![]() ![]() Software control of the PRISM instrument is provided by a specially developed Windows application, which communicates with IO Industries software through an IOI-provided library. Data are digitized to 14 bits and output to an IO Industries CORE® recorder utilizing removable solid state drives. If desired, the computer displays temperature data from the various sensor locations in the OHA, in addition to a "waterfall" display of the data being acquired. Dark frames are acquired automatically at those times. The operator's task is to click on a software "record" or "stop" button at the beginning and end of a flight line. Shutters for the SWIR radiometer and spectrometer provide dark frame acquisition. The spectrometer detector is running at a temperature of about 7☌. The temperature of the instruments inside the vacuum vessel is kept at 25☌ through bi-directional thermoelectric coolers. The remaining electronics are dedicated to thermal control and data logging. The drives are removed after the flight and the data downloaded to another computer for same-day processing. The control computer passes the high speed data stream to a CORE® DVR data recording unit where the data is stored on solid state drives with a total capacity of 1.5 TB (expandable). The control electronics can be configured in one or two racks. ![]() Three commercial vibration isolators prevent high frequency vibration from transmitting to the optics and detectors. The instrument retains this vacuum level through a typical flight without on-board pumping. The required vacuum level for stable operation is < 3 mTorr. The vacuum vessel shell is temperature-stabilized to around 26☌ with external strip heaters. At about 40 kg, the OHA comprises the vacuum vessel with the spectrometer and SWIR radiometer inside, an aircraft interface/mounting plate, an INS/GPS unit attached to the optical head for enabling precise orthorectification and geolocation, as well as the preamplifier and ADC (Analog Digital Converter) for the detector electronics. The complete sensor comprises the OHA (Optical Head Assembly) and control electronics. ![]() PRISM comprises a pushbroom imaging spectrometer covering the near UV to near IR range (350-1050 nm) and a separate spot radiometer covering two short wave infrared (SWIR) bands at 12 nm, respectively.įigure 1: Illustration of the PRISM instrument (image credit: NASA/JPL) The system is enabled by a rapid snapshot readout detector array and specially developed low-noise readout electronics. The PRISM design responds to these challenges by utilizing several innovations including:ġ) a design that minimizes the number of elements, maintains low angles of incidence on optical surfaces, allows large aperture (F/1.8), and minimizes distortions, andĢ) a polarization-insensitive diffraction grating fabricated by electron-beam lithography. This leads to the requirement for achieving a high signal-to-noise ratio in the visible and near infrared range and minimizing the polarization dependence of the sensor transmission, in addition to a robust atmospheric correction strategy. ![]() Sensors for Ocean Science measurements are distinguished from those used for land measurements by the fact that the reflectivity of water is generally low compared with the typical reflectivity of land targets. After a calibration flight, the instrument will prove its utility through a planned investigation of eelgrass beds in the Elkhorn Slough area of Monterey Bay in California, followed by delivery to NASA to be made available for on-demand use by the Ocean Science community. Development was initiated in September 2009 and delivery is expected in 2012. PRISM was conceived in response to a proposal call from NASA's Ocean Biology and Biogeochemsitry Program. PRISM is a NASA state-of-the-art imaging spectrometer optimized for the needs of coastal ocean science, providing high SNR and dynamic range, low polarization sensitivity, high spatial resolution, and high uniformity.The development of the PRISM instrument was supported by NASA ESTO (Earth Science Technology Office), Airborne Sciences Program, and the Ocean Biology and Biogeochemistry Division. Airborne Sensors PRISM (Portable Remote Imaging Spectrometer) Airborne Instrument ![]()
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