Hardware and software systems have grown to support the work on critical areas that used to be managed mostly by human beings. Concepts and challenges regarding critical systems have long been discussed by several authors, although communication-based aspects have not been explicitly considered. In this paper, we propose a procedure for designing interaction in critical systems under the communication perspective; the procedure results in a user interface wireframe as outcome. Semiotics is used as theoretical and methodological background in the proposed design procedure. The Scientific Satellite Payload Operation Support System (SAPOP) is used to illustrate the potentiality this perspective brings to safety-critical systems. 165172Basnyat, S., Palanque, P., Schupp, B., Wright, P., Formal socio-technical barrier modelling for safety-critical interactive systems design (2007) Safety Science, 45 (5). , June 2007. ISSN: 0925-7535Bonacin, R., Simoni, C.A.C., Melo, A.M., Baranauskas, M.C.C., Organisational semiotics: Guiding a service-oriented architecture for e-government (2006) 9th International Conference on Organisational Semiotics, pp. 47-58Carver, L., Turoff, M., Human-computer interaction: The human and computer as a team in emergency management information systems (2007) Communications of the ACM, 50 (3). , ACM PressCordeiro, J., Filipe, J., The semiotic pentagram framework - A perspective on the use of semiotics within organisational semiotics (2004) Proceedings of the 7th International Workshop on Organisational SemioticsFrancisco, M.F.M., Sagukawa, B.M., Safety in a web-based satellite flight plan supporting system (2006) SpaceOps 2006 Conference, , AIAA 2006-5773. American Institute of Aeronautics and Astronautics IncGuimarães, M.S., Baranauskas, M.C.C., A case study on modelling the communication structure of critical systems (2009) 11th International Conference on Informatics and Semiotics in Organisations, , IFIP WG 8.1Guimarães, M.S., Baranauskas, M.C.C., Martins, E., Communication-based modelling and inspection in critical systems (2008) 10th International Conference on Enterprise Information Systems, , INSTICC PressGuimarães, M.S., Baranauskas, M.C.C., Martins, E., A communication-based approach to requirements elicitation for safety-critical systems (2007) Proceedings of 10th International Conference on Organisational Semiotics, , ICOSHarrison, M., Aspects of human error: A brief introduction (2004) Workshop on Human Computer Interaction and Dependability, , http://www.laas.fr/IFIPWG/Workshops&Meetings/46/03-Harrison.pdf, Retrieved October, 2004 from 2004Liu, K., (2000) Semiotics in Information Systems Engineering, , Cambridge University PressMackie, J., Sommerville, I., Failures of healthcare systems (2000) First Dependability IRC Workshop, pp. 79-85. , Edinburg University PressPaulson, L.C., (1997) Software Engineering, , University of Cambridge Press. U.S.A(2008) European Network of Excellence ReSIST, , http://www.laas.fr/RESIST/index.html, ReSIST Deliverable D13: From Resilience-Building to Resilience-Scaling Technologies: Directions. Retrieved August, 2008 fromSalles, J.P., (2000) O Modelo Fractal de Comunicação: Criando Um Espaço de Análise para Inspeção do Processo de Design de Software, , PhD dissertation, Departamento de Ciência da Computaçã o, Instituto de Ciências Exatas. Universidade Federal de Minas GeraisSalles, J.P., Baranauskas, M.C.C., Bigonha, R.S., Towards a communication model applied to the interface design process (2001) Knowledge-Based Systems, 18 (8), pp. 455-459. , 2001Sommerville, I., (2003) Engenharia de Software, , Addison WesleyStamper, R.K., Social norms in requirements analysis - An outline of MEASUR (1993) Requirements Engineering Technical and Social Aspects, , Academic PressStamper, R.K., (1973) Information in Business and Administrative Systems, , John Wiley and Sons, NY