Solar B - EIS

1. INTRODUCTION

2. SCOPE

3. DOCUMENTS, GLOSSARY AND ACRONYMS

4. INSTRUMENT REQUIREMENTS

5. SYSTEM BREAKDOWN

6. SYSTEM DETAILS


APPENDIX A (Instrument Block Diagram)



1. INTRODUCTION
Solar-B will study the connections between fine magnetic field elements in the photosphere and the structure and dynamics of the entire solar atmosphere.
The mission will perform three basic types of observation with high spatial, spectral and temporal resolution :
Determination of the photospheric magnetic vector and velocity fields.
Observation of the properties of the resulting plasma structures in the transition region and
corona.
Measurement of the detailed density, temperature and velocity of these structures.
The EUV imaging spectrometer (EIS) will obtain plasma velocities to an accuracy of <= 10 km s^-1 along with temperatures and densities in the transition region and corona at <2 arc sec resolution.

2. SCOPE
The purpose of this document is to reflect the design of the EIS instrument that will satisfy the requirements, as stated in Section 4.

3. DOCUMENTS, GLOSSARY AND ACRONYMS

AD 1 MSSL/SLB-EIS/SP007 EIS Science Requirements
AD 2 MSSL/SLB-EIS/SP003 EIS Interface Control Document (ICD)

RD 1

3.3 Glossary and Acronyms
AD Applicable Document
Bfn Baffles
BU Birmingham University
CAM Camera
CCD Charge Coupled Device
CLM Clamshell
CUB Alignment Cube
EEPROM Electrically Erasable PROM
EIS E-UV Imaging Spectrometer
ENC Enclosure
EUV Extreme Ultra-Violet
EW East West
FFA Front Filter Assembly
FOV Field Of View
FPA Focal Plane Assembly
FPF Focal Plane Filter assembly
GRA Grating assembly
GSE Ground Support Equipment
ICD Interface Control Document
ICU Instrument Control Unit
ISAS Institute of Space and Astronautical Science (Japan)
LOK Launch Lock
MHC Mechanisms and Heater Controller
MIR Mirror assembly
MLI Multilayer Insulation
MSSL Mullard Space Science Laboratory
NAOJ National Astronomy Observatory, Japan
NRL National Research Laboratory, USA
NS North South
PROM Programmable Read Only Memory
PUR Instrument Purge harness
QCM Quartz Control Monitor
RAD Radiator
RAL Rutherford Appleton Laboratory, U.K.
RAM Random Access Memory
RD Reference Document
RMS Root Mean Square
ROE Readout Electronics
SHT Shutter assembly
SLA Slit assembly
SLB Solar-B
STR Spectrometer
S-PUR Spacecraft purge harness
S-VAC Spacecraft vacuum harness
S-WIR Spacecraft wiring harness
TBC To Be Confirmed
TBD To Be Defined
VAC Instrument Vacuum harness
WIR Instrument Wiring harness
XRT X-Ray Telescope (instrument on Solar-B)


4. INSTRUMENT REQUIREMENTS
4.1 Science Requirements
These are defined in AD1.
4.2 Performance requirements
The performance requirements for EIS are summarized in the following table:

Spacecraft interface details are specified in the EIS ICD (AD 2).

5. SYSTEM BREAKDOWN
A block diagram of the instrument is shown in Appendix A.
A list of the system hardware is shown below and references are made to the system software which will be described in separate documents.
5.1 Flight Equipment
5.1.1 Spectrometer

ENC Enclosure
BFn Baffles
LOK Launch lock
CLM Clamshell
FFA Front filter assembly
MIR Mirror assembly
SLA Slit assembly
FPF Focal plane filter assembly
GRA Grating assembly
SHT Shutter assembly
CUB Alignment cube
CAM Camera
FPA Focal plane assembly
ROE Readout electronics
QCM Quartz control monitor
MHC Mechanisms and heater controller
WIR Instrument wiring harness
PUR Instrument purge harness
VAC Instrument vacuum harness
MLI Multilayer insulation

5.1.2 Instrument Control Unit
The ICU is sited on the spacecraft bus and interfaces with the MDP on the spacecraft and the ROE and MHC on the Spectrometer.




5.1.3 Spacecraft Harnesses
S-WIR Spacecraft wiring harness (ICU to spacecraft and ICU to Spectrometer)
S-PUR Spacecraft purge harness (clean dry nitrogen line for purging the
Spectrometer)
S-VAC Spacecraft vacuum harness (vacuum line for the Clamshell)

5.2 Non-flight hardware

These items may be installed in the instrument during integration and test, but must be removed before launch. Typically they would consist of such things as:
Contamination witness plates
Aperture cover
Test interface connectors
Connector savers
Lifting attachments
Installation jigs
Shims
Alignment mirrors

5.3 Ground Support Equipment (GSE)
The following GSE would be provided:
Purge gas supply
Vacuum pump and accessories
Alignment jigs, light sources, targets etc
Electrical GSE
Quick-look data analysis workstations
Operational data center workstations


5.4 Logistics Elements
For logistical support, the following will be required:

Shipping containers
Support frames
Clean tents
Toolkits
Material supplies

EIS consists of a multi-layer coated single mirror telescope, and a stigmatic imaging spectrometer incorporating a multilayer coated diffraction grating. The image produced by the primary mirror is imaged onto an entrance slit/slot and the light which passes through this spectrometer aperture is dispersed and re-imaged in the focal plane of the CCD camera. The spectra will be focused on two CCD detectors.
There are two reflections in the system and the two wavelength bands are:
170-210Å and 250-290Å, as limited by the grating
180-204Å and 250-290Å useful ranges, as limited by the multilayer coatings

6.2 Field of View (FOV)
Extent of EW FOV 2080 arcsec on sun (given by sum of coarse and fine
telescope positioning)
Max EW scan range, fine only ±240 arcsec
Max extent of NS FOV 512 arcsec
Spectral scale
Spectral resolution

Spatial scale
Spatial resolution

Effective area
Scattered light

6.3 Filters
The primary incidence filter is an aluminium foil on a support mesh and fitted into a quadrant frame. The material for the focal plane filter is the same.
Transmission
Stray light throughput
Obscuration

6.4 Telescope Mirror
Type Off-axis paraboloid
Aperture 15 cm clear
Area 88.4 cm² per band
Focal length 1934 mm
Off-axis distance 70 mm
Plate scale at focus (slit) 9.37 microns/arcsec
Multilayer coating Mo/Si
Number of coats 20
Layer period, short wavelength 105 Å
Layer period, long wavelength 145 Å
Coarse position method Stepper motor
Range ± 800 arcsec solar image motion
Precision
Repeatability
Speed
Fine position method Piezo electric actuator
Range ± 240 arcsec solar image motion
Precision 1/3 arcsec per step
Repeatability
Speed

6.5 Slits (SLA)
Number 4
Sizes 1 1”
2 40”
3 TBD
4 TBD
Slit change time TBD
Alignment During integration
Exchange mechanism step size 15 arcmin
Tolerance perpendic. to optical axis 1 micron
Tolerance parallel to optical axis 13 microns

6.6 Shutter (SHT)
Type Rotary vane
Position in optical system Adjacent to slits
Maximum exposure time Could be infinite
Minimum exposure time 50ms
Repeatability of exposure time 5% of minimum
Lifetime 6x10⁷ operations

6.7 Grating (GRA)
Mount Magnifying
Slit distance 1m
Detector distance 1.4m
Diameter of optic 100mm
Figure Toroid
Radius in Saggital 1182.940mm
Radius in Tangential 1178.280mm
Substrate surface roughness 5Å RMS
Ruling density 4200 lines/mm
Ruling type Holographic with straight laminar grooves, uniform line
spacing
Groove depth 58Å
Multilayer Mo/Si
Number of coats 20
Layer period, short wavelength 105Å
Layer period, long wavelength 145Å


6.8 Focal Plane Assembly (FPA)
Number of detectors 2
Detector technology Back-illuminated CCD
Manufacturer Marconi (EEV)
Type CCD-42-20
Format - columns (spectral) 2048
Format - rows (spatial) 1024
Orientation of readout register Parallel to rows
Image mode Full frame, not frame transfer
Pixel size 13.5 microns
Minimum read noise 5 electrons
Maximum binned capacity >500,000 electrons
Full well capacity - image 90,000 electrons
Full well capacity - image 5,000 photons (190Å)
Full well capacity - image 6,570 photons (250Å)
Anti-blooming structures None
Quantum Efficiency 0.8
Hot pixels <100
Column defects 0
Operating temperature -55 C (TBD)
Position resolution FWHM 16 microns
Dark Current 0.1 electron/pixel @ -55 C
Electrons per photon @ 190Å 18
Electrons per photon @ 250Å 13.7
Shielding 15 mm Al equivalent

6.9 Read-out Electronics (ROE)
Digitisation Level 14 bits
Gain >5.5 electrons/DN
Number of readout ports 2 per CCD
Read-out time Variable
Number of ADC-chains 4
Simultaneous CCD operation Yes
Output links to ICU 2
Number of windows 2 per CCD
Restrictions of windows Same height on each CCD (TBC)

6.10.2 MHC Software
This is described in a separate document

6.11.1 ICU Hardware
CPU Temic TSC21020F

CPU speed 20 MHz

Instruction per cycle 1
Instruction word length 48 bits
SEU rate TBD
1 PROM - fixed program and boot TBD
2 EEPROM - re-writable program TBD
3 RAM for running program TBD
4 RAM data memory TBD
5 Mass memory - CCD data TBD

6.11.2 ICU Software
This is described in a separate document

6.12 EIS Internal Electrical Interfaces
6.12.1 High Speed Link
6.12.2 Control Link