell times in comment sections and to cause greater
respect and agreement concerning encountered opinions when compared to a
classic, time-sorted list interface. This shows the benefits of giving more
agency and tools to users when dealing with discussion platforms.

####  2.1.2. Balancer Browser Extension

The Balancer extension (Munson et al., 2013) provides a nudge with the intent
to diversify the selection of news sources consulted by the user. A
prominently positioned browser widget displays a stick figure carrying a block
in each hand, with their sizes representing the amount of either conservative
or liberal media pages visited. An uneven weight distribution between the two
boxes causes the figure to tilt to the corresponding side. In a supplementary
study a “small but real” (Munson et al., 2013, p. 427) effect could be seen in
the behaviour of participants with the visualization enabled. The work serves
as an example of a method that gives unopinionated feedback concerning the
user’s online behaviour and presents a design space that future approaches can
take into consideration.

####  2.1.3. Explanations for Supporting Algorithmic Transparency

In (Rader et al., 2018) Rader et al. explore methods of providing explicit
explanations for the algorithms in use by a given system. A representative
imaginary student admission algorithm was used to evaluate the effectiveness
of different approaches. Depending on the experiment conditions, either a
detailed visualization of the mapping between input and output (white-box) or
the algorithm’s binary result (black-box) was displayed. Additionally,
participants could either interactively adjust the input parameters to learn
their contribution to the result or were presented with only static values. A
user study showed that, while participants did not self-report a heightened
understanding of the system, the increased verbosity did have a positive
impact when objectively measured. This fact may stem from the aforementioned
Dunning-Kruger effect. People are only able to truly reflect on their
knowledge once confronted with the system’s internals. Thus, even if they
objectively gain knowledge, their self-assessment does not change as they are
made aware of further aspects that they do not know about. Such results can
serve as a pointer for future research when considering similar explanatory
methods.

####  2.1.4. Privacy Nudges

Almuhimedi et al. explore an idea in which they explicitly nudge users to
review their app permissions by telling them, for example, how often their
location has been requested by an app (Almuhimedi et al., 2015). The
supplementary permission manager AppOps further streamlines the process of
permission configuration. A study could show that such nudges, in tandem with
the additional management interface, cause significantly more users to review
and impose limits on the data that is accessible to applications. The basic
idea of these nudges can therefore serve as a basis for communicating even
more detailed information to users.

##  3\. Emancipatory Design

We now seek to propose ways in which the issues mentioned in subsection 1.1
can be counteracted. In what we call emancipatory design we envision
interfaces that, while still providing a low barrier of entry, give more
insight into the systems they interact with. Such interfaces can, of course,
not display the entirety of each system but only a carefully chosen subset of
aspects beyond their level of abstraction. This way, users are made aware of
the fact that they could benefit from actively searching out more information
about the technology at hand. Going further, such interface designs may
directly include possible methods of knowledge acquisition. They may also
allow autonomously exploring aspects of the underlying system. Designs
necessarily need to coincide with the concepts of minimalism and usability in
order to present a step beyond the current state-of-the-art.

Preferably, this approach is to be holistic. While individual systems are
likely to benefit from users gaining a more positive disposition towards
actively learning more about them, social implications could go far beyond
this. At best, users are at least partially aware of all aspects concerning
their everyday systems. Mental models then paint a simplified picture that
fits reality closely enough to prevent situations in which uneducated guesses
have to be made. We expect that, once one veil is lifted, users begin to
assess other aspects more critically as well. Such developments could then
help to counteract over- or underconfidence and protect users against false
advertising, fake news, and other types of misinformation. We believe that the
greatest benefit is to be had if such concepts are adopted in a consistent way
in many different types of interfaces that users come into contact with.

We assume that several approaches need to be considered. While some interfaces
provide opportunities to implement additional interactions used for
introducing low-level concepts, others may not. Such cases can arise due to
concepts that do not fit well into digestible visualizations or because of
platforms that explicitly attempt to hide design choices. Careful analysis has
to be conducted when considering the latter, as such approaches will
necessarily obstruct the user’s workflow within the application itself. Hence,
if a positive effect is to be had, the delivery must be kept short and
unobtrusive.

###  3.1. Examples

We will now give some examples for designs that could serve as a basis for
future research. First, we present interactions that can be introduced into
existing interfaces, followed by designs that are external to the system they
aim to explain.

####  3.1.1. Exploring Filter Bubbles

As previously explained, one key factor of increased exposure to
misinformation are filter bubbles (Pariser, 2011), which cause an apparent
amplification of otherwise fringe opinions. We therefore consider designs in
which the existence of such bubbles and the partisanship within is given
increased visibility. To avoid possible negative implications, care should be
taken to perform visualizations as objectively as possible, because they
should only serve as a tool that allows users to gain an understanding of the
otherwise difficult to comprehend network graph between profiles. Furthermore,
selective hiding or ranking of such bubbles should not occur, as existing
research suggests exposure to opposing viewpoints to be an aide in fostering
accurate beliefs (Hart et al., 2009).

One approach to study in future research could combine the design of Opinion
Space with an automated positioning of profiles via the social graph. Faridani
et al. suggested the need for an easy to understand scale in the
visualization, for which they proposed displaying selected public
personalities as landmarks (Faridani et al., 2010). When considering the
application of this idea on Twitter, this design can easily be translated by
selecting well-known profiles and always displaying those as landmarks in the
graph. Such visualizations may be enabled manually through an action presented
as zooming out. Users are first presented their regular, self-curated feed,
from which they can zoom out to see a slightly simplified overview of the
whole network using selected profiles as landmarks. Given such a view, one
could imagine being able to effectively zoom in and experience feeds or
discussions from the perspective of another bubble, which can allow people to
have an insight into sentiments outside their peer group.

####  3.1.2. Explaining Recommender Systems

While the aforementioned idea plays strongly on social groups, another concept
can be applied to recommendation systems. Considering video platforms such as
YouTube, automated content moderation is largely based on the selection of
videos the particular user has watched in the past (Covington et al., 2016).
In order to better represent the existence of clusters in such a system, users
should be given the chance to understand what selection of content contributed
most to each recommendation. In a possible solution, the list of
recommendations and a history of content viewed in the past could be combined.
To facilitate quickly assessing the information at hand, related entries in
the list of past content would be grouped. Then, for each recommended item the
connections to either individual entries or whole groups can be displayed.

While such visualizations and explanations can never paint a complete picture
and go into deep detail, a positive effect may still be had even with some
simplification. Edwards and Veale suggest that, even when given only
superficial information about machine learning practices, people are
sufficiently able to picture a “model-of-a-model” (Edwards and Veale, 2017) so
that meaningful conclusions about the system can be drawn.

####  3.1.3. Auxiliary Context Aware Learning

As already mentioned, factors can be at play that do not permit such measures
to be directly embedded in an application’s interface. Hence, approaches need
to be considered in which information stems from applications external to the
one that is to be explained. These ideas must go hand in hand with context
awareness, in order to be adequately effective and not be perceived as a
nuisance. Behavioural analysis should be applied to pinpoint moments during
which users are not actively performing a task, but in which they are
available to interact with a knowledge gathering application for a short time.
While research supporting such systems exists (Dingler et al., 2015), an
additional dimension to support such applications could be the users’ level of
knowledge about the system. In such cases, the system could monitor whether
intermediary users operate on a suboptimal plateau of performance. If they do,
new interactions or concepts could be introduced step-by-step. However,
further research is required to assess if—and to what degree—such information
can be gathered automatically.

One holistic approach could make use of gamification. Given a Jeopardy-style
selection of topics and corresponding pieces of information, users could be
motivated to gather knowledge about a wide assortment of topics. In fact,
applications with comparable approaches already exist. One example would be
the general knowledge gathering app getucated222https://getucated.de, which
focuses mostly on history, philosophy, and culture. Combined with context
awareness, such applications could put an emphasis on areas that are relevant
to the specific user and in which they display a lack of knowledge. In order
to further enhance the appeal of the idea, one could evaluate whether a
personification of the knowledge gathering application via a digital assistant
has a positive impact on user retention.

####  3.1.4. Judgemental interfaces

Given the fact that information given by external sources is free to emphasize
negatives, more strongly worded language can be employed. One could, for
example, measure the time users spend clicking through video recommendations
on YouTube. After a while, a notification could be shown explaining that the
recommended content is carefully chosen to maximise the time spent on the
platform in order to expose users to as many ads as possible. Such messages
should be shown regardless of the particular content on screen to prevent
users from assuming a bias concerning certain media pieces. Yet, in case users
become entrenched within single topics, such notifications could serve as a
nudge to take a step back from the content.

Going further, one could imagine texts that take into account even more
information from, for example, Google’s advertising profile of users. This
information could then serve as a basis for messages such as: “Google knows
you are in a relationship, did you?” or “Do you visit this restaurant often?
Google thinks so.” This idea is related to the aforementioned privacy nudges
(Almuhimedi et al., 2015).

##  4\. Discussion

The above-mentioned ideas reflect a subset of possible interface designs that
take emancipatory approaches into account, with a focus specifically on social
platforms. Therefore, mainly their potential social implications are
considered, with the emancipation of users regarding technical aspects being
less of a goal in this context. The particular selection of examples
represents ideas which we deem feasible in their realization. In the first two
examples we consider designs that would—beyond a prototyping stage—require
cooperation with social platforms themselves. The other two designs allow to
relax this requirement, as their basic functionality stems from locally
analysing user behaviour and serving an assisting purpose. We thus assume
those examples to present a valid starting point, with their prototypical
evaluation being feasible for first studies and evaluations, due to their
concepts being similar in scope to existing related work.

We envision that, once design approaches include the concept of presenting a
digestible look behind the veil of systems they abstract away or actively
offer an opportunity to seek out information, novice users are given an
incentive to learn about aspects concerning the systems they use. They do not
need to become experts, they just need to gain enough knowledge to develop an
increased ability to critically assess digital systems. We see the chance that
such developments can provide users with enough agency to overcome adversarial
practices that prey on their lack of critical knowledge. For social platforms
this should, at best, manifest in an awareness for the existence of social
bubbles, the aim of automated recommendation systems and the impact these
factors have on the selection of content. All aspects combined have the
potential to counteract increasing segregation into sub-communities within
platforms and thus factors that play a significant role in susceptibility to
fake news. Going further, other areas of personal computing can benefit from
an increased awareness as well. For example, an increased resistance of users
towards data harvesting practices or premature obsolescence of otherwise
functional systems.

Notably, our ideas do not directly involve automated fact checking or elements
from inoculation theory. Rather, we see part of the reason for the success of
online misinformation campaigns in a manifestation of learned helplessness
(Maier and Seligman, 1976) due to increasingly concise interface designs in
which users are taught to act passively. We theorize that users extend newly
gained critical thinking skills concerning platforms and devices towards the
content presented in them. In the same manner, we argue against automated
methods of confronting users with content sourced from outside their filter
bubble. However, exposure to only partisan sources reinstating one’s own
world-view and increased polarization accompany each other (Stroud, 2010) and
fostering communication between boundaries of in-groups has been proposed as
beneficial (Yardi and Boyd, 2010). In this, we see an excellent example where
increasing the visibility of such groups and providing tools for people to
broaden their scope themselves is more beneficial compared to the automated
counterpart, in which we see a hazard of users assuming malice. We see the
possibility of passively making people aware of their bubble’s scope and its
true size to be a viable option in preventing social segregation in online
spaces worthy of further research, whereas relying solely on automated
techniques merely shifts the problem space. In particular we see aspects of
inoculation theory already being used to instil beliefs in conspiracy
theories, such as nurturing a distrust in reputable sources or preemptively
giving non-factual counterarguments to any statement that would disprove the
theory333Instilling distrust in mainstream media and scientific sources is a
cornerstone in the QAnon conspiracy belief. Similarly, flat earth advocates
place a large emphasis on distributing incorrect evidence that is supposed to
preemptively prove the world-view..

We see the chance that, should such design ideas become more widespread, their
positive effects transcend their respective interface. Having formed a correct
mental model of one system and being made aware of non-expertise in certain
areas, users are able to carry the same understanding onto other applications.
This is especially important in cases where negative implications are
deliberately hidden.

Finally, we want to stress that maintaining a low bar of entry for everything
digital always needs to be pursued. Our ideas merely serve to prevent a
stagnation concerning the level of insight people can have into their systems.
Going further, measures towards preserving universal ease of use when
employing such design approaches are an important cornerstone. Interfaces
themselves must not become more difficult to understand or use, regardless of
any factors that users may be affected by. In the same vein, the usefulness of
any auxiliary information that is presented must not be lost on users.

##  5\. Future Research

The realm of users that are neither novices nor experts remains largely
underexplored in current HCI research. Acquisition of deeper insight is often
externalized to educational facilities or only made possible by actively
searching out information. Integrating a presentation of the presence of lower
levels of abstraction directly inside interface designs is a novel concept for
which we assume a large body of research needs to be conducted.

To conclude, we list a number of research questions that we deem worth
exploring as an initial starting point:

  * •

Can moments be inferred in which both the application context and a user’s
mental state allow teaching short bits of information?

  * •

To what extent can the functionality of lower layers be introduced via
interface design?

  * •

Are users incentivised to actively seek out information about the systems they
use, if they are given a digestible subset of information beyond their skill
set?

  * •

What mental models do novice users have about their technologies?

  * •

Are there ways to extract mental models by analysing computer usage and
inferring a user’s level of knowledge to detect false assumptions?

  * •

Do users significantly change their behaviour concerning their selection of
preferred content when made aware of different filter bubbles?

  * •

What roadblocks need to be overcome concerning the inclusivity of these
approaches? Are there relevant cultural differences? To what extent do
approaches need to be changed to accommodate for disabilities?

## References

  * (1)
  * Almuhimedi et al. (2015) Hazim Almuhimedi, Florian Schaub, Norman Sadeh, Idris Adjerid, Alessandro Acquisti, Joshua Gluck, Lorrie Faith Cranor, and Yuvraj Agarwal. 2015.  Your Location Has Been Shared 5,398 Times! A Field Study on Mobile App Privacy Nudging. In _Proceedings of the 33rd Annual ACM Conference on Human Factors in Computing Systems_ (Seoul, Republic of Korea) _(CHI ’15)_. Association for Computing Machinery, New York, NY, USA, 787–796.  https://doi.org/10.1145/2702123.2702210
  * Bennett et al. (2008) Sue Bennett, Karl Maton, and Lisa Kervin. 2008.  The ‘digital natives’ debate: A critical review of the evidence.  _British Journal of Educational Technology_ 39, 5 (2008), 775–786.  https://doi.org/10.1111/j.1467-8535.2007.00793.x
  * Bucher (2017) Taina Bucher. 2017\.  The algorithmic imaginary: exploring the ordinary affects of Facebook algorithms.  _Information, Communication & Society_ 20, 1 (2017), 30–44.  https://doi.org/10.1080/1369118X.2016.1154086
  * Bucher et al. (2017) Taina Bucher, Anne Helmond, et al. 2017\.  The affordances of social media platforms.  _The SAGE handbook of social media_ (2017), 233–253.
  * Covington et al. (2016) Paul Covington, Jay Adams, and Emre Sargin. 2016\.  Deep Neural Networks for YouTube Recommendations. In _Proceedings of the 10th ACM Conference on Recommender Systems_ (Boston, Massachusetts, USA) _(RecSys ’16)_. Association for Computing Machinery, New York, NY, USA, 191–198.  https://doi.org/10.1145/2959100.2959190
  * Davenport and Beck (2001) Thomas H. Davenport and John C. Beck. 2001.  The Attention Economy.  _Ubiquity_ 2001, May (May 2001), 1–es.  https://doi.org/10.1145/376625.376626
  * Dingler et al. (2015) Tilman Dingler, Markus Funk, and Florian Alt. 2015.  Interaction Proxemics: Combining Physical Spaces for Seamless Gesture Interaction. In _Proceedings of the 4th International Symposium on Pervasive Displays_ (Saarbruecken, Germany) _(PerDis ’15)_. ACM, New York, NY, USA, 107–114.  https://doi.org/10.1145/2757710.2757722
  * Edwards and Veale (2017) Lilian Edwards and Michael Veale. 2017.  Slave to the algorithm: Why a right to an explanation is probably not the remedy you are looking for.  _Duke L. & Tech. Rev._ 16 (2017), 18.  https://doi.org/10.2139/ssrn.2972855
  * Faridani et al. (2010) Siamak Faridani, Ephrat Bitton, Kimiko Ryokai, and Ken Goldberg. 2010.  _Opinion Space: A Scalable Tool for Browsing Online Comments_.  Association for Computing Machinery, New York, NY, USA, 1175–1184.  https://doi.org/10.1145/1753326.1753502
  * Gibbs et al. (2017) Shirley Gibbs, Kevin Moore, Gary Steel, and Alan McKinnon. 2017\.  The Dunning-Kruger Effect in a workplace computing setting.  _Computers in Human Behavior_ 72 (2017), 589 – 595.  https://doi.org/10.1016/j.chb.2016.12.084
  * Hart et al. (2009) William Hart, Dolores Albarracín, Alice H. Eagly, Inge Brechan, Matthew J. Lindberg, and Lisa Merrill. 2009.  Feeling validated versus being correct: A meta-analysis of selective exposure to information.  _Psychological Bulletin_ 135, 4 (2009), 555–588.  https://doi.org/10.1037/a0015701
  * Mahmood (2016) Khalid Mahmood. 2016\.  Do People Overestimate Their Information Literacy Skills? A Systematic Review of Empirical Evidence on the Dunning-Kruger Effect.  _Communications in Information Literacy_ 10, 2 (2016), 199–213.  https://doi.org/10.15760/comminfolit.2016.10.2.24
  * Maier and Seligman (1976) Steven F. Maier and Martin E. Seligman. 1976.  Learned helplessness: Theory and evidence.  _Journal of Experimental Psychology: General_ 105, 1 (1976), 3–46.  https://doi.org/10.1037/0096-3445.105.1.3
  * Munson et al. (2013) Sean Munson, Stephanie Lee, and Paul Resnick. 2013.  Encouraging Reading of Diverse Political Viewpoints with a Browser Widget.  _Proceedings of the International AAAI Conference on Web and Social Media_ 7, 1 (Jun. 2013).  https://ojs.aaai.org/index.php/ICWSM/article/view/14429
  * Pariser (2011) Eli Pariser. 2011\.  _The Filter Bubble: What the Internet Is Hiding from You_.  Penguin Books.
  * Rader et al. (2018) Emilee Rader, Kelley Cotter, and Janghee Cho. 2018\.  Explanations as Mechanisms for Supporting Algorithmic Transparency. In _Proceedings of the 2018 CHI Conference on Human Factors in Computing Systems_ (Montreal QC, Canada) _(CHI ’18)_. Association for Computing Machinery, New York, NY, USA, 1–13.  https://doi.org/10.1145/3173574.3173677
  * Stroud (2010) Natalie Jomini Stroud. 2010\.  Polarization and Partisan Selective Exposure.  _Journal of Communication_ 60, 3 (08 2010), 556–576.  https://doi.org/10.1111/j.1460-2466.2010.01497.x
  * Thompson and Warzel (2021) Stuart A. Thompson and Charlie Warzel. 2021.  _Opinion — They Used to Post Selfies. Now They’re Trying to Reverse the Election._ https://www.nytimes.com/2021/01/14/opinion/facebook-far-right.html (Retrieved 02/05/2021).
  * Union (2018) International Telecommunication Union. 2018\.  ICT Indicators (Edition 2018/1).  (2018).  https://doi.org/11.1002/pub_series/dataset/64cb0e71-en
  * Yardi and Boyd (2010) Sarita Yardi and Danah Boyd. 2010.  Dynamic Debates: An Analysis of Group Polarization Over Time on Twitter.  _Bulletin of Science, Technology & Society_ 30, 5 (2010), 316–327.  https://doi.org/10.1177/0270467610380011