The NIRSpec GTO program

In return for the provision of the NIRSpec spectrograph, the European Space Agency (ESA) has received an allocation of 900 hours of JWST guaranteed time (wall-clock time including direct and indirect overheads). This program is managed by the ESA JWST project scientist and is being prepared by the NIRSpec guaranteed-time observer (GTO) team.

On this site, you will find a brief description of each element of the NIRSpec GTO program.

The NIRSpec GTO program is built around one large core program focused on the theme of galaxy formation and evolution, and a set of 5 small and 2 medium programs covering a much wider range of astrophysical topics. Although scientific excellence has been the primary criterion when designing this GTO program, we have also made sure that in the course of these observations, the NIRSpec GTO team will probe the key modes and observation strategies / regimes of the NIRSpec instrument, with the aim to provide early feedback on the data quality and processing steps to the scientific operation center (STScI) and to the community. 





The physics of galaxy assembly – the NIRSpec GTO spectroscopic survey

NIRSpec instrument science team

724 hours (+21 hours of contingency)


DEEP MOS survey


148 hours




200 hours


WIDE MOS survey


106 hours


IFU survey


270 hours

Cosmic reionization and metal enrichment from quasar spectroscopy

C. Willott & P. Jakobsen

42 hours

Resolved structure and kinematics of the nuclear regions of nearby galaxies

T. Böker

16 hours

Transiting exoplanet characterization with JWST/NIRSpec

S. Birkmann & J. Valenti

50 hours

Direct spectroscopy of an exoplanet with the JWST/NIRSpec IFU

S. Birkmann

6 hours

Star formation in the local group

G. de Marchi

15 hours

The physics of brown dwarfs

C. Alves de Oliveira

17 hours

Surface composition of mid-sized TNOs: searching for ammonia

A. Guilbert-Lepoutre

9 hours


900 hours

Coordinated Parallels

When possible and scientifically valuable, we intend to propose obtaining NIRCam images in parallel to our NIRSpec multi-object spectroscopy (MOS) exposures. As the availability of the NIRCam / NIRSpec MOS coordinated-parallel capability for Cycle 1 has been confirmed by STScI only very recently, we are still working on the implementation of these parallel observations and unfortunately they could not be included in this early view of the NIRSpec GTO program.

What's new?

The overview of NIRSpec GTO program has been compiled and made publicly available via this site



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