SPEX airborne spectropolarimeter calibration and performance

Smit, J. M.; Rietjens, Jeroen; Harten, Gerard van; Noia, Antonio Di; Laauwen, W. M.; Rheingans, B. E.; Diner, David J.; Cairns, Brian; Wasilewski, A. P.; Knobelspiesse, Kirk; Ferrare, R. A.; Hasekamp, Otto

doi:10.1364/ao.58.005695

Cited by 44 publications

(48 citation statements)

References 37 publications

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“…Both effects are common in long-slit spectrometers. 14,28 Smile is corrected by doing the wavelength calibration per pixel row; a keystone correction is still in development.…”

Section: Wavelength Calibrationmentioning

confidence: 99%

A universal smartphone add-on for portable spectroscopy and polarimetry: iSPEX 2

Burggraaff

Perduijn²,

Hek³

et al. 2020

Micro- And Nanotechnology Sensors, Systems, and Applications XII

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Spectropolarimetry is a powerful technique for remote sensing of the environment. It enables the retrieval of particle shape and size distributions in air and water to an extent that traditional spectroscopy cannot. SPEX is an instrument concept for spectropolarimetry through spectral modulation, providing snapshot, and hence accurate, hyperspectral intensity and degree and angle of linear polarization. Successful SPEX instruments have included groundSPEX and SPEX airborne, which both measure aerosol optical thickness with high precision, and soon SPEXone, which will fly on PACE. Here, we present a low-cost variant for consumer cameras, iSPEX 2, with universal smartphone support. Smartphones enable citizen science measurements which are significantly more scaleable, in space and time, than professional instruments. Universal smartphone support is achieved through a modular hardware design and SPECTACLE data processing. iSPEX 2 will be manufactured through injection molding and 3D printing. A smartphone app for data acquisition and processing is in active development. Production, calibration, and validation will commence in the summer of 2020. Scientific applications will include citizen science measurements of aerosol optical thickness and surface water reflectance, as well as low-cost laboratory and portable spectroscopy.algorithm for c and a from multi-angular DoLP data. 9 Finally, spectropolarimetry of vegetation probes its physical characteristics, such as leaf orientation, and provides reflectance distribution functions, which are crucial for improving the accuracy of air-or space-based aerosol retrieval algorithms. 10Combining spectral and polarimetric measurements can be done in multiple ways. 11 First, regular spectroradiometers can be fitted with rotating polarizing filters, as was done in the aforementioned studies of water and vegetation. 9, 10 A second method is 'channeled' spectropolarimetry, where polarization information is encoded into the spectrum itself. One method for channeled linear spectropolarimetry is SPEX, 12 the basis for SPEXone. 6 In SPEX, incoming light is modulated with a sine wave with an amplitude and phase depending on the DoLP and the Angle of Linear Polarization (AoLP), respectively. 12 This is further explained in Sec. 2.2.The SPEX technique has been applied successfully in two high-end field-going instruments measuring aerosol optical thickness (AOT, sometimes termed aerosol optical depth, AOD), namely groundSPEX 13 and SPEX airborne. 14 GroundSPEX is a ground-based instrument based on a dual-channel fiber-optic spectrometer with SPEX optics on a moving mount, allowing sequential measurements at multiple angles. Its AOT measurements are well-correlated (Pearson r = 0.932) 13 with data from AERONET, the global network of photometers observing the solar almucantar and principal plane. 15 SPEX airborne, as the name implies, is an airborne instrument, simultaneously observing at nine fixed viewing angles. A 2017 campaign on a NASA ER-2 high-altitude aircraft demonstrated excellent...

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“…Both effects are common in long-slit spectrometers. 14,28 Smile is corrected by doing the wavelength calibration per pixel row; a keystone correction is still in development.…”

Section: Wavelength Calibrationmentioning

confidence: 99%

A universal smartphone add-on for portable spectroscopy and polarimetry: iSPEX 2

Burggraaff

Perduijn²,

Hek³

et al. 2020

Micro- And Nanotechnology Sensors, Systems, and Applications XII

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“…The SPEX airborne instrument (Smit et al, 2019) employs the spectral modulation technique (Snik et al, 2009), in which the degree and angle of linear polarization are encoded in a modulation of the radiance spectrum as a function of wavelength.…”

Section: The Airborne Spectrometer For Planetary Exploration (Spex Aimentioning

confidence: 99%

“…Studies of these observations in the context of PACE are active and underway (e.g. Smit et al, 2019, Fu et al, 2019.…”

Section: Plankton Aerosol Cloud Ocean Ecosystem (Pace) Missionmentioning

confidence: 99%

The Aerosol Characterization from Polarimeter and Lidar (ACEPOL) airborne field campaign

Knobelspiesse

Barbosa

Bradley

et al. 2020

Preprint

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Abstract. In the fall of 2017, an airborne field campaign was conducted from the NASA Armstrong Flight Research Center in Palmdale, California to advance the remote sensing of aerosols and clouds with Multi-angle Polarimeters (MAP) and Lidars. The Aerosol Characterization from Polarimeter and Lidar (ACEPOL) campaign was jointly sponsored by NASA and the Netherlands Institute for Space Research (SRON). Six instruments were deployed on the ER-2 high altitude aircraft. Four were MAPs: the Airborne Hyper Angular Rainbow Polarimeter (AirHARP), the Airborne Multiangle SpectroPolarimetric Imager (AirMSPI), the Airborne Spectrometer for Planetary EXploration (SPEX Airborne) and the Research Scanning Polarimeter (RSP). The remainder were Lidars, including the Cloud Physics Lidar (CPL) and the High Spectral Resolution Lidar 2 (HSRL2). The southern California base of ACEPOL enabled observation of a wide variety of scene types, including urban, desert, forest, coastal ocean and agricultural areas, with clear, cloudy, polluted and pristine atmospheric conditions. Flights were performed in coordination with satellite overpasses and ground based observations, including the Groundbased Multiangle SpectroPolarimetric Imager (GroundMSPI), sun photometers, and a surface reflectance spectrometer. ACEPOL is a resource for remote sensing communities as they prepare for the next generation of spaceborne MAP and lidar missions. Data are appropriate for algorithm development and testing, instrument intercomparison, and investigations of active and passive instrument data fusion. They are freely available to the public, at https://doi.org/10.5067/SUBORBITAL/ACEPOL2017/DATA001 (ACEPOL Science Team, 2017). This paper describes ACEPOL for potential data users, and also provides an outline of requirements for future field missions with similar objectives.

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“…CC BY 4.0 License. than 750 nm are excluded from our analysis due to a grating order overlap issue in the data (Smit et al, 2019;Fu et al, 2019).…”

Section: Datamentioning

confidence: 99%

“…In the fall of 2017, the Aerosol Characterization from Polarimeter and Lidar (ACEPOL) field campaign, a collaboration between NASA and Netherlands Institute for Space Research (SRON), was conducted with six passive and active instruments on the NASA ER2 high-altitude aircraft (Knobelspiesse and et al, to be submitted). These included four MAPs: airHARP (the airborne version of HARP2 and HARP Cubesat (McBride et al, 2019)), AirMSPI (the Airborne Multiangle SpectroPolarimetric Imager) (Diner et al, 2013), SPEX Airborne (the airborne version of SPEXone ) (Smit et al, 2019) and the RSP (Research Scanning Polarimeter) (Cairns et al, 1999), and two lidars: HSRL-2(the High Spectral Resolution Lidar-2) (Burton et al, 2015) and CPL (the Cloud Physics Lidar) (McGill et al, 2002). SPEX Airborne collects hyperspectral radiometry, and thus can be used as a proxy for OCI in developing hyperspectral ocean color algorithms.…”

Section: Introductionmentioning

confidence: 99%

Inversion of multi-angular polarimetric measurements from the ACEPOL campaign: an application of improving aerosol property and hyperspectral ocean color retrievals

Meng¹,

Zhai²,

Franz³

et al. 2020

Preprint

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Abstract. NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission, scheduled for launch in the timeframe of late 2022 to early 2023, will carry the Ocean Color Instrument (OCI), a hyperspectral scanning radiometer, and two multi-angle polarimeters (MAP), the UMBC Hyper-Angular Rainbow Polarimeter (HARP2) and the SRON Spectro-Polarimeter for Planetary EXploration one (SPEXone). One purpose of the PACE MAPs is to better characterize aerosols properties, which can then be used to improve atmospheric correction for the retrieval of ocean color in coastal waters. Though this is theoretically promising, the use of MAP data in the atmospheric correction of collocated hyperspectral ocean color measurements has not yet been well demonstrated. In this work, we performed aerosol retrievals using the MAP measurements from the Research Scanning Polarimeter (RSP), and demonstrate its application to the atmospheric correction of hyperspectral radiometric measurements from SPEX Airborne. Both measurements were collected on the same aircraft from the Aerosol Characterization from Polarimeter and Lidar (ACEPOL) field campaign in 2017. Two cases over ocean with small aerosol loading (aerosol optical depth ∼ 0.04) are identified including collocated RSP and SPEX Airborne measurements and Aerosol Robotic Network (AERONET) in-situ observations. The aerosol retrievals are performed and compared with two options: one uses reflectance only and the other use both reflectance and polarization. It is demonstrated that polarization information helps reduce the uncertainties of aerosol microphysical and optical properties. The retrieved aerosol properties are then used to compute the contribution of atmosphere and ocean surface for atmospheric correction over the discrete bands from RSP measurements and the hyperspectral SPEX Airborne measurements. The water leaving signals determined this way are compared with both AERONET and Moderate Resolution Imaging Spectroradiometer (MODIS) Ocean Color products with good agreement. The results and lessons-learned from this work will provide a basis to fully exploit the information from the unique combination of sensors on PACE for aerosol characterization and ocean ecosystem research.

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SPEX airborne spectropolarimeter calibration and performance

Cited by 44 publications

References 37 publications

A universal smartphone add-on for portable spectroscopy and polarimetry: iSPEX 2

A universal smartphone add-on for portable spectroscopy and polarimetry: iSPEX 2

The Aerosol Characterization from Polarimeter and Lidar (ACEPOL) airborne field campaign

Inversion of multi-angular polarimetric measurements from the ACEPOL campaign: an application of improving aerosol property and hyperspectral ocean color retrievals

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