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STIS Instrument DetectorsSTIS has three large-format (1024 x 1024 pixel) detectors: CCD
* When STIS began operating with "Side 2" electronics in July 2001,
CCD read noise increased from 4.4 to 5.3 e- for GAIN=1, and from 7.3
to 7.75 e- for GAIN=4. ETC calculations use the most recent estimates
of the read noise. The STIS/CCD is a low-noise device capable of high sensitivity in the visible and the near UV. It is a thinned, backside-illuminated device manufactured by Scientific Imaging Technologies (SITe). In order to provide a near-UV imaging performance, the CCD was backside-treated and coated with a wide-band anti-reflectance coating. The process produces acceptable near-UV quantum efficiency (QE) without compromising the high QE of the visible bandpass. The CCD has only one operating mode, ACCUM, for imaging and spectroscopy. Electrons which accumulate in the CCD wells are read out and converted to data numbers by the analog-to-digital converter. The conversion factor can be selected by the CCDGAIN parameter. While the default is CCDGAIN=1, a CCDGAIN=4 value can be chosen if CCD saturation is a concern. Scientific data are obtained on 1024 x 1024 pixels for a full readout. The CCD supports both on-chip binning and the use of sub-arrays. Additional CCD Information: CCD Bias Subtraction and Amplifier Non-LinearityDetector Backgrounds CCD Subarrays CCD Shutter Effects Cosmic Rays CCD Optical Performance Fringing due to the Order Sorter Filters IR Fringing Change to Side 2 operations Hot Pixels Charge Transfer Efficiency UV Light and the STIS CCD MAMA
The STIS MAMA detectors are photon-counting devices which process events serially. In MAMA ACCUM mode, photons are accumulated into a 2048 x 2048 array in the STIS data buffer memory as they are received. In TIME-TAG mode, the MAMA produces an event stream of data points with a time resolution of 125 microseconds. MAMA Bright Object ProtectionThe MAMAs are subject to catastrophic damage at high global and local count rates and cannot be used to observe sources which exceed the defined safety limits. Observers will have to adjust their observing strategies if a target exceeds these limits. The STIS Imaging and Spectroscopic Exposure Time Calculators issue a warning if an applicable limit is exceeded. Additional MAMA information: Saturation Overflowing the 16 Bit BufferMAMA Non-linearity On-board Doppler Compensation MAMA ACCUM and TIME-TAG Modes TIME-TAG Event Processing Spectral Mode Offsetting Out-of-Band Spectral Response of Clear Imaging Modes MAMA Dark Current MAMA Bright Object Protection |
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