1. 1 18-20 redux Can the focal plane accommodate both RSC and RVS as viable NIR venders C. Bebek 28 April 2005

2. 2 “How to maintain agility in the face of 18  m and 20  m MCT,” C. Bebek, 25 October 2002. Essentially, this was ignored because we didn’t take Raytheon seriously. Not the case any longer! In this round of focal plane design, we should revisit a non-vender-specific solution. Impacts Optics CCD Science data Mounts and focal plane Glossary RSC = Rockwell RVS = Raytheon MCT = HgCdTe

3. 3 2002

4. 4

5. 5 MCT vender package data Rockwell Raytheon

6. 6 MCT packages Some rations: Pixel size: 20/18 = 1.111 Longest package dimension: 44.520/42.160 = 1.060 Grid size: 45.520/43.160 = 1.055 RaytheonRockwell

7. 7 Area-matched CCD packages RaytheonRockwell SNAP V2 Keep 10.5 µm pixels in both cases

8. 8 Some numerology Focal plane inner and outer radii (mm) —R in = 3*(L max + L gap ) —R out = 3*S5*(L max + L gap ) —L gap = 1 mm L max R in R out RSC43.160129.48289.53 RVS45.520136.56305.36 RSC RVS

9. 9 RSC MCT and CCD

10. 10 RSC MCT and RVS CCD

11. 11 RVS MCT and CCD Reasonable

12. 12 RSC MCT and RVS CCD Reasonable

13. 13 Optics impact What plate scale (arcsec/pixel) do we want? Are Mike Lampton’s flexible TMAs flexible? How long can we delay nailing it down? Note, this is an opportunity to reduce CCD plate a bit. FL = 21.66 mFL = 24.07 m RSCRVSRSCRVS CCD0.100 0.090 MCT0.1710.1900.1540.171

14. 14 CCD impact Do we want to carry two CCD formats for a while? —Make one and only one CCD format, the one that matches Raytheon? —If we go with Rockwell, we still have more visible sq. degs. for weak lensing. Option —The blue shaded region is overall size of the CCD using SNAP V2 edge overheads. Could grow to the orange region, matching Raytheon physical package dimension. —Can move wire bond pads further from active pixel region making wire-bond package a more viable backup. —SNAP V2 HV improvements can deal with this larger overhead region.

15. 15 Science data With a 3900 x 3900 CCD there is more data; 548 vs 444 Mpixel. To acquire data, read CCDs at 128 kpixel/s or extend shutter closed time to 38 s. A corresponding amount more of memory is required. And a corresponding higher telemetry rate or telemetry time is requied.

16. 16 Mounts? What do we do to allow both MCT types to mount to the focal plane. Associated with this is the size of the penetrations in the focal plane for connecter and e-box cross section. E.g., mount RVS, RSC and CCD on structures with the same foot print at the focal plane interface.

17. 17 Summary I am sure you can develop a single design to accommodate both Rockwell and Raytheon devices. To support this, the CCD group needs to either support two CCD sizes and their associated packages or one CCD size matching Raytheon pixel area. The are data rate/volume costs at the 20% level. Optical prescription has to remain flexible up to the time of vender selection. A universal mount is possible, but can you force 3 interested parties into a common footprint. A design accommodating the two MCT venders is good industrial politics. Public display of this sends/reinforces the message that the venders are in competition.