From Cosmic Dreams - to Earthly Realities

1. From Cosmic Dreams - to Earthly Realities Niels Lund Danish National Space Center

2. The Soyuz ST envelope: • Maximum launch mass to the Lagrange point L2 or to a deep elliptical (7 days) orbit: 2100 kg (Take 300 kg for the detector spacecraft and 1800 kg for the lens spacecraft) • Maximum spacecraft diameter at launch: 3.8 m • Maximum spacecraft height at launch: 8 m GRI planning meeting, Ferrara | November 17-18 2005 | page 2

3. My recommendation for a Laue-lens at the time of the Bonifacio workshop Copper crystals Focal length: 150 m, crystal mass: 416 kg Takes all available weight – no reserves for a multilayer telescope ! GRI planning meeting, Ferrara | November 17-18 2005 | page 3

4. What have changed since Bonifacio ? • I realized that since the focal length may be chosen freely once we have decided to go for formation flying of two satellites there was no reason to keep the same focal length for all choices of crystals. Rather we should decide the radius in the lens for some specific energy (say 180 cm for 511 keV) and then see what focal length this requires with a given crystal type. In this way we will get a more correct comparison between the diffraction power of the different crystals. • The desire to include a multilayer telescope in the payload made it essential to save weight on the Laue lens without sacrificing on its performance. • So I took a second look at the relative merits of Copper, Silver and Gold crystals. All three have fcc structure, have high atomic density, and high quality crystals have already been grown of both copper and gold. GRI planning meeting, Ferrara | November 17-18 2005 | page 4

5. Comparison of performance and weight for Au, Ag and Cu All three have similar flux collection power as function of energy. But note the weights: Au: 246 kg Ag: 358 kg Cu: 401 kg The crystal thickness (below 511 keV) has been adjusted to keep the effective area constant GRI planning meeting, Ferrara | November 17-18 2005 | page 5

6. Laue-lens performance including 2nd and 3rd order GRI planning meeting, Ferrara | November 17-18 2005 | page 6

7. Combined Laue-lens and multilayer telescope The Laue-lens covers the energy band from 200 to 1000 keV. The multilayer telescope covers the energies below 200 keV. The Laue-lens has a central hole with a diameter of 1.8 m, the multilayer telescope (outside diam. 90 cm) fits easily here, and can be offset up to 45 cm to separate the two focal plane detectors. GRI planning meeting, Ferrara | November 17-18 2005 | page 7

8. Effective area of combined Laue-lens and multilayer telescope It appears that a dual system offering more than 1000 cm2 eff. area between 0.5 and 600 keV and 600 cm2 at 1000 keV is feasible with Soyuz. (Dont worry that the Focal lengths dont match, this is only a first try!) Combined mass 440 kg GRI planning meeting, Ferrara | November 17-18 2005 | page 8

9. What next on the spacecraft technical side ? • We need to get some good spacecraft engineers to look at the concepts for the lens and detector spacecrafts. (Look at the MAX study!) • Can we build rigid panels for the crystals? • How shall we deploy them and adjust to the correct angle? • What does the panel structure weigh? • What does the deployment weigh? • More weight for crystals and multilayer telescope? GRI planning meeting, Ferrara | November 17-18 2005 | page 9