RECOMMENDATIONS ON DETECTOR TYPE, INTENSIFIED VS. UNINTENSIFIED IMAGING AND VIDEO CAMERA SIZE FOR THE GOMER (Global Ozone Monitoring for the Earth - Rocket) PROJECT by James Giesbrecht, M.Sc, P.Eng. September 27, 1996 BACKGROUND The following data has been compiled from the references listed at the end of the report. 1) Detector Type -The most common solid state imagers are: a) CCDs (charge coupled devices); b) CIDs (charge injection devices); c) CPDs (charge priming devices); and d) MOS (metal-oxide semiconductor). -Imagers with 500 x 800 pixels are available. (Ref. [3]) -If CCD saturation becomes a problem in the intensified system, the gain of the intensifier should be reduced to the point where the detection of a single photoevent is not possible above the lowest quantization level . -Intensified CCDs are capable of photoevent counting of weak airglow signals of a few rayleighs. (Ref. [5]) -The dynamic range of the system can be increased by summing successive image frames. Moreover, SNR is improved and cooling requirements are eased by this technique. -It is desirable to keep integration time short and the readout rate as high as possible. (Ref. [1]) 2) Intensifier -There are three basic considerations for selecting an intensifier: a) achievable gain; b) mechanical and power requirements; and c) spectral response. (Ref. [3]) -Typical MCP signal gain is from 10^4 to 10^7 with temporal resolution <100ps and spatial resolution limited by interchannel spacing and channel diameter (typically 10um diameter channels on 12um centres) -Ion feedback is a problem in straight channel MCPs (gain 10^3 to 10^4) - it degrades the SNR. -MCPs operate in a linear fashion until output current reaches 10 to 15% of the bias current (10 to 100 uA). -The most ut systems are the: phosphor screen/photodiode array, or phosphor screen/CCD. -To maximize performance between the intensifier and the imager, the spectral response and persistence of the intensifier must match that of the imager. (Ref. [2]) 3) Video Camera -The spectral response of the Xybion Intensified Video Camera (model ISS-250-GQR-3) peaks at 40-45 mA/W in the 550nm to 750nm band of wavelengths. -The response of the camera is nonlinear. The system quickly saturates when the brightness of light exceeds 100kR. (Ref. [4]) RESULTS I contacted the companies below. All have associations with low-light level cameras, CCDs, and/or image intensifiers. Eastman Kodak Co. E-mail: masdkodak@aol.com k-Space Associates Inc. E-mail: kspace@dial.cic.net Electro-Physics Corp. E-mail: 73353.3272@compuserve.com GTFS Inc. E-mail: info@gtfs.com Johnson Scientific Corp. E-mail: 72360.1715@compuserve.com Hamatsu Corp. E-mail: hamacorp@interramp.com L.O.T Oriel Ltd. E-mail: 100613.1325@compuserve.com EMR PhotoElectric E-mail: pietras@princeton.wireline.slb.com Instruments SA E-mail: systems@isainc.com So far, I haven't received any useful information from them. RECOMMENDATIONS 1) Detector Type -A CCD is a good choice for a detector because 1) its use is widespread and hence there should be stable suppliers and a wide variety of sizes; 2) its characteristics are well known and there are CCDs sensitive to the band of wavelengths that we are interested in. -The CCD should be capable of frame tranbe high so that multiple frames can be summed. 2) Intensified vs. Unintensified Imaging -It seems that an intensified system is needed (gain should be <1000 to prevent the CCD from saturating). Perhaps a straight through MCP should be used because of its lower gain characteristics. 3) Video Camera Size -Available camera sizes are: N/A -A video camera of a size less than 4 in. X 4 in. X 4 in. should be chosen because of small payload space. 4) Acronym -Use GOMER as the project acronym: Global Ozone Monitoring for the Earth - Rocketpar REFERENCES [1] Babey, S. K.; Anger, C. D.; Green, B. D.; "Digital Charge Coupled Device (CCD) Camera System Architecture", SPIE: Solid State Imaging Arrays, vol. 570, 1985. [2] Corbett, Michael B.; Then, Alan; "Microchannel Plates: Principles of Using MCPs for Efficient Detection", The Photonics Design and Applications Handbook, 1995. [3] Hofmeister, Richard A.; "Intensified Solid State Cameras: Amplifying Photoelectric Energy in Low-Light Imaging Devices", The Photonics Design and Applications Handbook, 1995. [4] Moorhouse, Peter G.; "An Attitude Video Camera Using Stellar Images for the Gemini Experiment", M. Sc. Thesis, University of Saskatchewan, 1994, pp. 38 & 41. [5] Sandel, B. R.; Broadfoot, A. L.; "Statistical Performance of the Intensified Charge Coupled Device", Applied Optics, November 1986, vol. 25, no. 22.