Telescope Dome Specification

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Telescope Dome Specification

SOAR Telescope Project

August 25, 1999







Thomas A. Sebring





Gerald N. Cecil


Project Manager





Project Scientist






David Porter





Victor L. Krabbendam

Opto
-
Mechanical Engineer





Project Engin
eer




SOAR Dome Specification


D
SP99
-
013

2


INDEX



1. INTRODUCTION

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................................
................................
......................

8

1.1. Objective

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................................
................................
..............................

8

1.2. System Description

................................
................................
................................
..............

8

1.3. Scope

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................................
................................
................................
....

9

2. DESCRIPTIO
N AND SPECIFICATIONS

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................................
................

9

2.1. Steel Structure

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................................
................................
......................

9

2.1.1. Ring Beam

................................
................................
................................
..................

10

2.1.2. Arch Girders
................................
................................
................................
................

10

2.2. Panel System

................................
................................
................................
......................

10

2.3. Shutter and Windscreen System

................................
................................
........................

11

2.3.1. Shutter Door Description

................................
................................
............................

11

2.3.2. Shutter Drive System

................................
................................
................................
..

11

2.3.2.1. Shutter Drive Requirements

................................
................................
.................

12

2.3.2.1.1. Shutter Drive Performance

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................................
...........

12

2.3.3. Shutter Travel Limits

................................
................................
................................
..

13

2.3.3.1. Shutter Software Limits

................................
................................
.......................

13

2.3.3.2. Hardware Limits

................................
................................
................................
..

13

2.3.3.3. Hard Stops

................................
................................
................................
............

14

2.3.4. Settling Time

................................
................................
................................
...............

14

2.3.5. Shutter Manual Operation

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................................
...........................

14

2.3.6. Shutter Encoder

................................
................................
................................
...........

14

2.4. Dome Rotatio
n Drive System

................................
................................
............................

15

2.4.1. Dome Drive Assembly

................................
................................
................................

15

2.4.2. Dome Encoder

................................
................................
................................
............

15

2.4.3. Dome Drive Requirements

................................
................................
.........................

15

2.4.3.1. Performance Requiremen
ts

................................
................................
..................

15

2.4.4. Settling Time

................................
................................
................................
...............

16

2.5. Bogies

................................
................................
................................
................................

16

2.6. Dome Vents

................................
................................
................................
.......................

16

2.7. Dome Crane

................................
................................
................................
.......................

16

2.7.1. Crane Stowed Pos
ition and Interlocks

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................................
........

17

2.8. Seals

................................
................................
................................
................................
...

17

3. STRUCTURAL REQUIREMENTS

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................................
........................

17

3.1. Crane Loads

................................
................................
................................
.......................

17

3.1.1. Dome Stationary

................................
................................
................................
.........

17

3.1.2. Dome Moving

................................
................................
................................
.............

17

3.2. Mass Properties

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................................
................................
..................

17

3.2.1. Dome Weight

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................................
................................
..............

17

3.3. Deflections

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................................
................................
.........................

18

3.3.1. Ring Beam

................................
................................
................................
..................

18

3.3.1.1. Horizontal Plane
................................
................................
................................
...

18


SOAR Dome Specification


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3.3.1.2. Vertical Plane

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................................
................................
.......

18

3.3.2. Arch Girder

................................
................................
................................
.................

18

3.3.2.1. Vertical Plane

................................
................................
................................
.......

18

3.3.2.2. Lateral Plan
e

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................................
................................
........

18

3.3.3. Shutters

................................
................................
................................
.......................

18

4. ELECTRICAL REQUIREMENTS

................................
................................
..........................

19

4.1. Electrical Power

................................
................................
................................
.................

19

4.1.1. Voltage, Frequency, Current and Ground

................................
................................
...

19

4.1.2. Power Protection

................................
................................
................................
.........

19

4.1.3. Electromagnetic Compatibility (EMC)

................................
................................
.......

20

4.1.4. Lightning Protection

................................
................................
................................
...

20

4.2. Electrical Interface Requirements

................................
................................
......................

20

4.2.1. Connectors

................................
................................
................................
..................

20

4.2.2. Cables

................................
................................
................................
..........................

20

4.2.3. Cable Lengths

................................
................................
................................
.............

20

4.2.4. Slip Rings

................................
................................
................................
....................

21

4.3. Electronic Enclo
sure Requirements

................................
................................
...................

21

4.4. Dome Control Electronics in the Observing Area

................................
.............................

21

4.5. Electronic Equipment Mounting

................................
................................
........................

21

5. CONTROL SYSTEM

................................
................................
................................
...............

21

5
.1. General Scope

................................
................................
................................
....................

21

5.2. Operational States

................................
................................
................................
..............

22

5.2.1. Quiescent/Power
-
Off (QPO) State

................................
................................
..............

22

5.2.2. Power
-
On Self Test (POST) State

................................
................................
..............

22

5.2.
3. Base Ready (BR) State
................................
................................
................................

22

5.2.4. System Health Check (SHC) State

................................
................................
.............

23

5.2.5. Operational Ready (OPR) State

................................
................................
..................

23

5.2.6. Set Position (SP) State

................................
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...............................

23

5.2.7. Error State

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................................
...................

23

5.2.8. Abort State

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................................
..................

23

5.3. Operational Modes

................................
................................
................................
.............

24

5.3.1. Remote Operation Mode (TCS Control)
................................
................................
.....

24

5.3.2. Main
tenance and Diagnostic (MD) Mode (Dome Terminal)

................................
.....

24

5.3.3. Hand Paddle (Manual) Mode

................................
................................
......................

25

5.4. Platforms and Operating Systems

................................
................................
......................

25

5.5. Remote Communication Requirements

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................................
.............

25

5.6. Software

................................
................................
................................
.............................

25

5.6.1. Software Architecture

................................
................................
................................
.

26

5.6.2. System Database

................................
................................
................................
.........

26

5.6.3. System Diagnostics

................................
................................
................................
.....

26

5.7. Soft Travel Limit
................................
................................
................................
................

26

5.8. Reduced Speed Operation

................................
................................
................................
..

26

5.9. Emergency Stop System

................................
................................
................................
....

26

6. THERMAL REQUIREMENTS

................................
................................
...............................

27

6.1. Dissipated Pow
er

................................
................................
................................
...............

27

6.1.1. Electronics within the Observing Environment

................................
..........................

27


SOAR Dome Specification


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6.1.2. Electronics within Other Regions of the SOAR Facility

................................
............

27

6.2. Thermal Sensing, Control, and Condit
ioning of Dome Assemblies

................................
..

27

6.2.1. General Thermal Conditioning Strategy

................................
................................
.....

27

6.2.2. Actuators & Mountings
................................
................................
...............................

28

7. SOAR FAcility
................................
................................
................................
..........................

28

7.1. Ob
serving Area

................................
................................
................................
..................

28

7.2. Control Room
................................
................................
................................
.....................

28

7.3. Computer Room

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................................
................................
.................

28

7.4. Mechanical Equipment Building

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................................
.......................

28

7.5. Instrument Utility Room

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................................
................................
....

29

7.6. General Facility Space

................................
................................
................................
.......

29

7.7. Intra
-
Facility Distances

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................................
................................
......

29

7.8. SOAR Supplied Utilities

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................................
................................
....

29

8. INSTALLATION

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................................
................................
.....................

29

8.1. Site Installation

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................................
................................
..................

30

8.1.1. Dome Bogies and Drive

................................
................................
..............................

30

8.1.1.1. Bogie Alignment

................................
................................
................................
..

30

8.1.2. General Sensors

................................
................................
................................
..........

30

9. ENVIRONMENTAL CONDI
TIONS

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................................
......................

30

9.1. Operating Conditions

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................................
................................
.........

31

9.2. Survival Conditions

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................................
................................
...........

31

10. General Status and Sensing System

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................................
........................

32

10.1. Sensors

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................................
................................
.............................

32

11. SAFETY

................................
................................
................................
................................
.

32

11.1. Over Speed Protection

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................................
.....

32

11.2. Over Current Protection

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................................
................................
...

32

11.3. Interlock Procedures

................................
................................
................................
........

32

11.3.1. Do
me and Shutter Drives

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................................
..........................

32

11.3.2. Aerial Man
-
lift

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................................
................................
..........

32

11.3.3. Dome Crane

................................
................................
................................
..............

33

11.4. Captive Tools and Fasteners

................................
................................
............................

33

11.5. Mirror Cover

................................
................................
................................
....................

33

12. COATINGS

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................................
............................

33

12.1. Internal Coatings

................................
................................
................................
..............

33

12.2. External Coatings

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................................
................................
.............

33

13. RELIABILITY AND MAINTAINABILITY REQUIREMENTS

................................
.........

33

13.1. Duty Cycle

................................
................................
................................
.......................

34

13.2. Mean Time Between Failure (MTBF)

................................
................................
.............

34

13.3. Design Life
................................
................................
................................
.......................

34

13.4. Routine Servicing
................................
................................
................................
.............

34

13.5. Access
Panels

................................
................................
................................
...................

34

13.6. Critical Spares

................................
................................
................................
..................

34

13.7. Modularity
................................
................................
................................
........................

34

13.8. Special Tools and Equipment

................................
................................
..........................

34

13.9. Lifting points

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................................
................................
....................

35

13.10. Lifting Fixtures

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................................
................................
..............

35


SOAR Dome Specification


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13.11. Quick Release Attachments

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................................
...........................

35

13.12. Dome Drive Lifting Points
................................
................................
.............................

35

14. ACCEPTANCE TESTING

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................................
................................
.....

35

1
4.1. Required Tests

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................................
.................

35

14.2. Test Standards

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................................
..................

36

14.3. Test Masses

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................................
......................

36

14.4. Cabling and Hoses

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................................
...........

36

15. PACKAGING AND SHIPPING

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................................
............................

36

16. DOCUMENTATION

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................................
.............

36

16.1. Operation Manual

................................
................................
................................
............

36

16.2. Servicing Procedures

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................................
................................
.......

36

16.3. Test Results / Benchmarks

................................
................................
...............................

37

16.4.

Operations Log
................................
................................
................................
.................

37

16.5. Safety Plan / Procedures

................................
................................
................................
..

37

16.6. Documentation

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................................
.................

37

16.7. Installation Procedures

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................................
.....

37



APPENDIX A

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................................
................................
.............................

A
-
2

1. ABBREVIATIONS

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................................
................................
................

A
-
2

2. WORKMANSHIP

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................................
................................
..................

A
-
2

2.1. Fabrication and Assembly
................................
................................
................................

A
-
2

2.1.1. Welding

................................
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................................
.....................

A
-
3

2.1.2. Stress Relieving

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................................
................................
........

A
-
3

2.1.3. Edges

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................................
................................
.........................

A
-
3

3. MATERIALS

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................................
..........................

A
-
3

3.1. Material Certification

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................................
................................
.......

A
-
3

3.2. Structural Steel

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................................
................................
.................

A
-
3

3.3. Stru
ctural Steel Shapes, Plates, and Bars

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................................
.........

A
-
3

3.4. Round Steel Pipe

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................................
................................
..............

A
-
3

3.5. Square and Rectangular Tubing

................................
................................
.......................

A
-
3

3.6. Structural Bolts and Threaded Fasteners

................................
................................
.........

A
-
3

3.6.1. ASTM A325 Type 1

................................
................................
................................
.

A
-
4

3.6.2. Threaded Round Stock

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................................
..............................

A
-
4

3.6.3. Bolts and Nuts, High Strength Bolts

................................
................................
.........

A
-
4

3.6.4. Washers

................................
................................
................................
.....................

A
-
4

3.6.5. Stainless Steel Bolts and Nuts
................................
................................
...................

A
-
4

3.6.6. Load Indicator Washers

................................
................................
............................

A
-
4

3.6.7. Bolt Lubrication:

................................
................................
................................
.......

A
-
4

3.6.8. New Bolts
................................
................................
................................
..................

A
-
4

3.7. High Strength Bolting

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................................
................................
......

A
-
4

3.7.1. Applicable Specifications and Procedures

................................
................................

A
-
5

4. WELDING

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................................
................................
..............................

A
-
5

4.1. Electrodes

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................................
.........................

A
-
5

4.2. Welding Elect
rodes

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................................
................................
..........

A
-
5

4.3. Electrodes for Welding

................................
................................
................................
....

A
-
5


SOAR Dome Specification


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4.4. Applicable Codes and Standards

................................
................................
.....................

A
-
5

5. PAINTING AND CORROSION CONTROL

................................
................................
........

A
-
5

5.1. Quality Ass
urance

................................
................................
................................
............

A
-
6

5.2. Safety and Health Requirements

................................
................................
......................

A
-
6

5.3. Surface Preparation

................................
................................
................................
..........

A
-
6

5.4. Painting Sequence

................................
................................
................................
............

A
-
7

5.5. Exceptions to Painting R
equirements

................................
................................
..............

A
-
7

5.6. Contamination and Cleaning
................................
................................
............................

A
-
7



APPENDIX B
-
COMPONENT SPECIFICATIONS


APPENDIX C
-
DESIGN DRAWINGS


APPENDIX D
-
REFERENCE DOCUMENTS


APPENDIX E
-
PANEL SYSTEM SPECIFICATION

1. Pur
pose

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................................
................................
................................
.....

E
-
2

2. Scope

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................................
................................
................................
........

E
-
2

3. Background

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................................
..............................

E
-
2

4. Dome System Description

................................
................................
................................
.......

E
-
2

4.1. General

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................................
................................
..............................

E
-
2

4.2. Fixed Dome

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................................
.......................

E
-
2

4.3. Shutters

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................................
................................
.............................

E
-
2

4.4. Vents

................................
................................
................................
................................
.

E
-
2

4.5. External Ladder Attachment

................................
................................
.............................

E
-
3

4.6. Internal Lighting Attachment

................................
................................
............................

E
-
3

4.7. Lighting Protection

................................
................................
................................
...........

E
-
3

5. Requirements

................................
................................
................................
...........................

E
-
3

5.1. General

................................
................................
................................
..............................

E
-
3

5.2. Mechanical Requirements

................................
................................
................................
.

E
-
3

5.2.1. Panel Thickness

................................
................................
................................
.........

E
-
4

5.2.2. Core Thickness
................................
................................
................................
...........

E
-
4

5.2.3. Thermal Insulation

................................
................................
................................
.....

E
-
4

5.2.4. System Weight

................................
................................
................................
...........

E
-
4

5.2.5. Face Sheet Properties

................................
................................
................................
.

E
-
4

5.3. Environmental Conditions

................................
................................
................................

E
-
4

5.3.1. Operating Conditions

................................
................................
................................
.

E
-
4

5.3.2. Survival Conditions

................................
................................
................................
...

E
-
5

5.4. Deflections

................................
................................
................................
........................

E
-
5

5.4.1. Dome Panel
ing System

................................
................................
..............................

E
-
5

5.4.2. Shutters Panels

................................
................................
................................
...........

E
-
5

5.5. Interfaces

................................
................................
................................
...........................

E
-
5

5.5.1. Structural Steel

................................
................................
................................
...........

E
-
5

6. Coatings

................................
................................
................................
................................
...

E
-
6

6.1. Interior Coatings

................................
................................
................................
...............

E
-
6


SOAR Dome Specification


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6.2. Exterior Coatings

................................
................................
................................
..............

E
-
6

7. Reliability And Maintainability Requirements

................................
................................
........

E
-
6

7.1. Design Life
................................
................................
................................
........................

E
-
6

7.2. Rout
ine Servicing
................................
................................
................................
..............

E
-
6

7.3. Critical Spares

................................
................................
................................
...................

E
-
6

7.4. Modularity
................................
................................
................................
.........................

E
-
6

7.5. Special Tools and Equipment

................................
................................
...........................

E
-
6

7.6. Lifting points

................................
................................
................................
.....................

E
-
7

7.7. Lifting Fixtures

................................
................................
................................
.................

E
-
7

8. PAINTING AND CORROSION CONTROL

................................
................................
.........

E
-
7

8.1. Quality Assurance

................................
................................
................................
.............

E
-
7

8.2. Safety and Health Requirements

................................
................................
.......................

E
-
8

8.3. Surface Preparation

................................
................................
................................
...........

E
-
8

8.4. Painting Sequence

................................
................................
................................
.............

E
-
8

8.5. Exceptions to Painting Requirements

................................
................................
...............

E
-
8

8.6. Contamination and Cleaning
................................
................................
.............................

E
-
8



APPENDIX F
-
CONTROLS SYSTEM DESIGN

1.0

DOME Rotational Drives and Position Sensors

................................
................................
..

F
-
3


Figure 3
-

Dome / Shutter Drive Diagram.

................................
................................
..........

F
-
4

2.0 Dome and shutter drive controllers

................................
................................
........................

F
-
4

3.0

Shutter Drive CONTROL

................................
................................
................................
....

F
-
5


Figure 4
-

Slave Shutter Controller Diagram.

................................
................................
.......

F
-
5

4.0

Windscreen Coupling and Overload Switch

................................
................................
........

F
-
5

5.0

Crane Operation Unit and Interlock

................................
................................
.....................

F
-
6


Figure 4
-

Slave Dome Controller Diagram.

................................
................................
........

F
-
6

6.0

Data Aquistion i/o and Vents

................................
................................
...............................

F
-
6

7.0

Manual User Interface (MUI)

................................
................................
..............................

F
-
7

7.1 Hand Paddle

................................
................................
................................
.........................

F
-
7

7.2 Dome MUI………………………………………………………………………………...F
-
7



SOAR Dome Specification


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1.

INTRODUCTION

The SOAR Telescope Project, hereinafter referred to as SOAR, is in an eff
ort to design,
construct, and install a 4.2
-
meter clear aperture telescope and support facility. The telescope is to
be sited atop Cerro Pachón at the Cerro Tololo Inter
-
American Observatory (CTIO) in Chile.
The Project is a joint undertaking of the countr
y of Brazil, the University of North Carolina at
Chapel Hill (UNC
-
CH), Michigan State University, and the National Optical Astronomy
Observatories (NOAO). Project offices are sited at NOAO in Tucson, Arizona, U.S.A.


1.1.

Objective

This document is to guide th
e detailed design, fabrication, integration, test, debug, packaging,
shipping, and successful installation of the SOAR Telescope facility Dome. The Dome will
provide environmental protection, adequate strength to support all loading conditions, a
telescope

observing opening with shutters, and drive systems to have the opening follow the
Telescope during observing. The Dome is an important part in allowing the Telescope to gather
the finest quality images of any 4
-
meter class instrument.


This specification
provides a detailed design of the Dome as well as the performance
requirements. The performance requirements provide the parameters to which the Dome must
operate and survive, and represents the objectives of the design work performed to date. The
detailed

design is provided to sufficient detail to be the starting point for fabrication drawings
and controls design. The objective is to provide fully developed designs to remove the
engineering risk, allow detailed costing, and allow the contractor to start in
to fabrication details.
The contractor is expected to fully review the provided design, complete design details, perform
confirming and any other necessary analysis, and accept the desired Dome performance.
Attempts have been made during the design to choo
se parts available in both Brazil and Chile
but equivalent component substitutions are allowed with SOAR approval. Interfaces with other
components of the facility are also defined in this document. The Contractor shall provide the
exterior panel system to

meet the overall Dome requirements and those included in the Panel
System Specification provided in Appendix E. Contractors will be instructed to bid hours for
interactive design with the SOAR Project personnel and its Contractors to insure facility
compa
tibility and to assist in on
-
site Dome installation and commissioning.


Additional objectives are that the Dome include minimum part count and obtain its functionality
through fundamental elegance of design, exhibiting high efficiency usage of materials a
nd
components. To the extent possible, off
-
the
-
shelf components or subsystems previously
designed, built, and tested should be used to minimize cost and to optimize the ability to
maintain and procure spare parts. Design of components should be achieved us
ing the most
efficient and effective manufacturing processes to simplify all components and ensure lowest
design and maintenance costs.


1.2.

System Description

The Dome is a lightweight spherical structure of approximately 20 meters (66ft) diameter. The
5/8 sp
herical Dome consists of a steel frame covered with a lightweight composite or aluminum
weather tight panel system, shutter system, rotational friction drive system, overhead crane,
windscreen and vents. The volume enclosed by the Dome is actively air cond
itioned during the

SOAR Dome Specification


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day to the expected nighttime observing temperature. The panel system and steel are insulated to
enhance thermal resistance and reduce cooling loads. The Dome is supported on an integral ring
beam that transfers the loads to sixteen stat
ionary trucks or “bogies” attached to the top of the
facility silo. A labyrinth seal is used to provide a weather tight interface between the rotating
Dome and the stationary facility. The Dome structure is designed to the worst case combination
of the sur
vival loads defined in this specification. Electrical power for overhead lights, crane,
vents, and shutter are conveyed onto the rotating Dome by a slip ring.


The shutter on the Dome is a double door, over the top design. The two sections nest together as

they move over the top. The shutter doors are driven through a chain and sprocket drive on one
panel and a differential drive on the second panel. Each shutter frame is covered with the same
panels as is used on the rest of the Dome.


The drive systems f
or both the Dome Azimuth motion and the Shutter operate by command from
operator interfaces or the Telescope Control System. During telescope tracking operations the
drives of the dome will be commanded to make approximately 2 degree moves every 5 minutes
to allow the dome opening to “track” the telescope.


The Dome is designed with bolted joints between major substructures to allow fast assembly at
the SOAR site. The bogies and Dome drives shall be installed on the facility silo while a
temporary roof is i
n place. The Dome is partially assembled next to the facility, the temporary
roof is removed, and the partially assembled Dome will be lifted and emplaced on the stationary
bogies. The panel system will be lifted in sections and attached to the steel struc
ture.


1.3.

Scope

This specification and Appendices define the Dome steel structure, the paneling system, drives,
bogies, vents, crane, structural, thermal, electrical, controls, interfaces, assembly, documentation,
and performance requirements. Appendices of t
his specification include general workmanship
requirements, detailed assembly drawings for the Dome structure and subsystems, purchased
component specifications, procedure and analysis documentation for the provided design, the
Panel System Specification,
and the control system concept design.



2.

DESCRIPTION AND SPEC
IFICATIONS

This section provides functional descriptions and specifications for the Dome and subsystems.


2.1.

Steel Structure

The steel structure is a self
-
supporting welded and bolted steel construc
tion that provides support
to the shutter system, the panel system, and the crane. The structure is comprised of the ring
beam and two arch girders. The ring beam transfers the total Dome loads to the stationary
building through the rotational interface wi
th the fixed bogies. The ring beam also provides the
drive surface for the Dome rotation drive system.






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2.1.1.

Ring Beam

The ring beam is a welded circular ring that has a box beam section. The panel system is bolted
to the beam. The ring beam structure is d
esigned for vertical and lateral stiffness as defined in
Section 3.0. Drawing SD1, in Appendix B, shows the cross section. Vertical stiffness is required
to allow smooth Dome rotation. The lateral stiffness of the ring reacts the arch girder lateral load
t
ransfer as well as the friction drive normal forces. The ring beam is bolted together at the site.
The assembled beam shall be flat on the bearing surface to
+

2mm globally, as specified on
drawing SD6, to insure proper functioning of the Dome rotation.



A circular hardened plate is welded to the bottom of the ring beam to form a track for the Dome
to ride on the bogies. The inner diameter of the ring beam provides the rolling surface for the
four friction drives. The ring beam also carries the encoder sy
stem and supports the electrical slip
ring.


2.1.2.

Arch Girders

There are two arch girders. The arch girders are built up steel beam sections that provide the
track for the shutters and support for the panel system and crane rails. The girders are bolted to
the
ring beam for on
-
site assembly. See Appendix B for the arch girder construction. The girders
require high lateral stiffness as defined in Section 3.0, to maintain the shutter track alignment and
to react wind loads from the panel system. Two crane support
beams form a cord across each
arch girder to provide the crane track. The crane support beams are bolted to the arch girders at
site assembly. The required 5.0 meters diameter clear aperture for the telescope viewing
determines girder separation. Lateral c
ross beams tie the arch girders together where the
telescope viewing is not necessary. The viewing slit defined by the arch girders and cross
members is defined by the required telescope clear aperture and optical axis travel of 0.25º to 75º
from zenith


2.2.

P
anel System

The system is a monocoque structure, completely self
-
supporting, requiring no internal or
external support in static conditions. The prefabricated spherical panels use oriented
reinforcements and a catalyzed resin system to achieve a high speci
fic stiffness. The system
generates a true spherical dome.


The panel system envisioned is made up of insulated composite panels, such as fiberglass, or an
insulated aluminum geodesic system that bolts together and is sealed at the site. The interface to
t
he steel internal structure must accommodate the load transfer due to environmental loads, such
as caused by differential thermal expansion and wind loading. The panel system can rely on the
steel frame to react environmental loads and dead weight. All fie
ld assembly shall be
accomplished with bolted joints. All panel interfaces shall be defined by the Contractor. The
overall Dome must be watertight. The panel system provides the thermal barrier to maintain the
air
-
conditioned observing area at the expecte
d nighttime temperature. A thermal insulation value
of 36 ºC/W (R
-
19) is required. Panels are required to cover the two shutter door frames. The
panel system is assembled in sections on site and lifted onto the steel internal frame.


A panel system specifi
cation is included in this document in Appendix E.



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2.3.

Shutter and Windscreen System

A slit is required in the Dome for observing by the telescope. The slit is approximately 122


long, on a 9.9 meters radius, by 5 meters wide. The opening is defined by the Te
lescope clear
aperture of 4.2 meters and elevation travel from zenith pointing to 75º. A retractable shutter
system travels over the top of the Dome to open and close the slit. The shutter is comprised of
two nesting doors, a lower and upper door. The lowe
r door is driven with a gear motor and
sprocket drive attached to the doorframe through a fixed chain attached to each arch girder. The
upper door motion is slaved to the lower door through a differential chain and sprocket drive
mechanism for opening and
closing. The lower door nests under the upper door when fully open.
The shutter rides on a bearing track on each side of the door. One bearing rail shall provide
lateral and vertical restraint for the door and the opposite side shall have lateral freedom t
o
accommodate misalignment and relative motions. This bearing arrangement provides a semi
kinematic design. The effect of differences in vertical alignment between the bearing system
sides shall be considered. The shutter shall have software limits, limit
switches, and energy
absorbing stops at the ends of travel of each shutter door. A non
-
contacting labyrinth seal is used
to seal the shutter doors to the arch girders. Electrical power is transferred to the shutter control
assembly through a slip ring.


A

separate wind screen system, located in the lower quadrant of the opening is used to reduce
wind effects on the Telescope. The fabric “shutter” attenuates the wind affect on the telescope
but has relief cut outs to reduce the direct load on the windscreen
. The fabric is attached to
tubular cross members that provide stiffness and strength to the system. The cross members have
guide rollers at each end that are constrained to follow a track attached to each arch girder. One
roller is allowed to move axiall
y in the cross member to prevent binding between tracks. In the
retracted position the windscreen is rolled up on a spool at the bottom of the opening. The
windscreen is pulled up and unrolled from the spool by the lower shutter through two cables that
run

along each arch girder. The windscreen shall be removable from the shutter through an easily
accessible quick release coupling. Removal of the windscreen from the shutter shall not affect
the shutter performance.


The shutter and windscreen shall maintain

an opening of 5 meters by 5 meters, large enough to
satisfy the telescope clear aperture.


2.3.1.

Shutter Door Description

Each shutter door assembly is composed of a steel frame with four bearings and a panel. The
lower shutter door provides a mount for the dr
ive and control assembly. Structurally re
-
enforced
ice and snow scrapers are provided on the shutter doors.


2.3.2.

Shutter Drive System

The shutter drive system incorporates the drive motor, gearbox, brake, drive sprockets, drive
bearings, encoder read head, con
troller, and drive shaft. The shutter drive is attached to the lower
doorframe. A tensioned fixed chain on each arch girder engages a drive sprocket assembly on
each side of the moving door. The shutter drive pulls itself along the fixed chains. The drive
sprocket assemblies are driven through a drive shaft and gear motor. The drive sprockets engage
the chain on both sides of the shutter to provide smooth motion. The chain is tensioned with a

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spring to provide drive stiffness and following accuracy. The dri
ve motor incorporates a fail safe
brake (activated when power is removed) on the back end of the motor shaft.


The inner door drives the outer door via a differential drive. On both sides of the upper end of the
inner shutter is a 2:1 differential drive a
ssembly. A spring tensioned fixed chain is attached to
the top of both arc girders. The chain is routed through the inner shutter differential drive
sprocket assembly. Another chain is attached to both sides of the outer shutter. The other half of
the di
fferential drive assembly picks up the chain on the outer shutter. As the inner shutter
moves the outer shutter moves with it. The differential drive is rotated in the opposite direction
by the chain attached to the arc girder. This drive rotation is tr
ansferred to the outer shutter
through the differential drive into the chain attached to the outer shutter. The 2:1 speed
reduction of the differential drive has the net effect of moving the outer shutter at half the speed
of the inner shutter.


The shutt
er control electronics are mounted to the inner shutter door near the drive motor.
Communication between the Dome control system and the shutter control is via spread
-
spectrum
radio frequency (RF) modem. An encoder read head is attached to the shutter door
. Fixed bar
code labels are attached to the underside of one arch girder. Power is transferred to the shutter
via a slip ring as defined in Section 4.0.


The differential drive works on the same principle as the main shutter drive. There is no drive
motor

for this drive. The motion of the inner shutter controls the outer shutter as described in the
following text. A tensioned fixed chain is attached to the top of both arc girders. The spring is
tensioned with a spring mechanism. On both sides of the upp
er end of the inner shutter is the 2:1
differential drive assembly. The chain is routed through the inner shutter differential drive
sprocket assembly. Another chain is attached to both sides of the outer shutter. The other half of
the differential drive

assembly picks up the chain on the outer shutter. As the inner shutter
moves the outer shutter moves with it. The differential drive is rotated in the opposite direction
by the chain attached to the arc girder. This drive rotation is transferred to the

outer shutter
through the differential drive into the chain attached to the outer shutter. The 2:1 speed
reduction of the differential drive has the net effect of moving the outer shutter at half the speed
of the inner shutter.


2.3.2.1.

Shutter Drive Requirement
s

The following performance requirements shall be met in the design and development of the
shutter drive. The design shall target these requirements with factors of safety and margin as
appropriate to the particular designs. The shutter drive shall meet th
ese requirements under the
load and environmental conditions stated in other sections of this specification as well as all
other loads incurred by subsystems of the shutter. Opening the Shutter in presence of nominal
snow and ice shall be required. The shu
tter drive system is designed to provide this capability.


2.3.2.1.1.

Shutter Drive Performance

The shutter system shall have two speeds with associated acceleration profiles that can be
adjusted via software interface. One faster speed will be associated with large
shutter motions
and the slower speed settings will be used for the small motions associated with the “tracking” of

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the telescope. The shutter is not required to continuously move to track the telescope but will be
commanded to stop and start as required to

maintain the opening within 1


of telescope position.
The motion must be smooth and controlled.



Range of Motion:



Inner Shutter Door:




112.5


(
-
4.5


to 108


Elevation)



Outer Shutter Door:




56.25


(50


to 106.25


Elevation)



Velocity Range: (Inn
er Door):


0 to 2.5

/s



Acceleration Range (Inner Door):


0.1 to 0.25

/s
2





Position Accuracy (moves over 2

):


1




Position Accuracy (moves under 2

):


0.25




2.3.3.

Shutter Travel Limits

The shutter door travel shall not limit a 5
-
meter diameter clear ap
erture centered on the
Telescope optical axis as the axis travels the range of 0.25º to 75º from zenith. Each shutter door
shall have three levels of stops to limit the travel. The first limit is a software limit that gracefully
stops the shutter door at t
he end of travel. The second stop is a hardware limit (limit switch) that
is activated if the door does not stop after reaching the software limit. This limit shall gracefully
stop the door and not allow further commanded motion in the direction of travel
while generating
an alarm message. The final stop is an energy
-
absorbing hard stop that shall also remove the
drive power until the system is manually reset.


2.3.3.1.

Shutter Software Limits

The Dome control system software shall contain provisions for recognizing

pre
-
programmed
encoder readout limits at either end of travel of the inner shutter. When a software limit is
reached, the Dome control system shall gracefully stop the shutter motion within 1 second and
send a status line to the TCS identifying the limit
and encoder reading. A software
-
interlock shall
be imposed to prohibiting further motion in the direction of the exceeded limit. Additional
motion in this direction shall only be possible by issuing a special override command. The
software shutdown shall o
ccur in time to stop the shutter prior to activating the hardware limit.


2.3.3.2.

Hardware Limits

Each end of travel of the shutter door track shall have a normally closed limit switch located
outside the software range. When a hardware limit is reached, the Dome
control system shall
gracefully stop the shutter motion within 1 second and send a status line to the TCS identifying
the limit and encoder reading. The shutter door shall stop before reaching a hard stop.


A hardware
-
interlock shall be imposed to prohibit

further motion in the direction of the exceeded
limit. Additional travel in the limit direction shall be prohibited. Motion shall only be allowed in

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the opposite direction to the original motion, and only at less than or equal to one
-
tenth the
maximum sle
w speed.


2.3.3.3.


Hard Stops

Cushioned energy absorbing hard stops shall be located at the end of travel for each shutter door.
The location of the stops shall not limit the normal travel range of the doors. The hard stop shall
be outside of the hardware limit st
opping range described above. The hard stop shall absorb the
energy from a free fall of the shutter doors into the stops without damage to the doors, structure,
drives, or the stop.


A software
-
interlock shall be imposed to prohibit further motion in eith
er direction. Further servo
motion shall not be allowed until a manual reset is activated.


2.3.4.

Settling Time

The maximum settling time under normal operation conditions shall be 10 seconds from
maximum slew speed with maximum deceleration 0.25º/s
2
.


2.3.5.

Shutter
Manual Operation

A method to manually close the shutter shall be provided in the event the drive system fails.
Currently, the design incorporates a shaft extension on the motor for attaching a drill motor. The
manual operation shall be such that there is n
ot risk to personnel or equipment during the
operation. The Facility extension lift will be available to access the shutter manual drive.


2.3.6.

Shutter Encoder

The shutter encoder has a laser bar code read head attached to the inner shutter door with bar
code l
abels attached to the under side of the arc girder. The read head is attached to a stiff
bracket on the shutter. Adjustment for alignment of the read head shall be incorporated in the
mounting. All shutter drive control loop closure is performed on the shu
tter. Stray reflections
from the laser in the read head are unacceptable. The design incorporates a shield and brush seal
to contain the laser energy. The brushes also remove dirt from the bar code labels. The output of
the encoder is sent to the control e
lectronics on the shutter. The encoder resolution shall be
minimum of 0.1º to achieve the defined position accuracy.


2.3.7.

Windscreen System

The windscreen is a tight weave canvas fabric (trade name Sunbrella) treated to resist ultraviolet
radiation. The fabr
ic is attached to tubular cross members. Each cross member incorporates
wheels on each end that ride in a track attached to the arch girder. One wheel on each cross
member is allowed to float axially to prevent binding of the windscreen due to assembly
t
olerances and environmental loads. The fabric has cut outs as indicated in the attached drawings
in each panel to reduce the wind loading on the screen and mechanical components. The cut outs
reduced the maximum applied pressure due to wind to 383 Pa (8.
0 psf).


The windscreen is attached to a spool. A torsion spring attached to the spool provides constant
tension to the screen during opening and closing. The windscreen shall have a removable handle
for manual winding.



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2.4.

Dome Rotation Drive System

The Dom
e shall have unlimited bi
-
direction travel. The drive system consists of four identical
friction drive assemblies located 90


apart in azimuth. The diametrically opposed drive locations
provide for balancing the normal forces applied to the ring beam by th
e drive wheel. The normal
force is applied by a spring that provides a constant force through out the expected motion due to
eccentricities in the ring beam diameter and lateral motion of the Dome. The Dome drive system
is sized to operate with the combine
d maximum operating environmental conditions provided in
this specification.


2.4.1.

Dome Drive Assembly

The drive assembly consists of an electric gear motor with drive wheel, and electric fail safe
brake. The components are attached to a plate on linear slides
. The slides allow the assembly to
move radially in the plane of the ring beam. The assembly is spring loaded against the ring beam
through the drive wheel. The spring is adjustable to tune the drive wheel normal force at
assembly.


The brake mechanisms at
tached to the drive shall prevent Dome rotation due to the wind during
operating and survival conditions. The brakes also serve as an emergency stop system for the
Dome in the event the Dome poses a threat to personnel or equipment.


2.4.2.

Dome Encoder

The Dome
encoder is the combination of an absolute and a bi
-
directional incremental encoder.
The absolute encoder consists of metallic barcode labels attached to the rotational ring beam and
a laser read head attached at one drive location. Stray reflections from t
he laser in the read head
into the observing area are unacceptable. A shield and brush seal to contain the laser energy shall
be included. The brushes shall also serve to remove dirt from the bar code labels. This encoder’s
function is to synchronize the b
i
-
directional incremental encoder. The bi
-
directional incremental
encoder shall be coupled to the Dome ring beam through a rubber wheel with a spring
mechanism to insure continuous contact and avoid slippage. The overall resolution of the
encoder shall be
minimum 0.1º to maintain the ±1º tracking accuracy required with the telescope.
The high resolution bi
-
directional incremental encoder allows precise speed control as required
for a high performance torque feedback control loop.


2.4.3.

Dome Drive Requirements

Th
e following performance requirements shall be met in the design and development of the
Dome. The design shall meet these requirements with factors of safety and margin as appropriate
to the particular designs. The Dome shall meet these requirements under t
he load and
environmental conditions stated in other sections of this specification as well as all other loads
incurred by subsystems of the Dome.


2.4.3.1.

Performance Requirements

The Dome system shall have two speeds with associated acceleration profiles that ca
n be
adjusted via software interface. One faster speed will be associated with large Dome motions and
the slower speed settings will be used for the small motions associated with the “tracking” of the
telescope. The Dome is not required to continuously mov
e to track the telescope but will be

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commanded to stop and start as required to maintain the opening within 1


of telescope position.
The motion must be smooth and controlled.


Rotational Travel:




Continuous


Velocity Range:




0 to 2.5

/s



Acceleratio
n Range:




0.1 to 0.25

/s
2





Position Accuracy (moves over 2

):


1



Position Accuracy (moves under 2

):


0.25



2.4.4.

Settling Time

The maximum settling time under normal operation conditions shall be 10 seconds from
maximum slew speed with maximum decelera
tion of 0.25º/s
2
.


2.5.

Bogies

Sixteen (16) identical fixed bogies mounted to the top of the facility silo at each column location
shall be used to support the Dome. The bogies shall be sized to accommodate the combined
survival environmental loading, live load
s, and dead loads. Each bogie assembly has a single
compliant vertical support roller that forms the rolling surface for the Dome, a lateral roller to
maintain alignment of the Dome during rotation, and two vertical restraint rollers to react lifting
loads

on the Dome. The hardened steel track on the ring beam rides on the bogie assemblies. The
16 bogies are aligned coplanar on the facility silo at installation. The bogies shall be designed to
accommodate up to 25 mm of adjustment for initial installation.

The Bogie assemblies shall
maintain clear sight from each axle to the Dome center of rotation and each axle shall include the
space and features shown in the design for alignment fixtures. After alignment the bogies shall
be grouted and bolted in place.


2.6.

Dome Vent

A minimum of 2.5m
2

of ventilation area shall be provided at the top of the Dome but outside of
the shutter door track. Standard weatherproof “mushroom” type hoods shall be provided to
prevent the intrusion of precipitation, including rain, ice,

and snow. The vents shall be mounted
on the panel system. A grill mesh (flush with outer surface) shall be incorporated to prevent large
insects and fowl access into the Dome interior. Four (4) Greenhech Model GRS
-
36 gravity vents,
or equivalent, shall be

used. The vents shall include Greenhech VCD
-
23 powered back draft
louvered dampers or equivalent. Limit switches shall be installed to the dampers to sense opened
and closed positions. The Dome Contractor shall provide power and control of the dampers.
Co
ntrol of the louvers shall be available through the Dome Computer or from manual switches
located on the Dome.


2.7.

Dome Crane

A Dome crane shall be provided with the Dome for lifting telescope instruments and servicing of
the primary mirror. A minimum lifting

capacity of 10,000kg is required. The crane bridge moves
on the rails attached to the arch girders. The radial travel of the crane from the center of the

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Dome is 5.8m along the centerline of the Dome defined by the observing slit. The crane is fixed
in th
e center of the bridge and has no lateral motion along the bridge. Lateral positioning of the
crane shall be achieved by rotating the Dome at reduced speed. The bridge shall be designed to
provide maximum hook height and access to the telescope without int
erfering with the travel of
the bridge. The full lifting capacity will only be used with the Dome stationary. The lifting
capacity of the crane is reduced to 3,000kg if the Dome is to be rotated during the lifting
operation. Telescope personnel are require
d to operate the crane from the lower level of the
facility during Telescope maintenance. Therefore the crane shall include a wireless remote
control unit. Electrical interlocks shall be incorporated in the crane drive in the stowed position.
The crane sp
ecification is provided in Appendix B.


2.7.1.

Crane Stowed Position and Interlocks

The stowed position for the Dome crane is the maximum radial distance from the viewing slit
and the hoist ring fully retracted. The interlocks in the Dome Control System shall pro
vide an
output signal to the Telescope Control System (TCS) as to whether the crane is stowed or not.
The signal is used by the TCS to prevent motion of the Telescope Mount if the crane is not in the
stowed position.


2.8.

Seals

Weatherproof seals shall be pro
vided to prevent ice, snow, and water from entering the Dome
through the shutter, and rotational drive. Low friction or non
-
contacting labyrinth seals shall be
used to reduce the friction load on the drive systems. Seals must not be damaged by operation
du
ring freezing or ice
-
over conditions. The seals shall be as air tight as found practical to
maintain the low friction load, account for variations in manufacturing and assembly tolerances,
and motion tolerances. The complete Dome seal to the facility shall

be provided by the
Contractor. A method of adjustment of the seals at assembly shall be designed into the
mountings.


3.

STRUCTURAL REQUIREME
NTS


3.1.

Crane Loads

The Dome shall support the crane loads for the following conditions.


3.1.1.

Dome Stationary

The Dome sha
ll remain stationary when supporting the maximum crane load of 10,000kg. The
Dome design shall account for the moving load due to crane bridge through full motion


3.1.2.

Dome Moving

The Dome shall support the reduced crane load of 3,000kg when rotating at 10% o
f maximum
velocity. The crane bridge shall remain stationary during Dome rotation.


3.2.

Mass Properties

The mass properties of the Dome shall be consistent with the provided design.


3.2.1.

Dome Weight

The current total rotating Dome weight is estimated to not exceed

68,200kg.


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3.3.

Deflections

The stiffness of the steel support system shall be defined by the following values with the panel
system installed and the Dome installed on the compliant bogies. All deflections include
stiffening effects due to the panel system. T
he mechanical properties for the panel system can be
found in Appendix E.


3.3.1.


Ring Beam

The ring beam shall be fabricated to be circular in the horizontal plane when the dead load is
applied. That is, a camber is designed into the beam such that the dead lo
ad forms the desired
final shape.

3.3.1.1.

Horizontal Plane

Load Case: Survival snow and ice


Change of radius in the horizontal plane

(ovalizing of the ring):



±5.1mm


3.3.1.2.

Vertical Plane

Load Case: Dead load and fully loaded crane at center of Dome.

Bogie spring s
tiffness is 46,740kN/mm (265,000lb/in).


Differential deflection between arch girder connection

and a point located 90º away on the ring beam:


1.5mm


3.3.2.

Arch Girder

3.3.2.1.

Vertical Plane

Load Case: Dead load and fully loaded crane at center of Dome.

Bogie spring
stiffness is 46,740kN/mm (265,000lb/in).


Maximum deflection:


8.1mm


3.3.2.2.

Lateral Plane

Load Case: Dead load and fully loaded crane at center of Dome.

Bogie spring stiffness is 46,740kN/mm (265,000lb/in).


Maximum deflection:


6.3mm


Load Case:



Maximum wi
nd load



Arch Girders:



30.5mm





3.3.3.

Shutters


Load Case:



Dead and survival load 2,394 kPa



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Maximum deflection:


12.7 mm



4.

ELECTRICAL REQUIREME
NTS


4.1.

Electrical Power

Power to the Dome will be provided by SOAR at each major subsystem location. Electri
cal
design and equipment sizing shall be consistent with the requirements provided in this section,
the site and environmental conditions, and unless otherwise specified, Chilean standards and
practices.


4.1.1.

Voltage, Frequency, Current and Ground

A 350kVA ste
p
-
down power transformer is used to provide the 2.4kV medium
-
voltage facility
supply. The line frequency is 50Hz Chilean standard only. Frequency variation is expected to be
less than ±1Hz, as well as voltage variations less than ±10%. Primary available po
wer for heavy
loads is 380/220V, 3Ø Wye connection, grounded neutral, limited distribution. For instruments,
120V as well as 220V, single
-
phase electric power will be available at the locations of different
subsystems. When necessary, instruments can be co
nnected to an auxiliary 120V uninterruptible
power supply (UPS) also available, but not to be used for simple power filtering purposes.
SOAR power, even UPS power, shall not be considered filtered. Where required, the Contractor
shall provide a local filte
r/isolation transformer. Power may come from different sources (power
transformer, UPS, emergency generator, isolation transformer), therefore the Contractor shall
provide systems capable of tolerating random variations and uncontrolled power outages witho
ut
damage to equipment. The Contractor shall specify the required current for each subsystem
location. SOAR recommends the use of high efficiency and high power factor power supplies
where possible. Heat dissipation shall be minimized to control the cost a
nd size of the heat
extraction system. To ensure that line voltage waveforms supplied to all the system are
acceptably clean and to achieve high power distribution efficiency and low conducted noise,
equipment must avoid contaminating the line by drawing h
igh frequency or highly non
-
sinusoidal load currents. Appropriate specifications and certification procedures shall be adopted.
Ground connection is also available at the different locations. Ground specifications and/or
power requirements different from p
reviously stated must be made explicit by the Contractor in
their bid proposals.


4.1.2.

Power Protection

All electronic/electrical equipment must have over
-
current protections (thermal breakers, fuses,
lightning arrestors, surge protection, etc.). Fuses must be
easily accessible for replacement. All
electronic/electrical equipment must have a main line circuit breaker or power switch, and a
controlled light indicator for power status. All electrical/electronic installation must comply with
National Electrical Cod
e where applicable.


WARNING: All electrical and electronic equipment in the telescope facility must have safety
grounds!



SOAR Dome Specification


D
SP99
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013

20

4.1.3.

Electromagnetic Compatibility (EMC)

The Dome and its components shall minimize electromagnetic interference with scientific
instrumen
ts and other telescope systems. Emissions and immunity to EMI must be considered in
every part of the Dome. Electronic equipment used in the observing area must be EMI certified
and comply with FCC regulation Part 15, Class B limit for emissions. For equip
ment used in the
control or computer room, Class A limit is acceptable. All electronic equipment shall be certified
IEC1000
-
4
-
2 or better for electrostatic discharge (ESD) immunity and, IEC1000
-
4
-
3 and
IEC1000
-
4
-
6, or better, for RFI immunity. Immunity to
power
-
line disturbances (IEC1000
-
4
-
9,
IEC1000
-
4
-
13), electrical fast transient (IEC1000
-
4
-
4), and surges (IEC1000
-
4
-
5).


4.1.4.

Lightning Protection

Lightning protection shall be provided by the Contractor as an integral part of the panel system.
The installatio
n and design of the system shall meet the Lightning Protection Institute (LPI)
Code 175 and National Fire Protection Association (NFPA) 780. Installation shall be made by or
under the supervision of an LPI certified master installer. Complete installation

to receive
system certification including submittal of forms LPI 175
-
A and 175
-
B. Contractor shall provide
an adequate conductive path from the main body of the Dome to the ring beam, which serves as
the bearing journal for the Dome rotator. In addition,

the ring beam shall contain a conductive
surface suitable for contact by a system of brushes. The conductive surface shall exist opposite
the lateral support roller. The lightning protection system shall be defined during the
Contractor’s Detailed Design
and approved by SOAR.


4.2.

Electrical Interface Requirements

4.2.1.

Connectors

The Contractor shall define and provide electrical connectors, cabling, and conduit consistent
with high reliability operation and EMC constraints. Connectors shall be capable of being ra
pidly
disconnected for service of all assemblies of the Dome. Connectors shall be keyed so that
incorrect connection is not possible. Proper strain relief shall be provided to ensure reliability
and to minimize effect of cabling loads on the Dome performan
ce. Only high quality rough
service connectors may be used.


4.2.2.

Cables

Power and signal cables shall be shielded for low and high frequency interference. Whenever
possible, power and signal wires must be routed separately. The cabling design must avoid
ground

loops. Cables designated for power must also meet the specifications for voltage and
amperage capacities as per the U.S.A. National Electric Code.


Cabling routed on the Dome shall be installed in conduit, flexible or rigid, and securely attached
to the D
ome.


4.2.3.

Cable Lengths

The Contractor shall provide all cables and connections between the Dome and other elements of
the SOAR telescope and facility. Distances to specific rooms in the facility are defined in Section
7 of this specification. Additional dist
ances for cables that need to travel through the facility may
be determined through building layout drawings.



SOAR Dome Specification


D
SP99
-
013

21

4.2.4.

Slip Rings

Power and emergency control signals to the Dome and Shutter will be passed through shielded
type slip rings. The Dome slip ring will r
otate with the dome, while the trolleys will be
stationary. In particular, the Dome Contractor shall also incorporate mounting for the slip ring
trolleys to the fixed facility. For the Shutter, the slip ring will be stationary, while the trolley will
move
with the Shutter. In all cases adequate short circuit protection shall be provided. There
shall be no power interruptions due to poor contact between slip rings and trolleys in order to
guarantee the continuous operation of all control equipment installed
on the Dome and Shutter.
The maximum power required by the Dome across the slip ring shall be no greater than 50 kVA.


4.3.

Electronic Enclosure Requirements

The Contractor shall supply enclosures for Contractor supplied electronics. Enclosures shall be a
mode
l with metal side covers, front or top, full
-
length doors, and leveling feet or equivalent. All
electronics shall be on slide out drawers or mounted on an easily removable way. All cable