JWST template white - RIT - Center for Detectors Site

Detectors for the JWST Near
Infrared Spectrograph (NIRSpec)
B.J. Rauscher1, P. Strada2,
M.W. Regan3, D.F. Figer3, P. Jakobsen2, S.H.
Moseley1, T. Boeker2
Goddard Space Flight Center
2ESTEC/European Space Agency
3Space Telescope Science Institute
A pretty picture is not enough ..
Enter NIRSpec
Most observations probably
detector noise limited!
AAS, Atlanta, GA
8 January 2004
NIRSpec Modes
• R=100 (Exploratory spectroscopy, Verify
photometric redshifts)
– Single Prism 0.6 - 5.0 µm
– Micro-Shutter Array or Fixed Slits
• R=1000 (Emission line diagnostics)
– 3 Gratings 1.0 - 5.0 µm
– Micro-Shutter Array or Fixed Slit(s)
• R=3000 (Emission line kinematics)
– 3 Gratings 1.0 - 5.0 µm
– Fixed Slit or Integral Field Unit (TBC)
AAS, Atlanta, GA
8 January 2004
NASA/GSFC to Contribute
• Instrument built by European Industry
• 2K4KLeadership
under ESA Project
• Readout Electronics
• Presently Transitioning from Definition to
• Cable
• Two NASA-provided components:
– 4 x 384 x 175 Micro-Shutter Array
– 2 x 2k x 2k HgCdTe Detector Array
AAS, Atlanta, GA
8 January 2004
Focal Plane Array (FPA) Technology
• 2K4K FPA comprised of two 2K2K
sensor chip assemblies (SCAs)
• =0.6–5.0 m HgCdTe detectors
• FPA passively cooled to T=34–37 K
• Very successful Phase-A detector
– Raytheon and Rockwell produced outstanding detectors
consistent with requirements
– =0.6–5.0 m detectors meet challenging requirements
(e.g. total noise =6 electrons rms per t=1000 seconds
AAS, Atlanta, GA
8 January 2004
Detector Test Results
Conversion gain on this and
following plots =1.3 e-/ADU
Dark current versus temperature
Detector Test Results
Dark current histogram
Detector Test Results
Sampled-Up-the-Ramp Dark Signal
Use of Reference Pixels
With reference
Detector Test Results
Total noise versus number of non-destructive reads
Selected highlightes from
prototype testing
• Amplifier glow negligible! —Multiple nondestructive reads averaging down noise.
• Reference pixels work! —highly effective at
removing e.g. Pedestal Drifts.
• Dark current very low and independent of
temperature at T < 40 K
AAS, Atlanta, GA
8 January 2004
To learn more about JWST
detector prototype test results, see
Figer, D.F., Rauscher, B.J., Regan, M.W. et al.
2003, “Independent detector testing
laboratory and NGST detector
characterization project”, Proceedings Of
SPIE Vol. 4850, 981
AAS, Atlanta, GA
8 January 2004

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