CFHT – CAFE

CAssegrain Fibre Environment

Documentation - Maintenance Manual

People implied on the project

General Management and Optics :

Jacques BAUDRAND Observatoire de Paris-Meudon

Tel : (33) 1 45 07 75 17 E.mail : jacques.baudrand@obspm.fr

Electronics :

Rene VITRY Observatoire de Paris-Meudon

Tel : (33) 1 45 07 75 41 E.mail : : vitry@obspm.fr

Mechanics :

Michel LESSERTER CNRS Meudon Bellevue

Table of Contents

1 Overview................................................................................................ 5

1.1 Purpose of CAFE....................................................................................................................................... 5

1.2 Functional and Performance Specifications (high level)................................................................. 5

1.3 Main Features............................................................................................................................................ 7

2 Instrument Description.................................................................... 7

2.1 Sky Fibre..................................................................................................................................................... 7

2.1.1 Fibre optical characteristics............................................................................................................. 7

2.1.2 Fibre structure.................................................................................................................................... 8

2.1.3 Fibre terminations and connectors................................................................................................ 10

2.2 CAFE Head............................................................................................................................................... 11

2.2.1 Central Optical Sub-Assembly (COSA)........................................................................................ 14

2.2.1.1 Viewing Optics........................................................................................................................... 17

2.2.1.2 Calibration Optics...................................................................................................................... 17

2.2.2 Calibration facility.......................................................................................................................... 18

2.2.3 Mirror Wheel................................................................................................................................... 19

2.3 Gecko Interface....................................................................................................................................... 20

2.3.1 Mechanical design........................................................................................................................... 20

2.3.2 Optical design.................................................................................................................................. 21

3 Procedure for the Opto-mechanical Settings of CAFE......... 23

3.1 For the CAFE Head................................................................................................................................ 23

3.2 For the Gecko Interface........................................................................................................................ 24

4 Telescope Field acquisition and Tracking................................. 24

5 Instrument Efficiency on the Sky................................................ 25

5.1 Sky Fibre Link transparency................................................................................................................ 25

5.2 CAFE versus Coude Train Overall Efficiency.................................................................................. 27

6 Component Maintenance................................................................. 28

6.1 Spares........................................................................................................................................................ 28

6.2 Parts Replacement................................................................................................................................. 29

6.2.1 Calibration sources......................................................................................................................... 29

6.2.2 Opto-detector fork mount.............................................................................................................. 29

6.2.3 Moto-reducer and driving Belt....................................................................................................... 29

6.2.4 Sky Fibre.......................................................................................................................................... 29

7 Electronics........................................................................................ 30

7.1 Description.............................................................................................................................................. 30

7.2 Operation................................................................................................................................................. 33

7.2.1 General............................................................................................................................................. 33

7.2.2 About the Manual Command.......................................................................................................... 33

7.2.3 About the Loading of the Control Program.................................................................................. 35

7.2.4 About Automatic Safety.................................................................................................................. 35

7.2.4.1 LLLTV Interlock......................................................................................................................... 35

7.2.4.2 E.M Interlock.............................................................................................................................. 35

8 Control Program and Logic Syntax........................................... 36

8.1 Control Program Upper Level Flow Chart...................................................................................... 36

8.2 Program Logic Syntax........................................................................................................................... 39

9 Commercial Part List....................................................................... 42

10 Annexes................................................................................................ 44

10.1 Optical data......................................................................................................................................... 44

10.1.1 Viewing Optics................................................................................................................................ 44

10.1.2 Calibration Optics........................................................................................................................... 45

10.2 Electronics.......................................................................................................................................... 46

10.2.1 Cards Circuit Description............................................................................................................... 46

10.2.1.1 ThAr Card............................................................................................................................... 46

10.2.1.2 Logical Card........................................................................................................................... 48

10.2.1.3 Power Card............................................................................................................................. 53

10.2.1.4 LLLTV Interlock.................................................................................................................... 55

10.2.1.5 Manual Command Card......................................................................................................... 56

10.2.2 Tests points and Back Plane Connectors....................................................................................... 58

10.3 CAFE Control Program................................................................................................................... 60

10.3.1 Listing of the assembler program loaded into the micro-controller 68 HC 811...................... 60

10.3.1.1 Part 1 Main Program............................................................................................................ 60

10.3.1.2 Part 2 Serial Interpretation.................................................................................................. 63

10.3.1.3 Part 3 Interruptions............................................................................................................... 71

Table of Illustrations

Figure 1 Summary of CAFE main Functions and Specifications....................................... 6

Figure 2 Schematic view of the fibre optical characteristics...................................... 8

Figure 3 CeramOptec Transmission versus classical “Wet” and “Dry” fibres........ 9

Figure 4 Schematic view of the Fibre Radial Structure................................................... 10

Figure 5 Drawing view of the Precision Fibre Connector............................................... 10

Figure 6 Fibre ferrule extremities with their cemented microlens....................... 11

Figure 7 Picture of the CAFE Head fully assembled........................................................... 12

Figure 8 CAFE Head with Cover removed Mounted on Cass. Bonnette..................... 13

Figure 9 Drawing top view of the CAFE Head........................................................................... 13

Figure 10 Pictures of the Central Optical Sub-Assembly (COSA)................................... 14

Figure 11 COSA General Opto-mechanical Overview............................................................ 15

Figure 12 COSA general optical arrangement......................................................................... 16

Figure 13 Calibration Fibre Feed arrangement....................................................................... 18

Figure 14 Drawing view of the Mirror Wheel.......................................................................... 19

Figure 15 Drawing view of the Gecko Interface..................................................................... 20

Figure 16 Gecko Interface under test for control of output beam N.A.................. 21

Figure 17 Gecko Interface Optical Characteristic............................................................... 21

Figure 18 Views of the Bowen Wallraven Image slicer...................................................... 22

Figure 19 Photometric Attenuation Budget.............................................................................. 26

Figure 20 Comparison between CAFE and Coude Train Efficiencies............................. 27

Figure 21 Spare List................................................................................................................................... 28

Figure 22 Electronics Main Parts Presentation...................................................................... 31

Figure 23 General Organisation of the Electronics Main parts.................................. 31

Figure 24 General Architecture Synoptic of the Electronics....................................... 32

Figure 25 Manual Command Front Panel.................................................................................... 34

Figure 26 Upper Level Flow Charts of the Control Program........................................ 39

Figure 27 Table of the Logic Commands, Queries and Errors......................................... 40

Figure 28 Mirror Wheel Opto-Electrical-Logic Relations............................................... 41

Figure 29 Commercial Parts List and Suppliers/Manufacturers co-ordinates... 43

Figure 30 Viewing Optics Listing and Spot Diagrams............................................................. 44

Figure 31 Calibration Optics Listing and Density diagram............................................... 45

Figure 32 Block Diagram of the ThAr Card................................................................................ 46

Figure 33 Diagram showing the ThAr Card in its Electronics Environment.......... 47

Figure 34 Block Diagrams of the Logical Card Architecture....................................... 49

Figure 35 Component Layout of the Logical Card................................................................ 50

Figure 36 Circuit Diagrams of the Logical Card Architecture..................................... 52

Figure 37 Component Layout of the Power Card................................................................... 53

Figure 38 Circuit Diagrams of the Power Card Architecture........................................ 54

Figure 39 Detail of the LLLTV Interlock....................................................................................... 55

Figure 40 Component layout of the Manual Command Card......................................... 56

Figure 41 Circuit Diagram of the Manual Command Card Architecture................. 57

Figure 42 Test Point-Cabling Connections and Back Plane Connectors................. 59

1 Overview

This manual provides information on the functions, assembly, alignment procedures, supply and main characteristics-performances for the new telescope facility, the CAssegrain Fibre Environment (CAFE).

CAFE was designed and constructed during the period of May 98 to September 99 through the combined effort of the Observatoire de Paris-Meudon, the CNRS de Meudon, France and the Canada-France-Hawaii Telescope Corp, USA.

1.1 Purpose of CAFE

CAFE is a fibre feed for the Gecko spectrograph meant to replace the current Coude mirror train in the visible – red part of the spectrum (400 – 1000 nm). The fibre input end is mounted at the telescope F/8 Cassegrain focus and the fibre cord is routed to the Gecko spectrograph entrance through the west declination axis and down the west beam of the telescope. This system also provides full calibration capacity for the spectrograph and a viewing system for acquisition-guiding of the star image onto the fibre core entrance. At the other extremity the fibre end is coupled to a Bowen-Wallraven image slicer feeding the spectrograph with the required input optical characteristics.

1.2 Functional and Performance Specifications (high level)

CAFE has been designed and built to meet the following high level specifications:

• The CAFE Head shall be permanently mounted in the Cass. Bonnette side port on the south side of telescope. Its structure must not project inside or below the casting of the Cass. Bonnette.

• A viewing system must be implemented in the CAFE Head to see and guide the star image onto the fibre entrance with a 25 arcsec field of view and a sensibility allowing to work with stars up to magnitude 13.5. For this purpose it is imposed to use a tilted SiO2 plate to draw out from the telescope beam the necessary signal*. It is also demanded to use and incorporate in the system the TDC-200 Low Light Level TV camera provided by CFHT.

• The CAFE Head must contain a Th/Ar emission line comparison source and a flat field lamp, both easily accessible for replacement.

• A motorised mechanism will be implemented to allow for the selection between telescope and calibration injection into the fibre.

• Conversion optics shall be designed and provided to make the F/8 telescope beam with an unvignetted field of view of at least 1.5 arcsec matches the fibre entrance diameter

• At the fibre output end conversion optics and image slicer shall be designed and provided to give the spectrograph the required F/20 beam aperture and a 200 µm wide entrance slit.

• The fibre connectors at both ends must permit easy manual disconnection of the fibre while securing the precise positioning and orientation of the fibre extremities.

• The minimum length required for the fibre cord is measured to be 27 m.

• The optical throughput of CAFE should be optimised for the wavelength range 400 – 1000 nm.

• Spares should be provided for all fragile or expected short life parts

• The CAFE unit functions will be controlled by signals sent by the CFHT computer. An electronics control box, to be located in the Cassegrain environment, will interpret these signals and send/receive the ON/OFF and status signals to CAFE (lamps and motorised system for the telescope calibration selection).

The Figure 1 summarises these high level specifications and shows schematically the main functions and features that are to be given to the CAFE instrument.

Figure 1 Summary of CAFE main Functions and Specifications

* The tilted SiO2 plate was favoured over the scheme consisting to conjugate the fibre entrance with the central hole of a tilted mirror. Indeed this latter solution was not considered reliable for the auto-guiding as it was analysed that the sharp jumps of illumination produced by the random movements of the star image to and fro across the hole aperture could very possibly mislead the guiding system.

1.3 Main Features

The instrument is constituted of three distinct parts:

• The 27 m long fibre cord, the Sky Fibre, which optically links the telescope Cassegrain focus to the Gecko spectrograph entrance in the spectrograph Slit room. The fibre extremities are equipped with single micro optics for reshaping the optical beam at both input and output ends.

• The CAFE Head which is a small optical bench structure designed to be mounted to the South port of the Cassegrain Bonnette. It contains the precision connector for the fibre link input, a camera viewing system for targeting and tracking the telescope image onto the fibre entrance, a complete calibration unit with flat field lamp and wavelength comparison source and the motorised mechanism to select between telescope and calibration injection. The whole system is designed with a two orthogonal axis mounting which allows for the fine optical alignment with the telescope beam.

The electronics to control the functions in the CAFE Head is located in a 19” rack mounted on the Cassegrain environment.

• The Gecko Interface which supports a precision connector for the fibre output termination and the image slicer for reshaping the fibre image to the specified requirements. Both connector and image slicer are mounted onto a steering and linear motion stage to allow the optical adjustment of the fibre image injection into the spectrograph.

These different assemblies are specifically described in the following section.