Nasa has completed three of the seven stages to bring the 18 hexagonal segments of the James Webb space telescope’s primary mirror into alignment.
On 25 February, Nasa announced that the mirror segments were in place and their individual images stacking together. This means the separate images produced by the segments have been united to form a single image.
It marks the beginning of the segments working as a single mirror. Each segment is controlled by six motors that can move and tilt the reflective surfaces.
After the primary mirror’s deployment on 19 January, ground crews began commanding the motors to coax the segments into line. By 12 February, all 18 were directing unfocused starlight into the near infrared camera.
Next, the segments were moved so each image was focused, and now the segments have been tilted so the individual images fall on top of one another.
Fine-tuning will ensure the segments are optimally aligned with themselves and the four science instruments. This is likely to take until late spring. The first true images from the telescope are expected in early summer.