What does this number measure?
An infrared observatory protected by a large sunshield. The segmented mirror and the sunshield's five layers allow James Webb to observe at low temperature. The compared dimension is the length of the deployed sunshield, not the mirror's diameter.
Compare the stated dimensions
The comparison uses the number in each fact sheet: altitude, height, diameter, length or distance, depending on the reference. Two values in metres do not necessarily describe the same property.
Compare with Santa María · quincentenary replica in the explorer →
Source and limitations
Catalogue order of magnitude; a source is provided, but this measurement has not been individually audited.
James Webb deployed, sunshield aligned horizontally.
Launch: 2021. Proposed historical date; an existing documentary source is linked but was not consulted for this date in this session. Do not interpret this reference as the manufacturing date of the illustrated specimen. James Webb was launched in 2021; deployment and first scientific images followed in 2022.