41 research outputs found
Photometric characterization of Lucideon and Avian Technologies color standards including application for calibration of the Mastcam-Z instrument on the Mars 2020 rover
Several commercially available color standards exist, generated by a variety of manufacturers including LabSphere, Lucideon, and Avian Technologies. Previous work has characterized the photometric properties of LabSphere Spectralon targets. Here, we measure the visible and shortwave infrared (VSWIR; 0.4 to 2.5ââÎŒm) reflectance at multiple angles and determine the photometric properties of materials manufactured by Lucideon and Avian Technologies for potential use as calibration target materials for the Mars 2020 Mastcam-Z instrument. The Lucideon black, gray 33, green, and cyan samples are found to be significantly forward scattering. The yellow, red, and gray 70 samples are found to be weakly forward scattering. The Avian Technologies AluWhite98 sample was found to be weakly backward scattering. We characterize the absorptions observable and note the occurrence of wavelength-dependent photometric properties. The reflectance and photometric data collected and released here enable the use of these color standards for calibration of data from Mastcam-Z and other Mars-2020 rover instruments as well as provide key information for many other imaging and spectroscopy applications that require the calibration of data from multiple lighting or viewing geometries
Photometric characterization of Lucideon and Avian Technologies color standards including application for calibration of the Mastcam-Z instrument on the Mars 2020 rover
An Instrument Anomaly in the Mars Exploration Rover Pancam 1,009ânm Filter (R7): Characterization, Simulation, Correction, and Preliminary Verification
During preâflight calibration of the panoramic camera (Pancam) instrument on board the Mars Exploration Rovers MER A (Spirit) and MER B (Opportunity), a discrepancy was noted between 11âband spectra extracted from Pancam images of the camera's radiometric calibration target and reflectance spectra obtained with a spectrometer. This discrepancy was observed in the longestâwavelength filter of the camera (the longpass R7 filter with system λ_(eff) = 1,009 nm) and consisted of a reduction in contrast between bright and dark regions. Here we describe and characterize this effect. We propose that the effect arises because longâwavelength photons close to the silicon bandâgap at 1,100 nm are allowed through the R7 filter, pass through the bulk chargeâcoupled device, scatter from the backside, pass through the chargeâcoupled device again, and are registered in a pixel other than the pixel through which they originally entered. Based on this hypothesis we develop a model capable of accurately simulating the effect, and correct for it. We present preliminary results from testing this correction on preflight, as well as inâflight, images. The effect is small, but in some specific cases in small regions of high contrast, the effect is significant. In inâflight images of Martian terrain we observed the signal in dark shadows to be artificially inflated by up to ⌠33% and analysis of earlyâmission calibration target images indicated that the reduced contrast due to the artifact is equivalent to >100 DN (full well = 4095 DN) for a hypothetical perfectly dark pixel
An Instrument Anomaly in the Mars Exploration Rover Panoramic Camera (Pancam) 1009 nm Filter (R7): Characterisation, Simulation, Correction and Preliminary Verification
During preâflight calibration of the panoramic camera (Pancam) instrument on board the Mars Exploration Rovers MER A (Spirit) and MER B (Opportunity), a discrepancy was noted between 11âband spectra extracted from Pancam images of the camera's radiometric calibration target and reflectance spectra obtained with a spectrometer. This discrepancy was observed in the longestâwavelength filter of the camera (the longpass R7 filter with system λ_(eff) = 1,009 nm) and consisted of a reduction in contrast between bright and dark regions. Here we describe and characterize this effect. We propose that the effect arises because longâwavelength photons close to the silicon bandâgap at 1,100 nm are allowed through the R7 filter, pass through the bulk chargeâcoupled device, scatter from the backside, pass through the chargeâcoupled device again, and are registered in a pixel other than the pixel through which they originally entered. Based on this hypothesis we develop a model capable of accurately simulating the effect, and correct for it. We present preliminary results from testing this correction on preflight, as well as inâflight, images. The effect is small, but in some specific cases in small regions of high contrast, the effect is significant. In inâflight images of Martian terrain we observed the signal in dark shadows to be artificially inflated by up to ⌠33% and analysis of earlyâmission calibration target images indicated that the reduced contrast due to the artifact is equivalent to >100 DN (full well = 4095 DN) for a hypothetical perfectly dark pixel
Photometric characterization of Lucideon and Avian Technologies color standards including application for calibration of the Mastcam-Z instrument on the Mars 2020 rover
Several commercially available color standards exist, generated by a variety of manufacturers including LabSphere, Lucideon, and Avian Technologies. Previous work has characterized the photometric properties of LabSphere Spectralon targets. Here, we measure the visible and shortwave infrared (VSWIR; 0.4 to 2.5ââÎŒm) reflectance at multiple angles and determine the photometric properties of materials manufactured by Lucideon and Avian Technologies for potential use as calibration target materials for the Mars 2020 Mastcam-Z instrument. The Lucideon black, gray 33, green, and cyan samples are found to be significantly forward scattering. The yellow, red, and gray 70 samples are found to be weakly forward scattering. The Avian Technologies AluWhite98 sample was found to be weakly backward scattering. We characterize the absorptions observable and note the occurrence of wavelength-dependent photometric properties. The reflectance and photometric data collected and released here enable the use of these color standards for calibration of data from Mastcam-Z and other Mars-2020 rover instruments as well as provide key information for many other imaging and spectroscopy applications that require the calibration of data from multiple lighting or viewing geometries
Visible to near-infrared MSL/Mastcam multispectral imaging: Initial results from select high-interest science targets within Gale Crater, Mars
The Mastcam CCD cameras on the Mars Science Laboratory Curiosity Rover each use an 8-position filter wheel in acquiring up to 1600 Ă 1200 pixel images. The filter set includes a broadband near-infrared cutoff filter for RGB Bayer imaging on each camera and 12 narrow-band geology filters distributed between the two cameras, spanning the wavelength range 445â1013 nm. This wavelength region includes the relatively broad charge-transfer and crystal-field absorption bands that are most commonly due to the presence of iron-bearing minerals. To identify such spectral features, sequences of images taken with identical pointings through different filters have been calibrated to relative reflectance using pre-flight calibration coefficients and in-flight measurements of an onboard calibration target. Within the first 1000 sols of the mission, Mastcam observed a spectrally diverse set of materials displaying absorption features consistent with the presence of iron-bearing silicate, iron oxide, and iron sulfate minerals. Dust-coated surfaces as well as soils possess a strong positive reflectance slope in the visible, consistent with the presence of nanophase iron oxides, which have long been considered the dominant visible-wavelength pigmenting agent in weathered martian surface materials. Fresh surfaces, such as tailings produced by the drill tool and the interiors of rocks broken by the rover wheels, are grayer in visible wavelengths than their reddish, dust-coated surfaces but possess reflectance spectra that vary considerably between sites. To understand the mineralogical basis of observed Mastcam reflectance spectra, we focus on a subset of the multispectral data set for which additional constraints on the composition of surface materials are available from other rover instruments, with an emphasis on sample sites for which detailed mineralogy is provided by the results of CheMin X-ray diffraction analyses. We also discuss the results of coordinated observations with the ChemCam instrument, whose passive mode of operation is capable of acquiring reflectance spectra over wavelengths that considerably overlap the range spanned by the Mastcam filter set (Johnson et al. 2016). Materials that show a distinct 430 nm band in ChemCam data also are observed to have a strong near-infrared absorption band in Mastcam spectral data, consistent with the presence of a ferric sulfate mineral. Long-distance Mastcam observations targeted toward the flanks of the Gale crater central mound are in agreement with both ChemCam spectra and orbital results, and in particular exhibit the spectral features of a crystalline hematite layer identified in MRO/CRISM data. Variations observed in Mastcam multi-filter images acquired to date have shown that multispectral observations can discriminate between compositionally different materials within Gale Crater and are in qualitative agreement with mineralogies from measured samples and orbital data
Mastcam-Z multispectral database from the Perseverance roverâs traverse in the Jezero crater floor, Mars (sols 0-380)
NASAâs Mars-2020 Perseverance rover spent its first year in Jezero crater studying the mafic lava flows of the MĂĄaz formation and the ultramafic cumulates of the SĂ©Ătah formation. Perseveranceâs Mastcam-Z instrument, a pair of multispectral, stereoscopic zoom-lens cameras, provides broadband red/green/blue (RGB), narrowband visible to near-infrared color (VNIR, 440-1020 nm wavelength range). We compiled Mastcam-Z spectra from Perseveranceâs exploration of the Jezero crater floor in the first 380 sols of its mission. Here, we provide a database of ~2400 representative spectra with extensive metadata, and the locations of the regions of interest (ROIs) from which the spectra were extracted. We also include ânatural colorâ red, green, blue (RGB) images for context, âenhanced color imagesâ derived by stretching narrowband images, and âdecorrelation stretchâ (DCS) images. This dataset can serve as a baseline to interpret future observations from Perseveranceâs ongoing exploration of Jezero crater, Mars