The Broadband Radiometer (BBR) is an instrument being developed for the ESA EarthCARE satellite. The BBR instrument objective is to provide measurements of the reflected short-wave (0.25-4.0 μm) and emitted long-wave (4.0-50 μm) top of the atmosphere (TOA) radiance over three along-track views (forward, nadir and backward). The instrument has three fixed telescopes, one for each view, each containing a broadband detector. The BBR instrument is led by SEA in the UK with RAL responsible for the BBR optics unit (OU) while EADS Astrium is the EarthCARE prime contractor. A detailed description of the instrument is provided in [1].
The BBR detectors consist in three dedicated assemblies under the responsibility of INO. The detectors development started in 2008 and led to the design and implementation of a new gold black deposition facility at INO [2], in parallel with the preliminary and detailed design phases of the detector assemblies. As of today, two breadboard models and one engineering model have been delivered to RAL. In the BBR OU each detector mechanically interfaces with the telescope and electrically with the front-end electronics (FEE). The detectors’ development is now at the Critical Design Review (CDR) level.
This paper first provides a description of the detector design along with its principles of operation. It further presents and discusses measurement and analysis results for the performance characterization of the engineering model in the context of the applicable requirements. Detector-level qualification planning is finally discussed.
This paper presents a study of different approaches to the measurement of the above ground vapor plume created by the spill caused by a small 0.1 l/min (or less) leak in an underground liquid petroleum pipeline. The scenarios are those for the measurement from an airborne platform. The usual approach is that of IR absorption, but in the case of liquid petroleum products, there are drawbacks that will be discussed, especially when using alkanes to detect a leak. The optical measurements studied include UV enhanced Raman lidar, UV fluorescence lidar and IR absorption path integrated lidars. The breadboards used for testing the different approaches will be described along with the set-ups for leak simulation. Although IR absorption would intuitively be the most sensitive, it is shown that UV-Raman could be an alternative. When using the very broad alkane signature in the IR, the varying ground spectral reflectance are a problem. It is also determined that integrated path measurements are preferred, the UV enhanced Raman measurements showing that the vapor plume stays very close to the ground.
Recent advances in the INO broadband SWIR/MWIR spectroscopic lidar will be presented. The system is designed for the detection of gaseous pollutants via active infrared differential optical absorption spectroscopy (DOAS). Two distinctive features are a sub-nanosecond PPMgO:LN OPG capable of generating broadband (10 to <100 nm FWHM) and tunable (1.5 to 3.8 μm) SWIR/MWIR light, and an in-house gated MCT-APD focal plane array used in the output plane of a grating spectrograph. The operation consists in closely gating the returns from back-scattering off topographic features, and is thus, for now, a path integrated measurement. All wavelengths are emitted and received simultaneously, for low concentration measurements and DOAS fitting methods are then applied. The OPG approach enables the generation of moderate FWHM continua with high spectral energy density and tunable to absorption features of many molecules. Recent measurements demonstrating a minimum sensitivity of 10 ppm-m for methane around 3.3 μm with ∼ 2 mW average power in less than 10 seconds will be described. Results of enhancements to the laser source using small or large bandwidth seeds constructed from telecom off-the-shelf components indicate that the OPG output spectral energy density can have controllable spectral widths and shapes. It also has a slightly more stable spectral shape from pulse to pulse than without the seed (25 % enhancement). Most importantly, the stabilized output spectra will allow more sensitive measurements.
KEYWORDS: Sensors, Staring arrays, Gold, Aluminum, Simulation of CCA and DLA aggregates, Indium oxide, Readout integrated circuits, Ultrasonics, Interfaces, Epoxies
The Broadband Radiometer (BBR) is an instrument being developed for the ESA EarthCARE satellite. The BBR
instrument is led by SEA in the UK with RAL responsible for the BBR optics unit (OU) while EADS Astrium is the
EarthCARE prime contractor. The BBR detectors consist of three dedicated assemblies under the responsibility of INO.
The detectors development started in 2008 and led to the design and implementation of a new gold black deposition
facility at INO, in parallel with the preliminary and detailed design phases of the detector assemblies. As of today, two
breadboard models and one engineering model have been delivered to RAL. The engineering qualification model
manufacturing activities are on-going. This paper first provides an overview of the detectors assembly and principles of
operation, with emphasis given to processes developed for the assembly and integration of the detectors. Detector-level
qualification planning is finally discussed.
The Broadband Radiometer (BBR) is an instrument being developed for the ESA EarthCARE satellite. The BBR
instrument objective is to provide measurements of the reflected short-wave (0.25-4.0 μm) and emitted long-wave (4.0-
50 μm) TOA radiance over three along-track views (forward, nadir and backward). The instrument has three fixed
telescopes, one for each view, each containing a broadband detector. Each detector consists of an uncooled focal plane
array (FPA) hybridized with a readout integrated circuit (ROIC) and a proximity electronics circuit-card assembly
(CCA) packaged in an aluminum base plate with cover. The detectors, based on INO's VOx microbolometer technology,
are required to provide fast pixel response time (< 6 ms), uniform spectral response over the entire spectral range
(achieved by the development of a gold black absorber), and low NEDT under the instrument operating conditions. The
detectors development has now passed the critical design review (CDR) and various development units (among which
the most recent is the engineering model (EM)) have been shown to meet the specification requirements. This paper first
provides a description of the detector design, followed by its principles of operation. It further presents and discusses
measurement and analysis results for the performance characterization of the engineering model in the context of the
applicable requirements.
KEYWORDS: Sensors, Staring arrays, Indium oxide, Readout integrated circuits, Gold, Prototyping, Reflectivity, Radiometry, Electronics, Simulation of CCA and DLA aggregates
The Broadband Radiometer (BBR) is an instrument being developed for the ESA EarthCARE satellite. The BBR
instrument objective is to provide top-of-atmosphere (TOA) radiance measurements in two spectral channels, and over
three along-track directions. The instrument has three fixed telescopes (one for each view) each containing a broadband
detector. Each detector consists of an uncooled 30-pixel linear focal plane array (FPA) coated with gold black in order to
ensure uniform spectral responsivity from 0.2 μm to 50 μm. The FPA is hybridized with a readout integrated circuit
(ROIC) and a proximity electronics circuit-card assembly (CCA) packaged in an aluminum base plate with cover. This
paper provides a technical description of the detector design and operation. Performance data at the FPA pixel level as
well as unit-level test results on early prototypes of the detectors are also presented.
The design and application results of an affordable short range (less than 100 m) digital LIDAR (LIght Detection And
Ranging) system will be presented. This work was initiated because many short-range standoff detection applications
would benefit from such a system. The lidar features a fiber-based component integrated in the optical module, which
allows for hardware partial compensation of the backscattered signal losses observed at short distances due to a biaxial
configuration of the lidar optics. This is an important advantage for particle density computations. The digitized
backscattered laser signals are available for signal processing. A dedicated FPGA (Field Programmable Gate Array)
allows for real-time averaging of the signal waveforms captured at the maximum 50-kHz pulse repetition frequency of
the laser.
Several application-specific tests have been performed. The first of these was real-time onboard monitoring of pesticide
drift in agricultural spraying applications. The signal levels were sufficient for control of the spraying operations and
prevention of pesticide drift into sensitive areas. The second was a dust monitoring application. The lidar was installed in
a quarry and signals from dust clouds were recorded. Real-time monitoring capabilities were shown to be promising.
Other applications involving detection of solid targets in degraded visibility conditions caused by fog or snowfalls were
also tested and are discussed.
In many sensing systems, a highly coherent laser source is necessary to perform sensitive interferometric or coherent
measurements. At TeraXion, we have built a compact laser system that provides a stable laser frequency with a very
narrow linewidth using a 60 mW DFB semiconductor laser. The linewidth reduction system uses a frequency
discriminator to measure the laser frequency noise and provides an electrical feedback to reduce this noise over a given
bandwidth. Experimental work shows that the phase noise of the DFB semiconductor laser can be reduced by more than
4 orders of magnitude from 10 Hz to 100 kHz. We analyzed the effect of the particular frequency noise spectrum of
such a laser on its degree of coherence, its linewidth and the resulting interferometric noise. The laser linewidth
computed from the power spectral density of frequency noise of the laser is reduced from 570 kHz down to an
equivalent of 1.8 kHz when the output signal is observed for 30 ms, and from 370 kHz to 18 Hz for 1 ms. Similarly, the
coherence length is increased from 145 m up to 45 km for fringes observed over 30 ms. Each result is compared with
those obtained with a fiber laser.
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