Autonomous meridian scanning photometer for auroral observations

Autonomous meridian Autonomous meridian scanning scanning photometer for auroral observations Sean F. F. Johnston,* MEMBER SPIE Bomem Inc. Inc. 625, 625, rue rue Marais Vanier, Vanier, Quebec Quebec G1M G1M 2Y2, 2Y2, Canada Abstract. The design of an an automated automated meridian meridian scanning scanning phophoThe system system design tometer developed developed for Canadian Auroral Network Network is is described. for the Canadian described. The instrument operates unattended unattended year round in in an an arctic arctic environment. environment. instrument operates year round The has considerable considerable on on-board The instrument has -board processing processing capability for data analysis, functions, and and fail fail-safe operation. analysis, communication functions, -safe operation. Subject terms: photometers; photometers; meridian meridian scanning; automation; automation; aurora; aurora; cold cold enenSubject terms: vironments. Engineering 28(1), 020 020-024 (January 1989). 1989). Optical Engineering -024 (January CONTENTS 1. 1. Introduction 2. System description description 2. System 2.1. Operation 2.1. Operation 2.2. Optomechanical design design 2.2. Optomechanical 2.3. Control hardware hardware 2.3. Control 2.4. Software 2.4. Software 2.5. Environmental Environmental design design Calibration 3. Calibration 4. Performance 4. Performance 5. Acknowledgments 5. Acknowledgments References 6. References 1. INTRODUCTION 1. INTRODUCTION (MSP) has has been been developed developed A meridian scanning photometer (MSP) Bomem Inc. National Research Research by Bomem Inc. in conjunction with the National "Current Lloyd Instruments Instruments plc, pic, 11 Brook Brook Ave., Ave., Warsash, Warsash, *Current affiliation: affiliation: Lloyd Southampton Kingdom. Southampton SO3 SO3 6HP, 6HP, United Kingdom. Paper 2479 2479 received 1987; revised 5, 1988; received Oct. Oct. 2, 2, 1987; revised manuscript received Oct. 5, 1988; accepted for publication Oct. 5, 5, 1988; 1988; received received by by Managing Managing Editor Oct. 7, 1988. ©1989 Society Photo-Optical Engineers. ©1989 Society of Photo -Optical Instrumentation Instrumentation Engineers. Council Canada use in studies studies of the the aurora aurora Council Canada (NRCC) (NRCC) for for use borealis. These studies auspices of the Canaborealis. These studies are are under the auspices for the the Open Open Program Program Unified Unified Study dian Auroral Network for Study (CANOPUS). The network consists consists of aa complecomple(CANOPUS). The auroral network ment of instruments, including including the MSP, MSP, placed placed at at various various arctic sites sites near a single geomagnetic longitude. longitude.'1 The MSP is an evolved evolved version of of instruments instruments previously previously developed and elsewhere.2.3 elsewhere.2'3 ItIt isis the developed at NRCC and the most recent scanning program of of scanning photometer photometerdesign designfor for use use in in a program multistation observations.4,5 observations.4'5 Its advances include Its principal advances include significant significant on-board on -board processing processingpower power for for automated automated data collection, treatment, and and communication communication functions functions collection, data data treatment, and environmental packaging packaging to to allow allow year year-round unatand environmental -round unattended operation. The The instrument instrument has hasextensive tended operation. extensive self self-monitoring control capabilities capabilities to toensure ensurefail fail-safe monitoring and and control -safe operation. 2. SYSTEM SYSTEM DESCRIPTION 2.1. Operation Operation 2.1. The CANOPUS MSP measures measures sky sky brightness brightness within within aa 44°° circular view along north-south circular field field of view along a north -south arc, arc, or meridian. At each of of seven seven wavelengths, wavelengths, 510 510 measurements measurements are made / OPTICALENGINEERING ENGINEERING //January Vol. 28 28No. No. 11 020 / OPTICAL January 1989 //Vol. Downloaded From: http://spiedigitallibrary.org/ on 08/27/2013 Terms of Use: http://spiedl.org/terms AUTONOMOUS MERIDIAN MERIDIAN SCANNING SCANNING PHOTOMETER PHOTOMETER FOR FOR AURORAL AURORAL OBSERVATIONS OBSERVATIONS ACRYLIC ACRYLIC WINDOW WINDOW SCAN COWLING-TT SCAN MIRROR MIRROR AND AND COWLING PRIMARY LENS LENS-| f BAFFLE BAFFLE PRIMARY ANGULAR LIMITS LIMITS ANGULAR SCAN SCAN MOTOR MOTOR- 4° DIA. FIELD / OF VIEW OF OF BINS BINS 1 FILTER ENCLOSURE SHUTTER PMT ENCLOSURE HEIGHT OF AURORAL EMISSION EARTH'S SURFACE Fig. 2. Observing geometry. geometry. Fig. 2. Observing CPU BOARD POWER SUPPLIES SNOW BAFFLE HEAT EXCHANGER EXCHANGER HEAT CALICALI- BRATION BRATION SOURCE SOURCE » SKYLIGHT-1 SKYLIGHT SENSOR SENSOR Fig. MSP layout. Fig. 1. 1. MSP layout. during scans. Three Three wavelengths wavelengths are are during repetitive repetitive 30 30 ss scans. background correspond to auroral background channels; channels; the the other other four correspond emission emission wavelengths. wavelengths. The The measurements measurements are transmitted in a formatted formatted data stream stream directly directly to to aa local local data data port, from which which they they can can be be stored stored on on magnetic magnetic tape. tape. The data are also averaged into angular angular sectors sectors corresponding corresponding averaged by by "binning" "binning" into corrected for to 0.5 °° wide wide geomagnetic geomagnetic latitudes, latitudes, corrected fornonlinear nonlinear-ity, background, and then transmitted transmitted via ity, background, and dark count and then satellite link Two of of the the MSP MSP chanchansatellite link to to a central computer. Two nels, corresponding corresponding toto red red auroral auroral emission emission at at higher higher nels, wavelength, are binned binned into into 1.0 1.0°° altitude and a background wavelength, intervals. Internal calibrations calibrations and count measurements measurements are Internal and dark count made once (sandwiched into the 1.5 s of each scan once per per hour (sandwiched spent spent at the nadir position) and are reported along with the intensity intensity data. Communication one-way: decides Communication is is normally one -way: the MSP decides autonomously sends data autonomouslywhether whetherorornot not to to scan scan and and sends data and status information to the central computer of the instrument network. A hand hand-held used lonetwork. -held terminal, terminal, however, however, can can be used locally to updates. cally to request request special special functions functions or status updates. The instrument performs scans at night when the sky and local all systems systems have local environment environment are are dark dark and also after all been verified as operating correctly. Temperatures, voltages, voltages, light light intensities, intensities, and local local time time are monitored and used coolers, and used to to control control the the status status of a shutter, heaters, coolers, fans. 2.2. Optomechanical design 2.2. Optomechanical enclosure is shown in Fig. 1. The layout layout of the instrument enclosure is shown in Fig. 1. The optical design, which provides a solid angle times collecting area area product product of of 0.3 0.3 cm2. cm2»sr, consists of an an entrance entrance ting sr, consists aperture and primary lens lens that that aperture and plane plane scan scan mirror, mirror, an an f/3 primary focuses an field stop, stop, an an aspheric aspheric focuses an image image of of the the sky sky onto a field secondary lens secondary lens that that focuses focuses an an image image of the entrance stop detector, and and aafilter filterwheel wheel located onto the detector, located immediately immediately in in front of the the field field stop. The entrance aperture of of the the optics optics is mounted along with with the scan mirror in in aa rotating rotatingcowling. cowling. The The cowling cowling acts acts as as both support and and baffle baffle and andincorporates incorporates aamechanical mechanical both support horizon reference sensed by an optocoupler. optocoupler. The The assembly assembly is rotated by by aa stepping stepping motor motor (0.225 (0.225 °° steps) at a variable rate to attain aa nearly nearly constant constant averaging averaging time time for for different different to attain geomagnetic Fig. 2. 2. The The stepping stepping geomagnetic latitudes, latitudes, as illustrated in Fig. motor can be be commanded commanded by by software software totofollow followaavariable variable-speed particular step step (i.e., (i.e., angle). angle). The speed scan scan or or to to rotate to aa particular scan is as thin thin as as possible possible to to reduce reduce inertia inertia and and isis scan mirror mirror is cemented plate. cemented to to a shimmed aluminum support plate. An internal calibrator, calibrator, consisting consisting of of an anincandescent incandescent An internal lamp, absorption filters, filters, and and opal opalglass glass screen, screen, isis mounted mounted at the nadir position position of of the the scan. scan. The Thelamp lampisis supplied supplied with with at most 80010 80% ofofrated ratedpower powerand and isisgradually gradually ramped ramped on and off to ensure ensure long long life. life. The The lamp lamp and and calibrator calibrator filter filter are are chosen to simulate the midrange auroral auroralintensities intensities typically typically measured measured by each channel. The combination of of scan scan mirror mirrorand andsimple simpleplanoplano-convex convex primary lens yields the 25 25 mm mm diam diam yields a 11 mm diam image at the field point source source isis viewed. viewed. field stop when a point The filter wheel wheel isis rotated 1200 RPM by an ac ac synsynThe filter rotated at 1200 RPM by chronous motor. motor. The Theeight eightfilters filtersare areofoftripletriple-cavity band-cavity band pass type. Immediately the filter filter wheel, wheel, an an elecImmediatelyininfront front of of the electromagnetic shutter controls the transmission of light to the detector. It is commanded to close close under bright light condiconditions measurements. The shutter intions and during dark count measurements. incorporates optical sensor sensor to verify verify the position position of its its corporates an an optical blades; reported in in the the housekeeping housekeeping informainformablades; its its status is reported tion. aspheric field field lens lens ensures ensures that all all light light entering entering tion. The aspheric the instrument falls falls on on the thedetector, detector,a 16 a 16-stage photo-the instrument -stage photo multiplier operated in in pulsepulse-counting multiplier tube (PMT) operated counting mode. mode. fixed base The MSP enclosure can be dismounted from a fixed permanently mounted on the building roof. The The base base is inipermanently tially aligned of aasighting sighting telescope telescope and and levels levels tially aligned with with the aid of mounted on one one corner. corner. The The MSP MSP components components are are rigidly rigidly mounted an optical optical bench bench inside inside the the insulated insulated enclosure. mounted on an enclosure. The subenclosures subenclosures housing filter wheel wheel and and detector detector The housing the the filter assembly components to to be be easily easily assembly are are designed designed to allow the components removed The supports supports for forthe thesubenclosures, subenclosures, removed for transport. The lenses, and components are adjustable adjustable for for optical optical lenses, and other components allow unimpeded unimpeded access access to to devices devices mounted alignment and allow low in the enclosure. low Control hardware hardware 2.3. Control The control of the the MSP MSP isis separated separated into into two two hierarchical hierarchical The control and physical physical levels, diagrammed in Fig. 3. 3. The The master master levels, as as diagrammed in Fig. OPTICAL / January 021 OPTICALENGINEERING ENGINEERING / January1989 1989/ /Vol. Vol.2828No. No.1 1/ / 021 Downloaded From: http://spiedigitallibrary.org/ on 08/27/2013 Terms of Use: http://spiedl.org/terms JOHNSTON VOLTAGES TEMPERATURES i SKY STET SYNC flLrt* 9eHC» 5/C/A/ S NCNLIGHT LiamPHT £070*MO7oR RLTCR SKIN PMT MOTOR PMT [ftp ul,,p EATTERY 4444444444 PMr i CENTRAL PROCESSING UNIT CENTRAL PROCESSING uNir FILTER HEATERS BENCH ' ^7*.TeK FI'-TER voices_ HOTOK M oT°R ^ rn-TC-R PILTER SC.HSOK. SENSOR ST&r STEP MOTOR 1 4 (cpu) ' SNvTTCR PMT VOLTAGC i 4 DRIVE STC.P MOTOR OPTIONAL OPTIONAL PRIMTe*. PRINTER ti *- I i FILTER WMM? TERMINAL HANDHELD (ADC) ANALOG- TO- O /GITAL CONVERTER COOLERS 4-R MASrer* 7*oce*j/ v* MASTec PROCES3/N UNtT (MPU) UNIT (H PU) ' t W77C*/ T7**Y 8RT7ERY SHUTT&K SPUTTER SCHSO* SENSOR ^ HORitJDN NORItON 5C.HSOR. SC NSOR 1 PMT 1 , 1 ITRAmOur PORT 1 ICAMPAMN PORT coes GOES CLOCK trc? \OVAC 110 VAC PMT PREAMP 1 puLSC CDVNTER Fig. 3. MSP functional block diagram. diagram. Fig. 3. MSP functional block processing unit (MPU) performs performs the thehigher higher-level processing -level functions such such as as setting setting the the operational operational mode, sequencing scans, and formatting central processing processing unit (CPU) (CPU) perperformatting data. data. The central forms basic control control functions functions such such as as temperature temperature forms the the basic regulation, detailed detailed scan monitoring and and regulation, scan management, management, and monitoring control of individual individual components. components. For example, example, the scan scan control via mirror steps are synchronized with filter wheel rotations via sends the signal and other data to the the the CPU, which sends the PMT signal 16-bit insulated MPU as 16 -bitwords. words. The The CPU CPU is is located in the insulated MSP enclosure the site site building. building. MSP enclosure mounted mounted on on the the roof of the rack-mounted The MPU is rack -mounted in in the the building below. below. The MPU and CPU are linked by a signal cable and a power cable supplying ac and battery battery back plying -up power. back-up The MPU, an Intel Intel iSBC86 iSBC86 computer with associated electronics, receives receives time references from Geostatronics, time and and 11 Hz references from a GeostaEnvironmental Satellite Satellite (GOES) (GOES) clock. tionary Operational Environmental sends all the data to aa campaign campaign port. A A transmitter transmitter It sends all of the used to send send averaged, averaged, formatted satellite port is used formatted data to aa satellite transmitter. Because the usually operated operated far from from Because the instrument instrument isis usually technical aid, control itself, itself, report report its its condition, condition, technical aid, itit must control in the the worst worst case, case, fail fail without without damaging damaging other other subsuband, in systems. Table lists the protection protection systems systems employed. employed. systems. Table I lists 2.4. Software 2.4. Software 8086 assembler CPU firmware is written in 8086 assembler language. language. It can be commanded commanded by set of of 15 15 commands commands listed listed by an instruction set in Table II. The The status status data include include six six zone zone temperatures; temperatures; voltages voltages of of the detector, detector, calibration lamp, and batteries; detector signal and dark count; and status of shutter, light light sensors, heaters, coolers. and coolers. sequences of based on The MPU orders sequences of CPU commands based time of day, day, status status information, information, and and error error checking, checking, as as time listed in verifies the the quality quality of of satellite satellite clock clock listed in Table Table III. ItIt verifies signals, CPU communication, motor temperatures, temperatures, filter filter signals, CPU communication, wheel speed, wheel speed, and and sufficient sufficient darkness before ordering scans. error, the the MSP MSP During daylight hours, or in the event of any error, remains in remains in IDLE IDLE mode, mode, during which only status information is transmitted. TABLE Protection systems systems of of the theCANOPUS CANOPUS MSP. MSP. TABLE I.I. Protection Condition MSP action MSP On-axis On -axis light light too bright Closes shutter; off PMT PMT turns off Sky Sky light light too bright Closes shutter; off PMT; PMT; turns off switches to IDLE mode IDLE CPU awaits CPU speed proper speed IDLE Switches to IDLE wheel too Filter wheel slow Instrument too Instrument hot Status communicated Off-axis alarm, Off -axis sensor alarm, shutter closure, and and PMT PMT voltage voltage sensor signal, signal, Sky light sensor shutter closure, PMT PMT and mode mode voltage, and Filter wheel period zone IDLE mode, zone temperatures, status of temperatures, heaters heaters and and coolers Instrument Instrument too cold motors <0 <0°C, If motors °C, switches to Daytime CPU rotates scan CPU nadir mirror to nadir and turns and turns off and motors and PMT Nonrotating scan scan mirror Switches to IDLE IDLE Scan alarm Scan alarm bit GOES clock GOES clock fault IDLE Switches to IDLE Battery supplies power to filters, if needed. GOES alarm GOES alarm bit IDLE Power Power failure Zone temperatures, mode, mode, and and status status of heaters heaters and and coolers IDLE IDLE mode The MPU MPU program, program, written written principally principally in in PASCAL, PASCAL, The operates with aa combination combination ofofround round-robin scheduling operates -robin scheduling (i.e., an endless endless loop of sequentially sequentially executed executed routines routines that that when decisional decisional flags are set) set) and interrupts interrupts are performed when for the time time-critical -critical communication communication functions. is customized customized for each each site site by by constants constants The instrument is stored in in read read-only memory for for latitude latitude/longitude, site stored -only memory /longitude, site name, scan scan velocity name, velocity profile, profile, detector detector nonlinearity, nonlinearity, and and transmission times. 022 / OPTICAL / OPTICALENGINEERING ENGINEERING // January 1989 1989 //Vol. Vol. 28 28 No. No. 11 Downloaded From: http://spiedigitallibrary.org/ on 08/27/2013 Terms of Use: http://spiedl.org/terms AUTONOMOUS MERIDIAN MERIDIANSCANNING SCANNINGPHOTOMETER PHOTOMETERFOR FOR AURORAL AURORALOBSERVATIONS OBSERVATIONS AUTONOMOUS TABLE functions of of CPU. CPU. TABLE II. II. Software Software functions 11 22 3,4 5,6 7 7 8 8 9 10 11 11 12 13 14 15 Perform Perform 11 scan data Transmit status data Open/close Open /close shutter shutter Turn on/off Turn calibrator calibrator on /off Perform calibration Perform calibration Perform dark Perform dark count Position mirror to step xx Position Transmit combination for for xx samples samples Transmit data data for for specific filter combination Switch to DUTY DUTY mode Switch to IDLE IDLE mode mode Abort active command CPU Reset CPU MSP_________________________ Initialize MSP TABLE III. Software functions functions of of MPU. MPU._______________ TABLE III. Software 1 1 2 3 4 5 6 7 8 9 10 11 11 12 local dawn dawn/dusk date Calculate local /dusk for present date Set MSP MSP mode Set mode depending dependingon on time time and and conditions conditions Order scans at 00 and and 30 30 ss Order Correct and Correct and format data Send unaveraged every scan Send unaverageddata data to to campaign campaign port port after every scan Send port every every 2 min Send averaged averageddata data to to transmitter transmitter port Order Order calibration calibration at 30 s Order dark 30 min min 30 30 ss Order dark count at 30 Monitor Monitor GOES GOESclock clock time time signal signal Monitor Monitor all all instrument sensors and order protective action if needed needed Send optional printer printerand and/or Send status status data to optional /or terminal Communicate with hand hand-held -held terminal 2.5. Environmental design design 2.5. Environmental The requirement of unattended operation operation in all all seasons seasons The requirement of unattended demands Temperatures at arctic demands versatile versatile thermal thermal control. control. Temperatures arctic sites can range from from --55°C to more more than than + +30°C with sites can range 55 °C to 30 °C with 100% relative 125 100% relative humidity. humidity. The MSP must also withstand 125 km/h heating. km /h winds, winds, snow snow drifts, drifts, and solar heating. Various zones of the instrument are individually temperature controlled. The optical filters are maintained maintained at 20±5°C; below ambient 20 ± 5 °C;the thephotomultiplier photomultipliertube tube isis kept kept below noise; the the external external window of temperature to reduce thermal noise; instrument is is heated heated to 20 20 °C snow or water water is is the instrument °C so so that snow gradually cleared; of the the enclosure enclosure is is controlled cleared; and the rest of between the elecelecbetween 55 °C °Cand and 45 45°C °Ctotoensure ensure safe safe operation operation of the tronics. subenclosures, thermotronics. A combination of insulated subenclosures, thermoelectric coolers, adhesive foil foil resistance resistance heaters heaters are electric coolers, and and adhesive employed by by the the CPU CPU to to maintain satisfactory employed temperatures. used for for fail fail-safe temperatures. Thermostats are used -safe operation of the enclosure enclosure heaters heaters and and fans. The thermoelectric thermoelectric coolers, coolers, power power supplies, supplies, stepping stepping The motor, other devices devices generate generate some some 400 400 W waste motor, and other W of waste heat, which is dissipated dissipated within within the the insulated insulated enclosure. enclosure. heat, which Small Small fans, fans, thermostatically thermostatically controlled, controlled, are are used used for direct cooling cooling of of motors motors and thermoelectric heat sinks. At ambient temperatures °C, this this power must be removed temperatures above above -10 -10 °C, removed to to avoid overheating. overheating. A commercial commercial heat heat exchanger exchanger (VanEE (VanEE avoid Systems, Systems, Saskatoon, Saskatoon, Canada) Canada) isis employed employedto to transfer transfer heat heat from the air of of the the sealed sealed enclosure enclosure to tothe thecooler coolerotfitside oiftside air. TABLE IV. Optical characteristics characteristicsofofthe theCANOPUS CANOPUS meridian meridian scanscan­ TABLE IV. Optical ning ning photometer photometer channels. channels. Channel No. Wavelength A A Passband (FWHM) Sensitivity (counts/Rayleigh) (counts /Rayleigh) 1 1 6250 6250 (background) (background) 22 0.42 2 6300 22 0.61 3 4800 (background) 4800 22 1.7 4 4857 4857 22 1.6 22 1.7 4935 (background) 4935 25 1.5 5 § 7 4706 25 1.9 8 5577 22 0.11 The enclosure isis sealed all joints. The The exexThe enclosure sealed by by gaskets gaskets at at all changer is situated situated below below the enclosure, and both are are changer is the enclosure, and both mounted above ground level to prevent the accumulation of snow. exchanger air outlet include include baffles baffles to snow. The exchanger air inlet inlet and outlet prevent where prevent the entry of snow into the internal ductwork, where it could freeze freeze and block airflow. To reduce reduce the absorption of of sunlight, sunlight, the the instrument instrument exexterior painted white. white. During During the terior isis painted the day the the scan scan mirror mirror rotates to the nadir nadir position position to toexpose expose the the reflective reflective rear surface cowling to the external external window. window. face of the cowling 3. CALIBRATION 3. CALIBRATION The photomultiplier, photomultiplier photomultiplier The characteristics characteristics of the photomultiplier, preamplifier, bandpass filters, and internal calibrator and internal brightness brightness can can vary vary somewhat somewhat from unit to unit and so must be the MSP MSP response response to to sky sky brightness. brightness. be calibrated calibrated to relate the After alignment alignment of the scan scan plane plane and and telescope telescope axis, axis, the instrumental field field of of view view is verified by scanning a fixed exexternal point source. The The relative relative spectral responses of the instrument channels are measured using an external monochromator. The The absolute absolute response response and and the the nonlinear nonlinear-ity and counting counting circuits circuits are are determined determined ususity of the detector and ing external calibration calibration source source having number of ing an external having aa number known spectral irrairraknown intensities. intensities. This This external external source source of spectral diance traceable to international diance isis traceable international standards. standards. A A four four-segment programmed to corsegment quadratic quadratic polynomial polynomial isis then programmed rect rect the MSP response. In regular operation, hourly hourly automatic automatic measurements measurements of the internal calibration source ensure that drifts drifts in in sensitivsensitivity change or aging aging of components components ity caused caused by by temperature temperature change are noted. Stability of ±±5% per night and absolute accuracy accuracy 5% per of 30% are are achieved. achieved. 4. PERFORMANCE 4. PERFORMANCE Typical Channel 88 (5577 (5577 Typical sensitivities sensitivities are are listed listed in in Table IV. Channel A)) is intentionally less factor of of about about 10 10 A is intentionally less sensitive sensitiveby by aa factor because of the intense intense green green auroral auroral emission emission at this this because of the wavelength. Figure Figure 44 shows shows the the typical typical response. The maximum PMT pulse linearization is is about about 12 12 MHz. MHz. pulse counting counting rate after linearization The prototype prototype instrument instrument has has been been tested tested between The between temperatures operated sucsuctemperaturesof of --55°C 55 °C and ++40°C 40 °C and operated cessfully Gillam (Manitoba). Three cessfully for for more more than than a year at Gillam more instruments have recently been installed installed at Rankin Inlet (Northwest Territories), (Manitoba), and let (Northwest Territories), Pinawa Pinawa (Manitoba), and Fort Smith (Northwest Territories). Smith (Northwest OPTICAL / January 1989 / Vol. / / 023 OPTICALENGINEERING ENGINEERING / January 1989 / Vol.2828No. No.1 1 Downloaded From: http://spiedigitallibrary.org/ on 08/27/2013 Terms of Use: http://spiedl.org/terms JOHNSTON JOHNSTON REFERENCES 6. 6. REFERENCES King, W. King, R. W. Creutzberg, R. F. Creutzberg, Gattinger, F. L. Gattinger, R. L. Vallance Jones, A. A. Valiance Jones, R. Anger, J. D. Anger, C. D. Harris, C. R. Harris, F. R. McEwen, F. D. J.J. McEwen, Cogger, D. L. Cogger, L. L. P. Prikryl, L. CANOPUS comparison ofofCANOPUS "Acomparison Koehler, "A A. Koehler, R. A. and R. Murphee, and S. S. Murphee, camera," UV camera," Viking UV the Viking from the images from with images ground ground optical optical data data with (1987). 391 (1987). 14, 391 Geophys. Geophys. Res. Lett. 14, light "Spectrophotometry of faint light Reasoner, "Spectrophotometry S. Reasoner, R. S. Father and R. S. Eather 2. R. R. S. (1969). 227 (1969). Opt. 8,8, 227 sources sources with with aa tilting-filter tilting -filterphotometer," photometer," Appl. Opt. spectrum of the visible spectrum thevisible ofthe studyof andstudy detection and 'Thedetection Romick, "The 3. G. G. J. Romick, the Radiometry, D. Atmospheric Radiometry, for Atmospheric Methods for in Methods aurora and airglow," in D. P. P. (1976). 63-70 91,63 SPIE91, Proc. SPIE McNutt, McNutt, ed., Proc. -70 (1976). Jones, Vallance Jones, A.Valiance and A. Harris, and R. Harris, Creutzberg, R. 4. F. F. Creutzberg, R. L. Gattinger, F. R. electron auroras," Can. and electron relation to proton and "Pulsating auroras auroras in relation 1124(1981). 59, 1124 Phys. 59, J. Phys. (1981). Harris, R. Harris, F. R. Gattinger, and F. Creutzberg, R. L. Gattinger, Vallance Jones, 5. A. Valiance Jones, F. F. Creutzberg, I. photometers 1. meridian-scanning chainofofmeridian with aachain studies with "Auroral studies -scanning photometers magnetospheric auroraininmagnetospheric electron aurora and electron proton and Observations of Observations of proton s., (1982). 4489 (1982). 87,4489 Res.87, Geophys. Res. substorms," J.J.Geophys. 1. E à 3 l02 icr 1 03 10-* 10 l04 IOS RELATIVE BRIGHTNESS BRIGHTNESS RELATIVE Fig. 4.4. Relative Relative response. response.Sampling Sampling "window" "window" is ms. 4.9 ms. is 4.9 Fig. 5. ACKNOWLEDGMENTS ACKNOWLEDGMENTS 5. parMany individuals individualshave have contributed contributedtoto this design, parthis design, Many Berube, N. Bérubé, Trudel, J. N. ticularly G. G. Tremblay, Tremblay,S.S. Perry, Perry, C. C. Trudel, ticularly L. Chouinard, and M. M. Jacob and Inc., and Bomem, Inc., of Bomem, Jacob of Chouinard, and L. F. Creutzberg Creutzberg and and F. F. Harris of the National Research CounF. NRCC cil Canada. Canada. Development was undertaken undertaken for for the the NRCC Development was cil -2 -6541. 17SR.31098-2-6541. DSS17SR.31098 contractDSS under contract Edmonton, Johnston was born Sean Sean F. F. Johnston born in Edmonton, B.Sc. and received the B.Sc. 1956. He Canada, Canada, in 1956. He received Simon from Simon degrees in physics M.Sc. degrees M.Sc. physics from 1978 in 1978 Columbia) in (British Columbia) Fraser University (British Bomem joined Bomem He joined respectively. He 1980, respectively. and 1980, and 1981, where Inc. Inc. in 1981, where he he worked worked as as an an instrudevelopment of development manager of designer, manager ment ment designer, and MSP, and CANOPUS MSP, theCANOPUS as the such as projects such He is engineering. He systems engineering. for systems leader for group leader Analytical the Analytical engineer of presently presently chief chief engineer of the publicaHis publicaInstruments. His Lloyd Instruments. Division Division of Lloyd and spectroscopy, and infrared spectroscopy, design, infrared optical design, are in the areas of optical tions are SPIE. and SPIE. OSA and of OSA member of is aa member He is holography. He 024 January 1989 No 11 28No. Vol.28 1989/ /Vol. ENGINEERING // January / OPTICALENGINEERING 024 / OPTICAL Downloaded From: http://spiedigitallibrary.org/ on 08/27/2013 Terms of Use: http://spiedl.org/terms