# Presentation: 488261

## Integral Field Spectrograph 

**Laboratoire d’Astrophysique de Marseille**
**INSU - CNRS**
**10  July 2002**

- Integral Field Spectrograph
- R&D Phase
- WBS 2.3

## Spectrograph:  Overview

- Specifications
- Technology Trade-off
- Slicer technology
- Detectors
- Spectrograph Concept
- R&D plan

**Notes:**
Changed requirements to specifications

## Spectrograph

***Concept Trade-off***

## Spectrograph with dispersion element

**Spectrograph with dispersion element**

- Star

- Slit

- Collimator

- Dispersive Elmt

- Mirror

- Detector

**Notes:**
Changed name of “camera” to “mirror” (that name was confusing during rehearsal)

## Fourier Transform Spectrograph

**Fourier Transform Spectrograph**

- Star

- Collimator

- Michelson Principle

- Dichroic

- Translation stage

- Well suited for:
-  Longer Wavelength
-  Higher resolution
-  Larger Field of View

- Range: 250μm
- Positionning error: 2nm

## Technology trade-off

|  | Fourier transform (IFTS) | Long Slit | Integral
Field |
| --- | --- | --- | --- |
| Pointing accuracy | Low | Critical (~0.01”) | Low |
| Efficiency | Medium  | Good (but slit losses) | Good |
| Spectral resolution | Adjustable | Fixed | Fixed |
| 3D Spectro | Yes | No | Yes
Reformatting in slit |
| Complexity | High data volume | Centering object on slit | Low |
| Risk |  High: 
Precision Mechanism
And Metrology | May require
Centering Mechanism |  |

**Notes:**
******** why does it say “no accurate mechanism”  , so what is the risk here how much should we worry????
******** Will it be clear what an Integral Field is??  

## Technology trade-off

## Technology trade-off IFU

| IFU type | Lenslets | Lenslets+fibres | Image slicer |
| --- | --- | --- | --- |
| Throughput | 80% | 50-80% | >90% |
| Spectral domain | Limitated | Full Coverage | Full Coverage |
| Filling factor | 75-85% | 75-95% | 95% |
| Sensitivity | >4 px/ spatial elmt
( noise) | >4 px/ spatial elmt
( noise) | 1 px/ Spatial elmt |
| Risk | Diffuse light
Diffraction | Fiber/Lenset Glue
Diffraction | Mirror alignment
Diffraction |
| cooling | yes | difficult | yes |

## Spectrograph:  Baseline Selection

** ****Integral Field using the new generation of ****Image Slicer**
** ****Prism**** for low and “flat” resolution**
** ****2 detectors (****CCD, HgCdTe****)**
** ****Dichroic**** **

- Conceptual studies:

| Long Slit Spectrograph | Pointing accuracy and galaxy subtraction |
| --- | --- |
| 4 arms spectrograph with 3 spectral resolution | Complexity |
| Single channel spectrograph low resolution | Detector optimisation |
| Prism/grating evaluation (and prism material evaluation) |  |

- Baseline

## Spectrograph

***Specifications***

**Notes:**
Changed requirements to specifications

## Specifications for the Spectrograph

|  | Visible | NIR | Goal |
| --- | --- | --- | --- |
| Spatial resolution (arcsec) | 0.15 |  |  |
| Field-of-View (arcsec) | 3x3 |  |  |
| Wavelength  coverage (μm) | 0.35-1. | 1.-1.7 |  |
| Spectral Resolution | 100 | 100 |  |
| Detector Size | 1kx1k | 1kx1k |  |
| Pixel size (μm) | 15-20 | 18 |  |
| Detector Temperature(K) | 140 | 140 |  |
| Quantum  Efficiency(%) | 80 | 60 | NIR: >80 |
| Read Noise(e-) | 2 | 5 |  |
| Dark  Current(e-/s/pixel) | 0.001 | 0.02 | NIR: 0.005 |
| Individual Exposure time(s)  | 1000 | 1000 | ~3000 if CR rejection |
| Readout Time(s) | 20 | 20 |  |
| Exposure  control | Mechanical/
Electrical | Mechanical/
Electrical |  |

**Notes:**
Changed requirements to specifications, changed QE for NIR from 70 to 60, removed “>” sign on QE, changed NIR pixel size to 18 um.

## Spectrograph

***Slicer Technology***

## Spectrograph:  Slicer principles

- Telescope pupil on the pupil mirrors
- Aligned pupil mirrors
- Sub-Field imaged along an entrance slit

**Spectrograph:  Slicer principles**

- How to rearrange 2D field to enter spectrograph slit:

**Notes:**
You should say here that there are in fact 20 slices in the SNAP concept.

## Slicer Dev:  Background

- Gemini (Durham 2002)
- NGST (NIRSpec LAM 2010,MIRI Endimgourg, Proto LAM 2003)
- SNAP (LAM-2009)
- VLT-KMOS (LAM/Durham-2009)
- VLT-MUSE (CRAL – 2009)

*3 European teams working in collaboration for an equivalent FTE~10m/y*

## Slicer Dev:  Complexity

*# Elmts*

- T °K

- 30

- 77

- 300

***NGST***

***Gemini***

***SNAP***

***KMOS***

***MUSE***

***EASY***

- 20

- 60

- 200

- 500

## Slicer Dev:  Road Map

- 2000

- 2001

- 2002

- 2003

- 2004

- Individual Aluminium and glass slice
- Design Expertise

- Glass Slice Stack
- Aluminium Stack (BAD)

- Glass and aluminium pupil mirror

- Monolithic Pupil mirror line in aluminium

- Monolithic Pupil mirror line in glass

- Full representative prototype of slicer with 30 elmts in space environment
- (glass elements)

- Efforts: 	 Aluminium Durham
- 	 Glass CRAL - LAM

- Thin mirror pupil technology development (stack of mirror pupil) SNAP and KMOS

**TRL 5**

**TRL 6**

## Spectrograph

***Detectors***

## Detector Development

-  Baseline CCD + HgCdTe
-  Operating Temperature: 120-140 °K
-  1kx1k Detector

| NIR Detector | Specification | Goal
(Not detector noise limited) | Actual |
| --- | --- | --- | --- |
| Temperature | 140 | TBD | 140 |
| Read-out Noise | 5 e- | 2 e- | 4.6 e- |
| Dark Current | 0.02 e-/s/px | 0.005 e-/s/px | 0.016 e-/s/px |
| Integration time | 1000 | 3000 | 1000 |

***Actual 1kx1k detector is OK***
***Same solution than Imager (detector + Readout electronic)***

**Notes:**
Changed requirement to specification, changed “???” to TBD

## Detector Development

-  some choice: LBL, EEV, ... Driven by the QE, Dark Current and radiation hardness
-  Pixel size 15-20 μm (binning if less)

| CCD Detector | Specification | Actual |
| --- | --- | --- |
| Temperature | 140 | 140 |
| Read-out Noise | 2 e- | 2 e- |
| Dark Current | 0.001 e-/s/px | 0.001 e-/s/px |
| Integration time | 1000 | 1000 |

***Actual 1kx1k detector is OK***
***Same solution as Imager possible***

**Notes:**
Fixed English, changed requirement to specification

## Spectrograph:  Performances

**G.Aldering  snap note*
*Obscuration not included*

|  | Cumulative | HST/STIS*
cumulative | comments |
| --- | --- | --- | --- |
| Telescope | 0.92 | 0.74 | 2 Al vs 4 Ag |
| Spectrograph  | 0.57 | 0.26 | 4 Al+grating vs slicer-spectro |
| Vis channel  | 0.52 | 0.13 | 0.5 for HST CCD |
| NIR channel | 0.34(0.45) | no |  |

|  | telescope | Relay optics | Slicer
Optic  straylight diffra. |  |  | Spectro
Mirrors  prism  dichroic |  |  | Detector
Vis / NIR |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| #elements | 4 | 3 | 3 | 1 | 1 | 3 | 1 |   1  |    1 |  1 |
| Efficiency/ | 0.98 | 0.98 | 0.98 | 0.99 | 0.98 | 0.98 | 0.81 | 0.95 | 0.9 | 0.6
(0.8) |
| cumulative | 0.92 | 0.86 | 0.81 | 0.80 | 0.79 | 0.74 | 0.6 | 0.57 | 0.52 | 0.34
(0.45) |

## Performance:  efficiency

**Notes:**
Fixed English

## Spectrograph

***Concept description***

## Spectrograph:  System definition

|  | Visible | NIR | System description |
| --- | --- | --- | --- |
| Spatial resolution(arcsec)2 | 0.15 |  | 20 Slices 
0.9 x 18 mm |
| Field-of-View | 3x3 |  |  |
| Wavelength  coverage (μm) | 0.35-1.0 | 1.0-1.7 | dichroic |
| Spectral Resolution | 100 | 100 | Prism  |
| Detector Size | 1kx1k | 1kx1k | 800 x 200 useful |
| Pixel size | 15-20μm | 18μm | Camera F/D=12 |
| Detector Temperature(K) | 140 | 140 | Passive cooling |
| function | Dithering
Exposure
calibration
 |  | Dithering unit
Shutter unit
Lamp unit
Focus unit |

**Notes:**
Changed pixel size to 18 micron (the 18.5 micron is for the older Hawaii-I arrays, the Hawaii-2 are now 18.0), fixed spelling

## Spectrograph: Functional Overview

**Notes:**
I changed “Camera” to “Mirror”

## Spectrograph: Functional Overview

**Spectrograph: Functional Overview**

- Relay
- Optics

- Slicer
- Unit

- Collimator

- Prisms
- Dichroics

- NIR
- CAM

- VIS
- CAM

- NIR
- Focal plane

- Visible
- Focal plane

- Shutter

- Focus

- Dithering

- Thermal control

- Interface Electronics

- Science Software

*Optical Bench*

- Cal. Lamp

- OCU

**Notes:**
Fixed spelling

## Spectrograph:  Design Status

- The two channel version is under study

**Notes:**
******* Please change the name of “camera” to “mirror”, I fixed the english.

## Spectrograph:  Design Status

- Image quality close to the specification (~70% EE in 1 px)

**Notes:**
Changed requirement to specification

## Spectrograph:  Prism Trade-off

- Possible material:
- 	-BK7 (baseline)
- 	-ZNSE
- 	-CAF2
- 	-ZNS

## Spectrograph:  Dithering unit

**Spectrograph:  Dithering unit**

- 2 positions
-  = 5’ +/- 3”

- 2 positions
- d = 9 +/- 1μm

- Rotating the prism

- Translating the detector

## Spectrograph:  positioning tolerances

- Optical positioning stability :
-  +/- 150 μm: worst (collimator)
-  > +/- 200μm others
- Budget:
-  Mechanical alignment: +/- 75μm (fair)
-  Thermal displacement: +/- 65μm (cooling down)
-  Thermal stability: +/- 10μm

## Spectrograph:  Structural trade-off

| From 300°k down to 140°K | CTE
@300K | Density | Displacement on 300 mm | Comments |
| --- | --- | --- | --- | --- |
| Invar | 1.4 | 8.1 | 67 μm | Metallic: easy machining and interfaces
Joint with focal plane plate
Fair CTE match Zerodur |
| Molybdenum | 5.1 | 10.2 | 244 μm | Metallic: easy machining and interfaces
Joint with focal plane plate
CTE mismatch Zerodur |
| SiC
 | 2.6 | 2.9 | 124.8 μm | Non metallic
Optics in SiC |
| Zerodur | 0.03 | 2.2 |  | Optics in Zerodur as baseline |

*Longest axis of the instrument: 300 mm*

*Cooling down compatibility issues*

**Notes:**
“Bad with Zerodur” sounds alarmist!!!  What do you need, sounds like this just won’t work and there’s no solution.  What does “Metallic easy” mean?  

## Spectrograph

***Development plan***

## Optical development

-  Optical design
- Relay optics 				Moderate
- Two Channel Spectrograph			Classical
- Prism & Dichroic				Moderate
-  Optical tolerance
- Optical stability requirement		 Classical
- Optical positioning requirement		 Classical
- Alignment requirement			 Classical
-  Optical manufacturability		Classical

- Issues

**Notes:**
Last line looks like it has a formatting problem.

## Mechanical development

-  Structure
- Thermo-elastic analysis			 Classical
- Modal analysis 				 Classical
-  Opto-mechanical design
- Optics interface				 Classical
- Optical Bench				 Classical
- Interface with Base plate			 Classical

- Issues

## Instrument failure analysis 

| Item | Failure | Severity | Mitigation |
| --- | --- | --- | --- |
| shutter | Stuck | Fatal if closed | Second actuator |
| Focus unit | Stuck | Degraded performances | Second actuator
Focus with telescope |
| Dithering unit | Stuck | Degraded Performances | Second actuator ? |
| Structure / Temperature | Misalignment  | Degraded performances | Design and analysis
Safety Factor
Development plan |
| Optics | Figuring
Coating | Degraded performances | Design and analysis
Safety Factor
Development plan |
| Detector | Dead | One channel dead | Second detector with selection mechanism |

*Actual mitigation strategy: *
*	**duplicate risky component(s) & strong development plan*
*Last resort: duplicate the Spectrograph*

**Notes:**
Is the shutter electrical or mechanical?  If its mechanical then the top item doesn’t apply???  Earlier you have on a table that it could be electrical.
Is the second detector actually already in the beam, eg. 1.5x3 of the FOV goes to each of the two detectors.  Then its graceful degradation.
Next slide should be a schedule leading to your milestones.

## Summary 

- Development plane to CDR
**risk assessments **
**Trade studies on detectors and validation**
**Slicer prototype validation to TRL6**
**Develop integration & test plans**
**Performance specifications & tolerance analysis**
**Develop conceptual design**
**Develop preliminary cost & schedule ranges**
**Develop preliminary interface control specifications/documents**

- We propose an instrument:
-  **very powerful instrument**
** ****suited to the mission**
** ****using low  risk technology**
** ****Slicer unit will raise TRL 6 early before the CDR**

**Notes:**
Is the shutter electrical or mechanical?  If its mechanical then the top item doesn’t apply???  Earlier you have on a table that it could be electrical.
Is the second detector actually already in the beam, eg. 1.5x3 of the FOV goes to each of the two detectors.  Then its graceful degradation.
Next slide should be a schedule leading to your milestones.

## ANNEXE

## LAM: Most recent flight instruments (2000-2002)

**LAM: Most recent flight instruments ****(2000-2002)**

- ROSETTA-NAC: launch 2003

*TMA –telescope in SiC*
*CCD Detector*

*GALEX 75 g/mm CaF2 grism*
***: 1800-3000 (1st order) 1300-1900 (2nd Order)*

*Heritage of FUSE*

## Spectrograph:  Description

- :

| components |  function  |  elements |  complexity |
| --- | --- | --- | --- |
|  Relay optics | make the interface with the telescope |  3 mirrors | moderate
 in space |
| The slicer | field reformator | 20 Slicers / 20 pupil and slit mirrors | Challenging
New concept |
| The optical bench | Spectrograph:
Make the dispersion
visible/IR separation

 | 1 collimator mirror
1 prism
1 dichroic
 2 camera mirrors | Classical- 
Well known technologies |
| Focal plans
 visible and IR | pixelisation | 1 CCD detector
1 HgCdTe detector | To be studied
Performances |
| Additional components | Calibration
Exposure control
Focusing
dithering | Lamps
shutter 
 focus
 |     classical
    actuator
    actuator
    actuator |

## Spectrograph:  WBS phase A Overview

- 2.3.4.1
- Management

- 2.3.4.2
- System Engineering

- 2.3.4.3
- OptoMechanics

- 2.3.4.4
- Focal Planes

- 2.3.4.6
- AIT/AIV

- 2.3.4.8
- Software

*Project Management  *
*Documentation  *
*Interfaces  *

*Optical Analysis  *
*Thermal Analysis  *
*Structural Analysis  *

*Optical Bench*
*Slicer Unit  *
*Focus unit  *
*Dithering Unit  *
*Shutter Unit  *

*Detectors Trade-off  *
*Characterization Bench  *
*Selection procedure  *
*Read Out Electronics  *

- 2.3.4.5
- Interface  Electronics

*Computer  *
*Control Electronics  *
*ICS *

*Integration  *
*Verification  *
*Tests  *
*Ground Calibration  *
*GSE  *

*Simulation*
*Data reduction*
*Calibration*
*  *

- 2.3.4.7
- Calibration

*Procedure     *
*Lab Calibration *
*Space calibra  *

## R&D:  Instrument schedule