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General Observer Programs in Cycle 4

The 274 programs listed below establish the science program for JWST’s fourth year of operations, amounting to 8,500 hours of prime observing time. Cycle 4 observations include 241 GO, 8 Survey, 15 Regular Archival, 8 Theory Archival, and 2 Legacy Archival programs (two of the Archival programs are Calibrations and one is a Data Science Software program). STScI hosted the Cycle 4 Telescope Allocation Committee (TAC) in February 2025, comprised of 2 Executive Committee Chairs, 36 Panel Chairs and Vice Chairs, 183 Discussion Panelists, 315 External Panelists, and 220 Expert Reviewers.

The TAC was held in three stages:

  • The smallest proposals (<20 hours duration) were distributed to the external panels that graded them independently;
  • Small proposals (> 20 and ≤ 50 hours), Medium (> 50 and ≤ 130 hours) and  all Target of Opportunity and Survey proposals, regardless of size, were reviewed by 18 topical panels that met online from February 3-7, 2025;
  • And the Large (>130 hours), Treasury, Legacy, and other requests for substantial resources, such as large Pure Parallel programs were reviewed by the two Executive Committees (Galactic and Extra-galactic) that met in person at STScI from February 10-13, 2025.

To view details about a specific program, select a category below, then click the Program ID. It make take a few days following the announcement for the programs to be available in the database and for the links to work.

NOTE: The listing of Co-PIs in the tables below has been limited to 4. Proposals with more than 4 Co-PIs are denoted with an asterisk. The full listing is available with the proposal.

Science Categories for GO Proposals

Abbreviations:

BOTS = Bright Object Time-series

FS = Fixed Slit

GTS = Grism Time Series

IFU = Integral Field Unit

LRS = Low Resolution Spectroscopy

MOS = Multi-object Spectroscopy

MRS = Medium Resolution Spectroscopy

SOSS = Single-object Slitless Spectroscopy

TSO = Time Series Observation

WFSS = Wide Field Slitless Spectroscopy

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The NASA James Webb Space Telescope, developed in partnership with ESA and CSA, is operated by AURA’s Space Telescope Science Institute.