The structures fit the envelope of 1575mmx1150mm given by the GTC specifications. However, the distance from the focal plane to the flange of the telescope is 75mm. Because the instrument extends beyond the focal plane the most restrictive dimention is given by the size of the flange connecting the instrument to the telescope. Our solution consists of fixing the bulkhead forward in the bench instead of the standard solution at the front of the instrument. The front of the bench, focal plane masks/mechanisms and fold mirrors go inside of the instrument flange. Then, the bulhead divides the instrument shields in two cathegories: the front shields and the back shields. The back shields correspond to the active, passive and vacuum shields found in the standard configuration. Similar screens are found in the front of the instrument. Because they are surrounded by the G10 ring and the space is very limited the dimentioning and assembling requires a special solution. The activea and passive shields are mounted in first place. Then the G10 is screwed from the back of the bulkhead. The flange of the instrument extends to the bulhead in order to attach the back vacuum jacket. The front cover is a floating piece in order to access the focal plane mechanisms. Here, we enumerate these pieces and summarize their relation and the assembling steps.

Ref # Piece Number Attached to piece # (ref attachment letter)
1 Optical Bench 2 (A); 3(A or/and B)
2 Dewar 1 (A)
3 Instrument Ring 1 (A and/or B); 5(C); 7 (D); 10 (E)
4 Instrument Flange 6 (F); Telescope
5 G10 Ring 6 (G); 3 (C);
6 Front-Vacuum Shield 4 (F); 9 (H)
7 Front-Active Shield 3 (D); Entrance Window
8 Front-Passive Shield Floating Shield
9 Back-Vacuum Shield 6 (H)
10 Back-Active Shield 3 (E)
11 Back-Passive Shield Floating Shield

  • GROUP 1
    1. Dewar to Optical Bench
    2. Instrument Ring to Dewar/Bench
    3. Front-Active Shield to Instrument Ring
    4. Back-Active Shield to Instrument Ring
  • GROUP 2
    1. Front-Vacuum Shield to Instrument Flange
    2. Front-Vacuum Shield to G10 Ring
    1. Insert Front-Passive Shield
    2. Instrument Ring to G10 Ring
    3. Insert Back-Passive Shield
    4. Back-Vacuum Shield to Front-Vacuum Shield
    Bench Flexures
    Thermal Calculations

    Filter Box
    Focal Plane

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