Precision Alignment Mechanisms for the Nancy Grace Roman Space Telescope

One of the PAM flight models manufactured by MPIA and vH&S on its transport plate.
One of the PAM flight models manufactured by MPIA and vH&S on its transport plate.

One outstanding project we are proud to have contributed to is NASA’s Nancy Grace Roman Space Telescope (NGRST), formerly known as the Wide Field Infrared Survey Telescope (WFIRST). This telescope has the ambitious goal of investigating the immediate surroundings of distant stars, thereby enabling the direct observation of exoplanets, particularly gas giants. A central instrument of the NGRST is the coronagraph, which blocks emissioned light from stars to make fainter objects in their vicinity visible. To ensure the precise function of the coronagraph, it is necessary to position various optical elements extremely accurately (up to a few tens of nanometers) in the telescope’s optical beam path. This task is performed by a set of six Precision Alignment Mechanisms (PAM).

The PAM is used on the optical bench of the Coronagraph Instrument (CGI) within the NGRST. The coronagraph instrument with its 2.4 m primary mirror will be used for direct imaging of exoplanets from its position at the Lagrange point L2. There are six PAMs in total on the optical bench. All the PAMs are placed in the zigzag folded optical beam of the instrument. Each mechanism is carrying many individual optical elements, such as filters, mirrors lenses and masks on six different optical plates. An optical plate is mounted on the movable part of the mechanism. These plates can be moved precisely in horizontal and vertical direction to position the needed optical elements into the optical beam of the coronagraph.

Some optical elements are used to mask out an extrasolar star, to make planets beside the masked star visible. The PAMs are categorized in two models, small and large. The large ones have a longer mechanical travel range than the small ones. The optical plates with the optical elements are supplied by the NASA Jet Propulsion Laboratory (JPL).


To request more info, please send an E-Mail to Guido Krein, E-Mail: