- Varsity Tutors, St Louis, MO, USA
- Date: February 2022 – present
- Position: Freelance online instructor
- Pacific Architects and Engineers (PAE), Starr Commonwealth, Albion, MI, USA
- Date: June 2021 – November 2021
- Position: Instructor to unaccompanied minors from Central America and Afghanistan
- Department of Physics, Western Michigan University, Kalamazoo, USA
- Date: July 2016 – January 2021
- Position: Associate Research Fellow
- Physics Center, Venezuelan Institute for Scientific Research (IVIC), Caracas, Venezuela
- Date: July 2015 – present
- Position: Emeritus Research Fellow
- Department of Physics, Western Michigan University, Kalamazoo, USA
- Date: January 2013 – February 2014
- Position: Associate Research Fellow
- Venezuelan Association for the Advancement of Science (AsoVAC)
- Date: June 2006 – December 2008
- Position: General Secretary of Caracas Branch
- National Center for Scientific Computing Los Andes University (CeCalCULA).
- Date: April 2004 – July 2013
- Position: Associate Research Fellow
- Venezuelan Association for the Advancement of Science (AsoVAC).
- Date: March 2003 – June 2006
- Position: Member of the Board of Directors of Caracas Branch
- IVIC Association of Researchers (AsoInIVIC)
- Date: September 2002 – October 2003
- Position: President
- Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
- Date: September 2001 – August 2002
- Position: National Research Council Senior Research Associate
- Physics Center, Venezuelan Institute for Scientific Research (IVIC), Caracas, Venezuela
- Date: April 2000 – July 2015
- Position: Senior Research Fellow
- Université Paris 7, Paris, France
- Date: July 1999 – August 1999
- Position: Professeur Invité
- Observatoire de Paris, Meudon, France
- Date: June 1997 – September 1997
- Position: Poste Rouge du CNRS
- Physics Center, Venezuelan Institute for Scientific Research (IVIC), Caracas, Venezuela
- Date: January 1997 – April 2001
- Position: Head of Center
- Physics Center, Venezuelan Institute for Scientific Research (IVIC), Caracas, Venezuela
- Date: March 1995 – March 2000
- Position: Tenured Associate Research Fellow
- Computing Network, Venezuelan Institute for Scientific Research (IVIC), Caracas, Venezuela
- Date: January 1995 – November 1998
- Position: Head of Center
- Physics Center, Venezuelan Institute for Scientific Research (IVIC), Caracas, Venezuela
- Date: May 1994 – February 1995
- Position: Research Fellow III-3
- IBM Venezuela Scientific Center, Chuao, Caracas, Venezuela
- Date: November 1983 – May 1994
- Position: Research Consultant
- Physics Department, Simón Bolívar University (USB), Sartenejas, Venezuela
- Date: September 1982 – December 1985
- Position: Assistant Professor
- Department of Physics and Astronomy, University College London, Gower Street, LondonWC1E 6BT, England
- Date: October 1979 – September 1982
- Position: SERC Research Assistant
- Universidad Nacional Experimental del Táchira, San Cristóbal, Venezuela
- Date: May 1974 – August 1975
- Position: Assistant Professor