An approach and development plan for the production of replicated variable line spacing X-ray reflection
gratings on lightweight substrates is described. The gratings will be arrayed in spectrometers to analyze
the soft X-rays gathered by the telescopes flown aboard the European Space Agency (ESA) "X-ray Multi-
Mirror Mission" (XMM). The mission requires about 750 gratings to form 3 arrays. Each array provides
a grating area of approximately 5 square meters. From relatively few master gratings, the low blaze angle
gratings will be replicated onto 55 gram substrates having an equivalent length/thickness aspect ratio &square;40.
We will describe the criteria used for selecting the substrate design and material. A multi-phased study to
solve identified technical problems associated with the replication of these gratings is also described. We
will report on the present status of the substrates and replication process.