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IR camera 1
RATIR IR camera
• Two H2RG detectors 2048x2048 pix2
• Imaging bands:• detector 1:
• Z 830- 925 nm• Y 970-1070 nm ( UKIDSS Y and Z bands, http://www.ukidss.org/technical/instrument/filters.html)
• detector 2:• J 1170-1330 nm• H 1490-1780 nm
• Plate scale 0.2”/pix -- 6.8’x6.8’ FOV (0.3”/pixel w. demagnifying optics)• Image quality: FWHM ≤ 0.3” (derived requirement)
IR camera 2
Mechanical structure approach:decouple VIS from IR
VIS
IR
The most important results of the modeling (FEA):- displacements are negligible and will not affectimaging during typical camera operation.
IR camera 3
IR camera layout
Dichroic 1 to VIS channels
VIS 1Dichroic 2 to VIS 2 (out of plane)
IR dewar with IR det ZY and JH
Issues:
- tight space, thus difficulty with baffling- significant thermal background, possibly variable- poor control of scattered light
- oversampled image (x 2.5 linear, 6 times by area), thus longintegration times required to achieve background limitedregime, which is essential (if not critical) for GRB followup- small camera FOV
IR camera 4
IR camera withpowered optics
Dichroic 1 to VIS channels
VIS 1
Dichroic 2 to VIS 2 (out of plane)
Folding mirror
Cold Lyot stop -pupil location
Purpose:
- demagnify image by factor 1.5 :- 10’ x 10’ FOV- 0.3”pixel plate scale- factor of 2 gain in acquisition time (DetLim)
- create telescope pupil image:- eliminate (or greatly reduce) thermal bgnd- better control of ghosting- reduced scattered light
Optical design level is between concept anddesign, requires more detailed development. Weare actively working on finalizing optical designof the IR camera lens assembly.
IR camera 5
Ghosts
2MASSGSFC/WIRO cameraMrk 421
Ghosts(most likely flat surfaces in || beam)
IR camera 6
Camera functional bloc diagram
Software!!!
IR camera 7
Cryo systemH2RG detectors require to be cooled to LN2temperature for optimal performance.Cryomechanical cooler system is more reliable,thermally stable and requires less maintenance.
Cryostat (as currently baselined):• compressor: CH4 (Sumitomo)• cryocooler: CH104 (single state cryocooler)• cooling capacity 30 W at 77K• dewar assembly total weight: 64Kg• time between services: 13,000 hours• antivibration dempers (*)• watercooled (alternative CTI model - aircooled)
Operation:• power 3KW, 208V• compressor will be located outside of the dome
Status:• 2 quotes received (from IRLabs and ColdEdge Cryogenics)• delivery 3 month after order is placed• will be refined as needed depending on windows material and optics
vibration dampers
IR camera 8
Cryo MechanismsThere is a single focusing mechanism in the IR camera,the second detector will be focused using secondarymirror.
Cryogenic motors ARSAPE AM1524Used extensively in BAM, G-Wy IRcam, microshutters
Motors
Stages:
Status: available
CryogenizedNewark
CryostagesIRlabs
IR camera 9
Cryo details
vibration dampers
OFC cold straps
Cold space
Cold window - sapphire Dewar window - glass (TBR)
• Both windows are tiltedby ~4-5 deg to move theghosts out,• both windows are ARcoated
IR camera 10
Electronics: detectors H2RG• Detector
• detector drivers• detector data readout
Status: in the process of ordering
IR camera 11
Electronics• “Housekeeping”:
• temperature monitoring/control• pressure monitoring• focusing
• NI motor drivers
Status: available
Focusing/FW SW interface
LakeShore 340 temp. controller
Pressure monitor: requires vac gaugeorder
IR camera 12
Electronics: dewar cryo-harness• Internal harness:
• vaccum round connectors Tekdata manganine cables (woven)• detector drivers• detector data readout
MDM connectors
vacuum connectors
Status: available now;boards can be re-done to adapt todifferent MDM connectors
IR camera 13
SoftwareCryostat (as currently baselined):• Temperature sensors/control: available• Pressure monitorining : available• Focus/positioning : available
• Detectors DAC : requires work and interfaces to the existingTeledyne software
IR camera 14
Summary• design is modeled after the existing Goddard-Wyoming IR camera• optics: the existing concept has to be developed into a real design• most of the system control/monitor components are readily available• camera control software modules exist and can be adapted• data and communication interface software will require significantefforts
IR camera 15
Goddard-Wyoming IR camera
• 2’x2’ FOV• InSb (5.5um) detector (2562)• Cryomech cooler • 16K detector operation• 2 filter wheels, 10 positions/FW• detector focusing mechanism
IR camera 16
Test facility available
10K CTI cryocooler (WMAP legacy)