JWST, launched in 2021, produces revolutionary data on a daily basis. Part of MIRI was built in the Netherlands, between 2002 and 2008. In the 2016-2021 period, NOVA-funded scientists formed an integral part of the team calibrating, testing, and commissioning MIRI. The NL team led the fringe-correction effort for the MRS spectrometer, a crucial pipeline step. Another focal point was the support of science users. With numerous approved programs with Dutch PIs and CoIs, we’re starting to reap the benefits of this long-term investment.

Meet The Team


Michael “Migo” Mueller
Michael "Migo" Mueller has been working on MIRI characterization and calibration since 2015.  He participated in the commissioning of the instrument. His expertise is mostly with the MRS spectrometer, especially fringing. His science background is in Solar System research, mostly thermal studies of planetary surfaces, with side-steps to exoplanets and disks.

Contact: m.mueller[a]


Nicolas Crouzet
Nicolas Crouzet is an expert in the detection of transiting exoplanets and in the study of their atmosphere. He uses ground- and space-based telescopes including the JWST. He has a background in astronomical instrumentation and developed instruments to conduct his research. He joined the NOVA MIRI team in March 2022.

Contact: crouzet[at]


Guang Yang
Guang Yang is an expert in MIRI imaging and is a core team member of the JWST/CEERS collaboration. He studies the cosmic evolution of supermassive black holes and galaxies using MIRI surveys as well as other multi-wavelength data. He is one of the major developers for the astronomical software CIGALE. You can find more info about Guang on his personal website.

Contact: gyang[at]


Peter Roelfsema
Peter Roeflsema is the NL MIRI project manager. He is a senior scientist working at SRON. He also serves as the X-IFU/NL Project Manager and the SPICA collaboration lead.

Contact: P.R.Roelfsema[at]


Instrument Testing

Mueller and Lahuis were part of the MIRI test team

  • NASA Goddard (2015/16)
  • Johnson Space Center (2017)
  • In-orbit commissioning (2022)

The NL team led

  • MRS PSF: observation planning
  • MRS fringes: analysis and calibration
  • MRS glints: analysis MRS was declared science-ready in June 2022

MRS Fringe Correction

The MIRI/MRS observations suffer from fringe issues, i.e., sensitivity variation due to standing waves in the detector. The amplitude of this variation can be up to 40%! In order to obtain genuine spectra, it is important to correct the fringe effects ("defringe"). We have made significant efforts for the defringe process:

  • The pipeline reduces that amplitude to < 2% as required in two steps Division by a fringe flat (led by Mueller, Lahuis, Kester), based on in-flight data
  • Residual fringe correction via sinusoidal fit (based on legacy code by Lahuis, Kester) is also available.
  • A separate fringe-correction mechanism for point sources has been derived and validated (Leiden, Leuven, Groningen). In the future, we will make it accessible within the pipeline.

Community Support


Science Support

We organized numerous support meetings and workshops, both for the NL community at large and around the Guaranteed-Time (GTO) teams. This includes workshops on observation planning and data reduction. In the first round of General-Observers (GO) proposals, Dutch-led programs enjoyed an above-average rate of success. Specifically, 40% of programs with a Leiden-based PI were approved versus an average of ~24%. The first results start coming in. MIRI team members support numerous observing teams individually.

Public Outreach

Many talks/events/interviews by the NL team.